Douglas C. Schmidt - Concurrent object-oriented network programming in C++

8/8/2019 Douglas C. Schmidt - Concurrent object-oriented network programming in C++

1/48

C o n c u r r e n t O b j e c t - O r i e n t e d

N e t w o r k P r o g r a m m i n g w i t h C + +

D o u g l a s C . S c h m i d t

W a s h i n g t o n U n i v e r s i t y , S t . L o u i s

h t t p : w w w . c s . w u s t l . e d u s c h m i d t

s c h m i d t @ c s . w u s t l . e d u

1

M o t i v a t i o n f o r D i s t r i b u t i o n

B e n e t s o f d i s t r i b u t e d c o m p u t i n g :

C o l l a b o r a t i o n ! c o n n e c t i v i t y a n d i n t e r w o r k i n g

P e r f o r m a n c e ! m u l t i - p r o c e s s i n g a n d l o c a l i t y

R e l i a b i l i t y a n d a v a i l a b i l i t y ! r e p l i c a t i o n

S c a l a b i l i t y a n d p o r t a b i l i t y ! m o d u l a r i t y

E x t e n s i b i l i t y ! d y n a m i c c o n g u r a t i o n a n d r e c o n -

g u r a t i o n

C o s t e e c t i v e n e s s ! o p e n s y s t e m s a n d r e s o u r c e

s h a r i n g

2

C h a l l e n g e s a n d S o l u t i o n s

D e v e l o p i n g e c i e n t , r o b u s t , a n d e x t e n s i b l e

d i s t r i b u t e d a p p l i c a t i o n s i s c h a l l e n g i n g

e . g . , m u s t a d d r e s s c o m p l e x t o p i c s t h a t a r e l e s s

p r o b l e m a t i c o r n o t r e l e v a n t f o r n o n - d i s t r i b u t e d a n d

n o n - c o n c u r r e n t a p p l i c a t i o n s

O b j e c t - o r i e n t e d O O t e c h n i q u e s a n d C + +

l a n g u a g e f e a t u r e s e n h a n c e d i s t r i b u t e d s o f t -

w a r e q u a l i t y f a c t o r s

K e y O O t e c h n i q u e s ! d e s i g n p a t t e r n s a n d f r a m e -

w o r k s

K e y C + + l a n g u a g e f e a t u r e s ! c l a s s e s , i n h e r i t a n c e ,

d y n a m i c b i n d i n g , a n d p a r a m e t e r i z e d t y p e s

K e y s o f t w a r e q u a l i t y f a c t o r s ! m o d u l a r i t y , e x t e n -

s i b i l i t y , p o r t a b i l i t y , r e u s a b i l i t y , r e l i a b i l i t y , a n d c o r -

r e c t n e s s

3

C a v e a t s

O O a n d C + + a r e n o t a p a n a c e a

H o w e v e r , w h e n u s e d p r o p e r l y t h e y h e l p m i n i m i z e

a c c i d e n t a l " c o m p l e x i t y a n d i m p r o v e s o f t w a r e q u a l -

i t y

A d v a n c e d O S f e a t u r e s p r o v i d e a d d i t i o n a l f u n c -

t i o n a l i t y a n d p e r f o r m a n c e , e . g . ,

M u l t i - t h r e a d i n g

M u l t i - p r o c e s s i n g

S y n c h r o n i z a t i o n

E x p l i c i t d y n a m i c l i n k i n g

S h a r e d m e m o r y

C o m m u n i c a t i o n p r o t o c o l s a n d I P C m e c h a n i s m s

4


2/48

T u t o r i a l O u t l i n e

O u t l i n e k e y c h a l l e n g e s f o r d e v e l o p i n g d i s -

t r i b u t e d a p p l i c a t i o n s

P r e s e n t a n O O d e s i g n a n d i m p l e m e n t a t i o n

o f t h e f o l l o w i n g c o m m u n i c a t i o n a p p l i c a t i o n s :

1 D i s t r i b u t e d L o g g e r

2 A p p l i c a t i o n - l e v e l G a t e w a y

B o t h s i n g l e - t h r e a d e d a n d m u l t i - t h r e a d e d s o -

l u t i o n s a r e g i v e n

5

S o f t w a r e D e v e l o p m e n t

E n v i r o n m e n t

T h e t o p i c s d i s c u s s e d h e r e a r e l a r g e l y i n d e -

p e n d e n t o f O S , n e t w o r k , a n d p r o g r a m m i n g

l a n g u a g e

C u r r e n t l y b e i n g u s e d o n U N I X a n d W i n d o w s N T

p l a t f o r m s , r u n n i n g o n T C P I P a n d I P X S P X n e t -

w o r k s , w r i t t e n i n C + +

E x a m p l e s i l l u s t r a t e d w i t h f r e e l y a v a i l a b l e A D A P

T I V E C o m m u n i c a t i o n E n v i r o n m e n t A C E

O O t o o l k i t

A l t h o u g h A C E i s w r i t t e n i n C + + , t h e p r i n c i p l e s

a p p l y t o o t h e r O O l a n g u a g e s

6

S t a n d - a l o n e v s . D i s t r i b u t e d

A p p l i c a t i o n A r c h i t e c t u r e s

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7

S o u r c e s o f C o m p l e x i t y

D i s t r i b u t e d a p p l i c a t i o n d e v e l o p m e n t e x h i b i t s

b o t h i n h e r e n t a n d a c c i d e n t a l c o m p l e x i t y

I n h e r e n t c o m p l e x i t y r e s u l t s f r o m f u n d a m e n -

t a l c h a l l e n g e s i n t h e d i s t r i b u t e d a p p l i c a t i o n

d o m a i n , e . g . ,

A d d r e s s i n g t h e i m p a c t o f l a t e n c y

D e t e c t i n g a n d r e c o v e r i n g f r o m p a r t i a l f a i l u r e s o f

n e t w o r k s a n d h o s t s

L o a d b a l a n c i n g a n d s e r v i c e p a r t i t i o n i n g

C o n s i s t e n t o r d e r i n g o f d i s t r i b u t e d e v e n t s

8


3/48

S o u r c e s o f C o m p l e x i t y c o n t ' d

A c c i d e n t a l c o m p l e x i t y r e s u l t s f r o m l i m i t a -

t i o n s w i t h t o o l s a n d t e c h n i q u e s u s e d t o d e -

v e l o p d i s t r i b u t e d a p p l i c a t i o n s , e . g . ,

L a c k o f t y p e - s a f e , p o r t a b l e , r e - e n t r a n t , a n d e x t e n -

s i b l e s y s t e m c a l l i n t e r f a c e s a n d c o m p o n e n t l i b r a r i e s

I n a d e q u a t e d e b u g g i n g s u p p o r t

W i d e s p r e a d u s e o f a l g o r i t h m i c d e c o m p o s i t i o n

. F i n e f o r e x p l a i n i n g n e t w o r k p r o g r a m m i n g c o n -

c e p t s a n d a l g o r i t h m s b u t i n a d e q u a t e f o r d e v e l -

o p i n g l a r g e - s c a l e d i s t r i b u t e d a p p l i c a t i o n s

C o n t i n u o u s r e d i s c o v e r y a n d r e i n v e n t i o n o f c o r e c o n -

c e p t s a n d c o m p o n e n t s

9

O O C o n t r i b u t i o n s t o D i s t r i b u t e d

A p p l i c a t i o n D e v e l o p m e n t

D i s t r i b u t e d a p p l i c a t i o n i m p l e m e n t o r s t r a d i -

t i o n a l l y u s e d l o w - l e v e l I P C a n d O S m e c h a -

n i s m s , e . g . ,

s o c k e t s ! I O d e s c r i p t o r s , a d d r e s s f o r m a t s , b y t e -

o r d e r i n g , s i g n a l s , m e s s a g e b u e r i n g a n d f r a m i n g

s e l e c t ! b i t m a s k s , s i g n a l s , d e s c r i p t o r c o u n t s , t i m e -

o u t s

f o r k e x e c ! s i g n a l h a n d l i n g , I O d e s c r i p t o r s

P O S I X p t h r e a d s a n d S o l a r i s t h r e a d s

O O d e s i g n p a t t e r n s a n d f r a m e w o r k s e l e v a t e

f o c u s o n t o o n a p p l i c a t i o n r e q u i r e m e n t s a n d

p o l i c i e s , e . g . ,

S e r v i c e f u n c t i o n a l i t y

S e r v i c e c o n g u r a t i o n

S e r v i c e c o n c u r r e n c y

1 0

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D i s t r i b u t e d l o g g i n g s e r v i c e

1 1

D i s t r i b u t e d L o g g i n g S e r v i c e

S e r v e r l o g g i n g d a e m o n

C o l l e c t s , f o r m a t s , a n d o u t p u t s l o g g i n g r e c o r d s f o r -

w a r d e d f r o m c l i e n t l o g g i n g d a e m o n s r e s i d i n g t h r o u g h -

o u t a n e t w o r k o r i n t e r n e t w o r k

T h e a p p l i c a t i o n i n t e r f a c e i s s i m i l a r t o p r i n t f

A C E _ E R R O R L M _ E R R O R , " t c a n ' t f o r k i n f u n c t i o n s p

g e n e r a t e s o n s e r v e r h o s t

O c t 2 9 1 4 : 5 0 : 1 3 1 9 9 2 @ c r i m e e . i c s . u c i . e d u @ 2 2 7 6 6 @ 7 @ c l i e n

: : 4 c a n ' t f o r k i n f u n c t i o n s p a w n

A C E _ D E B U G L M _ D E B U G ,

" t s e n d i n g t o s e r v e r s " , s e r v e r _ h o s t ;

g e n e r a t e s o n s e r v e r h o s t

O c t 2 9 1 4 : 5 0 : 2 8 1 9 9 2 @ z o l a . i c s . u c i . e d u @ 1 8 3 5 2 @ 2 @ d r w h o

: : 6 s e n d i n g t o s e r v e r b a s t i l l e

1 2


4/48

C o n v e n t i o n a l L o g g i n g S e r v e r

D e s i g n

T y p i c a l a l g o r i t h m i c p s e u d o - c o d e f o r t h e s e r v e r

d a e m o n p o r t i o n o f t h e d i s t r i b u t e d l o g g i n g

s e r v i c e :

v o i d s e r v e r l o g g i n g d a e m o n v o i d

f

i n i t i a l i z e l i s t e n e r e n d p o i n t

l o o p f o r e v e r

f

w a i t f o r e v e n t s

h a n d l e d a t a e v e n t s

h a n d l e c o n n e c t i o n e v e n t s

g

g

T h e g r a n d m i s t a k e " :

A v o i d t h e t e m p t a t i o n t o s t e p - w i s e r e n e " t h i s

a l g o r i t h m i c a l l y d e c o m p o s e d p s e u d o - c o d e d i r e c t l y

i n t o t h e d e t a i l e d d e s i g n a n d i m p l e m e n t a t i o n o f t h e

l o g g i n g s e r v e r !

