connectors/jk/xdocs/config/workers.xml - tomcat55 - Git at Google

 <?xml version="1.0"?>
 <!DOCTYPE document [
   <!ENTITY project SYSTEM "project.xml">
 ]>
 <document url="workers.html">

     &project;

     <properties>
         <author email="mturk@apache.org">Mladen Turk</author>
         <title>workers.properties configuration</title>
     </properties>

 <body>

 <section name="Introduction">
 <br/>
 <p>
 A <b>Tomcat worker</b> is a Tomcat instance that is waiting to execute servlets or any other content
 on behalf of some web server. For example, we can have a web server such as
 Apache forwarding servlet requests to a Tomcat process (the worker) running behind it.
 </p>
 <p>
 The scenario described above is a very simple one;
 in fact one can configure multiple Tomcat workers to serve servlets on
 behalf of a certain web server.
 The reasons for such configuration can be:
 </p>
 <ul>
 <li>
 We want different contexts to be served by different Tomcat workers to provide a
 development environment where all the developers share the same web server but
 own a Tomcat worker of their own.
 </li>
 <li>
 We want different virtual hosts served by different Tomcat processes to provide a
 clear separation between sites belonging to different companies.
 </li>
 <li>
 We want to provide load balancing, meaning run multiple Tomcat workers each on a
 machine of its own and distribute the requests between them.
 </li>
 </ul>

 <p>
 There are probably more reasons for having multiple workers but I guess that this list is enough...
 Tomcat workers are defined in a properties file dubbed <b>workers.properties</b> and this tutorial
 explains how to work with it.
 </p>
 </section>

 <section name="Directives">
 <br/>
 <p>Each workers.properties directive consists of three words separated by dot. The first word is always
 <b>worker</b>. The second word is the worker name that can be any name. The worker name reflects the
 name of the <b>jvmRoute</b> defined in Tomcat's server.xml configuration file.
 </p>
 <p>
 <warn>
 The name of the worker can contain only the alphanumeric characters <b>[a-z][A-Z][0-9]</b> and is case insensitive.
 </warn>
 </p>

 <subsection name="Defining workers">
 <br/>
 <p>The generic workers.properties directive is in the form:</p>
 <p><strong>worker.&lt;worker name&gt;.&lt;directive&gt;=&lt;value&gt;</strong></p>
 <p>Defining workers to the Tomcat web server plugin can be done using a properties file
 (a sample file named workers.properties is available in the conf/ directory).
 </p>
 <directives>
 <directive name="worker.list" default="ajp13" required="true">
 A comma separated list of workers names that the JK will use. When starting up,
 the web server plugin will instantiate the workers whose name appears in the
 worker.list property, these are also the workers to whom you can map requests.
 </directive>
 <directive name="worker.maintain" default="60" required="false">
 Worker connection pool maintain timeout in seconds. If set to the positive
 value JK will scan all connections for all workers specified in worker.list
 directive and check if connections needs to be recycled.
 <p>
 This feature has been added in <b>jk 1.2.13</b>.
 </p>
 </directive>
 </directives>
 </subsection>

 <subsection name="Mandatory directives">
 <br/>
 <p>Mandatory directives are the one that each worker <b>must</b> contain. Without them the worker will
 be unavailable or will misbehave.
 </p>
 <directives>
 <directive name="type" default="ajp13" required="true">
 Type of the worker (can be one of ajp13, ajp14, jni, lb or status). The type of the worker
 defines the directives that can be applied to the worker.
 <p>AJP13 worker is the preferred worker type that JK uses for communication
 between web server and Tomcat. This type of worker uses sockets as communication
 channel. For detailed description of the AJP13 protocol stack browse to
 <a href="../common/ajpv13a.html">AJPv13 protocol specification</a>
 </p>
 </directive>
 </directives>
 </subsection>

