CouchDB for the web - fosdem 2010

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Benoît Chesneau

07/02/2010 FOSDEM 2010

CouchDB for the Web

Monday, February 8, 2010



[email protected], Couchbeam &Couchdbkit maintainer

Web craftmanminimal web & opensource

benoît chesneau


mailto:[email protected]









Document

OrientedMonday, February 8, 2010



DOCUMENT JSON

{

"_id": "foo", "_rev": "1-....",

"url": "http://apache.couchdb.org",

"vote": 1

}




API HTTP RESTGET / HTTP/1.1\r\nHost: 127.0.0.1:5984\r\n\r\n"

{"couchdb":"Welcome","version":"0.11.0b6ba76f83-git"}




API HTTP REST

• Web paradigm

GET / HTTP/1.1\r\nHost: 127.0.0.1:5984\r\n\r\n"





API HTTP REST

• Web paradigm

• Supported everywhere






API HTTP REST

• Web paradigm

• Supported everywhere

•

Lot of available tools/libs






MAP/REDUCE

http://wiki.apache.org/couchdb/Using_Views






MAP/REDUCE

• Map/Reduce to extract informations from documents







MAP/REDUCE


•

Javascript used to map documents







MAP/REDUCE


•


• Design Doc







MAP/REDUCE


•


• Design Doc

• /db/_design/ddocname/_view







VIEWS MAP/REDUCE[{ "url": "http://apache.couchdb.org",

"vote": 1

},{

"url": "http://apache.couchdb.org",

"vote": 1},{

"url": "http://mysql.com",

"vote": 0

},{

"url": "http://mysql.com",

"vote": -1}]


http://mysql.com/

http://mysql.com/



MAP.JSfunction(doc) {

if (doc.url && doc.vote)

emit(doc.url, doc.vote);

}

{

"total_rows":3, "offset":0,

"rows":[

{

"id":"15c92051cc81d564db4337a05087bc8d",

"key":"http://apache.couchdb.org",

"value":1

},

{

"id":"fa9658810d25cac893748e4ff15e7253",


"value":1

},

{

"id":"1fa0c68d8455196507b8b01645e65186",

"key":"http://mysql.com",

"value":-1

}]}

json

result


http://mysql.com/

http://mysql.com/

http://apache.couchdb.org/






REDUCE.JS

function(keys, values, rereduce) {

return sum(values);

}

{

"rows":[

{

"key":"http://mysql.com",

"value":-1

},

{


"value":2

}

]}

json

result




http://mysql.com/

http://mysql.com/



http://wiki.apache.org/couchdb/Basics






Futon




OTHER STUFF




OTHER STUFF

• Listen to changes via HTTP: /db/_changes




OTHER STUFF


• long-polling or continuous feed




OTHER STUFF



• Replicate via HTTP: /_replicate




OTHER STUFF




• continuous replication is possible




OTHER STUFF




• continuous replication is possible

• use other querying possibilities




standalone CouchDB applications




COUCHAPPS

• P2P web

• Local Data

• Offline mode

• Decentralize exchanges

• Script : couchapp




AIMPL.ORG

• full CouchApp....,

• ... behind Django

• Proxy auth handler

•

supported load without problem during the launch




WHAT YOU CAN DO

• show

• list

• update

• validation

• rewriting




SHOW

• simple javascript function

• /db/_design/ddocname/_show/funname

• /db/_design/ddocname/_show/funname/docid

• render a doc

• could be cached




HELLO.JS

function(doc, req) {

if (doc) {

return "Hello World";

} else {

if(req.id) {

return "New World";

} else {

return "Empty World";

}

}

}




REQUEST OBJECT

{

"info": {},

"id":null,

"method":"GET",

"path":[], "query":{},

"headers":{},

"body":"undefined",

"peer":"127.0.0.1",

"form":{},

"cookie":{}, "userCtx":{}

}




USER OBJECT

"userCtx":{

"db":"somedb",

"name":null,

"roles":["_admin"]}

•

Get username and roles




MORE

• `provides` function to render in the formatrequested by the user

• return a response obj : {

headers: {},

code: 200,

stop: true,

json: {},

body: "",base64, ""

}




LIST• simple javascript function

• /db/_design/ddocname/_list/funname/viewname

• Render a view

• no impact in ram. Sent line by line

• could be cached




LIST.JS

function(head, req) {

send("head");

var row;

while (row = getRow()) { log("row: " + toJSON(row));

send(row.key);

};

return "tail";

}




UPDATE

• Like a show but for PUT, POST & DELETE

• /db/_design/ddocname/_update/funname/docid

• Allows you to update a document




HELLO.JS

function(doc, req) {

if (!doc) {

if (req.id) {

return [

{ _id : req.id,

reqs : [req] },

"<p>New World</p>"];

};};

doc.world = "hello";

doc.reqs && doc.reqs.push(req);

doc.edited_by = req.userCtx;

return [doc, "<p>hello doc</p>"];

}




VALIDATE

• simple javascript function

• on update

• Allows you to throw https errors (forbidden,unauthorized ...)




UPDATE_VALIDATE.JSfunction (newDoc, oldDoc, userCtx) {

function forbidden(message) {

throw({forbidden : message});

};

function unauthorized(message) {

throw({unauthorized : message});

};

if (userCtx.roles.indexOf('_admin') == -1) {

// admin can edit anything, only check when not admin...

if (newDoc._deleted)

forbidden("You may not delete a doc.");

}

};




REWRITE

• Don’t want long & “ugly” urls starting with “_”

• Easy proxying of a CouchApp

• `rewrites` member in the design document

• simple pattern matching

• relative to design doc




SOME EXAMPLES

• Rewrite /* to /_show/someshow/*

• Rewrite /db -> ../../db :

{

"from": "*",

"to": "_show/page/*",

"method": "GET"}

{

"from": "/_db/*",

"to": "../../*"

}




COUCHAPP

• couchapp generate myapp

• couchapp push mydb

• couchapp clone http://benoitc.im/b/_design/blog

•

http://github.com/couchapp/couchapp


http://benoitc.im/b/_design/blog







THE FUTURE

• CouchApps on the desktop

• The browser is the OS

• On your phone


Stuart Langridge - Canonical



! !

g g




GO FURTHER

• COUCHDB : http://couchdb.apache.org

• book : http://books.couchdb.org/relax

• couchapp wiki : http://wiki.github.com/couchapp/couchapp

• irc #couchdb-fr sur freenodes

• Enki mul timedia : http://www.e-engura.com


http://www.e-engura.com/

http://wiki.github.com/couchapp/couchapp

http://books.couchdb.org/relax







http://couchdb.apache.org/

http://couchdb.apache.org/



Questions




Cette création est mise à disposition selon le ContratPaternité 2.0 France disponible en ligne http://

creativecommons.org/licenses/by/2.0/fr/ ou par courrier postal à Creative Commons, 171 Second Street, Suite

300, San Francisco, California 94105, USA.

http://creativecommons.org/licenses/by/2.0/fr/




CouchDB for the web - fosdem 2010

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