1 3

S e l e c t - b a s e d L o g g i n g S e r v e r

I m p l e m e n t a t i o n

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LOGGING DAEMONLOGGING DAEMON

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1 4

C o n v e n t i o n a l L o g g i n g S e r v e r

I m p l e m e n t a t i o n

N o t e t h e e x c e s s i v e a m o u n t o f d e t a i l r e q u i r e d

t o p r o g r a m a t t h e s o c k e t l e v e l : : :

M a i n p r o g r a m

s t a t i c c o n s t i n t P O R T = 1 0 0 0 0 ;

t y p e d e f u _ l o n g C O U N T E R ;

t y p e d e f i n t H A N D L E ;

C o u n t s t h e o f l o g g i n g r e c o r d s p r o c e s s e d

s t a t i c C O U N T E R r e q u e s t _ c o u n t ;

P a s s i v e - m o d e s o c k e t d e s c r i p t o r

s t a t i c H A N D L E l i s t e n e r ;

H i g h e s t a c t i v e d e s c r i p t o r n u m b e r , p l u s 1

s t a t i c H A N D L E m a x h p 1 ;

S e t o f c u r r e n t l y a c t i v e d e s c r i p t o r s

s t a t i c f d _ s e t r e a d _ h a n d l e s ;

S c r a t c h c o p y o f r e a d _ h a n d l e s

s t a t i c f d _ s e t t m p _ h a n d l e s ;

1 5

R u n m a i n e v e n t l o o p o f s e r v e r l o g g i n g d a e m o n .

i n t m a i n i n t a r g c , c h a r * a r g v

i n i t i a l i z e _ l i s t e n e r _ e n d p o i n t

a r g c 1 ? a t o i a r g v 1 : P O R T ;

L o o p f o r e v e r p e r f o r m i n g l o g g i n g s e r v e r p r o c e s s i n g .

f o r ; ;

t m p _ h a n d l e s = r e a d _ h a n d l e s ; s t r u c t a s s i g n m e n t .

W a i t f o r c l i e n t I O e v e n t s

s e l e c t m a x h p 1 , & t m p _ h a n d l e s , 0 , 0 , 0 ;

F i r s t r e c e i v e p e n d i n g l o g g i n g r e c o r d s

h a n d l e _ d a t a ;

T h e n a c c e p t p e n d i n g c o n n e c t i o n s

h a n d l e _ c o n n e c t i o n s ;

1 6


5/48

I n i t i a l i z e t h e p a s s i v e - m o d e s o c k e t d e s c r i p t o r

s t a t i c v o i d i n i t i a l i z e _ l i s t e n e r _ e n d p o i n t u _ s h o r t p o r t

s t r u c t s o c k a d d r _ i n s a d d r ;

C r e a t e a l o c a l e n d p o i n t o f c o m m u n i c a t i o n

l i s t e n e r = s o c k e t P F _ I N E T , S O C K _ S T R E A M , 0 ;

S e t u p t h e a d d r e s s i n f o r m a t i o n t o b e c o m e a s e r v e r

m e m s e t v o i d * & s a d d r , 0 , s i z e o f s a d d r ;

s a d d r . s i n _ f a m i l y = A F _ I N E T ;

s a d d r . s i n _ p o r t = h t o n s p o r t ;

s a d d r . s i n _ a d d r . s _ a d d r = h t o n l I N A D D R _ A N Y ;

A s s o c i a t e a d d r e s s w i t h e n d p o i n t

b i n d l i s t e n e r , s t r u c t s o c k a d d r * & s a d d r , s i z e o f s a d d r ;

M a k e e n d p o i n t l i s t e n f o r c o n n e c t i o n r e q u e s t s

l i s t e n l i s t e n e r , 5 ;

I n i t i a l i z e d e s c r i p t o r s e t s

F D _ Z E R O & t m p _ h a n d l e s ;

F D _ Z E R O & r e a d _ h a n d l e s ;

F D _ S E T l i s t e n e r , & r e a d _ h a n d l e s ;

m a x h p 1 = l i s t e n e r + 1 ;

1 7

R e c e i v e p e n d i n g l o g g i n g r e c o r d s

s t a t i c v o i d h a n d l e _ d a t a v o i d

l i s t e n e r + 1 i s t h e l o w e s t c l i e n t d e s c r i p t o r

f o r H A N D L E h = l i s t e n e r + 1 ; h m a x h p 1 ; h + +

i f F D _ I S S E T h , & t m p _ h a n d l e s

s s i z e _ t n ;

G u a r a n t e e d n o t t o b l o c k i n t h i s c a s e !

i f n = h a n d l e _ l o g _ r e c o r d h , 1 0

+ + r e q u e s t _ c o u n t ; C o u n t t h e o f l o g g i n g r e c o

e l s e i f n = = 0 H a n d l e c o n n e c t i o n s h u t d o w n .

F D _ C L R h , & r e a d _ h a n d l e s ;

c l o s e h ;

i f h + 1 = = m a x h p 1

S k i p p a s t u n u s e d d e s c r i p t o r s

w h i l e ! F D _ I S S E T - - h , & r e a d _ h a n d l e s

c o n t i n u e ;

m a x h p 1 = h + 1 ;

1 8

R e c e i v e a n d p r o c e s s l o g g i n g r e c o r d s

s t a t i c s s i z e _ t h a n d l e _ l o g _ r e c o r d

H A N D L E i n _ h , H A N D L E o u t _ h

s s i z e _ t n ;

s i z e _ t l e n ;

L o g _ R e c o r d l o g _ r e c o r d ;

T h e f i r s t r e c v r e a d s t h e l e n g t h s t o r e d a s a

f i x e d - s i z e i n t e g e r o f a d j a c e n t l o g g i n g r e c o r d .

n = r e c v i n _ h , c h a r * & l e n , s i z e o f l e n , 0 ;

i f n = 0 r e t u r n n ;

l e n = n t o h l l e n ; C o n v e r t b y t e - o r d e r i n g

T h e s e c o n d r e c v t h e n r e a d s L E N b y t e s t o o b t a i n t h e

a c t u a l r e c o r d

f o r s i z e _ t n r e a d = 0 ; n r e a d l e n ; n r e a d + = n

n = r e c v i n _ h , c h a r * & l o g _ r e c o r d + n r e a d ,

l e n - n r e a d , 0 ;

D e c o d e a n d p r i n t r e c o r d .

d e c o d e _ l o g _ r e c o r d & l o g _ r e c o r d ;

w r i t e o u t _ h , l o g _ r e c o r d . b u f , l o g _ r e c o r d . s i z e ;

r e t u r n n ;

1 9

C h e c k i f a n y c o n n e c t i o n r e q u e s t s h a v e a r r i v e d

s t a t i c v o i d h a n d l e _ c o n n e c t i o n s v o i d

i f F D _ I S S E T l i s t e n e r , & t m p _ h a n d l e s

s t a t i c s t r u c t t i m e v a l p o l l _ t v = 0 , 0 ;

H A N D L E h ;

H a n d l e a l l p e n d i n g c o n n e c t i o n r e q u e s t s

n o t e u s e o f s e l e c t ' s " p o l l i n g " f e a t u r e

d o

h = a c c e p t l i s t e n e r , 0 , 0 ;

F D _ S E T h , & r e a d _ h a n d l e s ;

G r o w m a x . s o c k e t d e s c r i p t o r i f n e c e s s a r y .

i f h = m a x h p 1

m a x h p 1 = h + 1 ;

w h i l e s e l e c t l i s t e n e r + 1 , & t m p _ h a n d l e s ,

0 , 0 , & p o l l _ t v = = 1 ;

2 0


6/48

L i m i t a t i o n s w i t h A l g o r i t h m i c

D e c o m p o s i t i o n T e c h n i q u e s

A l g o r i t h m i c d e c o m p o s i t i o n t i g h t l y c o u p l e s

a p p l i c a t i o n - s p e c i c f u n c t i o n a l i t y a n d t h e f o l -

l o w i n g c o n g u r a t i o n - r e l a t e d c h a r a c t e r i s t i c s :

S t r u c t u r e

. T h e n u m b e r o f s e r v i c e s p e r p r o c e s s

. T i m e w h e n s e r v i c e s a r e c o n g u r e d i n t o a p r o c e s s

C o m m u n i c a t i o n M e c h a n i s m s

. T h e u n d e r l y i n g I P C m e c h a n i s m s t h a t c o m m u n i -

c a t e w i t h o t h e r p a r t i c i p a t i n g c l i e n t s a n d s e r v e r s

. E v e n t d e m u l t i p l e x i n g a n d e v e n t h a n d l e r d i s p a t c h -

i n g m e c h a n i s m s

E x e c u t i o n A g e n t s

. T h e p r o c e s s a n d o r t h r e a d a r c h i t e c t u r e t h a t e x -

e c u t e s s e r v i c e s a t r u n - t i m e

2 1

O v e r c o m i n g L i m i t a t i o n s v i a O O

T h e a l g o r i t h m i c d e c o m p o s i t i o n i l l u s t r a t e d

a b o v e s p e c i e s m a n y l o w - l e v e l d e t a i l s

F u r t h e r m o r e , t h e e x c e s s i v e c o u p l i n g s i g n i c a n t l y

c o m p l i c a t e s r e u s a b i l i t y , e x t e n s i b i l i t y , a n d p o r t a b i l i t y

I n c o n t r a s t , O O f o c u s e s o n a p p l i c a t i o n - s p e c i c

b e h a v i o r , e . g . ,

i n t L o g g i n g _ H a n d l e r : : s v c v o i d

s s i z e _ t n ;

n = h a n d l e _ l o g _ r e c o r d p e e r . g e t _ h a n d l e , 1 ;

i f n 0

+ + r e q u e s t _ c o u n t ; C o u n t t h e o f l o g g i n g r e c o r d

r e t u r n n = 0 ? - 1 : 0 ;

2 2

O O C o n t r i b u t i o n s

O O a p p l i c a t i o n f r a m e w o r k s a c h i e v e l a r g e -

s c a l e d e s i g n a n d c o d e r e u s e

F r a m e w o r k s e m p h a s i z e t h e c o l l a b o r a t i o n a m o n g

s o c i e t i e s o f c l a s s e s a n d o b j e c t s i n a d o m a i n

I n c o n t r a s t , t r a d i t i o n a l t e c h n i q u e s f o c u s o n t h e

f u n c t i o n s a n d a l g o r i t h m s t h a t s o l v e p a r t i c u l a r r e -

q u i r e m e n t s

O O d e s i g n p a t t e r n s f a c i l i t a t e t h e l a r g e - s c a l e

r e u s e o f s o f t w a r e a r c h i t e c t u r e

E v e n w h e n r e u s e o f a l g o r i t h m s , d e t a i l e d d e s i g n s ,

a n d i m p l e m e n t a t i o n s i s n o t f e a s i b l e

2 3

T h e A D A P T I V E C o m m u n i c a t i o n

E n v i r o n m e n t A C E

THREADTHREAD

LIBRARYLIBRARY

DYNAMICDYNAMIC

LINKINGLINKING

MEMORYMEMORY

MAPPINGMAPPING

SELECTSELECT//POLLPOLL

SYSTEMSYSTEM

VV IPCIPCSTREAMSTREAM

PIPESPIPES

NAMEDNAMED

PIPESPIPES

CAPIS

SOCKETSSOCKETS//TLITLI

COMMUNICATIONCOMMUNICATION

SUBSYSTEMSUBSYSTEM

VIRTUAL MEMORYVIRTUAL MEMORY

SUBSYSTEMSUBSYSTEM

GENERAL POSIX AND WIN32SERVICES

PROCESSPROCESS//THREADTHREADSUBSYSTEMSUBSYSTEM

SYNCHSYNCH

WRAPPERSWRAPPERS

FRAMEWORKS

AND CLASS

CATEGORIES

ACCEPTORACCEPTOR CONNECTORCONNECTOR

DISTRIBUTED

SERVICES AND

COMPONENTS

NAMENAME

SERVERSERVER

TOKENTOKEN

SERVERSERVER

LOGGINGLOGGING

SERVERSERVER

GATEWAYGATEWAY

SERVERSERVER

SOCKSOCK__SAPSAP//TLITLI__SAPSAP

FIFOFIFO

SAPSAP

LOGLOG

MSGMSG

SERVICESERVICE

HANDLERHANDLER

TIMETIME

SERVERSERVER

OSADAPTATION LAYER

C++

WRAPPERS

THREADTHREAD

MANAGERMANAGER

SPIPESPIPE

SAPSAP

CORBACORBA

HANDLERHANDLER

SYSVSYSVWRAPPERSWRAPPERS

REACTORREACTOR

SHAREDSHARED

MALLOCMALLOC

ADAPTIVE SERVICE EXECUTIVEADAPTIVE SERVICE EXECUTIVE (ASX)(ASX)

