multicast-discovery.html - tomee-site-pub - Git at Google

 <!DOCTYPE html>
 <html lang="en">
   <head>

     <meta charset="UTF-8">
       <title>Multicast (UDP) Discovery</title>
     <meta name="description" content="Apache TomEE">
     <meta name="author" content="Apache TomEE">
     <meta name="google-translate-customization" content="f36a520c08f4c9-0a04e86a9c075ce9-g265f3196f697cf8f-10">
     <meta http-equiv="Pragma" content="no-cache">
     <meta http-equiv="Expires" content="0">
     <meta http-equiv="Cache-Control" content="no-store, no-cache, must-revalidate, max-age=0">

     <!-- Le HTML5 shim, for IE6-8 support of HTML elements -->
     <!--[if lt IE 9]>
       <script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script>
     <![endif]-->

     <!-- Le styles -->
     <link href="./resources/css/bootstrap.css" rel="stylesheet">
     <link href="./resources/css/prettify.css" rel="stylesheet">
     <!--link href="./resources/css/bootstrap-mods.css" rel="stylesheet"-->
     <link href="./resources/css/main.css" rel="stylesheet">
     <link href="./resources/font-awesome-4.6.3/css/font-awesome.min.css" rel="stylesheet">

     <script type="text/javascript">
         var t = encodeURIComponent(document.title.replace(/^\s+|\s+$/g,""));
         var u = encodeURIComponent(""+document.URL);

       function fbshare () {
           window.open(
                   "http://www.facebook.com/sharer/sharer.php?u="+u,
                   'Share on Facebook',
                   'width=640,height=426');
       };
       function gpshare () {
           window.open(
                   "https://plus.google.com/share?url="+u,
                   'Share on Google+',
                   'width=584,height=385');
       };
       function twshare () {
           window.open(
                   "https://twitter.com/intent/tweet?url="+u+"&text="+t,
                   'Share on Twitter',
                   'width=800,height=526');
       };
       function pinshare () {
           window.open("//www.pinterest.com/pin/create/button/?url="+u+"&media=http%3A%2F%2Ftomee.apache.org%2Fresources%2Fimages%2Ffeather-logo.png&description="+t,
                   'Share on Pinterest',
                   'width=800,height=526');
       };
     </script>

     <!-- Le fav and touch icons -->
     <link rel="shortcut icon" href="./favicon.ico">
     <link rel="apple-touch-icon" href="./resources/images/apple-touch-icon.png">
     <link rel="apple-touch-icon" sizes="72x72" href="./resources/images/apple-touch-icon-72x72.png">
     <link rel="apple-touch-icon" sizes="114x114" href="./resources/images/apple-touch-icon-114x114.png">

     <script src="./resources/js/prettify.js" type="text/javascript"></script>
     <script src="./resources/js/jquery-latest.js"></script>
     <script src="http://platform.twitter.com/widgets.js" type="text/javascript"></script>
     <script src="./resources/js/common.js"></script>
     <script src="./resources/js/prettyprint.js"></script>
     <!--script src="//assets.pinterest.com/js/pinit.js" type="text/javascript" async></script//-->

     <script type="text/javascript">

       var _gaq = _gaq || [];
       _gaq.push(['_setAccount', 'UA-2717626-1']);
       _gaq.push(['_setDomainName', 'apache.org']);
       _gaq.push(['_trackPageview']);

       (function() {
         var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
         ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
         var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
       })();