 <subsection name="Connection directives">
 <p>Connection directives defines the parameters needed to connect and maintain
 the connections pool of persistent connections between JK and remote Tomcat.
 </p>
 <directives>

 <directive name="host" default="localhost" required="false">
 Host name or IP address of the backend Tomcat instance. The remote Tomcat must
 support the ajp13 protocol stack. The host name can have a <b>port</b> number
 embedded separated by the colon (':') character.
 </directive>

 <directive name="port" default="8009" required="false">
 Port number of the remote Tomcat instance listening for defined protocol requests.
 The default value depends on the worker type. For AJP13 workers the default port is
 <b>8009</b>, while for AJP14 type of worker that value is <b>8011</b>.
 </directive>

 <directive name="socket_timeout" default="0" required="false">
 Socket timeout in seconds used for communication channel between JK and remote host.
 If remote host does not respond inside that timeout the JK will generate an error,
 and retry again. If set to value zero (default) the JK will wait for infinite
 on all socket operations.
 </directive>

 <directive name="socket_keepalive" default="False" required="false">
 This directive should be used when you have a firewall between your webserver
 and the Tomcat engine, who tend to drop inactive connections. This flag will told Operating System
 to send <code>KEEP_ALIVE</code> message on inactive connections (interval depend on global OS settings,
 generally 120ms), and thus prevent the firewall to cut the connection.
 To enable keepalive set this property value to the number greater then <b>0</b>.
 <p>
 The problem with Firewall cutting inactive connections is that sometimes, neither webserver or tomcat
 have information about the cut and couldn't handle it.
 </p>
 </directive>

 <directive name="recycle_timeout" default="0" required="false">
 The number of seconds that told webserver to cut an ajp13 connection after some time of
 inactivity. When choosing an endpoint for a request and the assigned socket is open, it will be
 closed if it was not used for the configured time.
 It's a good way to ensure that there won't too old threads living on Tomcat side,
 with the extra cost you need to reopen the socket next time a request be forwarded.
 This property is very similar to <b>cache_timeout</b> but works also in non-cache mode.
 If set to value zero (default) no recycle will took place.
 </directive>

 <directive name="retries" default="3" required="false">
 The number of retries that the worker will try in case of error returned from remote
 Tomcat. If the number of retries set is greater then three (the default value), on
 each retry after default an extra wait of 100ms will be inserted.
 </directive>

 <directive name="cachesize" default="1" required="false">
 Cachesize defines the number of connections made to the AJP backend that
 are maintained as a connection pool.
 It will limit the number of those connection that each web server child
 process can made.
 <p>
 Cachesize property is used only for multi threaded
 web servers such as Apache 2.0 (worker), IIS and Netscape. The cachesize property
 should reflect the number of threads per child process. JK will discover
 the number of threads per child process on Apache 2 web server with worker-mpm and set
 its default value to match the ThreadsPerChild Apache directive. For IIS the default
 value is 10. For other web servers this value has to be set manually.
 </p>
 <warn>Do not use cachesize with values higher then 1 on <b>Apache 2.x prefork</b> or <b>Apache 1.3.x</b>!</warn>
 </directive>

 <directive name="cache_timeout" default="0" required="false">
 Cache timeout property should be used with <b>cachesize</b> to specify how to time JK should keep
 an open socket in cache before closing it. This property should be used to reduce the number of threads
 on the Tomcat WebServer.
 <p>
 Each child could open an ajp13 connection if it have to forward a request to Tomcat, creating
 a new ajp13 thread on Tomcat side.
 </p>
 <p>
 The problem is that after an ajp13 connection is created, the child won't drop it
 until killed. And since the webserver will keep its childs/threads running
 to handle high-load, even it the child/thread handle only static contents, you could
 finish having many unused ajp13 threads on the Tomcat side.
 </p>.
 </directive>

