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| <!DOCTYPE document [ |
| <!ENTITY project SYSTEM "project.xml"> |
| ]> |
| <document url="engine.html"> |
| |
| &project; |
| |
| <properties> |
| <author email="craigmcc@apache.org">Craig R. McClanahan</author> |
| <title>The Engine Container</title> |
| </properties> |
| |
| <body> |
| |
| <section name="Table of Contents"> |
| <toc/> |
| </section> |
| |
| <section name="Introduction"> |
| |
| <p>The <strong>Engine</strong> element represents the entire request |
| processing machinery associated with a particular Catalina |
| <a href="service.html">Service</a>. It receives and processes |
| <em>all</em> requests from one or more <strong>Connectors</strong>, |
| and returns the completed response to the Connector for ultimate |
| transmission back to the client.</p> |
| |
| <p>Exactly one <strong>Engine</strong> element MUST be nested inside |
| a <a href="service.html">Service</a> element, following all of the |
| corresponding Connector elements associated with this Service.</p> |
| |
| </section> |
| |
| |
| <section name="Attributes"> |
| |
| <subsection name="Common Attributes"> |
| |
| <p>All implementations of <strong>Engine</strong> |
| support the following attributes:</p> |
| |
| <attributes> |
| |
| <attribute name="backgroundProcessorDelay" required="false"> |
| <p>This value represents the delay in seconds between the |
| invocation of the backgroundProcess method on this engine and |
| its child containers, including all hosts and contexts. |
| Child containers will not be invoked if their delay value is not |
| negative (which would mean they are using their own processing |
| thread). Setting this to a positive value will cause |
| a thread to be spawn. After waiting the specified amount of time, |
| the thread will invoke the backgroundProcess method on this engine |
| and all its child containers. If not specified, the default value for |
| this attribute is 10, which represent a 10 seconds delay.</p> |
| </attribute> |
| |
| <attribute name="className" required="false"> |
| <p>Java class name of the implementation to use. This class must |
| implement the <code>org.apache.catalina.Engine</code> interface. |
| If not specified, the standard value (defined below) will be used.</p> |
| </attribute> |
| |
| <attribute name="defaultHost" required="true"> |
| <p>The default host name, which identifies the |
| <a href="host.html">Host</a> that will process requests directed |
| to host names on this server, but which are not configured in |
| this configuration file. This name MUST match the <code>name</code> |
| attributes of one of the <a href="host.html">Host</a> elements |
| nested immediately inside.</p> |
| </attribute> |
| |
| <attribute name="jvmRoute" required="false"> |
| <p>Identifier which must be used in load balancing scenarios to enable |
| session affinity. The identifier, which must be unique across all |
| Tomcat servers which participate in the cluster, will be appended to |
| the generated session identifier, therefore allowing the front end |
| proxy to always forward a particular session to the same Tomcat |
| instance.</p> |
| <p> |
| Note that the <code>jvmRoute</code> can also be set using the |
| <code>jvmRoute</code> system property. The <code>jvmRoute</code> |
| set in an <code><Engine></code> attribute will override |
| any <code>jvmRoute</code> system property. |
| </p> |
| </attribute> |
| |
| <attribute name="name" required="true"> |
| <p>Logical name of this Engine, used in log and error messages. <em>When |
| using multiple <a href="service.html">Service</a> elements in the same |
| <a href="server.html">Server</a>, each Engine MUST be assigned a unique |
| name.</em></p> |
| </attribute> |
| |
| <attribute name="startStopThreads" required="false"> |
| <p>The number of threads this <strong>Engine</strong> will use to start |
| child <a href="host.html">Host</a> elements in parallel. The special |
| value of 0 will result in the value of |
| <code>Runtime.getRuntime().availableProcessors()</code> being used. |
| Negative values will result in |
| <code>Runtime.getRuntime().availableProcessors() + value</code> being |
| used unless this is less than 1 in which case 1 thread will be used. If |
| not specified, the default value of 1 will be used. </p> |
| </attribute> |
| |
| </attributes> |
| |
| </subsection> |
| |
| |
| <subsection name="Standard Implementation"> |
| |
| <p>The standard implementation of <strong>Engine</strong> is |
| <strong>org.apache.catalina.core.StandardEngine</strong>. |
| It supports the following additional attributes (in addition to the |
| common attributes listed above):</p> |
| |
| <attributes> |
| |
| </attributes> |
| |
| </subsection> |
| |
| |
| </section> |
