Developing CouchApps

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CouchDB application development Developing and deploying CouchApps Jakob Westhoff <jakob@php.net> PHPBarcamp.at May 1, 2010 http://westhoffswelt.de jakob@westhoffswelt.de slide: 1 / 35

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About Me Jakob Westhoff PHP developer for more several years Computer science student at the TU Dortmund Co-Founder of the PHP Usergroup Dortmund Active in different Open Source projects http://westhoffswelt.de jakob@westhoffswelt.de slide: 2 / 35

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Asking the audience Who is actively using CouchDB? Who played with CouchDB just for fun? Who has heard of CouchDB, but never used it? Who has already developed a CouchApp? Who does not know at all, what a CouchApp is? http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 3 / 35

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Goals of thissession Understand what a CouchApp actually is Learn what features of CouchDB can be used to realize a CouchApp Get a glimpse of third party tools and frameworks for CouchApp development http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 4 / 35

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What is CouchDB? Document based NoSQL database Written in Erlang MapReduce based indexing Javascript uses as embedded language RESTful JSON API Build in incremental bi-directional replication http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 5 / 35

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CouchDB document example Documents are stored as JSON { ” i d ” : ” r e c i p e −some−r e c i p e ” , ” r e v ” : ”1−859 e 8 f 9 a 0 6 b 8 6 4 e b c a 3 a 9 2 9 7 5 0 c 1 7 5 3 7 ” , ” date ” : 1270067388 , ” t i t l e ” : ”Some r e c i p e ” , ”ingredients”: [ ” Sugar ” , ” Flour ” ], ” i n s t r u c t i o n s ” : ”Some i n s t r u c t i o n s ” , ” u s e r ” : ” u s e r −f o o b a r ” , } http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 6 / 35

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CouchDB document example Documents are stored as JSON { ” i d ” : ” r e c i p e −some−r e c i p e ” , ” r e v ” : ”1−859 e 8 f 9 a 0 6 b 8 6 4 e b c a 3 a 9 2 9 7 5 0 c 1 7 5 3 7 ” , ” date ” : 1270067388 , ” t i t l e ” : ”Some r e c i p e ” , ”ingredients”: [ ” Sugar ” , ” Flour ” ], ” i n s t r u c t i o n s ” : ”Some i n s t r u c t i o n s ” , ” u s e r ” : ” u s e r −f o o b a r ” , } http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 6 / 35

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What is aCouchApp? Application build on top of CouchDB which fits the following criteria: Using CouchDB as data store Stored inside the CouchDB Served using the CouchDB Http-Server Most CouchApps are Mostly written in Javascript Using some sort of Javascript library CouchDB replication can be used to deploy applications http://westhoffswelt.de jakob@westhoffswelt.de slide: 7 / 35

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Excursion: Futon Futon is CouchDBs adminstration interface Automatically available on every CouchDB http://localhost:5984/ utils/ http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 8 / 35

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Which CouchDB Versionto use? CouchDB 0.11 or greater User management Authentication API: Cookie, OAuth, plain-HTTP Per-db reader access lists Validation functions Url rewriting Vhost configuration http://westhoffswelt.de jakob@westhoffswelt.de slide: 9 / 35

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CouchApp techniques Store all application files as document attachments Attachments can be stored for any document inside CouchDB Can be directly accesed using the RESTful interface Use CouchDBs authentication backend for user management Use validation function for access restrictions Use show and list functions to output HTML Access CouchDB using Javascript and XHR Use CouchDB vhosts and url rewriting for nice urls http://westhoffswelt.de jakob@westhoffswelt.de slide: 10 / 35

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Authentication backend: UserManagement Managing users: Futon: RESTful API: Create a new document in the users database http://localhost:5984/ users/org.couchdb.user:foo http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 11 / 35

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Authentication backend: Loggingin (Cookie) Logging in: POST username and password to http://localhost:5984/ session Parameters user and password application/x-www-form-urlencoded encoded Post: name=f o o&p a s s w o r d=b a r Response: { ” ok ” : t r u e , ”name” : ” f o o ” , ” r o l e s ” : [ ] } http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 12 / 35

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Excursion: Design documents Design documents supply certain special functionallities per db Stored with special id design/some-id Multiple design documents allowed per database Used to define: View functions (Map&Reduce) List functions Show functions Validation functions ... http://westhoffswelt.de jakob@westhoffswelt.de slide: 13 / 35

