tomcat HTTP处理—— Request的生命历程和相应Connector配置解析

gmdzxx

　　Request的生命历程，可以参见常量类org.apache.coyote.Constants.java

    // Request states
public static final int STAGE_NEW = 0;
public static final int STAGE_PARSE = 1;
public static final int STAGE_PREPARE = 2;
public static final int STAGE_SERVICE = 3;
public static final int STAGE_ENDINPUT = 4;
public static final int STAGE_ENDOUTPUT = 5;
public static final int STAGE_KEEPALIVE = 6;
public static final int STAGE_ENDED = 7;
　　和用到这些常量的地方 Http11Processor.java (代码贴的比较多，可以用浏览器的 查找功能来查找上面的常量)

while (started && !error && keepAlive && !endpoint.isPaused()) {
// Parsing the request header
try {
if (keptAlive) {
if (keepAliveTimeout > 0) {
socket.setSoTimeout(keepAliveTimeout);
}
else if (soTimeout > 0) {
socket.setSoTimeout(soTimeout);
}
}
inputBuffer.parseRequestLine();
request.setStartTime(System.currentTimeMillis());
keptAlive = true;
if (disableUploadTimeout) {
socket.setSoTimeout(soTimeout);
} else {
socket.setSoTimeout(timeout);
}
inputBuffer.parseHeaders();
} catch (IOException e) {
error = true;
break;
} catch (Throwable t) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("http11processor.header.parse"), t);
}
// 400 - Bad Request
response.setStatus(400);
adapter.log(request, response, 0);
error = true;
}
if (!error) {
// Setting up filters, and parse some request headers
rp.setStage(org.apache.coyote.Constants.STAGE_PREPARE);
try {
prepareRequest();
} catch (Throwable t) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("http11processor.request.prepare"), t);
}
// 400 - Internal Server Error
response.setStatus(400);
adapter.log(request, response, 0);
error = true;
}
}
if (maxKeepAliveRequests > 0 && --keepAliveLeft == 0)
keepAlive = false;
// Process the request in the adapter
if (!error) {
try {
rp.setStage(org.apache.coyote.Constants.STAGE_SERVICE);
adapter.service(request, response);
// Handle when the response was committed before a serious
// error occurred.  Throwing a ServletException should both
// set the status to 500 and set the errorException.
// If we fail here, then the response is likely already
// committed, so we can't try and set headers.
if(keepAlive && !error) { // Avoid checking twice.
error = response.getErrorException() != null ||
statusDropsConnection(response.getStatus());
}
} catch (InterruptedIOException e) {
error = true;
} catch (Throwable t) {
log.error(sm.getString("http11processor.request.process"), t);
// 500 - Internal Server Error
response.setStatus(500);
adapter.log(request, response, 0);
error = true;
}
}
// Finish the handling of the request
try {
rp.setStage(org.apache.coyote.Constants.STAGE_ENDINPUT);
// If we know we are closing the connection, don't drain input.
// This way uploading a 100GB file doesn't tie up the thread
// if the servlet has rejected it.
if(error)
inputBuffer.setSwallowInput(false);
inputBuffer.endRequest();
} catch (IOException e) {
error = true;
} catch (Throwable t) {
log.error(sm.getString("http11processor.request.finish"), t);
// 500 - Internal Server Error
response.setStatus(500);
adapter.log(request, response, 0);
error = true;
}
try {
rp.setStage(org.apache.coyote.Constants.STAGE_ENDOUTPUT);
outputBuffer.endRequest();
} catch (IOException e) {
error = true;
} catch (Throwable t) {
log.error(sm.getString("http11processor.response.finish"), t);
error = true;
}
// If there was an error, make sure the request is counted as
// and error, and update the statistics counter
if (error) {
response.setStatus(500);
}
request.updateCounters();
rp.setStage(org.apache.coyote.Constants.STAGE_KEEPALIVE);
// Don't reset the param - we'll see it as ended. Next request
// will reset it
// thrA.setParam(null);
// Next request
inputBuffer.nextRequest();
outputBuffer.nextRequest();
}
rp.setStage(org.apache.coyote.Constants.STAGE_ENDED);
// Recycle
inputBuffer.recycle();
outputBuffer.recycle();
this.socket = null;
// Recycle ssl info
sslSupport = null;
}
　　Connector配置解析：
　　官方文档：
　　http://tomcat.apache.org/tomcat-6.0-doc/config/http.html
　　文档中讲了比较多的选项的用法，其中，我把比较重要的几个列举下：
　　maxKeepAliveRequests
　　在服务器关闭socket连接之前，能保持的最大请求数。
　　maxThreads
　　服务器的最大线程数。讲白了就是Worker的最大数目，当然如果配置开启了Executor的话，这个配置项便是没有用的。
　　这里你会不会有疑问，线程数和请求数有什么关系。根据我上一篇文章tomcat分配请求 的分析，一个Worker线程对应一个请求。
　　那么你会不会有更多的疑问，maxThreads如何设置得比 maxKeepAliveRequests 小会怎么办？
　　请看下面这段代码
　　Http11Processor.java