 <directive name="lbfactor" default="1" required="false">
 Integer number used when the worker will be used inside load balancer worker,
 this is the load-balancing factor for the worker.
 The load-balancing factor is <i>how much we expect this worker to work</i>, or
 <i>the worker's work quota</i>. Load balancing factor is compared with other workers
 that makes the load balancer. For example if one worker has lb_factor 5 times higher then
 other worker, then it will receive five times more requests.
 </directive>

 </directives>
 </subsection>

 <subsection name="Load balancing directives">
 <br/>
 <p>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 it's worker type is <b>lb</b>.
 See worker's <b>type</b> directive. The workers that
 are member of load balancer must not appear in the <b>worker.list</b> directive.
 </p>
 <p>Loadbalancer directives defines the parameters needed to create a workers that are
 connecting to a remote cluster of backend Tomcat servers. Each cluster node has to
 have a worker defined.
 </p>
 <p>
 Load balancer 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 fall-backing 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 properties that the lb worker can accept:
 </p>

 <directives>
 <directive name="balance_workers" default="" required="true">
 A comma separated list of workers that the load balancer
 need to manage.
 <p>
 This directive replaces old <b>balanced_workers</b> directive and
 can be used only with mod_jk versions 1.2.7 and up.
 </p>
 <warn>These workers should <b>not</b> appear in the worker.list property!</warn>
 </directive>

 <directive name="sticky_session" default="True" required="false">
 Specifies whether requests with SESSION ID's should be routed back to the same
 Tomcat worker. If sticky_session is set to <b>True</b> or <b>1</b> sessions are sticky, otherwise
 sticky_session is set to <b>False</b>. Set sticky_session to <b>False</b> 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.
 </directive>

 <directive name="sticky_session_force" default="False" required="false">
 Specifies whether requests with SESSION ID's for workers that are in error state
 should be rejected. If sticky_session_force is set to <b>True</b> or <b>1</b>
 and the worker that matches that SESSION ID is in error state, client will
 recieve 500 (Server Error). If set to <b>False</b> or <b>0</b> failover on
 another worker will be issued with loosing client session. This directive is
 used only when you set <b>sticky_session=True</b>.
 <p>
 This feature has been added in <b>jk 1.2.9</b>.
 </p>
 </directive>

 <directive name="method" default="Request" required="false">
 Specifies what method load balancer is using for electing best worker.
 If method is set to <b>R[equest]</b> balancer will use number of requests
 to find the best worker. If set to <b>T[raffic]</b> balancer will use
 the network traffic between JK and Tomcat to find the best worker.
 <p>
 This feature has been added in <b>jk 1.2.9</b>.
 </p>
 </directive>

 <directive name="lock" default="Optimistic" required="false">
 Specifies what lock method the load balancer will use for synchronizing
 shared memory runtime data.
 If lock is set to <b>O[ptimistic]</b> balancer will not use shared memory lock
 to find the best worker. If set to <b>P[essimistic]</b> balancer will use
 shared memory lock. The balancer will work more accurately in case of
 Pessimistic locking, but can slow down the average response time.
 <p>
 This feature has been added in <b>jk 1.2.13</b>.
 </p>
 </directive>

 <directive name="secret" default="" required="false">
 Set a default secret word for all defined workers.
 See worker secret attribute description for more info.
 <p>
 This feature has been added in <b>jk 1.2.12</b>.
 </p>
 </directive>

 </directives>

 </subsection>

 <subsection name="Status Worker directives">
 <br />
 <p>
 The status worker does not communicate with Tomcat.
 Instead it is responsible for the load balancer management.
 </p>
 <directives>
 <directive name="css" default="" required="false">
 Specifies the url for cascading stylesheet to use.
 </directive>
 </directives>
 </subsection>