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Validation functions: Validateupdates Validation of document creations or updates using Javascript functions Registration: Property validate doc update on any design document Multiple validation functions on different design documents possible Called one after another No defined execution order: Functions need to be isolated One fails: validation fails http://westhoffswelt.de jakob@westhoffswelt.de slide: 14 / 35

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Validation functions: Validateupdates II Example Ensure all documents have a type field added is not allowed to be changed after document creation f u n c t i o n ( newDoc , oldDoc , u s e r C t x ) { i f ( ! newDoc . t y p e ) { throw ( { f o r b i d d e n : ” Mandatory f i e l d ’ type ’ i s m i s s i n g ” }) ; } i f ( ol dD oc && toJSON ( oldDoc . added ) != toJSON ( newDoc . added ) ) { throw ( . . . ) } } http://westhoffswelt.de jakob@westhoffswelt.de slide: 15 / 35

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Validation functions: Accesscontrol Use validation doc update function as access control system Ensure the user is logged in Ensure username and author field are identical f u n c t i o n ( newDoc , oldDoc , u s e r C t x ) { i f ( ! u s e r C t x . name ) { throw ( { f o r b i d d e n : ”You need t o be l o g g e d i n t o c h a n g e documents . ” } ) ; } i f ( ( ol dD oc && u s e r C t x . name != oldDoc . a u t h o r ) | | u s e r C t x . name != newDoc . a u t h o r ) { throw ( . . . ) } } http://westhoffswelt.de jakob@westhoffswelt.de slide: 16 / 35

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Show and listfunctions User formatted data instead of plain JSON Show functions format documents List functions format views Multiple show and list functions are allowed per-design-document Stored as shows and lists object ” shows ” : { ” summary ” : ” f u n c t i o n ( doc , r e q ) { . . . } ” , ” d e t a i l ” : ” f u n c t i o n ( doc , r e q ) { . . . } ” } http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 17 / 35

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Show function tooutput HTML Arguments doc - Document to be returned req - Request object User context GET parameter Accept header ... Return value is a response object body - Content returned to the caller headers - HTML headers (Can be used to set Content-Type) base64 - Can be used instead of body to send binary data http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 18 / 35

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Show function tooutput HTML II Example Output document type and author as HTML f u n c t i o n ( doc , r e q ) { return { body : [ ”<h1>The ” , doc . t y p e , ” document h a s been c r e a t e d by ” , doc . a u t h o r , ”</h1>” ] . j o i n ( ”” ) ; }; } http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 19 / 35

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List functions: StreamingAPI Arguments head - Statistical data about the view req - Request object Return value is not used Streaming API getRow() - Retrieve next row from the view, or null at the end send(data) - Send out the next piece of data to the caller http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 20 / 35

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List functions: Example Example Output authors in list as unordered HTML list f u n c t i o n ( head , r e q ) { var cur ; s e n d ( ’<u l > ’ ) ; w h i l e ( c u r = getRow ( ) ) { s e n d ( ’< l i > ’ + c u r . a u t h o r + ’</ l i > ’ ) ; } s e n d ( ’</u l > ’ ) ; } http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 21 / 35

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Query show andlist functions Queried based on design document and name Show functions GET /db/ design/mydesign/ show/show-name/doc-id List functions GET /db/ design/mydesign/ list/list-name/view-name http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 22 / 35

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Show and listfunctions in real applications Use a templating system Javscript micro template language based on John Resigs idea http://github.com/furf/jquery-template Use integrated provides and registerType functions to serve multiple formats based on the accept header Maybe do some sort of user authentication before showing content http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 23 / 35

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Url rewriting Urls like this one are neither readable nor usable /db/ design/mydesign/ list/list-name/view-name?limit=5 CouchDB supports internal url rewriting Defined as array of rewrites on any design document ”rewrites”: [ { ” from ” : ” / i n d e x ” , ” t o ” : ” l i s t / l i s t −name/ view −name? l i m i t =5” } ] http://westhoffswelt.de jakob@westhoffswelt.de slide: 24 / 35

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Advanced url rewriting Using named placeholders Match each path segment ” from ” : ” / e n t r y / : doc ” , ” t o ” : ” show / show−name / : doc ” Using match all at the end of an url Appends given query parameters ” from ” : ” / e n t r y /∗ ” , ” t o ” : ” show / show−name /∗ ” http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 25 / 35

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Advanced url rewriting Using named placeholders Match each path segment ” from ” : ” / e n t r y / : doc ” , ” t o ” : ” show / show−name / : doc ” Using match all at the end of an url Appends given query parameters ” from ” : ” / e n t r y /∗ ” , ” t o ” : ” show / show−name /∗ ” http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 25 / 35