SERVICESERVICE

CONFIGCONFIG--URATORURATOR

MEMMEM

MAPMAP

A s e t o f C + + w r a p p e r s , c l a s s c a t e g o r i e s ,

a n d f r a m e w o r k s b a s e d o n d e s i g n p a t t e r n s

2 4


7/48

C l a s s C a t e g o r i e s i n A C E

StreamFramework

ServiceServiceConfiguratorConfigurator

APPLICATIONSAPPLICATIONSAPPLICATIONAPPLICATION--SPECIFICSPECIFIC

ConcurrencyConcurrencyglobalglobal

InterprocessInterprocessCommunicationCommunication

APPLICATION-INDEPENDENT

ServiceServiceInitializationInitialization

ReactorReactor

NetworkNetworkServicesServices

APPLICATIONSAPPLICATIONSAPPLICATIONSAPPLICATIONS

2 5

C l a s s C a t e g o r i e s i n A C E c o n t ' d

R e s p o n s i b i l i t i e s o f e a c h c l a s s c a t e g o r y

I P C e n c a p s u l a t e s l o c a l a n d o r r e m o t e I P C m e c h -

a n i s m s

S e r v i c e I n i t i a l i z a t i o n e n c a p s u l a t e s a c t i v e p a s s i

c o n n e c t i o n e s t a b l i s h m e n t m e c h a n i s m s

C o n c u r r e n c y e n c a p s u l a t e s a n d e x t e n d s m u l t i - t h r e a d i

a n d s y n c h r o n i z a t i o n m e c h a n i s m s

R e a c t o r p e r f o r m s e v e n t d e m u l t i p l e x i n g a n d e v e n t

h a n d l e r d i s p a t c h i n g

S e r v i c e C o n f i g u r a t o r a u t o m a t e s c o n g u r a t i o n

a n d r e c o n g u r a t i o n b y e n c a p s u l a t i n g e x p l i c i t d y -

n a m i c l i n k i n g m e c h a n i s m s

S t r e a m F r a m e w o r k m o d e l s a n d i m p l e m e n t s l a y e r s

a n d p a r t i t i o n s o f h i e r a r c h i c a l l y - i n t e g r a t e d c o m m u -

n i c a t i o n s o f t w a r e

N e t w o r k S e r v i c e s p r o v i d e s d i s t r i b u t e d n a m i n g ,

l o g g i n g , l o c k i n g , a n d r o u t i n g s e r v i c e s

2 6

G r a p h i c a l N o t a t i o n

PROCESS

THREAD

OBJECT

: CLASS

CLASS

CLASS

CATEGORY

CLASS

UTILITY

INHERITS

CONTAINS

INSTANTIATES

A

ABSTRACT

CLASSUSES

TEMPLATE

CLASS

2 7

D e s i g n P a t t e r n s

D e s i g n p a t t e r n s r e p r e s e n t s o l u t i o n s t o p r o b -

l e m s t h a t a r i s e w h e n d e v e l o p i n g s o f t w a r e

w i t h i n a p a r t i c u l a r c o n t e x t

i . e . , P a t t e r n s = = p r o b l e m s o l u t i o n p a i r s i n a c o n -

t e x t "

P a t t e r n s c a p t u r e t h e s t a t i c a n d d y n a m i c s t r u c -

t u r e a n d c o l l a b o r a t i o n a m o n g k e y p a r t i c i -

p a n t s i n s o f t w a r e d e s i g n s

T h e y a r e p a r t i c u l a r l y u s e f u l f o r a r t i c u l a t i n g h o w

a n d w h y t o r e s o l v e n o n - f u n c t i o n a l f o r c e s

P a t t e r n s f a c i l i t a t e r e u s e o f s u c c e s s f u l s o f t -

w a r e a r c h i t e c t u r e s a n d d e s i g n s

2 8


8/48

D e s i g n P a t t e r n s i n t h e

D i s t r i b u t e d L o g g e r

ActiveActiveObjectObject

AcceptorAcceptorServiceService

ConfiguratorConfigurator

ReactorReactor

FactoryFactoryMethodMethodIteratorIterator AdapterAdapter

TemplateTemplateMethodMethod

TACTICAL

PATTERNS

STRATEGIC

PATTERNS

2 9


D i s t r i b u t e d L o g g e r c o n t ' d

R e a c t o r p a t t e r n

D e c o u p l e e v e n t d e m u l t i p l e x i n g a n d e v e n t h a n d l e r

d i s p a t c h i n g f r o m a p p l i c a t i o n s e r v i c e s p e r f o r m e d i n

r e s p o n s e t o e v e n t s

A c c e p t o r p a t t e r n

D e c o u p l e t h e p a s s i v e i n i t i a l i z a t i o n o f a s e r v i c e f r o m

t h e t a s k s p e r f o r m e d o n c e t h e s e r v i c e i s i n i t i a l i z e d

3 0


D i s t r i b u t e d L o g g e r c o n t ' d

S e r v i c e C o n g u r a t o r p a t t e r n

D e c o u p l e t h e b e h a v i o r o f n e t w o r k s e r v i c e s f r o m

p o i n t i n t i m e a t w h i c h s e r v i c e s a r e c o n g u r e d i n t o

a n a p p l i c a t i o n

A c t i v e O b j e c t p a t t e r n

D e c o u p l e m e t h o d i n v o c a t i o n f r o m m e t h o d e x e c u -

t i o n a n d s i m p l i e s s y n c h r o n i z e d a c c e s s t o s h a r e d

r e s o u r c e s b y c o n c u r r e n t t h r e a d s

3 1

O O L o g g i n g S e r v e r

T h e o b j e c t - o r i e n t e d s e r v e r l o g g i n g d a e m o n

i s d e c o m p o s e d i n t o s e v e r a l m o d u l a r c o m p o -

n e n t s t h a t p e r f o r m w e l l - d e n e d t a s k s :

1 A p p l i c a t i o n - s p e c i c c o m p o n e n t s

P r o c e s s l o g g i n g r e c o r d s r e c e i v e d f r o m c l i e n t s

2 C o n n e c t i o n - o r i e n t e d a p p l i c a t i o n c o m p o n e n t s

S v c H a n d l e r

. P e r f o r m s I O - r e l a t e d t a s k s w i t h c o n n e c t e d c l i e n t s

A c c e p t o r f a c t o r y

. P a s s i v e l y a c c e p t s c o n n e c t i o n r e q u e s t s f r o m c l i e n t s

. D y n a m i c a l l y c r e a t e s a S v c H a n d l e r o b j e c t f o r

e a c h c l i e n t a n d a c t i v a t e s " i t

3 A p p l i c a t i o n - i n d e p e n d e n t A C E f r a m e w o r k c o m p o -

n e n t s

P e r f o r m I P C , e x p l i c i t d y n a m i c l i n k i n g , e v e n t d e -

m u l t i p l e x i n g , e v e n t h a n d l e r d i s p a t c h i n g , m u l t i -

t h r e a d i n g , e t c .

3 2


9/48

C l a s s D i a g r a m f o r O O L o g g i n g

S e r v e r

LoggingAcceptor

Logging_HandlerSOCK_Acceptor

LoggingHandler

SOCK_StreamNull_Synch

SvcHandlerAcceptor

SVC_HANDLERPEER_ACCEPTOR

PEER_STREAMSYNCH

CONNECTION

CONNECTION--

ORIENTED

ORIENTED

COMPONENTS

COMPONENTS

APPLICATION

APPLICATION--

SPECIFIC

SPECIFIC

COMPONENTS

COMPONENTS

ACE

ACE

FRAMEWORK

FRAMEWORK

COMPONENTS

COMPONENTS

PEERACCEPTOR

PEERSTREAM

StreamStream

ServiceService



IPC_SAPIPC_SAP

ConnectionConnection

ReactorReactor

ACTIVATES

1 n

3 3

T h e R e a c t o r P a t t e r n

I n t e n t

D e c o u p l e e v e n t d e m u l t i p l e x i n g a n d e v e n t h a n -

d l e r d i s p a t c h i n g f r o m t h e s e r v i c e s p e r f o r m e d i n

r e s p o n s e t o e v e n t s "

T h i s p a t t e r n r e s o l v e s t h e f o l l o w i n g f o r c e s

f o r e v e n t - d r i v e n s o f t w a r e :

H o w t o d e m u l t i p l e x m u l t i p l e t y p e s o f e v e n t s f r o m

m u l t i p l e s o u r c e s o f e v e n t s e c i e n t l y w i t h i n a s i n g l e

t h r e a d o f c o n t r o l

H o w t o e x t e n d a p p l i c a t i o n b e h a v i o r w i t h o u t r e q u i r -

i n g c h a n g e s t o t h e e v e n t d i s p a t c h i n g f r a m e w o r k

3 4

S t r u c t u r e o f t h e R e a c t o r P a t t e r n

ReactorReactorhandle_events()register_handler(h)remove_handler(h)expire_timers()

11

11

11

Event_HandlerEvent_Handler

handle_input()handle_output()handle_signal()handle_timeout()get_handle()

A11

nn

nn

ConcreteConcreteEvent_HandlerEvent_Handler

Timer_QueueTimer_Queue

schedule_timer(h)cancel_timer(h)expire_timer(h)

11

11

select (handles);select (handles);foreach h in handles {foreach h in handles {

if (h is output handler)if (h is output handler)table[h]->handle_output () ;table[h]->handle_output () ;

if (h is input handler)if (h is input handler)table[h]->handle_input ();table[h]->handle_input ();

if (h is signal handler)if (h is signal handler)table[h]->handle_signal ();table[h]->handle_signal ();

}}this->expire_timers ();this->expire_timers ();

nnHandlesHandles

11

APPLICATION

APPLICATION--

DEPENDENT

DEPENDENTAPPLICATION-

INDEPENDENT

n

3 5

C o l l a b o r a t i o n i n t h e R e a c t o r

P a t t e r n

mainmainprogramprogram

INITIALIZEINITIALIZE

REGISTER HANDLERREGISTER HANDLER

callback :callback :ConcreteConcrete

Event_HandlerEvent_Handler

START EVENT LOOPSTART EVENT LOOP

DATA ARRIVESDATA ARRIVES

OK TO SENDOK TO SEND

reactorreactor: Reactor: Reactor

handle_events()

FOREACH EVENT DOFOREACH EVENT DOhandle_input()

select()

Reactor()

register_handler(callback)

handle_output()

SIGNAL ARRIVESSIGNAL ARRIVES

TIMER EXPIRESTIMER EXPIRES

handle_signal()

handle_timeout()

get_handle()EXTRACT HANDLEEXTRACT HANDLE

REMOVE HANDLERREMOVE HANDLERremove_handler(callback)