     </script>
   </head>

   <body>

     <div class="topbar" data-dropdown="dropdown">
       <div class="fill">
         <div class="container">
           <a class="brand" href="./index.html">Apache TomEE</a>
           <ul class="nav">
               <li class="dropdown">
                   <a class="dropdown-toggle" data-toggle="dropdown" href="#">
                   Apache
                       <b class="caret"></b>
                   </a>
                   <ul class="dropdown-menu">
                      <!-- <li><a href="./misc/whoweare.html">Who we are?</a></li> -->
                      <!-- <li><a href="./misc/heritage.html">Heritage</a></li> -->
                      <li><a href="http://www.apache.org">Apache Home</a></li>
                      <!-- <li><a href="./misc/resources.html">Resources</a></li> -->
                      <li><a href="./misc/contact.html">Contact</a></li>
                      <li><a href="./misc/legal.html">Legal</a></li>
                      <li><a href="http://www.apache.org/foundation/sponsorship.html">Sponsorship</a></li>
                      <li><a href="http://www.apache.org/foundation/thanks.html">Thanks</a></li>
                      <li class="divider"/>
                      <li><a href="http://www.apache.org/security">Security</a></li>
                   </ul>
               </li>
               <li><a href="./index.html">Home</a></li>
               <li><a href="./downloads.html">Downloads</a></li>
               <li><a href="./documentation.html">Documentation</a></li>
               <li><a href="./examples-trunk/index.html">Examples</a></li>
               <li><a href="./support.html">Support</a></li>
               <li><a href="./contribute.html">Contribute</a></li>
               <li><a href="./security/index.html">Security</a></li>
           </ul>

             <!-- Google CSE Search Box Begins  -->
             <FORM class="pull-right" id="searchbox_010475492895890475512:_t4iqjrgx90" action="http://www.google.com/cse">
                 <INPUT type="hidden" name="cx" value="010475492895890475512:_t4iqjrgx90">
                 <INPUT type="hidden" name="cof" value="FORID:0">
                 <INPUT size="18" width="130" style="width:130px" name="q" type="text" placeholder="Search">
             </FORM>
             <!--<SCRIPT type="text/javascript" src="http://www.google.com/coop/cse/brand?form=searchbox_010475492895890475512:_t4iqjrgx90"></SCRIPT>-->
             <!-- Google CSE Search Box Ends -->
         </div>
       </div>
     </div>

     <div class="container">


 <div class="page-header">
     <small><a href="./index.html">Home</a></small><br>
     <h1>Multicast (UDP) Discovery

         <div style="float: right; position: relative; bottom: -10px; ">
             <a onclick="javascript:gpshare()" class="gp-share sprite" title="Share on Google+">share [gp]</a>
             <a onclick="javascript:fbshare()" class="fb-share sprite" title="Share on Facebook">share [fb]</a>
             <a onclick="javascript:twshare()" class="tw-share sprite" title="Share on Twitter">share [tw]</a>
             <a onclick="javascript:pinshare()" class="pin-share sprite" title="Share on Pinterest">share [pin]</a>
             <a data-toggle="modal" href="#edit" class="edit-page" title="Contribute to this Page">contribute</a>
         </div>
     </h1>
 </div>

 <p>Multicast is the preferred way to broadcast the heartbeat on the network.
 The simple technique of broadcasting a non-changing service URI on the
 network has specific advantages to multicast.  The URI itself is
 essentially stateless and there is no "i'm alive" URI or an "i'm dead" URI.</p>

 <p>In this way the issues with UDP being unordered and unreliable melt away as
 state is no longer a concern and packet sizes are always small.
 Complicated libraries that ride atop UDP and attempt to offer reliability
 (retransmission) and ordering on UDP can be avoided.  As well the
 advantages UDP has over TCP are retained as there are no java layers
 attempting to force UDP communication to be more TCP-like.  The simple
 design means UDP/Multicast is only used for discovery and from there on out
 critical information is transmitted over TCP/IP which is obviously going to
 do a better job at ensuring reliability and ordering.</p>

 <h1>Server Configuration</h1>

 <p>When you boot the server there should be a <code>conf/multicast.properties</code> file
 containing:</p>

 <pre><code>server      = org.apache.openejb.server.discovery.MulticastDiscoveryAgent
 bind        = 239.255.2.3
 port        = 6142
 disabled    = true
 group       = default
 </code></pre>

 <p>Just need to enable that by setting <code>disabled=false</code>.  All of the above
 settings except <code>server</code> can be changed.  The <code>port</code> and <code>bind</code> must
 be valid for general multicast/udp network communication.</p>

 <p>The <code>group</code> setting can be changed to further group servers that may use
 the same multicast channel.  As shown below the client also has a <code>group</code>
 setting which can be used to select an appropriate server from the
 multicast channel.</p>

