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![Long Polling <?php ... $twitterSearch = new Zend_Service_Twitter_Search('json'); $hashtag = 'dpc11'; if (isset($_GET['hashtag'])) { $hashtag = $_GET['hashtag']; } $result = false; while($result === false) { if (isset($_GET['since_id']) && $_GET['since_id'] > 0) { $since_id = (int) $_GET['since_id'] + 1; $searchResults = $twitterSearch->search($hashtag, array('lang' => 'en', 'rpp' => 30,'since_id' => $since_id)); } else { $searchResults = $twitterSearch->search($hashtag, array('lang' => 'en','rpp' => 30)); } if (isset($searchResults['results']) && count($searchResults['results'])) { $result = json_encode($searchResults['results'][0]); } } echo $result;](https://image.slidesharecdn.com/comet-and-php-slideshare-dpc-2011-110521112623-phpapp02/75/Implementing-Comet-using-PHP-45-2048.jpg)
Implementing Comet using PHP
- 1. Implement Comet usingPHP Dutch PHP Conference 2011 Jonas Mariën – King Foo www.king-foo.be
- 2. Jonas Mariën, KingFoo www.king-foo.be Author “Zend Framework Web Services” (php|architect) Online since 93 (yep). PHP for fun since 96, professional since 2001. Master in Biological and Genetic Engineering, University of Leuven.
- 3. Comet = datapush from server to client
- 4. Comet aka ReverseAjax HTTP server Push Ajax Push HTTP streaming ... abused/umbrella term
- 5. Use case Exampleupdates being pushed: ticker info
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- 11.
- 12. feedback on processesthat take time to complete
- 13.
- 14. Push? But, but... a browser pulls and the server responds, no? Fake push using polling trickery
- 15. Connection is keptopen as long as possible
- 16.
- 17. Does the trickfor now
- 18.
- 19. Short polling Clienttries to get something new from the server and polls at regular and short intervals.
- 20. Responsiveness at thecost of performance (on the server side). Wasteful in terms of resources.
- 21. Easy, but notreally what we are looking for.
- 22.
- 23. Short polling function getUpdate() { $.ajax({ type: "POST", url: "server.php", data: "type=news&category=PHP", success : function(msg){ $('#feed').append(msg);/** we do something **/ setTimeout("getUpdate()", 2000); } }); } $(document).ready(function() { getUpdate(); }
- 24.
- 25. The forever frameAn iframe keeps loading, never stops (or reloads occasionally)
- 26.
- 27. Dirty, e.g IEdoesn't like this
- 28. The forever frameIn the page: <script type="text/javascript">function updateResult(/** do something **/)</script>) <iframe style='width: 0px; height: 0px' src='./serverside.php'></iframe> On the server: <?php set_time_limit(0); header("Cache-Control: no-cache, must-revalidate"); header("Expires: Mon, 24 Jul 1974 05:00:00 GMT"); flush(); ob_flush();//if ob_start (implicitly) called before while(true) { $result = date('Y-m-d H:i:s'); echo '<script type="text/javascript">parent.updateResult(\''.$result.'\');</script>'; flush(); ob_flush(); $sleeptimer = rand(1, 15); sleep($sleeptimer); }
- 29.
- 30.
- 31. Output 'busy' &&sleep() on the server side untill finishing
- 32. We need toget the status before oncomplete/onsuccess Note: there is also multipart/x-mixed-replace as part of XHR
- 33. XHR “ TheXMLHttpRequest object can be in several states. The readyState attribute must return the current state, which must be one of the following values” * http://www.w3.org/TR/XMLHttpRequest/#states UNSENT (0) The object has been constructed. OPENED (1) The open() method has been successfully invoked. During this state request headers can be set using setRequestHeader() and the request can be made using the send() method. HEADERS_RECEIVED (2) All redirects (if any) have been followed and all HTTP headers of the final response have been received. Several response members of the object are now available. LOADING (3) The response entity body is being received. DONE (4) The data transfer has been completed or something went wrong during the transfer (e.g. infinite redirects).
- 34. XHR Sine jQuery1.5, no direct access to the underlying XHR object
- 35. No access toloading state
- 36. Can use afilter: http://bugs.jquery.com/ticket/8327
- 37.
- 38. Mixed results usingdifferent browsers for direct XHR manipulation
- 39. XHR xhr.onreadystatechange =function() { if(http.readyState == 3 && http.status == 200) { //do something document.write(xhr.responseText); } }
- 40. Long polling Longerintervals
- 41. Each time something is returned from the server, a new request is started
- 42.