 <subsection name="Advanced worker directives">
 <br />
 <directives>
 <directive name="connect_timeout" default="0" required="false">
 Connect timeout property told webserver to send a PING request on ajp13 connection after
 connection is established. The parameter is the delay in milliseconds to wait for the PONG reply.
 <p>
 This features has been added in <b>jk 1.2.6</b> to avoid problem with hung tomcat's and require ajp13
 ping/pong support which has been implemented on Tomcat <b>3.3.2+, 4.1.28+ and 5.0.13+</b>.
 Disabled by default.
 </p>
 </directive>

 <directive name="prepost_timeout" default="0" required="false">
 Prepost timeout property told webserver to send a PING request on ajp13 connection before
 forwarding to it a request. The parameter is the delay in milliseconds to wait for the PONG reply.
 <p>
 This features has been added in <b>jk 1.2.6</b> to avoid problem with hung tomcat's and require ajp13
 ping/pong support which has been implemented on <b>Tomcat 3.3.2+, 4.1.28+ and 5.0.13+</b>.
 Disabled by default.
 </p>
 </directive>

 <directive name="reply_timeout" default="0" required="false">
 Reply_timeout property told webserver to wait some time for reply to a forwarded request
 before considering the remote tomcat is dead and eventually switch to another tomcat in a cluster
 group. By default webserver will wait forever which could be an issue for you.
 The parameter is the number of milliseconds to wait for reply, so adjust it carefully if you
 have long running servlets.
 <p>
 This features has been added in <b>jk 1.2.6</b> to avoid problem with hung tomcat's and works on all
 servlet engines supporting ajp13.
 Disabled by default.
 </p>
 </directive>

 <directive name="recovery_options" default="0" required="false">
 Recovery options property told webserver how to handle recovery when
 it detect that tomcat failed.
 By default, webserver will forward the request to another tomcat in LB mode
 (or to another ajp thread in ajp13 mode).
 values are : 0 (full recovery), 1 (don't recover if tomcat failed after getting the request),
 2 (don't recover if tomcat failed after sending the headers to client), 3 (don't recover if tomcat failed
 getting the request or after sending the headers to client).
 <p>
 This features has been added in <b>jk 1.2.6</b> to avoid problem with hung/broken tomcat's
 and works on all servlet engines supporting ajp13.
 Full recovery by default.
 </p>
 </directive>

 <directive name="domain" default="" required="false">
 Domain directive can be used only when the worker is a member of the load balancer.
 Workers that share the same domain name are treated as single worker. If sticky_session
 is used, then the domain name is used as session route.
 <p>This directive is used for large system with more then 6 Tomcats, to be able
 to cluster the Tomcats in two groups and thus lowering the session replication
 transfer between them.
 </p>
 <p>
 This feature has been added in <b>jk 1.2.8</b>.
 </p>
 </directive>

 <directive name="redirect" default="" required="false">
 Set to the preferred failover worker. If worker matching SESSION ID is in
 error state then the redirect worker will be used instead. It will be used
 even if being disabled, thus offering hot standby.
 <p>
 This feature has been added in <b>jk 1.2.9</b>.
 </p>
 </directive>

 <directive name="disabled" default="False" required="false">
 If set to <b>True</b> or <b>1</b> the worker will be disabled if member
 of load balancer. This flag can be changed at runtime using status worker.
 <p>
 This feature has been added in <b>jk 1.2.9</b>.
 </p>
 </directive>

 <directive name="stopped" default="False" required="false">
 If set to <b>True</b> or <b>1</b> the worker will be stopped if member
 of load balancer. The flag is needed for stop complete traffic of a sticky session
 worker. It is only usefull, when you have a cluster that replicated the sessions.
 This flag can be changed at runtime using status worker.
 <p>
 This feature has been added in <b>jk 1.2.11</b>.
 </p>
 </directive>

 <directive name="secret" default="" required="false">
 If set to AJP Connector secret keyword, only request with this keyword are successfull responding.
 Use <b>request.useSecret="true"</b> and <b>request.secret="secret key word"</b> at your tomcat ajp
 Connector configuration.
 </directive>