| |
| |
| <section name="Nested Components"> |
| |
| <p>You can nest one or more <a href="host.html">Host</a> elements inside |
| this <strong>Engine</strong> element, each representing a different virtual |
| host associated with this server. At least one <a href="host.html">Host</a> |
| is required, and one of the nested <a href="host.html">Hosts</a> MUST |
| have a name that matches the name specified for the |
| <code>defaultHost</code> attribute, listed above.</p> |
| |
| <p>You can nest at most one instance of the following utility components |
| by nesting a corresponding element inside your <strong>Engine</strong> |
| element:</p> |
| <ul> |
| <li><a href="realm.html"><strong>Realm</strong></a> - |
| Configure a realm that will allow its |
| database of users, and their associated roles, to be shared across all |
| <a href="host.html">Hosts</a> and <a href="context.html">Contexts</a> |
| nested inside this Engine, unless overridden by a |
| <a href="realm.html">Realm</a> configuration at a lower level.</li> |
| </ul> |
| |
| </section> |
| |
| |
| <section name="Special Features"> |
| |
| |
| <subsection name="Logging"> |
| |
| <p>An engine is associated with the |
| <code>org.apache.catalina.core.ContainerBase.[enginename]</code> |
| log category. Note that the brackets are actually part of the name, |
| don't omit them.</p> |
| |
| </subsection> |
| |
| |
| <subsection name="Access Logs"> |
| |
| <p>When you run a web server, one of the output files normally generated |
| is an <em>access log</em>, which generates one line of information for |
| each request processed by the server, in a standard format. Catalina |
| includes an optional <a href="valve.html">Valve</a> implementation that |
| can create access logs in the same standard format created by web servers, |
| or in any number of custom formats.</p> |
| |
| <p>You can ask Catalina to create an access log for all requests |
| processed by an <a href="engine.html">Engine</a>, |
| <a href="host.html">Host</a>, or <a href="context.html">Context</a> |
| by nesting a <a href="valve.html">Valve</a> element like this:</p> |
| |
| <source><![CDATA[<Engine name="Standalone" ...> |
| ... |
| <Valve className="org.apache.catalina.valves.AccessLogValve" |
| prefix="catalina_access_log." suffix=".txt" |
| pattern="common"/> |
| ... |
| </Engine>]]></source> |
| |
| <p>See <a href="valve.html#Access_Logging">Access Logging Valves</a> |
| for more information on the configuration attributes that are |
| supported.</p> |
| |
| </subsection> |
| |
| |
| <subsection name="Lifecycle Listeners"> |
| |
| <p>If you have implemented a Java object that needs to know when this |
| <strong>Engine</strong> is started or stopped, you can declare it by |
| nesting a <strong>Listener</strong> element inside this element. The |
| class name you specify must implement the |
| <code>org.apache.catalina.LifecycleListener</code> interface, and |
| it will be notified about the occurrence of the corresponding |
| lifecycle events. Configuration of such a listener looks like this:</p> |
| |
| <source><![CDATA[<Engine name="Standalone" ...> |
| ... |
| <Listener className="com.mycompany.mypackage.MyListener" ... > |
| ... |
| </Engine>]]></source> |
| |
| <p>Note that a Listener can have any number of additional properties |
| that may be configured from this element. Attribute names are matched |
| to corresponding JavaBean property names using the standard property |
| method naming patterns.</p> |
| |
| </subsection> |
| |
| |
| <subsection name="Request Filters"> |
| |
| <p>You can ask Catalina to check the IP address, or host name, on every |
| incoming request directed to the surrounding |
| <a href="engine.html">Engine</a>, <a href="host.html">Host</a>, or |
| <a href="context.html">Context</a> element. The remote address or name |
| will be checked against configured "accept" and/or "deny" |
| filters, which are defined using <code>java.util.regex</code> Regular |
| Expression syntax. Requests that come from locations that are |
| not accepted will be rejected with an HTTP "Forbidden" error. |
| Example filter declarations:</p> |
| |
| <source><![CDATA[<Engine name="Standalone" ...> |
| ... |
| <Valve className="org.apache.catalina.valves.RemoteHostValve" |
| allow=".*\.mycompany\.com|www\.yourcompany\.com"/> |
| <Valve className="org.apache.catalina.valves.RemoteAddrValve" |
| deny="192\.168\.1\.\d+"/> |
| ... |
| </Engine>]]></source> |
| |
| <p>See <a href="valve.html#Remote_Address_Filter">Remote Address Filter</a> |
| and <a href="valve.html#Remote_Host_Filter">Remote Host Filter</a> for |
| more information about the configuration options that are supported.</p> |
| |
| </subsection> |
| |
| |
| </section> |
| |
| |
| </body> |
| |
| |
| </document> |