- 43. Server: checks forupdates for a few cycles and keeps a counter. If counter limit reached, 'false' or 'error' message goes back. If an update is available before that, exit the loop and return an 'ok' message with payload.
- 44. Long Polling functiongetUpdate(){ $.ajax({ type: "GET", url: "server.php", async: true, cache: false, timeout:50000, success: function(data) { /** do something **/ setTimeout ( 'getUpdate()', 1000 ); }, error: function(XMLHttpRequest, textStatus, errorThrown){ /**show error notice**/ setTimeout ( 'getUpdate()', "20000"); }, }); }; $(document).ready(function(){ getUpdate(); });
- 45. Long Polling <?php... $twitterSearch = new Zend_Service_Twitter_Search('json'); $hashtag = 'dpc11'; if (isset($_GET['hashtag'])) { $hashtag = $_GET['hashtag']; } $result = false; while($result === false) { if (isset($_GET['since_id']) && $_GET['since_id'] > 0) { $since_id = (int) $_GET['since_id'] + 1; $searchResults = $twitterSearch->search($hashtag, array('lang' => 'en', 'rpp' => 30,'since_id' => $since_id)); } else { $searchResults = $twitterSearch->search($hashtag, array('lang' => 'en','rpp' => 30)); } if (isset($searchResults['results']) && count($searchResults['results'])) { $result = json_encode($searchResults['results'][0]); } } echo $result;
- 46.
- 47. Thoughts & notesPiggybacking
- 48. Long polling issues:Requests are kept open for a while
- 49. Objects (other thenthe ones being pulled/pushed) on server side can be changed, need to have these changes fed to the client. Piggybacking to the rescue again?
- 50. One or morelong polling requests open and then an AJAX call: might give you browser problems with simultaneous requests
- 51. Server performance: weneed event driven solutions (message queues and/or something like node.js) to fix this
- 52. Proxies (chunking stuff)and firewalls (dropping long connections). Some Comet libs (next slides) try to detect intermediate proxies Comet is not mature. Uses HTTP against most of the basic assumptions and no real standards available. Not a real standard.
- 53. Thoughts & NotesPerformance is the biggest problem A Comet server should be able to handle as much connections as fast as possible, with a high troughput and low latency. Long polling requests stay idle for a while, so claiming a thread is not ok.
- 54.
- 55. DWR Direct WebRemoting (http://directwebremoting.org)
- 56. Nice, but Java only
- 57. Fallback different polling mechanisms
- 58. Dynamic Javascript generation
- 59. Attempts at PHPimplementations, one could use something like json-rpc to mimic this Could use a Java bridge from PHP perhaps?
- 60. Cometd & BayeuxDojo Foundation
- 61. Cometd: reference implementation(in Java, Perl and Python). Java implementation uses Jetty.
- 62. Bayeux: protocol, JSONfor request/response
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- 64.
- 65.
- 66. /chat/** Now hassome WS support too (haven't tested that, see http://cometdproject.dojotoolkit.org/node/124 and https://www.dojotoolkit.org/reference-guide/_static/js/dojox/socket/)
- 67. http://cometd.org/documentation/installation http://cometd.org/documentation/howtos/primer Also,keep an eye on: http://opencoweb.org/
- 68. Bayeux Handshake [ { "channel": "/meta/handshake", "version": "1.0", "minimumVersion": "1.0beta", "supportedConnectionTypes": ["long-polling", "callback-polling", "iframe"] } ] [ { "channel": "/meta/handshake", "version": "1.0", "minimumVersion": "1.0beta", "supportedConnectionTypes": ["long-polling","callback-polling"], "clientId": "Un1q31d3nt1f13r", "successful": true, "authSuccessful": true, "advice": { "reconnect": "retry" } } ] http://cometdproject.dojotoolkit.org/documentation/bayeux
- 69.
- 70. Subscribe [ {"channel": "/meta/subscribe", "clientId": "Un1q31d3nt1f13r", "subscription": "/chat/**" } ] [ { "channel": "/meta/subscribe", "clientId": "Un1q31d3nt1f13r", "subscription": "/chat/**", "successful": true, "error": "" } ]
- 71. Bayeux dojo.require("dojox.cometd"); dojox.cometd.init("http://example.com/cometd");dojox.cometd.subscribe("/slideshow/change", function(comet) { $('#slideimg').attr('src', comet.data.src); }); }); .... dojox.cometd.publish("/slideshow/change", { 'src': src }); http://simonwillison.net/2007/Dec/5/comet/
- 72. Cometd/Bayeux Download distributionfrom: http://downloads.dojotoolkit.org/cometd/ $ tar zxvf cometd-1.1.4.tgz $ cd cometd-1.1.4/ $ cd cometd-1.1.4/ $ cd cometd-demo $ mvn jetty:deploy-war http://localhost:8080/ And a demo..