 </directives>
 </subsection>

 </section>

 </body>
 </document>
	<?xml version="1.0"?>
	<!DOCTYPE document [
	<!ENTITY project SYSTEM "project.xml">
	]>
	<document url="workers.html">

	&project;

	<properties>
	<author email="mturk@apache.org">Mladen Turk</author>
	<title>workers.properties configuration</title>
	</properties>

	<body>

	<section name="Introduction">
	<br/>
	<p>
	A <b>Tomcat worker</b> is a Tomcat instance that is waiting to execute servlets or any other content
	on behalf of some web server. For example, we can have a web server such as
	Apache forwarding servlet requests to a Tomcat process (the worker) running behind it.
	</p>
	<p>
	The scenario described above is a very simple one;
	in fact one can configure multiple Tomcat workers to serve servlets on
	behalf of a certain web server.
	The reasons for such configuration can be:
	</p>
	<ul>
	<li>
	We want different contexts to be served by different Tomcat workers to provide a
	development environment where all the developers share the same web server but
	own a Tomcat worker of their own.
	</li>
	<li>
	We want different virtual hosts served by different Tomcat processes to provide a
	clear separation between sites belonging to different companies.
	</li>
	<li>
	We want to provide load balancing, meaning run multiple Tomcat workers each on a
	machine of its own and distribute the requests between them.
	</li>
	</ul>

	<p>
	There are probably more reasons for having multiple workers but I guess that this list is enough...
	Tomcat workers are defined in a properties file dubbed <b>workers.properties</b> and this tutorial
	explains how to work with it.
	</p>
	</section>

	<section name="Directives">
	<br/>
	<p>Each workers.properties directive consists of three words separated by dot. The first word is always
	<b>worker</b>. The second word is the worker name that can be any name. The worker name reflects the
	name of the <b>jvmRoute</b> defined in Tomcat's server.xml configuration file.
	</p>
	<p>
	<warn>
	The name of the worker can contain only the alphanumeric characters <b>[a-z][A-Z][0-9]</b> and is case insensitive.
	</warn>
	</p>

	<subsection name="Defining workers">
	<br/>
	<p>The generic workers.properties directive is in the form:</p>
	<p><strong>worker.<worker name>.<directive>=<value></strong></p>
	<p>Defining workers to the Tomcat web server plugin can be done using a properties file
	(a sample file named workers.properties is available in the conf/ directory).
	</p>
	<directives>
	<directive name="worker.list" default="ajp13" required="true">
	A comma separated list of workers names that the JK will use. When starting up,
	the web server plugin will instantiate the workers whose name appears in the
	worker.list property, these are also the workers to whom you can map requests.
	</directive>
	<directive name="worker.maintain" default="60" required="false">
	Worker connection pool maintain timeout in seconds. If set to the positive
	value JK will scan all connections for all workers specified in worker.list
	directive and check if connections needs to be recycled.
	<p>
	This feature has been added in <b>jk 1.2.13</b>.
	</p>
	</directive>
	</directives>
	</subsection>

	<subsection name="Mandatory directives">
	<br/>
	<p>Mandatory directives are the one that each worker <b>must</b> contain. Without them the worker will
	be unavailable or will misbehave.
	</p>
	<directives>
	<directive name="type" default="ajp13" required="true">
	Type of the worker (can be one of ajp13, ajp14, jni, lb or status). The type of the worker
	defines the directives that can be applied to the worker.
	<p>AJP13 worker is the preferred worker type that JK uses for communication
	between web server and Tomcat. This type of worker uses sockets as communication
	channel. For detailed description of the AJP13 protocol stack browse to
	<a href="../common/ajpv13a.html">AJPv13 protocol specification</a>
	</p>
	</directive>
	</directives>
	</subsection>

	<subsection name="Connection directives">
	<p>Connection directives defines the parameters needed to connect and maintain
	the connections pool of persistent connections between JK and remote Tomcat.
	</p>
	<directives>