 <h1>Multicast Client</h1>

 <p>The multicast functionality is not just for servers to find each other in a
 cluster, it can also be used for EJB clients to discover a server.  A
 special <code>multicast://</code> URL can be used in the <code>InitialContext</code> properties to
 signify that multicast should be used to seed the connection process.  Such
 as:</p>

 <pre><code>Properties p = new Properties();
 p.put(Context.INITIAL_CONTEXT_FACTORY,
 "org.apache.openejb.client.RemoteInitialContextFactory");
 p.put(Context.PROVIDER_URL, "multicast://239.255.2.3:6142?group=default");
 InitialContext remoteContext = new InitialContext(p);
 </code></pre>

 <p>The URL has optional query parameters such as <code>schemes</code> and <code>group</code> and
 <code>timeout</code> which allow you to zero in on a particular type of service of a
 particular cluster group as well as set how long you are willing to wait in
 the discovery process till finally giving up.  The first matching service
 that it sees "flowing" around on the UDP stream is the one it picks and
 sticks to for that and subsequent requests, ensuring UDP is only used when
 there are no other servers to talk to.</p>

 <p>Note that EJB clients do not need to use multicast to find a server.  If
 the client knows the URL of a server in the cluster, it may use it and
 connect directly to that server, at which point that server will share the
 full list of its peers.</p>

 <h1>Multicast Servers with TCP Clients</h1>

 <p>Note that clients do not need to use multicast to communicate with servers.
 Servers can use multicast to discover each other, but clients are still
 free to connect to servers in the network using the server's TCP address.</p>

 <pre><code>Properties p = new Properties();
 p.put(Context.INITIAL_CONTEXT_FACTORY,  "org.apache.openejb.client.RemoteInitialContextFactory");
 p.put(Context.PROVIDER_URL, "ejbd://192.168.1.30:4201");
 InitialContext remoteContext = new InitialContext(p);
 </code></pre>

 <p>When the client connects, the server will send the URLs of all the servers
 in the group and failover will take place normally.</p>


         <div id="edit" class="modal hide fade in" style="display: none; ">
             <div class="modal-header">
                 <a class="close" data-dismiss="modal">x</a>

                 <h3>Thank you for contributing to the documentation!</h3>
             </div>
             <div class="modal-body">
                 <h4>Any help with the documentation is greatly appreciated.</h4>
                 <p>All edits are reviewed before going live, so feel free to do much more than fix typos or links.  If you see a page that could benefit from an entire rewrite, we'd be thrilled to review it.  Don't be surprised if we like it so much we ask you for help with other pages :)</p>
                 <small>NOTICE: unless indicated otherwise on the pages in question, all editable content available from apache.org is presumed to be licensed under the Apache License (AL) version 2.0 and hence all submissions to apache.org treated as formal Contributions under the license terms.</small>
                 <!--[if gt IE 6]>
                 <h4>Internet Explorer Users</h4>
                 <p>If you are not an Apache committer, click the Yes link and enter a <i>anonymous</i> for the username and leave the password empty</p>
                 <![endif]-->

             </div>
             <div class="modal-footer">
                 Do you have an Apache ID?
                 <a href="javascript:void(location.href='https://cms.apache.org/redirect?uri='+escape(location.href))" class="btn">Yes</a>
                 <a href="javascript:void(location.href='https://anonymous:@cms.apache.org/redirect?uri='+escape(location.href))" class="btn">No</a>
             </div>
         </div>
         <script src="./resources/js/bootstrap-modal.js"></script>

         <footer>
             <p>Copyright &copy; 1999-2016 The Apache Software Foundation, Licensed under the Apache License, Version 2.0.
                 Apache TomEE, TomEE, Apache, the Apache feather logo, and the Apache TomEE project logo are trademarks of The Apache Software Foundation.
                 All other marks mentioned may be trademarks or registered trademarks of their respective owners.</p>
         </footer>

     </div> <!-- /container -->

     <!-- Javascript
     ================================================== -->
     <!-- Placed at the end of the document so the pages load faster -->
     <script src="./resources/js/bootstrap-dropdown.js"></script>