- 73.
- 74. Phomet/Bayeux client Usephomet to talk Bayeux to Cometd $phomet = new Bayeux(’http://example.com/cometd’); $phomet->publish(’/chat/developersonly’, array( 'user' => 'jonas', 'message' => 'bayeux'. . 'is ... well ... euhm')); http://morglog.alleycatracing.com/bayeux.class.inc.phps
- 75. WebSync Commercial solutionbased on ASP.NET/IIS, also On-Demand
- 76. Comes with an OnDemand SDK for other languages, has some PHP sample code
- 77. APE APE - Ajax Push Engine
- 78. Comet but theyclaim WebSockets support
- 79.
- 80. Written in C,has SpiderMonkey (js) bindings allowing for serverside modules in js
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- 87.
- 88. Gateway, handles Comet and WebSockets
- 89.
- 90. http://tech.kaazing.com/documentation/ Commercial, freedev license for testing
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- 93.
- 94.
- 95. node.js git clonehttps://github.com/joyent/node.git cd node git tag -l git checkout v0.4.7 ./configure make make install
- 96.
- 97.
- 98. Socket.io curl http://npmjs.org/install.sh| sh npm install socket.io
- 99.
- 100. Want more? socket.ioserver side: https://github.com/LearnBoost/Socket.IO-node
- 101. socket.io client side:https://github.com/LearnBoost/Socket.IO
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- 104.
- 105. Other solutions nginxpush module (http://pushmodule.slact.net/)
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- 110. Jetty 6 /Grizzly / Tomcat 6
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- 113.
- 114. Noloh (has somepush support)
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- 118.
- 119. “HTTP callbacks usingPOST, for notification” PubSubHubbub http://code.google.com/p/pubsubhubbub/
- 120. “Server-to-server publish/subscribe usingwebhooks” ReverseHTTP http://reversehttp.net/
- 121. “Server in thebrowser” WebSockets & Server-Sent Events
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- 126.
- 127. http://riteshsblog.blogspot.com/2011/03/rabbitmq-adapter-for-zend-queue-using.html (uses AMQPand AMQP extension) XMPP
- 128. any PHP basedsolutions?
- 129. PHP? DIY -have a look at existing attempts Phico (http://www.3site.eu/phico.php)
- 130.
- 131.
- 132. Other? NoBayeux/Cometd replacement in PHP, but doable if you really want to
- 133.
- 134. PHP? Write adaemon Using nanoweb ?
- 135. Using Appserver-in-PHP ? (https://github.com/indeyets/appserver-in-php)
- 136. Use Phet (https://github.com/Tim-Smart/phet) Use existing comet server solutions and add/read data using PHP
- 137. Use something likenode.js + socket.io and think in terms of upcoming websocket support in all browsers
- 138. Try to implementa node.js alternative using http://php.net/libevent (which could be a really interesting solution)
- 139. Real-time web Realpush WebSockets
- 140.
- 141. SSE Client: <!DOCTYPEhtml> <html> <head> <meta charset="utf-8" /> </head> <body> <script> var source = new EventSource('./server.php'); source.onmessage = function (event) { document.getElementById('output').innerHTML += event.data + '<br>'; }; </script> <div id="output"></div> </body> </html> Server: <?php header("Content-Type: text/event-stream\n\n"); echo 'data: ' . date('Y-m-d H:i:s') . "\n"; http://googlecodesamples.com/html5/sse/sse.html
- 142.
- 143. WebSockets http://code.google.com/p/phpwebsocket/ Anotheroption: www.waterspout.com
- 144.
- 145. Conclusions Push! Gofor a solution that bridges the gap while waiting for websockets and SSE Do keep an eye on the real-time web evolution. It will be here very (very) soon and will impact your job.
- 146. Credits “ Cometand Reverse Ajax: The next Generation Ajax 2.0” by Dave Crane and Phil McCarthy
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- 149.
- 150. Plus: various linksshowed in the slides
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- 152.
- 153. http://joind.in/3237 Questions? Wantus to work for you? [email_address] www.king-foo.be www.king-foo.net/blog @jonasmarien