INITIALIZATION

INITIALIZATION

MODE

MODE

EVENTHANDLING

EVENTHANDLING

MODE

MODE

handle_close()CLEANUPCLEANUP

3 6


10/48

U s i n g t h e R e a c t o r P a t t e r n i n t h e

L o g g i n g S e r v e r

:: ReactorReactor

REGISTERED

OBJECTS

FRAMEWORK

FRAMEWORK

LEVEL

KERNEL

LEVEL

APPLIC

ATION

APPLIC

ATION

LEV

EL

LEV

EL

:Timer:TimerQueueQueue

: Signal: SignalHandlersHandlers

: Handle: HandleTableTable

: Event: EventHandlerHandler

: Logging: Logging

Handler


: Logging: Logging

HandlerHandler

1: handle_input()1: handle_input()

5: handle_input()6: recv(msg)6: recv(msg)7:process(msg)


: Logging: LoggingAcceptorAcceptor

2: sh = new Logging_Handler2: sh = new Logging_Handler3: accept (*sh)3: accept (*sh)

4: sh->open()4: sh->open()

OS EVENT DEMULTIPLEXING INTERFACE

3 7

T h e A c c e p t o r P a t t e r n

I n t e n t

D e c o u p l e t h e p a s s i v e i n i t i a l i z a t i o n o f a s e r v i c e

f r o m t h e t a s k s p e r f o r m e d o n c e t h e s e r v i c e i s i n i -

t i a l i z e d "


f o r n e t w o r k s e r v e r s u s i n g i n t e r f a c e s l i k e s o c k -

e t s o r T L I :

1 H o w t o r e u s e p a s s i v e c o n n e c t i o n e s t a b l i s h m e n t c o d e

f o r e a c h n e w s e r v i c e

2 H o w t o m a k e t h e c o n n e c t i o n e s t a b l i s h m e n t c o d e

p o r t a b l e a c r o s s p l a t f o r m s t h a t m a y c o n t a i n s o c k -

e t s b u t n o t T L I , o r v i c e v e r s a

3 H o w t o e n a b l e e x i b l e p o l i c i e s f o r c r e a t i o n , c o n -

n e c t i o n e s t a b l i s h m e n t , a n d c o n c u r r e n c y

4 H o w t o e n s u r e t h a t a p a s s i v e - m o d e d e s c r i p t o r i s

n o t a c c i d e n t a l l y u s e d t o r e a d o r w r i t e d a t a

3 8

S t r u c t u r e o f t h e A c c e p t o r P a t t e r n

ReactorReactor11

AcceptorAcceptor

SVC_HANDLERSVC_HANDLER

PEER_ACCEPTORPEER_ACCEPTOR

ConcreteConcreteAcceptorAcceptor

Concrete_Svc_HandlerConcrete_Svc_Handler

SOCK_AcceptorSOCK_Acceptor11ConcreteConcrete

Svc HandlerSvc Handler

SOCK_StreamSOCK_Stream

open()

nn

REACTIVE

REACTIVE

LAYER

LAYER

CO

NNECTION

CO

NNECTION

LAYER

LAYER

APPLICATION

APPLICATION

LAYER

LAYER

INITS

SvcSvcHandlerHandler

PEER_STREAMPEER_STREAM

open()

AA

sh = make_svc_handler();sh = make_svc_handler();

accept_svc_handler (sh);accept_svc_handler (sh);

activate_svc_handler (sh);activate_svc_handler (sh);

nn

EventEventHandlerHandlerhandle_input()

AA

make_svc_handler()accept_svc_handler()activate_svc_handler()

open()handle_input()

3 9

C o l l a b o r a t i o n i n t h e A c c e p t o r

P a t t e r n

ServerServer


START EVENT LOOPSTART EVENT LOOP

CONNECTION EVENTCONNECTION EVENT


FOR CLIENTFOR CLIENT I/OI/O

FOREACH EVENT DOFOREACH EVENT DO

EXTRACT HANDLEEXTRACT HANDLE

INITIALIZE PASSIVEINITIALIZE PASSIVE

ENDPOINTENDPOINT

acc :acc :AcceptorAcceptor

handle_input()

handle_close()

reactor :reactor :ReactorReactor

select()

sh:sh:Svc_HandlerSvc_Handler

handle_input()

get_handle()EXTRACT HANDLEEXTRACT HANDLE

DATA EVENTDATA EVENT

CLIENT SHUTDOWNCLIENT SHUTDOWN

svc()PROCESS MSGPROCESS MSG

open()

CREATECREATE,, ACCEPTACCEPT,,AND ACTIVATE OBJECTAND ACTIVATE OBJECT

SERVER SHUTDOWNSERVER SHUTDOWNhandle_close()

ENDPOINT

INITIALIZATION

PHASE

SERVICE

INIT

IALIZATION

PHASE

SERVICE

PROCESSING

PHASE

peer_acceptor_peer_acceptor_: SOCK: SOCK

AcceptorAcceptor

handle_events()

get_handle()

register_handler(acc)

sh = make_svc_handler()accept_svc_handler (sh)activate_svc_handler (sh)

open()

register_handler(sh)

A c c e p t o r f a c t o r y c r e a t e s , c o n n e c t s , a n d a c -

t i v a t e s a S v c H a n d l e r

4 0


11/48

U s i n g t h e A c c e p t o r P a t t e r n i n t h e


PASSIVE

LISTENER

ACTIVE

CONNECTIONS

: SvcHandler

: LoggingHandler

: SvcHandler

: LoggingHandler

: SvcHandler

: LoggingHandler

: SvcHandler

: LoggingHandler

: Acceptor

: LoggingAcceptor

1: handle_input()2: sh = make_svc_handler()3: accept_svc_handler(sh)4: activate_svc_handler(sh)

: Reactor

4 1

A c c e p t o r C l a s s P u b l i c I n t e r f a c e

A r e u s a b l e t e m p l a t e f a c t o r y c l a s s t h a t a c -

c e p t s c o n n e c t i o n s f r o m c l i e n t s

t e m p l a t e c l a s s S V C _ H A N D L E R , T y p e o f s e r v i c e

c l a s s P E E R _ A C C E P T O R A c c e p t s c o n n e c t i o n s

c l a s s A c c e p t o r : p u b l i c S e r v i c e _ O b j e c t

I n h e r i t s f r o m E v e n t _ H a n d l e

p u b l i c :

I n i t i a l i z a t i o n .

v i r t u a l i n t o p e n c o n s t P E E R _ A C C E P T O R : : P E E R _ A D D R &

T e m p l a t e M e t h o d o r S t r a t e g y f o r c r e a t i n g ,

c o n n e c t i n g , a n d a c t i v a t i n g S V C _ H A N D L E R ' s .

v i r t u a l i n t h a n d l e _ i n p u t H A N D L E ;

D e m u l t i p l e x i n g h o o k s .

v i r t u a l H A N D L E g e t _ h a n d l e v o i d c o n s t ;

v i r t u a l i n t h a n d l e _ c l o s e H A N D L E , R e a c t o r _ M a s k ;

4 2

A c c e p t o r C l a s s P r o t e c t e d a n d

P r i v a t e I n t e r f a c e s

O n l y v i s i b l e t o t h e c l a s s a n d i t s s u b c l a s s e s

p r o t e c t e d :

F a c t o r y m e t h o d t h a t c r e a t e s a s e r v i c e h a n d l e r .

v i r t u a l S V C _ H A N D L E R * m a k e _ s v c _ h a n d l e r v o i d ;

F a c t o r y m e t h o d t h a t a c c e p t s a n e w c o n n e c t i o n .

v i r t u a l i n t a c c e p t _ s v c _ h a n d l e r S V C _ H A N D L E R * ;

F a c t o r y m e t h o d t h a t a c t i v a t e s a s e r v i c e h a n d l e r .

v i r t u a l i n t a c t i v a t e _ s v c _ h a n d l e r S V C _ H A N D L E R * ;

p r i v a t e :

P a s s i v e c o n n e c t i o n m e c h a n i s m .

P E E R _ A C C E P T O R p e e r _ a c c e p t o r _ ;

;

4 3

A c c e p t o r C l a s s I m p l e m e n t a t i o n

S h o r t h a n d n a m e s .

d e f i n e S H S V C _ H A N D L E R

d e f i n e P A P E E R _ A C C E P T O R

I n i t i a l i z a t i o n .

t e m p l a t e c l a s s S H , c l a s s P A i n t

A c c e p t o r S H , P A : : o p e n c o n s t P A : : P E E R _ A D D R & a d d r

F o r w a r d i n i t i a l i z a t i o n t o c o n c r e t e p e e r a c c e p t o r

p e e r _ a c c e p t o r _ . o p e n a d d r ;

R e g i s t e r w i t h R e a c t o r .

S e r v i c e _ C o n f i g : : r e a c t o r - r e g i s t e r _ h a n d l e r

t h i s , E v e n t _ H a n d l e r : : R E A D _ M A S K ;

4 4


12/48

T e m p l a t e M e t h o d o r S t r a t e g y F a c t o r y t h a t c r e a t e s ,

c o n n e c t s , a n d a c t i v a t e s n e w S V C _ H A N D L E R o b j e c t s .


A c c e p t o r S H , P A : : h a n d l e _ i n p u t H A N D L E

F a c t o r y M e t h o d t h a t m a k e s a s e r v i c e h a n d l e r .

S H * s v c _ h a n d l e r = m a k e _ s v c _ h a n d l e r ;

A c c e p t t h e c o n n e c t i o n .

a c c e p t _ s v c _ h a n d l e r s v c _ h a n d l e r ;

D e l e g a t e c o n t r o l t o t h e s e r v i c e h a n d l e r .

a c t i v a t e _ s v c _ h a n d l e r s v c _ h a n d l e r ;

4 5

F a c t o r y m e t h o d f o r c r e a t i n g a s e r v i c e h a n d l e r .

C a n b e o v e r r i d d e n b y s u b c l a s s e s t o d e f i n e n e w

a l l o c a t i o n p o l i c i e s s u c h a s S i n g l e t o n s , e t c . .

t e m p l a t e c l a s s S H , c l a s s P A S H *

A c c e p t o r S H , P A : : m a k e _ s v c _ h a n d l e r H A N D L E

r e t u r n n e w S H ; D e f a u l t b e h a v i o r .

A c c e p t c o n n e c t i o n s f r o m c l i e n t s c a n b e o v e r r i d d e n .


A c c e p t o r S H , P A : : a c c e p t _ s v c _ h a n d l e r S H * s v c _ h a n d l e r

p e e r _ a c c e p t o r _ . a c c e p t * s v c _ h a n d l e r ;

A c t i v a t e t h e s e r v i c e h a n d l e r c a n b e o v e r r i d d e n .


A c c e p t o r S H , P A : : a c t i v a t e _ s v c _ h a n d l e r S H * s v c _ h a n d l e r

i f s v c _ h a n d l e r - o p e n = = - 1

s v c _ h a n d l e r - c l o s e ;

4 6

R e t u r n s u n d e r l y i n g I O d e s c r i p t o r c a l l e d b y R e a c t o r .

t e m p l a t e c l a s s S H , c l a s s P A H A N D L E

A c c e p t o r S H , P A : : g e t _ h a n d l e v o i d c o n s t

r e t u r n p e e r _ a c c e p t o r _ . g e t _ h a n d l e ;

P e r f o r m t e r m i n a t i o n a c t i v i t i e s w h e n r e m o v e d f r o m R e a c t o r .