   </body>
 </html>
	<!DOCTYPE html>
	<html lang="en">
	<head>

	<meta charset="UTF-8">
	<title>Multicast (UDP) Discovery</title>
	<meta name="description" content="Apache TomEE">
	<meta name="author" content="Apache TomEE">
	<meta name="google-translate-customization" content="f36a520c08f4c9-0a04e86a9c075ce9-g265f3196f697cf8f-10">
	<meta http-equiv="Pragma" content="no-cache">
	<meta http-equiv="Expires" content="0">
	<meta http-equiv="Cache-Control" content="no-store, no-cache, must-revalidate, max-age=0">

	<!-- Le HTML5 shim, for IE6-8 support of HTML elements -->
	<!--[if lt IE 9]>
	<script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script>
	<![endif]-->

	<!-- Le styles -->
	<link href="./resources/css/bootstrap.css" rel="stylesheet">
	<link href="./resources/css/prettify.css" rel="stylesheet">
	<!--link href="./resources/css/bootstrap-mods.css" rel="stylesheet"-->
	<link href="./resources/css/main.css" rel="stylesheet">
	<link href="./resources/font-awesome-4.6.3/css/font-awesome.min.css" rel="stylesheet">

	<script type="text/javascript">
	var t = encodeURIComponent(document.title.replace(/^\s+\|\s+$/g,""));
	var u = encodeURIComponent(""+document.URL);

	function fbshare () {
	window.open(
	"http://www.facebook.com/sharer/sharer.php?u="+u,
	'Share on Facebook',
	'width=640,height=426');
	};
	function gpshare () {
	window.open(
	"https://plus.google.com/share?url="+u,
	'Share on Google+',
	'width=584,height=385');
	};
	function twshare () {
	window.open(
	"https://twitter.com/intent/tweet?url="+u+"&text="+t,
	'Share on Twitter',
	'width=800,height=526');
	};
	function pinshare () {
	window.open("//www.pinterest.com/pin/create/button/?url="+u+"&media=http%3A%2F%2Ftomee.apache.org%2Fresources%2Fimages%2Ffeather-logo.png&description="+t,
	'Share on Pinterest',
	'width=800,height=526');
	};
	</script>

	<!-- Le fav and touch icons -->
	<link rel="shortcut icon" href="./favicon.ico">
	<link rel="apple-touch-icon" href="./resources/images/apple-touch-icon.png">
	<link rel="apple-touch-icon" sizes="72x72" href="./resources/images/apple-touch-icon-72x72.png">
	<link rel="apple-touch-icon" sizes="114x114" href="./resources/images/apple-touch-icon-114x114.png">

	<script src="./resources/js/prettify.js" type="text/javascript"></script>
	<script src="./resources/js/jquery-latest.js"></script>
	<script src="http://platform.twitter.com/widgets.js" type="text/javascript"></script>
	<script src="./resources/js/common.js"></script>
	<script src="./resources/js/prettyprint.js"></script>
	<!--script src="//assets.pinterest.com/js/pinit.js" type="text/javascript" async></script//-->

	<script type="text/javascript">

	var _gaq = _gaq \|\| [];
	_gaq.push(['_setAccount', 'UA-2717626-1']);
	_gaq.push(['_setDomainName', 'apache.org']);
	_gaq.push(['_trackPageview']);

	(function() {
	var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
	ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
	var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
	})();