	<directive name="host" default="localhost" required="false">
	Host name or IP address of the backend Tomcat instance. The remote Tomcat must
	support the ajp13 protocol stack. The host name can have a <b>port</b> number
	embedded separated by the colon (':') character.
	</directive>

	<directive name="port" default="8009" required="false">
	Port number of the remote Tomcat instance listening for defined protocol requests.
	The default value depends on the worker type. For AJP13 workers the default port is
	<b>8009</b>, while for AJP14 type of worker that value is <b>8011</b>.
	</directive>

	<directive name="socket_timeout" default="0" required="false">
	Socket timeout in seconds used for communication channel between JK and remote host.
	If remote host does not respond inside that timeout the JK will generate an error,
	and retry again. If set to value zero (default) the JK will wait for infinite
	on all socket operations.
	</directive>

	<directive name="socket_keepalive" default="False" required="false">
	This directive should be used when you have a firewall between your webserver
	and the Tomcat engine, who tend to drop inactive connections. This flag will told Operating System
	to send <code>KEEP_ALIVE</code> message on inactive connections (interval depend on global OS settings,
	generally 120ms), and thus prevent the firewall to cut the connection.
	To enable keepalive set this property value to the number greater then <b>0</b>.
	<p>
	The problem with Firewall cutting inactive connections is that sometimes, neither webserver or tomcat
	have information about the cut and couldn't handle it.
	</p>
	</directive>

	<directive name="recycle_timeout" default="0" required="false">
	The number of seconds that told webserver to cut an ajp13 connection after some time of
	inactivity. When choosing an endpoint for a request and the assigned socket is open, it will be
	closed if it was not used for the configured time.
	It's a good way to ensure that there won't too old threads living on Tomcat side,
	with the extra cost you need to reopen the socket next time a request be forwarded.
	This property is very similar to <b>cache_timeout</b> but works also in non-cache mode.
	If set to value zero (default) no recycle will took place.
	</directive>

	<directive name="retries" default="3" required="false">
	The number of retries that the worker will try in case of error returned from remote
	Tomcat. If the number of retries set is greater then three (the default value), on
	each retry after default an extra wait of 100ms will be inserted.
	</directive>

	<directive name="cachesize" default="1" required="false">
	Cachesize defines the number of connections made to the AJP backend that
	are maintained as a connection pool.
	It will limit the number of those connection that each web server child
	process can made.
	<p>
	Cachesize property is used only for multi threaded
	web servers such as Apache 2.0 (worker), IIS and Netscape. The cachesize property
	should reflect the number of threads per child process. JK will discover
	the number of threads per child process on Apache 2 web server with worker-mpm and set
	its default value to match the ThreadsPerChild Apache directive. For IIS the default
	value is 10. For other web servers this value has to be set manually.
	</p>
	<warn>Do not use cachesize with values higher then 1 on <b>Apache 2.x prefork</b> or <b>Apache 1.3.x</b>!</warn>
	</directive>

	<directive name="cache_timeout" default="0" required="false">
	Cache timeout property should be used with <b>cachesize</b> to specify how to time JK should keep
	an open socket in cache before closing it. This property should be used to reduce the number of threads
	on the Tomcat WebServer.
	<p>
	Each child could open an ajp13 connection if it have to forward a request to Tomcat, creating
	a new ajp13 thread on Tomcat side.
	</p>
	<p>
	The problem is that after an ajp13 connection is created, the child won't drop it
	until killed. And since the webserver will keep its childs/threads running
	to handle high-load, even it the child/thread handle only static contents, you could
	finish having many unused ajp13 threads on the Tomcat side.
	</p>.
	</directive>