A c c e p t o r S H , P A : : h a n d l e _ c l o s e H A N D L E , R e a c t o r _ M a s k

p e e r _ a c c e p t o r _ . c l o s e ;

4 7

S v c H a n d l e r C l a s s P u b l i c I n t e r f a c e

P r o v i d e s a g e n e r i c i n t e r f a c e f o r c o m m u n i -

c a t i o n s e r v i c e s t h a t e x c h a n g e d a t a w i t h a

p e e r o v e r a n e t w o r k c o n n e c t i o n

t e m p l a t e c l a s s P E E R _ S T R E A M , C o m m u n i c a t i o n m e c h a n i

c l a s s S Y N C H S y n c h r o n i z a t i o n p o l i c y .

c l a s s S v c _ H a n d l e r : p u b l i c T a s k S Y N C H

p u b l i c :

S v c _ H a n d l e r v o i d ; C o n s t r u c t o r .

A c t i v a t e t h e c l i e n t h a n d l e r .

v i r t u a l i n t o p e n v o i d * ;

R e t u r n s u n d e r l y i n g P E E R _ S T R E A M .

o p e r a t o r P E E R _ S T R E A M & ;

O v e r l o a d e d n e w o p e r a t o r t h a t d e t e c t s

w h e n a S v c _ H a n d l e r i s a l l o c a t e d d y n a m i c a l l y .

v o i d * o p e r a t o r n e w s i z e _ t n ;

R e t u r n u n d e r l y i n g I P C m e c h a n i s m .

P E E R _ S T R E A M & p e e r v o i d ;

4 8


13/48


14/48

O O D e s i g n I n t e r l u d e

Q : H o w c a n w e d e t e r m i n e i f a n o b j e c t i s

a l l o c a t e d d y n a m i c a l l y ? "

A : O v e r l o a d c l a s s - s p e c i c o p e r a t o r n e w a n d

u s e t h r e a d - s p e c i c s t o r a g e t o a s s o c i a t e t h e

p o i n t e r s , e . g . ,

t e m p l a t e c l a s s P S , c l a s s S Y N C H v o i d *

S v c _ H a n d l e r P S , S Y N C H : : o p e r a t o r n e w s i z e _ t n

v o i d * a l l o c a t e d = : : n e w c h a r n ;

s e t _ t h r e a d _ s p e c i f i c k e y _ , a l l o c a t e d ;

r e t u r n a l l o c a t e d ;

t e m p l a t e c l a s s P S , c l a s s S Y N C H

S v c _ H a n d l e r P S , S Y N C H : : S v c _ H a n d l e r v o i d

v o i d * a l l o c a t e d = g e t _ t h r e a d _ s p e c i f i c k e y _ ;

i s _ d y n a m i c _ = a l l o c a t e d = = t h i s ;

5 3

O b j e c t D i a g r a m f o r O O L o g g i n g

S e r v e r

: LoggingHandler

: ServiceRepository

: ServiceConfig

: Reactor

SERVER

SERVER

LOGGING

DAEMON

: ServiceManager

: LoggingHandler

: Logging

Acceptor

CONNECTION

REQUEST

REMOTE

CONTROL

OPERATIONS

CLIENT

LOGGING

RECORDS

CLIENT CLIENTCLIENT

5 4

T h e L o g g i n g H a n d l e r a n d

L o g g i n g A c c e p t o r C l a s s e s

T h e s e i n s t a n t i a t e d t e m p l a t e c l a s s e s i m p l e -

m e n t a p p l i c a t i o n - s p e c i c s e r v e r l o g g i n g d a e -

m o n f u n c t i o n a l i t y

P e r f o r m s I O w i t h c l i e n t l o g g i n g d a e m o n s .

c l a s s L o g g i n g _ H a n d l e r :

p u b l i c S v c _ H a n d l e r S O C K _ S t r e a m , N U L L _ S Y N C H

p u b l i c :

R e c v a n d p r o c e s s r e m o t e l o g g i n g r e c o r d s .

v i r t u a l i n t h a n d l e _ i n p u t H A N D L E ;

p r o t e c t e d :

c h a r h o s t _ n a m e _ M A X H O S T N A M E L E N + 1 ; C l i e n t .

;

L o g g i n g _ H a n d l e r f a c t o r y .

c l a s s L o g g i n g _ A c c e p t o r :

p u b l i c A c c e p t o r L o g g i n g _ H a n d l e r , S O C K _ A c c e p t o r

p u b l i c :

D y n a m i c l i n k i n g h o o k s .

v i r t u a l i n t i n i t i n t a r g c , c h a r * a r g v ;

v i r t u a l i n t f i n i v o i d ;

;

5 5


IPC_SAP

A

SOCK_SAP TLI_SAP FIFO_SAPSPIPE_SAP

SOCKET

API

TRANSPORT

LAYER

INTERFACE API

STREAM PIPE

API

NAMED PIPE

API

Q : W h a t a r e t h e S O C K * c l a s s e s a n d w h y

a r e t h e y u s e d r a t h e r t h a n u s i n g s o c k e t s d i -

r e c t l y ?

A : S O C K * a r e w r a p p e r s " t h a t e n c a p s u l a t e

n e t w o r k p r o g r a m m i n g i n t e r f a c e s l i k e s o c k -

e t s a n d T L I

T h i s i s a n e x a m p l e o f t h e W r a p p e r p a t t e r n "

5 6


15/48

1

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socket()bind()connect()listen()accept()read()write()readv()writev()recv()send()

recvfrom()sendto()recvmsg()sendmsg()setsockopt()getsockopt()getpeername()getsockname()gethostbyname()getservbyname()

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TYPE OF COMMUNICATION SERVICETYPE OF COMMUNICATION SERVICE

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DOMAIN

CONNECTION

CONNECTION

ROLE

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accept(PF_UNIX

)

accept(PF_UNIX

)

listen()send()/recv()


socket(PF_UNIX)

socket(PF_UNIX)

bind()sendto()

bind()sendto()

socket(PF_UNX)

socket(PF_UNX)

bind()recvfrom()

bind()recvfrom()

socket(PF_INET)

socket(PF_INET)

bind()recvfrom()

bind()recvfrom()

socket(PF_INET)

socket(PF_INET)

bind()sendto()

bind()sendto()

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bind()connect()send()

bind()connect()send()

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6

0


16/48

S O C K S A P C l a s s S t r u c t u r e

LOCAL LOCAL/REMOTE

STREAM

ACTIVE

PASSIVE

DATA

GRAM

CONNECTED

DATAGRAM

LOCK_ConnectorLSOCK_Stream

SOCK_ConnectorSOCK_Stream

SOCK_AcceptorSOCK_Stream

SOCK_Dgram

LSOCK_CODgram SOCK_CODgram

LSOCK_Dgram SOCK_Dgram_Bcast

LSOCK_Dgram SOCK_Dgram

LSOCK_Dgram

LSOCK_AcceptorLSOCK_Stream

SOCK_Dgram_Mcast

SOCK_Dgram

TYPEOFCOMMUNICATIONSERVICE

COMMUNICATION DOMAIN

CONN

ECTION

ROLE

6 1

S O C K S A P F a c t o r y C l a s s

I n t e r f a c e s

c l a s s S O C K _ C o n n e c t o r : p u b l i c S O C K

p u b l i c :

T r a i t s

t y p e d e f I N E T _ A d d r P E E R _ A D D R ;

t y p e d e f S O C K _ S t r e a m P E E R _ S T R E A M ;

i n t c o n n e c t S O C K _ S t r e a m & n e w _ s a p , c o n s t A d d r & r e m o t e

T i m e _ V a l u e * t i m e o u t , c o n s t A d d r & l o c a l _ a

. . .

;

c l a s s S O C K _ A c c e p t o r : p u b l i c S O C K

p u b l i c :

T r a i t s

t y p e d e f I N E T _ A d d r P E E R _ A D D R ;

t y p e d e f S O C K _ S t r e a m P E E R _ S T R E A M ;

S O C K _ A c c e p t o r c o n s t A d d r & l o c a l _ a d d r ;

i n t a c c e p t S O C K _ S t r e a m & , A d d r * , T i m e _ V a l u e * c o n s

. . .

;

6 2

S O C K S A P S t r e a m a n d

A d d r e s s i n g C l a s s I n t e r f a c e s

c l a s s S O C K _ S t r e a m : p u b l i c S O C K

p u b l i c :

t y p e d e f I N E T _ A d d r P E E R _ A D D R ; T r a i t .

s s i z e _ t s e n d c o n s t v o i d * b u f , i n t n ;

s s i z e _ t r e c v v o i d * b u f , i n t n ;

s s i z e _ t s e n d _ n c o n s t v o i d * b u f , i n t n ;

s s i z e _ t r e c v _ n v o i d * b u f , i n t n ;

s s i z e _ t s e n d _ n c o n s t v o i d * b u f , i n t n , T i m e _ V a l u e * ;

s s i z e _ t r e c v _ n v o i d * b u f , i n t n , T i m e _ V a l u e * ;

i n t c l o s e v o i d ;

. . .

;

c l a s s I N E T _ A d d r : p u b l i c A d d r

p u b l i c :

I N E T _ A d d r u _ s h o r t p o r t _ n u m b e r , c o n s t c h a r h o s t ;

u _ s h o r t g e t _ p o r t _ n u m b e r v o i d ;

i n t 3 2 g e t _ i p _ a d d r v o i d ;

. . .

;

6 3


Q : W h y d e c o u p l e t h e S O C K A c c e p t o r a n d

t h e S O C K C o n n e c t o r f r o m S O C K S t r e a m ?

A : F o r t h e s a m e r e a s o n s t h a t A c c e p t o r a n d

C o n n e c t o r a r e d e c o u p l e d f r o m S v c H a n d l e r ,

e . g . ,

A S O C K S t r e a m i s o n l y r e s p o n s i b l e f o r d a t a t r a n s -

f e r

. R e g a r d l e s s o f w h e t h e r t h e c o n n e c t i o n i s e s t a b -

l i s h e d p a s s i v e l y o r a c t i v e l y

T h i s e n s u r e s t h a t t h e S O C K * c o m p o n e n t s a r e n e v e r

u s e d i n c o r r e c t l y

. e . g . , y o u c a n ' t a c c i d e n t a l l y r e a d o r w r i t e o n

S O C K C o n n e c t o r s o r S O C K A c c e p t o r s , e t c .

6 4


17/48

S O C K S A P H i e r a r c h y

LSOCKDgram

SOCKDgram

SOCKCODgram

LSOCKCODgram

LSOCKConnector

LSOCKAcceptor

SOCKAcceptor

SOCKConnector

SOCK

A

LSOCK

A

IPCSAP

A

SOCKDgramMcast

SOCKDgramBcast

GROUP

COMM

DATAGRAM

COMM

STREAM

COMM

CONNECTION

ESTABLISHMENT

SOCKStream

LSOCKStream

S h a r e d b e h a v i o r i s i s o l a t e d i n b a s e c l a s s e s

D e r i v e d c l a s s e s i m p l e m e n t d i e r e n t c o m -

m u n i c a t i o n s e r v i c e s , c o m m u n i c a t i o n d o m a i n s ,

a n d c o n n e c t i o n r o l e s

6 5


Q : H o w c a n y o u s w i t c h b e t w e e n d i e r e n t

I P C m e c h a n i s m s ? "

A : B y p a r a m e t e r i z i n g I P C M e c h a n i s m s w i t h

C + + T e m p l a t e s !

i f d e f i n e d A C E _ U S E _ S O C K E T S

t y p e d e f S O C K _ A c c e p t o r P E E R _ A C C E P T O R ;

e l i f d e f i n e d A C E _ U S E _ T L I

t y p e d e f T L I _ A c c e p t o r P E E R _ A C C E P T O R ;

e n d i f * A C E _ U S E _ S O C K E T S *

c l a s s L o g g i n g _ H a n d l e r : p u b l i c

S v c _ H a n d l e r P E E R _ A C C E P T O R : : P E E R _ S T R E A M ,

N U L L _ S Y N C H

* . . . * ;

c l a s s L o g g i n g _ A c c e p t o r : p u b l i c

A c c e p t o r L o g g i n g _ H a n d l e r , P E E R _ A C C E P T O R

* . . . * ;

6 6

L o g g i n g H a n d l e r I m p l e m e n t a t i o n

I m p l e m e n t a t i o n o f t h e a p p l i c a t i o n - s p e c i c

l o g g i n g m e t h o d

C a l l b a c k r o u t i n e t h a t r e c e i v e s l o g g i n g r e c o r d s .