	</script>
	</head>

	<body>

	<div class="topbar" data-dropdown="dropdown">
	<div class="fill">
	<div class="container">
	<a class="brand" href="./index.html">Apache TomEE</a>
	<ul class="nav">
	<li class="dropdown">
	<a class="dropdown-toggle" data-toggle="dropdown" href="#">
	Apache
	<b class="caret"></b>
	</a>
	<ul class="dropdown-menu">
	<!-- <li><a href="./misc/whoweare.html">Who we are?</a></li> -->
	<!-- <li><a href="./misc/heritage.html">Heritage</a></li> -->
	<li><a href="http://www.apache.org">Apache Home</a></li>
	<!-- <li><a href="./misc/resources.html">Resources</a></li> -->
	<li><a href="./misc/contact.html">Contact</a></li>
	<li><a href="./misc/legal.html">Legal</a></li>
	<li><a href="http://www.apache.org/foundation/sponsorship.html">Sponsorship</a></li>
	<li><a href="http://www.apache.org/foundation/thanks.html">Thanks</a></li>
	<li class="divider"/>
	<li><a href="http://www.apache.org/security">Security</a></li>
	</ul>
	</li>
	<li><a href="./index.html">Home</a></li>
	<li><a href="./downloads.html">Downloads</a></li>
	<li><a href="./documentation.html">Documentation</a></li>
	<li><a href="./examples-trunk/index.html">Examples</a></li>
	<li><a href="./support.html">Support</a></li>
	<li><a href="./contribute.html">Contribute</a></li>
	<li><a href="./security/index.html">Security</a></li>
	</ul>

	<!-- Google CSE Search Box Begins -->
	<FORM class="pull-right" id="searchbox_010475492895890475512:_t4iqjrgx90" action="http://www.google.com/cse">
	<INPUT type="hidden" name="cx" value="010475492895890475512:_t4iqjrgx90">
	<INPUT type="hidden" name="cof" value="FORID:0">
	<INPUT size="18" width="130" style="width:130px" name="q" type="text" placeholder="Search">
	</FORM>
	<!--<SCRIPT type="text/javascript" src="http://www.google.com/coop/cse/brand?form=searchbox_010475492895890475512:_t4iqjrgx90"></SCRIPT>-->
	<!-- Google CSE Search Box Ends -->
	</div>
	</div>
	</div>

	<div class="container">


	<div class="page-header">
	<small><a href="./index.html">Home</a></small><br>
	<h1>Multicast (UDP) Discovery

	<div style="float: right; position: relative; bottom: -10px; ">
	<a onclick="javascript:gpshare()" class="gp-share sprite" title="Share on Google+">share [gp]</a>
	<a onclick="javascript:fbshare()" class="fb-share sprite" title="Share on Facebook">share [fb]</a>
	<a onclick="javascript:twshare()" class="tw-share sprite" title="Share on Twitter">share [tw]</a>
	<a onclick="javascript:pinshare()" class="pin-share sprite" title="Share on Pinterest">share [pin]</a>
	<a data-toggle="modal" href="#edit" class="edit-page" title="Contribute to this Page">contribute</a>
	</div>
	</h1>
	</div>

	<p>Multicast is the preferred way to broadcast the heartbeat on the network.
	The simple technique of broadcasting a non-changing service URI on the
	network has specific advantages to multicast. The URI itself is
	essentially stateless and there is no "i'm alive" URI or an "i'm dead" URI.</p>

	<p>In this way the issues with UDP being unordered and unreliable melt away as
	state is no longer a concern and packet sizes are always small.
	Complicated libraries that ride atop UDP and attempt to offer reliability
	(retransmission) and ordering on UDP can be avoided. As well the
	advantages UDP has over TCP are retained as there are no java layers
	attempting to force UDP communication to be more TCP-like. The simple
	design means UDP/Multicast is only used for discovery and from there on out
	critical information is transmitted over TCP/IP which is obviously going to
	do a better job at ensuring reliability and ordering.</p>

	<h1>Server Configuration</h1>

	<p>When you boot the server there should be a <code>conf/multicast.properties</code> file
	containing:</p>

	<pre><code>server = org.apache.openejb.server.discovery.MulticastDiscoveryAgent
	bind = 239.255.2.3
	port = 6142
	disabled = true
	group = default
	</code></pre>

	<p>Just need to enable that by setting <code>disabled=false</code>. All of the above
	settings except <code>server</code> can be changed. The <code>port</code> and <code>bind</code> must
	be valid for general multicast/udp network communication.</p>

	<p>The <code>group</code> setting can be changed to further group servers that may use
	the same multicast channel. As shown below the client also has a <code>group</code>
	setting which can be used to select an appropriate server from the
	multicast channel.</p>