	<directive name="lbfactor" default="1" required="false">
	Integer number used when the worker will be used inside load balancer worker,
	this is the load-balancing factor for the worker.
	The load-balancing factor is <i>how much we expect this worker to work</i>, or
	<i>the worker's work quota</i>. Load balancing factor is compared with other workers
	that makes the load balancer. For example if one worker has lb_factor 5 times higher then
	other worker, then it will receive five times more requests.
	</directive>

	</directives>
	</subsection>

	<subsection name="Load balancing directives">
	<br/>
	<p>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 it's worker type is <b>lb</b>.
	See worker's <b>type</b> directive. The workers that
	are member of load balancer must not appear in the <b>worker.list</b> directive.
	</p>
	<p>Loadbalancer directives defines the parameters needed to create a workers that are
	connecting to a remote cluster of backend Tomcat servers. Each cluster node has to
	have a worker defined.
	</p>
	<p>
	Load balancer 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 fall-backing 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 properties that the lb worker can accept:
	</p>

	<directives>
	<directive name="balance_workers" default="" required="true">
	A comma separated list of workers that the load balancer
	need to manage.
	<p>
	This directive replaces old <b>balanced_workers</b> directive and
	can be used only with mod_jk versions 1.2.7 and up.
	</p>
	<warn>These workers should <b>not</b> appear in the worker.list property!</warn>
	</directive>

	<directive name="sticky_session" default="True" required="false">
	Specifies whether requests with SESSION ID's should be routed back to the same
	Tomcat worker. If sticky_session is set to <b>True</b> or <b>1</b> sessions are sticky, otherwise
	sticky_session is set to <b>False</b>. Set sticky_session to <b>False</b> 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.
	</directive>

	<directive name="sticky_session_force" default="False" required="false">
	Specifies whether requests with SESSION ID's for workers that are in error state
	should be rejected. If sticky_session_force is set to <b>True</b> or <b>1</b>
	and the worker that matches that SESSION ID is in error state, client will
	recieve 500 (Server Error). If set to <b>False</b> or <b>0</b> failover on
	another worker will be issued with loosing client session. This directive is
	used only when you set <b>sticky_session=True</b>.
	<p>
	This feature has been added in <b>jk 1.2.9</b>.
	</p>
	</directive>

	<directive name="method" default="Request" required="false">
	Specifies what method load balancer is using for electing best worker.
	If method is set to <b>R[equest]</b> balancer will use number of requests
	to find the best worker. If set to <b>T[raffic]</b> balancer will use
	the network traffic between JK and Tomcat to find the best worker.
	<p>
	This feature has been added in <b>jk 1.2.9</b>.
	</p>
	</directive>

	<directive name="lock" default="Optimistic" required="false">
	Specifies what lock method the load balancer will use for synchronizing
	shared memory runtime data.
	If lock is set to <b>O[ptimistic]</b> balancer will not use shared memory lock
	to find the best worker. If set to <b>P[essimistic]</b> balancer will use
	shared memory lock. The balancer will work more accurately in case of
	Pessimistic locking, but can slow down the average response time.
	<p>
	This feature has been added in <b>jk 1.2.13</b>.
	</p>
	</directive>

	<directive name="secret" default="" required="false">
	Set a default secret word for all defined workers.
	See worker secret attribute description for more info.
	<p>
	This feature has been added in <b>jk 1.2.12</b>.
	</p>
	</directive>

	</directives>

	</subsection>

	<subsection name="Status Worker directives">
	<br />
	<p>
	The status worker does not communicate with Tomcat.
	Instead it is responsible for the load balancer management.
	</p>
	<directives>
	<directive name="css" default="" required="false">
	Specifies the url for cascading stylesheet to use.
	</directive>
	</directives>
	</subsection>

	<subsection name="Advanced worker directives">
	<br />
	<directives>
	<directive name="connect_timeout" default="0" required="false">
	Connect timeout property told webserver to send a PING request on ajp13 connection after
	connection is established. The parameter is the delay in milliseconds to wait for the PONG reply.
	<p>
	This features has been added in <b>jk 1.2.6</b> to avoid problem with hung tomcat's and require ajp13
	ping/pong support which has been implemented on Tomcat <b>3.3.2+, 4.1.28+ and 5.0.13+</b>.
	Disabled by default.
	</p>
	</directive>

