Java EE 8: What Servlet 4 and HTTP2 Mean

Alex Theedom @readlearncode

Java EE 8: What Servlet 4.0 and

HTTP/2 mean?

@readlearncode readlearncode.com

Who am I?

Alex Theedom

Author Trainer

Blogger

Speaker

What’s on?


• Why Do We Need HTTP/2• Work-Arounds to HTTP1.1• HTTP Sockets• Topline HTTP/2 Features• Servlet 4.0 Features• Server Support• Status Update• Q&A

What’s on?

Why Do We Need HTTP/2?


• Increase perceived performance of web• HTTP protocol not suitable• Since April 2011 average web page size • increased by over 300%

• The problem with HTTP/1.1

300%Source: HTTPArchive.com

Why Do We Need HTTP/2? The Goal of HTTP/2


• Requests resources in parallel HTTP 1.0

• One request per TCP connection

• HTTP1.1 Pipelining: multiple requests

• Responds in sequence

• Delay causes head-of-line blocking

How a browser loads a webpage?

open

close

client serverno pipelining

index.html

style_1.css

logo.jpg

open

close

client serverpipelining

time

index.html

style_1.csslogo.jpg

Why Do We Need HTTP/2?

Work-Arounds


• Multiple connections

• Acceptable but has issues

• TCP sockets expensive

• Browser max connections

Work-Arounds to HTTP1.1Solution to Head-Of-Line Blocking

open

close

client server

connection 1style_1.css

open

close

client server

connection 2javaScript_1.js

open

close

client server

connection 3image_1.png


Work-Arounds to HTTP1.1CSS/JavaScript File Concatenation

background.cssheader.cssmenu.cssstyle.css


Work-Arounds to HTTP1.1CSS and JavaScript Inlining

…


• Embed image in web page

• Base 64 encoded

• Time spent decoding

• Caching difficult

Work-Arounds to HTTP1.1Inlined Assets


• One image file consists of many smaller images

Work-Arounds to HTTP1.1Image Sprite Sheet

Image sprites from Amazon, Google and Facebook.


Work-Arounds to HTTP1.1Domain Sharding

web pagey.example.com

x.example.com

server 2

server 1

logo.jpg

icon.jpg

header.css

menu.css

HTTP Sockets


• Not much specified

• Throw away resources

• No maximum open sockets

HTTP SocketsWhat HTTP1.1 Says About Sockets


• Much is specified

• Scares resources

• Ideally only open one socket

HTTP SocketsWhat HTTP/2 Says About Sockets


HTTP SocketsAll connections now operate as one connection

open

close

client server

open

close

client server

open

close

client server

open

close

client server open

close

client serveropen

close

client server

Topline HTTP/2 Features


• HTTP/2 is comprised of two specifications

• Hypertext Transfer Protocol version 2 - RFC7540

• HPACK - Header Compression for HTTP/2 - RFC7541

• Binary Protocol Based on Frames

Topline HTTP/2 FeaturesWhat’s new


• Request/Response Multiplexing

• Binary Framing

• Header Compression

• Stream Prioritization

• Server Push

Topline HTTP/2 FeaturesFeatures


• Most important feature• Request and response is multiplexed • Fully bi-directional communication

• Concepts• Connection - A TCP socket• Stream – A channel of communication• Message – A request/response and control message• Frame –The smallest unit within a communication

• Resolves head-of-line blocking• Communication broken down into frames• Frames facilitate interweaving the logical stream

Topline HTTP/2 FeaturesRequest/Response Multiplexing


• Hierarchical structure of logical communication blocks


connectionstream

frame frame frameframe frame frame

message

stream


messageframe frame frameframe frame frame

message

stream




message


• Request/response multiplexing

• Interweave the logical stream over a single TCP

• Stream 3 send header then body and server responds with stream 2 before it receives completed stream 3


STREAM 1HEADERS

STREAM 3DATA

STREAM 1DATA

STREAM 2HEADERS

STREAM 3HEADERS

STREAM 2DATA

browser

server


• Decomposition of the frame

• Type fields can be• HEADERS corresponds to the HTTP headers• DATA corresponds to the HTTP request body• PUSH_PROMISE server notifies of push intent • RST_STREAM notifying error, client rejects push• PRIORITY specifies stream priority• SETTING, PING, GOAWAY, WINDOW_UPDATE, CONTINUATION