int keepAliveLeft = maxKeepAliveRequests;
int soTimeout = endpoint.getSoTimeout();
// When using an executor, these values may return non-positive values
int curThreads = endpoint.getCurrentThreadsBusy();
int maxThreads = endpoint.getMaxThreads();
if (curThreads > 0 && maxThreads > 0) {
// Only auto-disable keep-alive if the current thread usage % can be
// calculated correctly
if ((curThreads*100)/maxThreads > 75) {
keepAliveLeft = 1; // 当前使用线程是最大线程数的75%的时候，会自动禁用keepAlive
}
}

while (started && !error && keepAlive) {
……
if (maxKeepAliveRequests > 0 && --keepAliveLeft == 0)
keepAlive = false;
……
}
　　 
　　当前使用线程是最大线程的75% 的时候，会自动禁用keepAlive
　　所以maxThreads设置得比maxKeepAliveRequests 小，则这个maxKeepAliveRequests 设置时没有效果的。
　　当maxThreads设置肯定要比 maxKeepAliveRequests 来的大，而且 maxKeepAliveRequests 不会超过maxThreads的75%！！
　　默认：maxThreads 为 200
　　maxKeepAliveRequests  为100
　　keepAliveTimeout
　　 服务器Socket读取HTTP请求行到来的限制时间。 以millionseconds为单位。默认和connectionTimeout 的值一样。
　　connectionTimeout
　　单位是毫秒，Connector从接受连接到提交URI请求数据的等待的时间。
　　开始这个我没搞懂，不过找到了这篇文章： http://twotwoandapple.blogbus.com/logs/62770043.html  上面的解释和测试。
　　也可以看下面的代码：Http11Processor.java

while (started && !error && keepAlive) {
// Parsing the request header
try {
if (keptAlive) {
if (keepAliveTimeout > 0) {
socket.setSoTimeout(keepAliveTimeout);
}
else if (soTimeout > 0) {
socket.setSoTimeout(soTimeout);
}
}
// 服务器获取客户端请求行,这里会调用inputBuffer的read 方法，引起socket阻塞，阻塞时间超过soTimeout的话就会SocketTimeOutException
inputBuffer.parseRequestLine();
　　disableUploadTimeout
　　是否允许在上传操作的时候给与更长的socketTimeOut时间。默认false不允许。
　　如果设置为true，则默认为5分钟限制，超过5分钟则会报SocketTimeOut异常。
　　如果要改这个时间，需要用这个Attribute： timeout 这个官方文档没有写，不知道为什么，可能不建议修改吧，因为5分钟是和apache 的httpd的时间保持一致的。
　　类似：

    <Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" disableUploadTimeout="false" timeout="600000"/>
　　  其中HTTP 协议，最好参考下RFC的文档 结合Http11Protocal 和 Http11Processor来看比较好