T h i s i s t h e m a i n c o d e s u p p l i e d b y a d e v e l o p e r !

t e m p l a t e c l a s s P S , c l a s s S Y N C H i n t

L o g g i n g _ H a n d l e r P S , S Y N C H : : h a n d l e _ i n p u t H A N D L E

C a l l e x i s t i n g f u n c t i o n t o r e c v

l o g g i n g r e c o r d a n d p r i n t t o s t d o u t .

h a n d l e _ l o g _ r e c o r d p e e r . g e t _ h a n d l e , 1 ;

6 7

A u t o m a t i c a l l y c a l l e d w h e n a L o g g i n g _ A c c e p t o r o b j e c t

i s d y n a m i c a l l y l i n k e d .

L o g g i n g _ A c c e p t o r : : i n i t i n t a r g c , c h a r * a r g v

G e t _ O p t g e t _ o p t a r g c , a r g v , " p : " , 0 ;

I N E T _ A d d r a d d r ;

f o r i n t c ; c = g e t _ o p t ! = - 1 ;

s w i t c h c

c a s e ' p ' :

a d d r . s e t a t o i g e t o p t . o p t a r g ;

b r e a k ;

d e f a u l t :

b r e a k ;

I n i t i a l i z e e n d p o i n t a n d r e g i s t e r w i t h t h e R e a c t o r

o p e n a d d r ;

A u t o m a t i c a l l y c a l l e d w h e n o b j e c t i s d y n a m i c a l l y u n l i

L o g g i n g _ A c c e p t o r : : f i n i v o i d

h a n d l e _ c l o s e ;

6 8


18/48


19/48

D y n a m i c L i n k i n g a S e r v i c e

A p p l i c a t i o n - s p e c i c f a c t o r y f u n c t i o n u s e d t o

d y n a m i c a l l y c r e a t e a s e r v i c e

D y n a m i c a l l y l i n k e d f a c t o r y f u n c t i o n t h a t a l l o c a t e s

a n e w L o g g i n g _ A c c e p t o r o b j e c t d y n a m i c a l l y

e x t e r n " C " S e r v i c e _ O b j e c t * m a k e _ L o g g e r v o i d ;

S e r v i c e _ O b j e c t *

m a k e _ L o g g e r v o i d

r e t u r n n e w L o g g i n g _ A c c e p t o r ;

F r a m e w o r k a u t o m a t i c a l l y d e l e t e s m e m o r y .

T h e m a k e L o g g e r f u n c t i o n p r o v i d e s a h o o k

b e t w e e n a n a p p l i c a t i o n - s p e c i c s e r v i c e a n d

t h e a p p l i c a t i o n - i n d e p e n d e n t A C E m e c h a n i s m s

A C E h a n d l e s a l l m e m o r y a l l o c a t i o n a n d d e a l l o c a -

t i o n

7 3

S e r v i c e C o n g u r a t i o n

T h e l o g g i n g s e r v i c e i s c o n g u r e d a n d i n i -

t i a l i z e d b a s e d u p o n t h e c o n t e n t s o f a c o n -

g u r a t i o n s c r i p t c a l l e d s v c . c o n f :

c a t . s v c . c o n f

D y n a m i c a l l y c o n f i g u r e t h e l o g g i n g s e r v i c e

d y n a m i c L o g g e r S e r v i c e _ O b j e c t *

l o g g e r . d l l : m a k e _ L o g g e r " - p 2 0 1 0 "

G e n e r i c e v e n t - l o o p t o d y n a m i c a l l y c o n g u r e

s e r v i c e d a e m o n s

i n t

m a i n i n t a r g c , c h a r * a r g v

S e r v i c e _ C o n f i g d a e m o n ;

I n i t i a l i z e t h e d a e m o n a n d c o n f i g u r e s e r v i c e s

d a e m o n . o p e n a r g c , a r g v ;

R u n f o r e v e r , p e r f o r m i n g c o n f i g u r e d s e r v i c e s

d a e m o n . r u n _ r e a c t o r _ e v e n t _ l o o p ;

* N O T R E A C H E D *

7 4

S t a t e - c h a r t D i a g r a m f o r t h e

S e r v i c e C o n g u r a t o r P a t t e r n

INITIALIZEDINITIALIZED

CONFIGURE/CONFIGURE/Service_ConfigService_Config::::process_directivesprocess_directives()()

NETWORKNETWORK EVENT/EVENT/ReactorReactor::::dispatchdispatch()()

RECONFIGURE/RECONFIGURE/Service_ConfigService_Config::::process_directivesprocess_directives()()

SHUTDOWN/SHUTDOWN/Service_ConfigService_Config::::closeclose()() AWAITINGAWAITING

EVENTSEVENTS

CALLCALL HANDLER/HANDLER/Event_HandlerEvent_Handler::::handle_inputhandle_input()()

IDLEIDLE

PERFORMPERFORMCALLBACKCALLBACK

STARTSTART EVENTEVENT LOOP/LOOP/Service_ConfigService_Config::::run_event_looprun_event_loop()()

N o t e t h e s e p a r a t i o n o f c o n c e r n s b e t w e e n

o b j e c t s : : :

7 5

C o l l a b o r a t i o n o f P a t t e r n s i n t h e

S e r v e r L o g g i n g D a e m o n

: ServiceConfig

LoggerDaemon

REGISTER SERVICE

START EVENT LOOP

CONNECTION EVENT

DATA EVENT

REGISTER HANDLER

FOR CLIENT I/O

PROCESS LOGGING

RECORD

FOREACH EVENT DO

STORE IN REPOSITORY

CONFIGURE

FOREACH SVC ENTRY DO

A :LoggingAcceptor

: Reactor

handle_events()

handle_input()

register_handler(C)

handle_input()

write()

: ServiceRepository

process_directives()

insert()

C :LoggingHandler

EXTRACT HANDLE

EXTRACT HANDLE

get_handle()

INITIALIZE SERVICE

DAEMON SHUTDOWN

fini()

LINK SERVICElink_service()

remove()unlink_service()

ALLOCATE ANDACTIVATE OBJECT

CLIENT SHUTDOWN

handle_close()

UNLINK SERVICE

remove_handler(C)

C = new Logging_Handleraccept (C);C->open(A)

register_handler(A)

run_event_loop()

Service_Config()

get_handle()

init(argc, argv)

handle_close()

remove_handler(A)

7 6


20/48

A d v a n t a g e s o f O O L o g g i n g

S e r v e r

T h e O O a r c h i t e c t u r e i l l u s t r a t e d t h u s f a r d e -

c o u p l e s a p p l i c a t i o n - s p e c i c s e r v i c e f u n c t i o n -

a l i t y f r o m :

* T i m e w h e n a s e r v i c e i s c o n g u r e d i n t o a p r o c e s s

* T h e n u m b e r o f s e r v i c e s p e r - p r o c e s s

* T h e t y p e o f I P C m e c h a n i s m u s e d

* T h e t y p e o f e v e n t d e m u l t i p l e x i n g m e c h a n i s m u s e d

W e c a n u s e t h e t e c h n i q u e s d i s c u s s e d t h u s

f a r t o e x t e n d a p p l i c a t i o n s w i t h o u t :

1 M o d i f y i n g , r e c o m p i l i n g , a n d r e l i n k i n g e x i s t i n g c o d e

2 T e r m i n a t i n g a n d r e s t a r t i n g e x e c u t i n g d a e m o n s

T h e r e m a i n d e r o f t h e s l i d e s e x a m i n e a s e t o f

t e c h n i q u e s f o r d e c o u p l i n g f u n c t i o n a l i t y f r o m

c o n c u r r e n c y m e c h a n i s m s , a s w e l l

7 7

C o n c u r r e n t O O L o g g i n g S e r v e r

T h e s t r u c t u r e o f t h e s e r v e r l o g g i n g d a e m o n

c a n b e n e t f r o m c o n c u r r e n t e x e c u t i o n o n a

m u l t i - p r o c e s s o r p l a t f o r m

T h i s s e c t i o n e x a m i n e s A C E C + + c l a s s e s

a n d d e s i g n p a t t e r n s t h a t e x t e n d t h e l o g g i n g

s e r v e r t o i n c o r p o r a t e c o n c u r r e n c y

N o t e h o w m o s t e x t e n s i o n s r e q u i r e m i n i m a l c h a n g e s

t o t h e e x i s t i n g O O a r c h i t e c t u r e

T h i s e x a m p l e a l s o i l l u s t r a t e s a d d i t i o n a l A C E

c o m p o n e n t s i n v o l v i n g s y n c h r o n i z a t i o n a n d

m u l t i - t h r e a d i n g

7 8

C o n c u r r e n t O O L o g g i n g S e r v e r

A r c h i t e c t u r e

NETWORK

SERVERSERVER

LOGGING DAEMONLOGGING DAEMON

CLIENTCLIENT

SERVERSERVER

: logging: loggingacceptoracceptor

: logging: logginghandlerhandler

CONNECTION

REQUEST

LOGGING

RECORDS

CLIENTCLIENT

CLIENTCLIENT

: logging: logginghandlerhandler

LOGGING

RECORDS

T h r e a d - b a s e d i m p l e m e n t a t i o n

7 9

P s e u d o - c o d e f o r C o n c u r r e n t

S e r v e r

P s e u d o - c o d e f o r m u l t i - t h r e a d e d L o g g i n g H a n d

f a c t o r y s e r v e r l o g g i n g d a e m o n

v o i d h a n d l e r f a c t o r y v o i d

f

i n i t i a l i z e l i s t e n e r e n d p o i n t

f o r e a c h p e n d i n g c o n n e c t i o n r e q u e s t f

a c c e p t r e q u e s t

s p a w n a t h r e a d t o h a n d l e r e q u e s t

c a l l l o g g e r h a n d l e r a c t i v e o b j e c t

g

g

P s e u d o - c o d e f o r s e r v e r l o g g i n g d a e m o n a c -

t i v e o b j e c t

v o i d l o g g i n g h a n d l e r v o i d

f

f o r e a c h i n c o m i n g l o g g i n g r e c o r d s f r o m c l i e n t

c a l l h a n d l e l o g r e c o r d

e x i t t h r e a d

g

8 0


21/48

A p p l i c a t i o n - s p e c i c L o g g i n g C o d e

T h e O O i m p l e m e n t a t i o n l o c a l i z e s t h e a p p l i c a t i o n -

s p e c i c p a r t o f t h e l o g g i n g s e r v i c e i n a s i n -

g l e p o i n t , w h i l e l e v e r a g i n g o r e u s a b l e A C E

c o m p o n e n t s

H a n d l e a l l l o g g i n g r e c o r d s f r o m a p a r t i c u l a r c l i e n t

r u n i n e a c h s l a v e t h r e a d .

i n t

T h r _ L o g g i n g _ H a n d l e r : : s v c v o i d

P e r f o r m a " b l o c k i n g " r e c e i v e a n d p r o c e s s l o g g i n g

r e c o r d s u n t i l t h e c l i e n t c l o s e s d o w n t h e c o n n e c t i o n .