Topline HTTP/2 FeaturesBinary Framing

LENGTH (24)TYPE (8) FLAGS (8)

R STREAM IDENTIFIER (31)FRAME PAYLOADS (0.. n)


• Mapping the HTTP Request to Frames

Topline HTTP/2 FeaturesHeader Compression

HTTP request Header FrameGET /index.html HTTP/1.1Host: example.comAccept: text/html

HEADERS - END_STREAM + END_HEADERS :method: GET :scheme: http :path: /index.html :authority: example.com accept: text/html


• Mapping the HTTP Response to Frames

Topline HTTP/2 FeaturesHeader Compression

HTTP response FramesHTTP/1.1 200 OKContent-Length: 11Content-Type: text/htmlMay The Force Be With You

HEADERS - END_STREAM + END_HEADERS :status: 200 content-length: 11 content-type: text/htmlDATA + END_STREAMMay The Force Be With You


Topline HTTP/2 FeaturesHPACK header compression

HTTP Request 1:method GET:scheme https:host example.com:path /index.html:authority example.org:accept text/htmluser-agent Mozilla/5.0

HTTP Request 2:method GET:scheme https:host example.com:path /info.html:authority example.org:accept text/htmluser-agent Mozilla/5.0

HEADERS frame (Stream 1):method GET:scheme https:host example.com:path /index.html:authority example.org:accept text/htmluser-agent Mozilla/5.0

HEADERS frame (Stream 3):path /info.html


• Attach priority information to streams

• Priority located in the header frame or the priority frame

• Only a suggestion to the server

Topline HTTP/2 FeaturesStream Prioritization

B D C

A

2 14 10

B C

A

4 8


• Eliminate the need for resource inlining

• The sever can proactively send resources to the client

• Client can reject PUSH_PROMISE by responding RST_STREAM

Topline HTTP/2 FeaturesServer Push

Servlet 4.0 Features


Servlet 4.0 FeaturesServer Push

• Servlet 4.0 appropriate abstraction

• Most visible improvements in servlets

• Best place to know what resources a request needs

• Not a replacement for websockets


Servlet 4.0 FeaturesPushBuilder


• Browser requests index.html• Server discovers need for css and js• Get PushBuilder from HTTP request• Set path to css and invoke push• Set path to js and invoke push• Then responds with index.html• The PushBuilder can be reused

Servlet 4.0 FeaturesTypical Journey


Servlet 4.0 FeaturesPushBuilder Dive Deeper

• Constructed with request method set to GET by default• Conditional, range, expectation, authorization and request

headers are removed• Cookies are only added if the maxAge has not expired• Only required setting is the URI path to the resource• Must be set before every call to push()


• Simple usage

Servlet 4.0 FeaturesServlets and ServerPush


Servlet 4.0 FeaturesFilters and Server Push


• SETTINGS_ENABLE_PUSH clients disable server push

• RST_STREAM rejects cached resources

• Servlet containers must honour request to not receive

Servlet 4.0 FeaturesDisable/Reject Server Push


• Perfectly backward compatible

• Rework to take advantage of Server Push

• Consider removing frontend HTTP 1.1 work-arounds

Servlet 4.0 FeaturesBackward Compatible

Server Support


• GlassFish 5.0 Reference implementation

• Payara 5.0Has a branch for Java EE 8 development

• Jetty Stable-9 (9.4.2.v20170220)org.eclipse.jetty.servlets.PushCacheFilter/

PushBuilder

Server ImplementationServlet Support


• WildFly 10 (Undertow)

Initial PushBuilder support implemented in Undertow master

• Tomcat 9.0.0.M17Initial PushBuilder Supports Servlets 4.0's

PushBuilder in the javax.servlets.http package

• Netty 4.1HTTP/2 implementation takes full advantage of

headline features

Server ImplementationServlet Support

Status Update


• Currently in the early draft review

• Public review draft in Quarter 3 2017

• Issue Tracker: java.net/jira/browse/SERVLET_SPEC

• JCP Specification: jcp.org/en/jsr/detail?id=369

• Twitter: @servlet_spec

Status UpdateJSP 369: Servlet Specification


Q & A

Alex Theedom @readlearncode

Java EE 8: What Servlet 4.0 and

HTTP/2 mean?

Java EE 8: What Servlet 4 and HTTP2 Mean

Technology

Transcript of Java EE 8: What Servlet 4 and HTTP2 Mean