connectors/jk/xdocs/generic_howto/loadbalancers.xml - tomcat55 - Git at Google

 <?xml version="1.0" encoding="ISO-8859-1"?>
 <!DOCTYPE document [
   <!ENTITY project SYSTEM "project.xml">
 ]>
 <document url="loadbalancers.html">

   &project;
 <copyright>
    Licensed to the Apache Software Foundation (ASF) under one or more
    contributor license agreements.  See the NOTICE file distributed with
    this work for additional information regarding copyright ownership.
    The ASF licenses this file to You under the Apache License, Version 2.0
    (the "License"); you may not use this file except in compliance with
    the License.  You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
 </copyright>
 <properties>
 <title>LoadBalancer HowTo</title>
 <author email="mturk@apache.org">Mladen Tur</author>
 <date>$Date$</date>
 </properties>
 <body>
 <section name="Introduction">
 <br/>
 <p>A Load balancer is a virtual worker that does not really communicate with Tomcat workers.
 Instead it is responsible for the management of several "real" workers.
 The worker is supposed to be a load balancer if its worker type is <b>lb</b>.
 See workers <b>type</b> directive. For a complete reference of all load balancer configuration
 items, please consult the worker <a href="../reference/workers.html">reference</a>.
 The comprehensive status management features of the load balancer together with the status worker,
 makes its use an interesting option, even if only combined with a single "real" worker.
 <warn>The workers that are member of load balancer do not need to appear in the
 <b>worker.list</b> directive.</warn>
 </p>

 <subsection name="lb Worker properties">
 <p>
 The load-balancing worker does not really communicate with Tomcat workers.
 Instead it is responsible for the management of several "real" workers.
 This management includes:
 </p>

 <ul>
 <li>
 Instantiating the workers in the web server.
 </li>
 <li>
 Using the worker's load-balancing factor, perform weighed-round-robin load balancing where
 high lbfactor means stronger machine (that is going to handle more requests)
 </li>
 <li>
 Keeping requests belonging to the same session executing on the same Tomcat worker.
 </li>
 <li>
 Identifying failed Tomcat workers, suspending requests to them and instead falling-back on
 other workers managed by the lb worker.
 </li>
 </ul>

 <p>
 The overall result is that workers managed by the same lb worker are load-balanced (based on their lbfactor and current user session) and also fall-backed so a single Tomcat process death will not "kill" the entire site.
 The following table specifies some properties that the lb worker can accept:
 <ul>
 <li><b>balance_workers</b> is a comma separated list of workers that the load balancer need to manage.
 These workers do not need to appear in the worker.list property. This directive can be used multiple times for the same load balancer.</li>
 <li><b>sticky_session</b> specifies whether requests with SESSION ID's should be routed back to the same
 Tomcat worker. You can set sticky_session to False when Tomcat is using a Session Manager which
 can persist session data across multiple instances of Tomcat. By default sticky_session is set to True.</li>
 </ul>
 </p>

 <source>
   # The worker balance1 while use "real" workers worker1 and worker2
   worker.balance1.balance_workers=worker1, worker2
 </source>

 </subsection>

 <subsection name="Advanced lb Worker properties">
 <p>
 With JK 1.2.x, new load-balancing and fault-tolerant support has been added via
 2 new properties, <b>redirect</b> and <b>activation</b>.
 </p>

 <p>
 Let's take an example environment:
 </p>

 <p>
 A cluster with two nodes (worker1+worker2), running a webserver + tomcat tandem on each node and
 a loadbalancer in front of the nodes.
 </p>

 <source>
   # The advanced router LB worker
   worker.list=router

   # Define a worker using ajp13
   worker.worker1.port=8009
   worker.worker1.host=node1.domain.org
   worker.worker1.type=ajp13
   worker.worker1.lbfactor=1
   # Define prefered failover node for worker1
   worker.worker1.redirect=worker2

   # Define another worker using ajp13
   worker.worker2.port=8009
   worker.worker2.host=node2.domain.org
   worker.worker2.type=ajp13
   worker.worker2.lbfactor=1
   # Disable worker2 for all requests except failover
   worker.worker2.activation=disabled

   # Define the LB worker
   worker.router.type=lb
   worker.router.balance_workers=worker1,worker2
 </source>

 <p>
 The <b>redirect</b> flag on worker1 tells the <b>lb_worker</b> to redirect the requests
 to worker2 only if worker1 is in error state. In other cases worker2 will not receive
 any requests, thus acting like a hot standby.
 </p>


 </subsection>

 <subsection name="Status Worker properties">
 <p>
 The status worker does not communicate with Tomcat.
 Instead it is responsible for the load balancer management.
 </p>
 <source>
   # Add the status worker to the worker list
   worker.list=jkstatus
   # Define a 'jkstatus' worker using status
   worker.jkstatus.type=status
 </source>
 <p>Next thing is to mount the requests to the jkstatus worker. For Apache
 web servers use the:</p>
 <source>
   # Add the jkstatus mount point
   JkMount /jkmanager/* jkstatus
 </source>
 <p>To obtain a higher level of security use the:</p>
 <source>
   # Enable the JK manager access from localhost only
  &lt;Location /jkmanager/&gt;
     JkMount jkstatus
     Order deny,allow
     Deny from all
     Allow from 127.0.0.1
  &lt;/Location&gt;
 </source>