D a n g e r ! r a c e c o n d i t i o n s . . .

f o r ; ; + + r e q u e s t _ c o u n t

h a n d l e _ l o g _ r e c o r d g e t _ h a n d l e , 1 ;


r e t u r n 0 ;

8 1

C l a s s D i a g r a m f o r C o n c u r r e n t

O O L o g g i n g S e r v e r

ThrLoggingAcceptor

Thr_Logging_HandlerSOCK_Acceptor

ThrLoggingHandler

SOCK_StreamNULL_SYNCH

SvcHandler

Acceptor

SVC_HANDLERPEER_ACCEPTOR PEER_STREAM

SYNCH

CONNECTION

CONNECTION--

ORIENTED

ORIENTED

COMPONENTS

COMPONENTS

APPLICATION

APPLICATION--

SPECIFIC

SPECIFIC

COMPONENTS

COMPONENTS

ACE

ACE

FRAMEWORK

FRAMEWORK

COMPONENTS

COMPONENTS

PEER

ACCEPTORPEER

STREAM

StreamStream

ServiceService



IPC_SAPIPC_SAP

ConnectionConnection

ReactorReactor

INITS

1 n

8 2

A C E T a s k s

A n A C E T a s k b i n d s a s e p a r a t e t h r e a d o f

c o n t r o l t o g e t h e r w i t h a n o b j e c t ' s d a t a a n d

m e t h o d s

M u l t i p l e a c t i v e o b j e c t s m a y e x e c u t e i n p a r a l l e l i n

s e p a r a t e l i g h t w e i g h t o r h e a v y w e i g h t p r o c e s s e s

T a s k o b j e c t s c o m m u n i c a t e b y p a s s i n g t y p e d

m e s s a g e s t o o t h e r T a s k s

E a c h T a s k m a i n t a i n s a q u e u e o f p e n d i n g m e s s a g e s

t h a t i t p r o c e s s e s i n p r i o r i t y o r d e r

A C E T a s k a r e a l o w - l e v e l m e c h a n i s m t o s u p -

p o r t a c t i v e o b j e c t s "

8 3

T a s k I n h e r i t a n c e H i e r a r c h y

EventEventHandlerHandler

handle_input()handle_output()handle_exception()handle_signal()handle_timeout ()handle_close()get_handle()=0

A

SharedSharedObjectObject

init()=0fini ()=0info()=0

A

ServiceService

ServiceServiceObjectObject

A

APPL

ICATION-

SPEC

IFIC AP

PLIC

ATION-

INDEP

ENDEN

T

TaskTask

A

SYNCHSYNCH

MessageMessageQueueQueue

SYNCHSYNCH

SYNCHSYNCH

suspend()=0

resume()=0

open()=0close()=0put()=0svc()=0

S u p p o r t s d y n a m i c a l l y c o n g u r e d s e r v i c e s

8 4


22/48

T a s k C l a s s P u b l i c I n t e r f a c e

C + + i n t e r f a c e f o r m e s s a g e p r o c e s s i n g

* T a s k s c a n r e g i s t e r w i t h a R e a c t o r

* T h e y c a n b e d y n a m i c a l l y l i n k e d

* T h e y c a n q u e u e d a t a

* T h e y c a n r u n a s a c t i v e o b j e c t s "

e . g . ,

t e m p l a t e c l a s s S Y N C H

c l a s s T a s k : p u b l i c S e r v i c e _ O b j e c t

p u b l i c :

I n i t i a l i z a t i o n t e r m i n a t i o n r o u t i n e s .

v i r t u a l i n t o p e n v o i d * a r g s = 0 = 0 ;

v i r t u a l i n t c l o s e u _ l o n g f l a g s = 0 = 0 ;

T r a n s f e r m s g t o q u e u e f o r i m m e d i a t e p r o c e s s i n g .

v i r t u a l i n t p u t M e s s a g e _ B l o c k * , T i m e _ V a l u e * = 0 = 0 ;

R u n b y a d a e m o n t h r e a d f o r d e f e r r e d p r o c e s s i n g .

v i r t u a l i n t s v c v o i d = 0 ;

T u r n t h e t a s k i n t o a n a c t i v e o b j e c t .

i n t a c t i v a t e l o n g f l a g s ;

8 5

T a s k C l a s s P r o t e c t e d I n t e r f a c e

T h e f o l l o w i n g m e t h o d s a r e m o s t l y u s e d w i t h i n

p u t a n d s v c

A c c e s s o r s t o i n t e r n a l q u e u e .

M e s s a g e _ Q u e u e S Y N C H * m s g _ q u e u e v o i d ;

v o i d m s g _ q u e u e M e s s a g e _ Q u e u e S Y N C H * ;

A c c e s s o r s t o t h r e a d m a n a g e r .

T h r e a d _ M a n a g e r * t h r _ m g r v o i d ;

v o i d t h r _ m g r T h r e a d _ M a n a g e r * ;

I n s e r t m e s s a g e i n t o t h e m e s s a g e l i s t .

i n t p u t q M e s s a g e _ B l o c k * , T i m e _ V a l u e * t v = 0 ;

E x t r a c t t h e f i r s t m e s s a g e f r o m t h e l i s t b l o c k

i n t g e t q M e s s a g e _ B l o c k * & m b , T i m e _ V a l u e * t v = 0 ;

H o o k i n t o t h e u n d e r l y i n g t h r e a d l i b r a r y .

s t a t i c v o i d * s v c _ r u n T a s k S Y N C H * ;

8 6


Q : W h a t i s t h e s v c r u n f u n c t i o n a n d w h y

i s i t a s t a t i c m e t h o d ?

A : O S t h r e a d s p a w n A P I s r e q u i r e a C - s t y l e

f u n c t i o n a s t h e e n t r y p o i n t i n t o a t h r e a d

T h e S t r e a m c l a s s c a t e g o r y e n c a p s u l a t e s t h e

s v c r u n f u n c t i o n w i t h i n t h e T a s k : : a c t i v a t e

m e t h o d :

t e m p l a t e c l a s s S Y N C H i n t

T a s k S Y N C H : : a c t i v a t e l o n g f l a g s , i n t n _ t h r e a d s

i f t h r _ m g r = = N U L L

t h r _ m g r S e r v i c e _ C o n f i g : : t h r _ m g r ;

t h r _ m g r - s p a w n _ n

n _ t h r e a d s , & T a s k S Y N C H : : s v c _ r u n ,

v o i d * t h i s , f l a g s ;

8 7

O O D e s i g n I n t e r l u d e c o n t ' d

T a s k : : s v c r u n i s s t a t i c m e t h o d u s e d a s t h e

e n t r y p o i n t t o e x e c u t e a n i n s t a n c e o f a s e r -

v i c e c o n c u r r e n t l y i n i t s o w n t h r e a d

t e m p l a t e c l a s s S Y N C H v o i d *

T a s k S Y N C H : : s v c _ r u n T a s k S Y N C H * t

T h r e a d _ C o n t r o l t c t - t h r _ m g r ; R e c o r d t h r e a d

R u n s e r v i c e h a n d l e r a n d r e c o r d r e t u r n v a l u e .

v o i d * s t a t u s = v o i d * t - s v c ;

t c . s t a t u s s t a t u s ;

t - c l o s e u _ l o n g s t a t u s ;

S t a t u s b e c o m e s ` r e t u r n ' v a l u e o f t h r e a d . . .

r e t u r n s t a t u s ;

T h r e a d r e m o v e d f r o m t h r _ m g r

a u t o m a t i c a l l y o n r e t u r n . . .

8 8


23/48


Q : H o w c a n g r o u p s o f c o l l a b o r a t i n g t h r e a d s

b e m a n a g e d a t o m i c a l l y ? "

A : D e v e l o p a t h r e a d m a n a g e r " c l a s s

T h r e a d M a n a g e r i s a c o l l e c t i o n c l a s s

. I t p r o v i d e s m e c h a n i s m s f o r s u s p e n d i n g a n d r e -

s u m i n g g r o u p s o f t h r e a d s a t o m i c a l l y

. I t i m p l e m e n t s b a r r i e r s y n c h r o n i z a t i o n o n t h r e a d

e x i t s

T h r e a d M a n a g e r a l s o s h i e l d s a p p l i c a t i o n s f r o m i n -

c o m p a b i t i l i t i e s b e t w e e n d i e r e n t O S t h r e a d l i b r a r i e s

. I t i s i n t e g r a t e d i n t o A C E v i a t h e T a s k : : a c t i v a t e

m e t h o d

8 9

T h e A c t i v e O b j e c t P a t t e r n

I n t e n t

D e c o u p l e m e t h o d e x e c u t i o n f r o m m e t h o d i n v o -

c a t i o n a n d s i m p l i e s s y n c h r o n i z e d a c c e s s t o s h a r e d

r e s o u r c e s b y c o n c u r r e n t t h r e a d s "


f o r c o n c u r r e n t c o m m u n i c a t i o n s o f t w a r e :

H o w t o a l l o w b l o c k i n g r e a d a n d w r i t e o p e r a t i o n s

o n o n e e n d p o i n t t h a t d o n o t d e t r a c t f r o m t h e q u a l -

i t y o f s e r v i c e o f o t h e r e n d p o i n t s

H o w t o s e r i a l i z e c o n c u r r e n t a c c e s s t o s h a r e d o b j e c t

s t a t e

H o w t o s i m p l i f y c o m p o s i t i o n o f i n d e p e n d e n t s e r -

v i c e s

9 0

S t r u c t u r e o f t h e A c t i v e O b j e c t

P a t t e r n

ClientClientInterfaceInterface

ResultHandle m1()ResultHandle m2()ResultHandle m3()

ActivationActivationQueueQueueinsert()

remove()

SchedulerScheduler

dispatch()m1'()m2'()m3'()

ResourceResourceRepresentationRepresentation

MethodMethodObjectsObjects

loop {m = actQueue.remove()dispatch (m)

}

INVISIBLEINVISIBLE

TOTO

CLIENTSCLIENTS

VISIBLEVISIBLE

TOTO

CLIENTSCLIENTS

nn

11

1111

11

11

T h e S c h e d u l e r i s a m e t a - o b j e c t " t h a t d e -

t e r m i n e s t h e s e q u e n c e t h a t M e t h o d O b j e c t s

a r e e x e c u t e d

9 1

C o l l a b o r a t i o n i n t h e A c t i v e

O b j e c t P a t t e r n

INVOKEINVOKE

INSERT ININSERT INPRIORITY QUEUEPRIORITY QUEUE

cons(m1')

remove(m1')DEQUEUE NEXTDEQUEUE NEXTMETHOD OBJECTMETHOD OBJECT

RETURN RESULTRETURN RESULT

EXECUTEEXECUTE

clientclient: Client: Client

InterfaceInterface: Activation: Activation

QueueQueue

insert(m1')

dispatch(m1')

METHODOBJECT

METHODOBJECT

CONSTRUCTION

CONSTRUCTION

SCHEDULING/

EXECUTION

COMPLETION

m1()

: Represent-: Represent-ationation

: Scheduler: Scheduler

CREATE METHODOBJECT

reply_to_future()

future()RETURN RESULTRETURN RESULTHANDLEHANDLE

9 2


24/48

A C E T a s k S u p p o r t f o r A c t i v e

O b j e c t s

ACTIVEACTIVE

::MessageMessageQueueQueue

tt22 : Task: Task

2: enqueue (msg)2: enqueue (msg)

1: put (msg)1: put (msg)

ACTIVEACTIVE


tt11 : Task: Task

ACTIVEACTIVE


tt33 : Task: Task

6: put (msg)6: put (msg)