	<h1>Multicast Client</h1>

	<p>The multicast functionality is not just for servers to find each other in a
	cluster, it can also be used for EJB clients to discover a server. A
	special <code>multicast://</code> URL can be used in the <code>InitialContext</code> properties to
	signify that multicast should be used to seed the connection process. Such
	as:</p>

	<pre><code>Properties p = new Properties();
	p.put(Context.INITIAL_CONTEXT_FACTORY,
	"org.apache.openejb.client.RemoteInitialContextFactory");
	p.put(Context.PROVIDER_URL, "multicast://239.255.2.3:6142?group=default");
	InitialContext remoteContext = new InitialContext(p);
	</code></pre>

	<p>The URL has optional query parameters such as <code>schemes</code> and <code>group</code> and
	<code>timeout</code> which allow you to zero in on a particular type of service of a
	particular cluster group as well as set how long you are willing to wait in
	the discovery process till finally giving up. The first matching service
	that it sees "flowing" around on the UDP stream is the one it picks and
	sticks to for that and subsequent requests, ensuring UDP is only used when
	there are no other servers to talk to.</p>

	<p>Note that EJB clients do not need to use multicast to find a server. If
	the client knows the URL of a server in the cluster, it may use it and
	connect directly to that server, at which point that server will share the
	full list of its peers.</p>

	<h1>Multicast Servers with TCP Clients</h1>

	<p>Note that clients do not need to use multicast to communicate with servers.
	Servers can use multicast to discover each other, but clients are still
	free to connect to servers in the network using the server's TCP address.</p>

	<pre><code>Properties p = new Properties();
	p.put(Context.INITIAL_CONTEXT_FACTORY, "org.apache.openejb.client.RemoteInitialContextFactory");
	p.put(Context.PROVIDER_URL, "ejbd://192.168.1.30:4201");
	InitialContext remoteContext = new InitialContext(p);
	</code></pre>

	<p>When the client connects, the server will send the URLs of all the servers
	in the group and failover will take place normally.</p>




	<div id="edit" class="modal hide fade in" style="display: none; ">
	<div class="modal-header">
	<a class="close" data-dismiss="modal">x</a>

	<h3>Thank you for contributing to the documentation!</h3>
	</div>
	<div class="modal-body">
	<h4>Any help with the documentation is greatly appreciated.</h4>
	<p>All edits are reviewed before going live, so feel free to do much more than fix typos or links. If you see a page that could benefit from an entire rewrite, we'd be thrilled to review it. Don't be surprised if we like it so much we ask you for help with other pages :)</p>
	<small>NOTICE: unless indicated otherwise on the pages in question, all editable content available from apache.org is presumed to be licensed under the Apache License (AL) version 2.0 and hence all submissions to apache.org treated as formal Contributions under the license terms.</small>
	<!--[if gt IE 6]>
	<h4>Internet Explorer Users</h4>
	<p>If you are not an Apache committer, click the Yes link and enter a <i>anonymous</i> for the username and leave the password empty</p>
	<![endif]-->

	</div>
	<div class="modal-footer">
	Do you have an Apache ID?
	<a href="javascript:void(location.href='https://cms.apache.org/redirect?uri='+escape(location.href))" class="btn">Yes</a>
	<a href="javascript:void(location.href='https://anonymous:@cms.apache.org/redirect?uri='+escape(location.href))" class="btn">No</a>
	</div>
	</div>
	<script src="./resources/js/bootstrap-modal.js"></script>

	<footer>
	<p>Copyright © 1999-2016 The Apache Software Foundation, Licensed under the Apache License, Version 2.0.
	Apache TomEE, TomEE, Apache, the Apache feather logo, and the Apache TomEE project logo are trademarks of The Apache Software Foundation.
	All other marks mentioned may be trademarks or registered trademarks of their respective owners.</p>
	</footer>

	</div> <!-- /container -->

	<!-- Javascript
	================================================== -->
	<!-- Placed at the end of the document so the pages load faster -->
	<script src="./resources/js/bootstrap-dropdown.js"></script>

	</body>
	</html>