 </subsection>

 </section>

 </body>
 </document>
	<?xml version="1.0" encoding="ISO-8859-1"?>
	<!DOCTYPE document [
	<!ENTITY project SYSTEM "project.xml">
	]>
	<document url="loadbalancers.html">

	&project;
	<copyright>
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	</copyright>
	<properties>
	<title>LoadBalancer HowTo</title>
	<author email="mturk@apache.org">Mladen Tur</author>
	<date>$Date$</date>
	</properties>
	<body>
	<section name="Introduction">
	<br/>
	<p>A Load balancer is a virtual worker that does not really communicate with Tomcat workers.
	Instead it is responsible for the management of several "real" workers.
	The worker is supposed to be a load balancer if its worker type is <b>lb</b>.
	See workers <b>type</b> directive. For a complete reference of all load balancer configuration
	items, please consult the worker <a href="../reference/workers.html">reference</a>.
	The comprehensive status management features of the load balancer together with the status worker,
	makes its use an interesting option, even if only combined with a single "real" worker.
	<warn>The workers that are member of load balancer do not need to appear in the
	<b>worker.list</b> directive.</warn>
	</p>

	<subsection name="lb Worker properties">
	<p>
	The load-balancing worker does not really communicate with Tomcat workers.
	Instead it is responsible for the management of several "real" workers.
	This management includes:
	</p>

	<ul>
	<li>
	Instantiating the workers in the web server.
	</li>
	<li>
	Using the worker's load-balancing factor, perform weighed-round-robin load balancing where
	high lbfactor means stronger machine (that is going to handle more requests)
	</li>
	<li>
	Keeping requests belonging to the same session executing on the same Tomcat worker.
	</li>
	<li>
	Identifying failed Tomcat workers, suspending requests to them and instead falling-back on
	other workers managed by the lb worker.
	</li>
	</ul>

	<p>
	The overall result is that workers managed by the same lb worker are load-balanced (based on their lbfactor and current user session) and also fall-backed so a single Tomcat process death will not "kill" the entire site.
	The following table specifies some properties that the lb worker can accept:
	<ul>
	<li><b>balance_workers</b> is a comma separated list of workers that the load balancer need to manage.
	These workers do not need to appear in the worker.list property. This directive can be used multiple times for the same load balancer.</li>
	<li><b>sticky_session</b> specifies whether requests with SESSION ID's should be routed back to the same
	Tomcat worker. You can set sticky_session to False when Tomcat is using a Session Manager which
	can persist session data across multiple instances of Tomcat. By default sticky_session is set to True.</li>
	</ul>
	</p>

	<source>
	# The worker balance1 while use "real" workers worker1 and worker2
	worker.balance1.balance_workers=worker1, worker2
	</source>

	</subsection>

	<subsection name="Advanced lb Worker properties">
	<p>
	With JK 1.2.x, new load-balancing and fault-tolerant support has been added via
	2 new properties, <b>redirect</b> and <b>activation</b>.
	</p>

	<p>
	Let's take an example environment:
	</p>

	<p>
	A cluster with two nodes (worker1+worker2), running a webserver + tomcat tandem on each node and
	a loadbalancer in front of the nodes.
	</p>

	<source>
	# The advanced router LB worker
	worker.list=router

	# Define a worker using ajp13
	worker.worker1.port=8009
	worker.worker1.host=node1.domain.org
	worker.worker1.type=ajp13
	worker.worker1.lbfactor=1
	# Define prefered failover node for worker1
	worker.worker1.redirect=worker2

	# Define another worker using ajp13
	worker.worker2.port=8009
	worker.worker2.host=node2.domain.org
	worker.worker2.type=ajp13
	worker.worker2.lbfactor=1
	# Disable worker2 for all requests except failover
	worker.worker2.activation=disabled

	# Define the LB worker
	worker.router.type=lb
	worker.router.balance_workers=worker1,worker2
	</source>

	<p>
	The <b>redirect</b> flag on worker1 tells the <b>lb_worker</b> to redirect the requests
	to worker2 only if worker1 is in error state. In other cases worker2 will not receive
	any requests, thus acting like a hot standby.
	</p>


	</subsection>

	<subsection name="Status Worker properties">
	<p>
	The status worker does not communicate with Tomcat.
	Instead it is responsible for the load balancer management.
	</p>
	<source>
	# Add the status worker to the worker list
	worker.list=jkstatus
	# Define a 'jkstatus' worker using status
	worker.jkstatus.type=status
	</source>
	<p>Next thing is to mount the requests to the jkstatus worker. For Apache
	web servers use the:</p>
	<source>
	# Add the jkstatus mount point
	JkMount /jkmanager/* jkstatus
	</source>
	<p>To obtain a higher level of security use the:</p>
	<source>
	# Enable the JK manager access from localhost only
	<Location /jkmanager/>
	JkMount jkstatus
	Order deny,allow
	Deny from all
	Allow from 127.0.0.1
	</Location>
	</source>

	</subsection>

	</section>

	</body>
	</document>