简单介绍tomcat中maxThreads，acceptCount，connectionTimeout

<?xml version='1.0' encoding='utf-8'?>
<Server port="8005" shutdown="SHUTDOWN">
  <Listener className="org.apache.catalina.startup.VersionLoggerListener" />
  <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
  <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html -->
  <Listener className="org.apache.catalina.core.JasperListener" />
  <!-- Prevent memory leaks due to use of particular java/javax APIs-->
  <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" />
  <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />
  <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" />

  <GlobalNamingResources>
    <Resource name="UserDatabase" auth="Container"
              type="org.apache.catalina.UserDatabase"
              description="User database that can be updated and saved"
              factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
              pathname="conf/tomcat-users.xml" />
  </GlobalNamingResources>

	<Service name="Catalina">
	<!--
    <Connector port="8080" protocol="HTTP/1.1"   connectionTimeout="20000"   redirectPort="8443" />-->

    <!-- Define an AJP 1.3 Connector on port 8080 -->
	<!-- maxThreads 请求处理线程的最大数量。默认值是200（Tomcat7和8都是的）。
	如果该Connector绑定了Executor，这个值会被忽略，因为该Connector将使用绑定的Executor，而不是内置的线程池来执行任务-->

	<!-- acceptCount accept队列的长度；当accept队列中连接的个数达到acceptCount时，队列满，进来的请求一律被拒绝。默认值是100-->

	<!-- connectionTimeout Tomcat在任意时刻接收和处理的最大连接数。当Tomcat接收的连接数达到maxConnections时，
	Acceptor线程不会读取accept队列中的连接；这时accept队列中的线程会一直阻塞着，
	直到Tomcat接收的连接数小于maxConnections。如果设置为-1，则连接数不受限制。-->
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" maxThreads="600" minSpareThreads="100" maxSpareThreads="500" acceptCount="700" connectionTimeout="20000"/>

    <Engine name="Catalina" defaultHost="localhost">

      <Realm className="org.apache.catalina.realm.LockOutRealm">
      <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/>
      </Realm>

      <Host name="localhost"  appBase="webapps" unpackWARs="true" autoDeploy="true">

        <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
               prefix="localhost_access_log." suffix=".txt"
               pattern="%h %l %u %t "%r" %s %b" />

      </Host>
    </Engine>
  </Service>
</Server>

　　

http://tomcat.apache.org/ 我们点击左侧导航栏中“Documentation”下的Tomcat 7.0，进入到这个链接中：http://tomcat.apache.org/tomcat-7.0-doc/index.html ，详细的信息我们不用都看，在左侧导航栏中有一个链接Configuration，我们点进去之后，再点击其左侧导航栏中connector一项的HTTP，就进入到HTTP连接数及其他相关属性的设置页面了。在这里（http://tomcat.apache.org/tomcat-7.0-doc/config/http.html）我们可以看到，在Connector的属性配置中，压根就没有maxProcessors等的设置选项。其中这句话已经介绍得很清楚：

If more simultaneous requests are received than can be handled by the currently available request processing threads, additional threads will be created up to the configured maximum (the value of the maxThreads attribute). If still more simultaneous requests are received, they are stacked up inside the server socket created by the Connector, up to the configured maximum (the value of the acceptCount attribute).

所以我们需要设置的是maxThreads和acceptCount这两个值：

其中，maxThreads的介绍如下：

The maximum number of request processing threads to be created by this Connector, which therefore determines the maximum number of simultaneous requests that can be handled. If not specified, this attribute is set to 200. If an executor is associated with this connector, this attribute is ignored as the connector will execute tasks using the executor rather than an internal thread pool.

而acceptCount的介绍为：

The maximum queue length for incoming connection requests when all possible request processing threads are in use. Any requests received when the queue is full will be refused. The default value is 100.