3: svc ()3: svc ()4: dequeue (msg)4: dequeue (msg)5: do_work(msg)5: do_work(msg)

9 3

C o l l a b o r a t i o n i n A C E A c t i v e

O b j e c t s

PRODUCER TASK

ENQUEUE MSG

put(msg)

dequeue_head(msg)

RUN SVC()ASYNCHRONOUSLY

PASS MSG

DEQUEUE MSG

t1 :

Task

t2 :

Task

t3 :

Task

t2msg_q :

Message_Queue

enqueue_tail(msg)

put(msg)

work()CONSUMER TASK

PRODU

CER

PHA

SE

QUEUEING

PHASE

CONSUMER

PHASE

PASS MSG

work()

svc()

9 4

T h r L o g g i n g A c c e p t o r a n d

T h r L o g g i n g H a n d l e r

T e m p l a t e c l a s s e s t h a t c r e a t e , c o n n e c t , a n d

a c t i v a t e a n e w t h r e a d t o h a n d l e e a c h c l i e n t

c l a s s T h r _ L o g g i n g _ H a n d l e r

: p u b l i c S v c _ H a n d l e r S O C K _ S t r e a m , N U L L _ S Y N C H

p u b l i c :

O v e r r i d e d e f i n i t i o n i n t h e S v c _ H a n d l e r c l a s s

s p a w n s a n e w t h r e a d ! .

v i r t u a l i n t o p e n v o i d * ;

P r o c e s s r e m o t e l o g g i n g r e c o r d s .

v i r t u a l i n t s v c v o i d ;

;

c l a s s T h r _ L o g g i n g _ A c c e p t o r :

p u b l i c A c c e p t o r T h r _ L o g g i n g _ H a n d l e r ,

S O C K _ A c c e p t o r

S a m e a s L o g g i n g _ A c c e p t o r . . .

;

9 5

O v e r r i d e d e f i n i t i o n i n t h e S v c _ H a n d l e r c l a s s

s p a w n s a n e w t h r e a d i n t h i s c a s e ! .

i n t

T h r _ L o g g i n g _ H a n d l e r : : o p e n v o i d *

I N E T _ A d d r c l i e n t _ a d d r ;

p e e r . g e t _ l o c a l _ a d d r c l i e n t _ a d d r ;

s t r n c p y h o s t _ n a m e _ , c l i e n t _ a d d r . g e t _ h o s t _ n a m e ,

M A X H O S T N A M E L E N + 1 ;

S p a w n a n e w t h r e a d t o h a n d l e

l o g g i n g r e c o r d s w i t h t h e c l i e n t .

a c t i v a t e T H R _ B O U N D | T H R _ D E T A C H E D ;

9 6


25/48

P r o c e s s r e m o t e l o g g i n g r e c o r d s .

i n t

T h r _ L o g g i n g _ H a n d l e r : : s v c v o i d

L o o p u n t i l t h e c l i e n t t e r m i n a t e s t h e c o n n e c t i o n .

f o r ; ; + + r e q u e s t _ c o u n t

C a l l e x i s t i n g f u n c t i o n t o r e c v l o g g i n g

r e c o r d a n d p r i n t t o s t d o u t .

h a n d l e _ l o g _ r e c o r d p e e r . g e t _ h a n d l e , 1 ;


r e t u r n 0 ;

D y n a m i c a l l y l i n k e d f a c t o r y f u n c t i o n t h a t

a l l o c a t e s a n e w t h r e a d e d l o g g i n g A c c e p t o r o b j e c t .

e x t e r n " C " S e r v i c e _ O b j e c t * m a k e _ L o g g e r v o i d ;

S e r v i c e _ O b j e c t *

m a k e _ L o g g e r v o i d

r e t u r n n e w T h r _ L o g g i n g _ A c c e p t o r ;

9 7

D y n a m i c a l l y R e c o n g u r i n g t h e


T h e c o n c u r r e n t l o g g i n g s e r v i c e i s c o n g u r e d

a n d i n i t i a l i z e d b y m a k i n g a s m a l l c h a n g e t o

t h e s v c . c o n f l e :

c a t . s v c . c o n f

D y n a m i c a l l y c o n f i g u r e t h e l o g g i n g s e r v i c e


s v c s l o g g e r . d l l : m a k e _ L o g g e r " - p 2 0 1 0 "

r e m o v e L o g g e r


t h r _ l o g g e r . d l l : m a k e _ L o g g e r " - p 2 0 1 0 "

S e n d i n g a S I G H U P s i g n a l r e c o n g u r e s t h e

s e r v e r l o g g e r d a e m o n p r o c e s s

T h e o r i g i n a l s e q u e n t i a l v e r s i o n o f t h e L o g g e r s e r -

v i c e i s d y n a m i c a l l y u n l i n k e d a n d r e p l a c e d w i t h t h e

n e w c o n c u r r e n t v e r s i o n

9 8

C a v e a t s

T h e c o n c u r r e n t s e r v e r l o g g i n g d a e m o n h a s

s e v e r a l p r o b l e m s

1 . O u t p u t i n t h e h a n d l e l o g r e c o r d f u n c t i o n i s n o t

s e r i a l i z e d

2 . T h e a u t o - i n c r e m e n t o f g l o b a l v a r i a b l e r e q u e s t c o u n t

i s a l s o n o t s e r i a l i z e d

L a c k o f s e r i a l i z a t i o n l e a d s t o e r r o r s o n m a n y

s h a r e d m e m o r y m u l t i - p r o c e s s o r p l a t f o r m s : : :

N o t e t h a t t h i s p r o b l e m i s i n d i c a t i v e o f a l a r g e c l a s s

o f e r r o r s i n c o n c u r r e n t p r o g r a m s

T h e f o l l o w i n g s l i d e s c o m p a r e a n d c o n t r a s t a

s e r i e s o f t e c h n i q u e s t h a t a d d r e s s t h i s p r o b -

l e m

9 9

E x p l i c i t S y n c h r o n i z a t i o n

M e c h a n i s m s

O n e a p p r o a c h f o r s e r i a l i z a t i o n u s e s O S m u -

t u a l e x c l u s i o n m e c h a n i s m s e x p l i c i t l y , e . g . ,

a t f i l e s c o p e

m u t e x _ t l o c k ; S u n O S 5 . x s y n c h r o n i z a t i o n m e c h a n i s m

. . .

h a n d l e _ l o g _ r e c o r d H A N D L E i n _ h , H A N D L E o u t _ h

i n m e t h o d s c o p e . . .

m u t e x _ l o c k & l o c k ;


m u t e x _ u n l o c k & l o c k ;

. . .

H o w e v e r , a d d i n g t h e s e m u t e x c a l l s e x p l i c i t l y

i s i n e l e g a n t , t e d i o u s , e r r o r - p r o n e , a n d n o n -

p o r t a b l e

1 0 0


26/48

C + + W r a p p e r s f o r

S y n c h r o n i z a t i o n

T o a d d r e s s p o r t a b i l i t y p r o b l e m s , d e n e a

C + + w r a p p e r :

c l a s s M u t e x

p u b l i c :

M u t e x v o i d

m u t e x _ i n i t & l o c k _ , U S Y N C H _ T H R E A D , 0 ;

~ M u t e x v o i d m u t e x _ d e s t r o y & l o c k _ ;

i n t a c q u i r e v o i d r e t u r n m u t e x _ l o c k & l o c k _ ;

i n t t r y a c q u i r e v o i d r e t u r n m u t e x _ t r y l o c k & l o c k ;

i n t r e l e a s e v o i d r e t u r n m u t e x _ u n l o c k & l o c k _ ;

p r i v a t e :

m u t e x _ t l o c k _ ; S u n O S 5 . x s e r i a l i z a t i o n m e c h a n i s m .

v o i d o p e r a t o r = c o n s t M u t e x & ;

v o i d M u t e x c o n s t M u t e x & ;

;

N o t e , t h i s m u t u a l e x c l u s i o n c l a s s i n t e r f a c e

i s p o r t a b l e t o o t h e r O S p l a t f o r m s

1 0 1

P o r t i n g M u t e x t o W i n d o w s N T

W I N 3 2 v e r s i o n o f M u t e x

c l a s s M u t e x

p u b l i c :

M u t e x v o i d

l o c k _ = C r e a t e M u t e x 0 , F A L S E , 0 ;

~ M u t e x v o i d

C l o s e H a n d l e l o c k _ ;

i n t a c q u i r e v o i d

r e t u r n W a i t F o r S i n g l e O b j e c t l o c k _ , I N F I N I T E ;

i n t t r y a c q u i r e v o i d

r e t u r n W a i t F o r S i n g l e O b j e c t l o c k _ , 0 ;

i n t r e l e a s e v o i d

r e t u r n R e l e a s e M u t e x l o c k _ ;

p r i v a t e :

H A N D L E l o c k _ ; W i n 3 2 l o c k i n g m e c h a n i s m .

. . .

1 0 2

U s i n g t h e C + + M u t e x W r a p p e r

U s i n g C + + w r a p p e r s i m p r o v e s p o r t a b i l i t y

a n d e l e g a n c e

a t f i l e s c o p e

M u t e x l o c k ; I m p l i c i t l y " u n l o c k e d " .

. . .

h a n d l e _ l o g _ r e c o r d H A N D L E i n _ h , H A N D L E o u t _ h

i n m e t h o d s c o p e . . .

l o c k . a c q u i r e ;


l o c k . r e l e a s e ;

. . .

H o w e v e r , t h i s d o e s n ' t r e a l l y s o l v e t h e t e -

d i u m o r e r r o r - p r o n e n e s s p r o b l e m s

1 0 3

A u t o m a t e d M u t e x A c q u i s i t i o n a n d

R e l e a s e

T o e n s u r e m u t e x e s a r e l o c k e d a n d u n l o c k e d ,

w e ' l l d e n e a t e m p l a t e c l a s s t h a t a c q u i r e s

a n d r e l e a s e s a m u t e x a u t o m a t i c a l l y

t e m p l a t e c l a s s L O C K

c l a s s G u a r d

p u b l i c :

G u a r d L O C K & m : l o c k m l o c k _ . a c q u i r e ;

~ G u a r d v o i d l o c k _ . r e l e a s e ;

p r i v a t e :

L O C K & l o c k _ ;

G u a r d u s e s t h e C + + i d i o m w h e r e b y a c o n -

s t r u c t o r a c q u i r e s a r e s o u r c e a n d t h e d e s t r u c -

t o r r e l e a s e s t h e r e s o u r c e

1 0 4


27/48


Q : W h y i s G u a r d p a r a m e t e r i z e d b y t h e t y p e

o f L O C K ?

A : s i n c e t h e r e a r e m a n y d i e r e n t a v o r s o f

l o c k i n g t h a t b e n e t f r o m t h e G u a r d f u n c -

t i o n a l i t y , e . g . ,

* N o n - r e c u r s i v e v s r e c u r s i v e m u t e x e s

* I n t r a - p r o c e s s v s i n t e r - p r o c e s s m u t e x e s

* R e a d e r s w r i t e r m u t e x e s

* S o l a r i s a n d S y s t e m V s e m a p h o r e s

* F i l e l o c k s

* N u l l m u t e x

I n A C E , a l l s y n c h r o n i z a t i o n w r a p p e r s u s e t o

A d a p t e r p a t t e r n t o p r o v i d e i d e n t i c a l i n t e r -

f a c e s w h e n e v e r p o s s i b l e t o f a c i l i t a t e p a r a m -

e t e r i z a t i o n

1

Douglas C. Schmidt - Concurrent object-oriented network programming in C++

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