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Advanced url rewritingII Rewriting to query parameters ” from ” : ” / page / : s t a r t ” , ” t o ” : ” l i s t / l i s t −name/ p a g e s ” , ” query ” : { ” startkey ”: ”: start ” } Adress a context outside of the design document Targets are always relative to the design document Relative navigation with .. is allowed ” from ” : ” / raw / : doc ” , ” t o ” : ” . . / . . / : doc ” http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 26 / 35

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Advanced url rewritingII Rewriting to query parameters ” from ” : ” / page / : s t a r t ” , ” t o ” : ” l i s t / l i s t −name/ p a g e s ” , ” query ” : { ” startkey ”: ”: start ” } Adress a context outside of the design document Targets are always relative to the design document Relative navigation with .. is allowed ” from ” : ” / raw / : doc ” , ” t o ” : ” . . / . . / : doc ” http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 26 / 35

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Advanced url rewritingIII Rewriting based on HTTP methods { ” from ” : ” / e n t r y /∗ ” , ” t o ” : ” show / show−name /∗ ” , ” method ” : ”GET” }, { ” from ” : ” / e n t r y /∗ ” , ” t o ” : ” u p d a t e / update −name /∗ ” , ” method ” : ”POST” }, http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 27 / 35

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Query rewritten urls Queried on design document using special rewrite path /db/ design/mydesign/ rewrite/some-url Better, but far from being perfect → Vhost configuration http://westhoffswelt.de jakob@westhoffswelt.de slide: 28 / 35

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Vhost configuration CouchDB supports url changing based on the provided Host Custom root path for every host/domain Configured in local.ini Direct all requests to the rewrite handler [ vhosts ] e x a m p l e . com = /mydb/ d e s i g n / m y d e s i g n / r e w r i t e http://westhoffswelt.de jakob@westhoffswelt.de slide: 29 / 35

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Using CouchApp fordeployment CouchApp does not only categorize these application type It is a utillity written in Python http://github.com/couchapp/couchapp Deployment system for CouchApps to CouchDBs Providing some common widgets like login or profile http://westhoﬀswelt.de jakob@westhoﬀswelt.de slide: 30 / 35

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CouchApp: Javascript preprocessing CouchApps preprocesses Javascript before deploying it Provides two useful macros: !code and !json // !code lib/helper/validation utillities.js Include Javascript code from any other file Reuse code throughout your application functions // !json lib.templates.mytemplate Dot notation of path to .json file Available using the full object path: lib.templates.mytemplate http://westhoffswelt.de jakob@westhoffswelt.de slide: 32 / 35

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CouchApp: Deployment Specifying all parameters on the commandline couchapp push http://user:pw@localhost:5984/mydb Use .couchapprc file { ” env ” : { ” default ”: { ” db ” : ” h t t p : / / u s e r : p w @ l o c a l h o s t : 5 9 8 4 / mydb−dev ” }, ” production ” : { ” db ” : ” h t t p : / / / u s e r : pw@example . com/mydb” } } } http://westhoffswelt.de jakob@westhoffswelt.de slide: 33 / 35

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CouchApp: Deployment Specifying all parameters on the commandline couchapp push http://user:pw@localhost:5984/mydb Use .couchapprc file { ” env ” : { ” default ”: { ” db ” : ” h t t p : / / u s e r : p w @ l o c a l h o s t : 5 9 8 4 / mydb−dev ” }, ” production ” : { ” db ” : ” h t t p : / / / u s e r : pw@example . com/mydb” } } } http://westhoffswelt.de jakob@westhoffswelt.de slide: 33 / 35

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Further reading Things we didn’t have time to discuss Update functions http://wiki.apache.org/couchdb/Document Update Handlers View functions http://wiki.apache.org/couchdb/Introduction to CouchDB views changes stream http://books.couchdb.org/relax/reference/change-notifications Evently javascript library http://vimeo.com/9847214 Further documentation CouchDB: The definitive guide http://books.couchdb.org/relax/ The CouchDB wiki http://wiki.apache.org/couchdb/ http://westhoffswelt.de jakob@westhoffswelt.de slide: 34 / 35

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Thanks for listening Questions, comments or annotations? Slides: http://westhoffswelt.de/portfolio.htm Contact: Jakob Westhoff <jakob@php.net> Twitter: @jakobwesthoff Please leave comments and vote at: http://joind.in/1612 http://westhoffswelt.de jakob@westhoffswelt.de slide: 35 / 35

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