apache2 - Tomcat 当前线程数

Question

Tomcat和appache2通过AJP连接。我对 tomcat 和 apache 有这些配置:

<Connector port="8009" protocol="AJP/1.3"
           URIEncoding="UTF-8"
           redirectPort="8443"
           connectionTimeout="20000"
           maxThreads="512" />


<IfModule mpm_event_module>
    StartServers          5
    MinSpareThreads      25
    MaxSpareThreads      75
    ThreadLimit          64
    ThreadsPerChild      25
    ServerLimit        1024
    MaxClients          512
    MaxRequestsPerChild   0
</IfModule>

当我转到 tomcat 管理器时，我看到:

"ajp-bio-8009"
Max threads: 512 Current thread count: 256 Current thread busy: 231

当前线程繁忙有时达到256。为什么当前线程数不设置为512？

Answer 1

当前线程由apache动态管理。

来自apache源代码中的worker.c:线程根据需要启动。以下是启动工作线程的主要流程。

static int worker_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s)
  startup_children(remaining_children_to_start);  //server/mpm/worker/worker.c
     if (make_child(ap_server_conf, i) < 0) {     //server/mpm/worker/worker.c
       child_main(slot);                          //server/mpm/worker/worker.c
         rv = apr_thread_create(&start_thread_id, thread_attr, start_threads
         rv = apr_thread_create(&threads[i], thread_attr, worker_thread, my_info, pchild);     

当空闲线程> max_spare_threads时，apache会尝试通过杀死子进程/线程来减少空闲线程，以减少空闲线程数。

if (idle_thread_count > max_spare_threads) {
    /* Kill off one child */
    ap_worker_pod_signal(pod, TRUE);
    retained->idle_spawn_rate = 1;
}

apache内部管理这些子进程，并使用信号与子进程通信以根据需要调整线程。所有线程均在 ap_scoreboard_image->servers[i][j];

中管理

apache将监视线程计数，并使用套接字发送出去让infoCollector知道。大致通过以下代码(无关行已删除)

./httpd/modules/cluster/mod_heartbeat.c
    for (i = 0; i < ctx->server_limit; i++) {
         ....
            for (j = 0; j < ctx->thread_limit; j++) {
                ws = &ap_scoreboard_image->servers[i][j];
                if (res == SERVER_READY && ps->generation == mpm_generation) {
                    ready++;
                }
            }
        }

    len = apr_snprintf(buf, sizeof(buf), "v=%u&ready=%u&busy=%u", MSG_VERSION, ready, busy);
    ...
    rv = apr_socket_sendto(sock, ctx->mcast_addr, 0, buf, &len);

在 Tomcat 中:这些线程信息由以下人员接收:./tomcat/java/org/apache/catalina/ha/backend/CollectedInfo.java并显示为:/Users/twer/lab/tomcat/java/org/apache/catalina/manager/StatusTransformer.java

writer.write(" currentThreadCount=\"" + mBeanServer.getAttribute(tpName, "currentThreadCount") + "\"");

这里显示的大部分代码都是主流程，无关的行被删除。下载源代码以了解更多信息。下载apache src:http://www.apache.org/dist/httpd/?C=S;O=A下载tomcat src:http://tomcat.apache.org/download-70.cgi