	<directive name="prepost_timeout" default="0" required="false">
	Prepost timeout property told webserver to send a PING request on ajp13 connection before
	forwarding to it a request. The parameter is the delay in milliseconds to wait for the PONG reply.
	<p>
	This features has been added in <b>jk 1.2.6</b> to avoid problem with hung tomcat's and require ajp13
	ping/pong support which has been implemented on <b>Tomcat 3.3.2+, 4.1.28+ and 5.0.13+</b>.
	Disabled by default.
	</p>
	</directive>

	<directive name="reply_timeout" default="0" required="false">
	Reply_timeout property told webserver to wait some time for reply to a forwarded request
	before considering the remote tomcat is dead and eventually switch to another tomcat in a cluster
	group. By default webserver will wait forever which could be an issue for you.
	The parameter is the number of milliseconds to wait for reply, so adjust it carefully if you
	have long running servlets.
	<p>
	This features has been added in <b>jk 1.2.6</b> to avoid problem with hung tomcat's and works on all
	servlet engines supporting ajp13.
	Disabled by default.
	</p>
	</directive>

	<directive name="recovery_options" default="0" required="false">
	Recovery options property told webserver how to handle recovery when
	it detect that tomcat failed.
	By default, webserver will forward the request to another tomcat in LB mode
	(or to another ajp thread in ajp13 mode).
	values are : 0 (full recovery), 1 (don't recover if tomcat failed after getting the request),
	2 (don't recover if tomcat failed after sending the headers to client), 3 (don't recover if tomcat failed
	getting the request or after sending the headers to client).
	<p>
	This features has been added in <b>jk 1.2.6</b> to avoid problem with hung/broken tomcat's
	and works on all servlet engines supporting ajp13.
	Full recovery by default.
	</p>
	</directive>

	<directive name="domain" default="" required="false">
	Domain directive can be used only when the worker is a member of the load balancer.
	Workers that share the same domain name are treated as single worker. If sticky_session
	is used, then the domain name is used as session route.
	<p>This directive is used for large system with more then 6 Tomcats, to be able
	to cluster the Tomcats in two groups and thus lowering the session replication
	transfer between them.
	</p>
	<p>
	This feature has been added in <b>jk 1.2.8</b>.
	</p>
	</directive>

	<directive name="redirect" default="" required="false">
	Set to the preferred failover worker. If worker matching SESSION ID is in
	error state then the redirect worker will be used instead. It will be used
	even if being disabled, thus offering hot standby.
	<p>
	This feature has been added in <b>jk 1.2.9</b>.
	</p>
	</directive>

	<directive name="disabled" default="False" required="false">
	If set to <b>True</b> or <b>1</b> the worker will be disabled if member
	of load balancer. This flag can be changed at runtime using status worker.
	<p>
	This feature has been added in <b>jk 1.2.9</b>.
	</p>
	</directive>

	<directive name="stopped" default="False" required="false">
	If set to <b>True</b> or <b>1</b> the worker will be stopped if member
	of load balancer. The flag is needed for stop complete traffic of a sticky session
	worker. It is only usefull, when you have a cluster that replicated the sessions.
	This flag can be changed at runtime using status worker.
	<p>
	This feature has been added in <b>jk 1.2.11</b>.
	</p>
	</directive>

	<directive name="secret" default="" required="false">
	If set to AJP Connector secret keyword, only request with this keyword are successfull responding.
	Use <b>request.useSecret="true"</b> and <b>request.secret="secret key word"</b> at your tomcat ajp
	Connector configuration.
	</directive>

	</directives>
	</subsection>

	</section>

	</body>
	</document>