tomcat8.5

org/apache/tomcat/util/net/NioEndpoint.java

ServerSocketChannel serverSock = ServerSocketChannel.open();
socketProperties.setProperties(serverSock.socket());
InetSocketAddress addr = (getAddress()!=null?new InetSocketAddress(getAddress(),getPort()):new InetSocketAddress(getPort()));
serverSock.socket().bind(addr,getAcceptCount());
        
public void bind(SocketAddress endpoint, int backlog) throws IOException

backlog 
requested maximum length of the queue of incoming connections.

accept队列长度  默认 100
accept队列中连接的个数达到acceptCount时， 进来的请求会被拒绝


maxConnections

接收和处理的最大连接数 ，处理连接数达到maxConnections时，Acceptor线程不会读取accept队列中的连接 ，
这时会一直阻塞，直到处理的连接数小于maxConnections ，设置为-1，连接数不受限制。

默认值与协议有关
NIO 10000  
APR/native 8192
BIO 默认值为maxThreads（配置了Executor 为 Executor的maxThreads）

protected class Acceptor extends AbstractEndpoint.Acceptor {

state = AcceptorState.RUNNING;

                try {
                
                    //if we have reached max connections, wait
                    countUpOrAwaitConnection();

                    SocketChannel socket = null;
                    try {
                        // Accept the next incoming connection from the server
                        // socket
                        socket = serverSock.accept();
                    } catch (IOException ioe) {
                        // We didn't get a socket
                        countDownConnection();
                        if (running) {
                            // Introduce delay if necessary
                            errorDelay = handleExceptionWithDelay(errorDelay);
                            // re-throw
                            throw ioe;
                        } else {
                            break;
                        }
                    }
                    
                    
                    


 // if we have reached max connections, wait
 countUpOrAwaitConnection();
                    
 protected void countUpOrAwaitConnection() throws InterruptedException {
        if (maxConnections==-1) return;
        LimitLatch latch = connectionLimitLatch;
        if (latch!=null) latch.countUpOrAwait();
    }
    
connectionLimitLatch = new LimitLatch(getMaxConnections());



                   

maxThreads
请求处理最大线程数 ，默认值 200
如果Connector绑定了Executor ，则使用 Executor 的配置

可处理的连接数 maxConnections，可同时接收的连接数 maxConnections+acceptCount 
acceptCount 过大 请求等待时间会很长 ，过小  容易 返回 connection refused

线程池Executor


<Executor name="tomcatThreadPool" namePrefix ="catalina-exec-" maxThreads="150" minSpareThreads="4" />
<Connector executor="tomcatThreadPool" port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" acceptCount="1000" />



maxIdleTime 线程最大空闲时间  ms 默认 60000（1分钟）



org.apache.tomcat.util.threads.ThreadPoolExecutor

org.apache.catalina.core.StandardThreadExecutor

 taskqueue = new TaskQueue(maxQueueSize);
 TaskThreadFactory tf = new TaskThreadFactory(namePrefix,daemon,getThreadPriority());
 executor = new ThreadPoolExecutor(getMinSpareThreads(), getMaxThreads(), maxIdleTime, TimeUnit.MILLISECONDS,taskqueue, tf);
 executor.setThreadRenewalDelay(threadRenewalDelay);
        
        
        

NioEndpoint

    public void createExecutor() {
        internalExecutor = true;
        TaskQueue taskqueue = new TaskQueue();
        TaskThreadFactory tf = new TaskThreadFactory(getName() + "-exec-", daemon, getThreadPriority());
        executor = new ThreadPoolExecutor(getMinSpareThreads(), getMaxThreads(), 60, TimeUnit.SECONDS,taskqueue, tf);
        taskqueue.setParent( (ThreadPoolExecutor) executor);
    }