org.eclipse.jetty.servlets
类 QoSFilter

java.lang.Object
  org.eclipse.jetty.servlets.QoSFilter

所有已实现的接口：

Filter

public class QoSFilter
extends Object
implements Filter

Quality of Service Filter. This filter limits the number of active requests to the number set by the "maxRequests" init parameter (default 10). If more requests are received, they are suspended and placed on priority queues. Priorities are determined by the getPriority(ServletRequest) method and are a value between 0 and the value given by the "maxPriority" init parameter (default 10), with higher values having higher priority.

This filter is ideal to prevent wasting threads waiting for slow/limited resources such as a JDBC connection pool. It avoids the situation where all of a containers thread pool may be consumed blocking on such a slow resource. By limiting the number of active threads, a smaller thread pool may be used as the threads are not wasted waiting. Thus more memory may be available for use by the active threads.

Furthermore, this filter uses a priority when resuming waiting requests. So that if a container is under load, and there are many requests waiting for resources, the getPriority(ServletRequest) method is used, so that more important requests are serviced first. For example, this filter could be deployed with a maxRequest limit slightly smaller than the containers thread pool and a high priority allocated to admin users. Thus regardless of load, admin users would always be able to access the web application.

The maxRequest limit is policed by a Semaphore and the filter will wait a short while attempting to acquire the semaphore. This wait is controlled by the "waitMs" init parameter and allows the expense of a suspend to be avoided if the semaphore is shortly available. If the semaphore cannot be obtained, the request will be suspended for the default suspend period of the container or the valued set as the "suspendMs" init parameter.

If the "managedAttr" init parameter is set to true, then this servlet is set as a ServletContext attribute with the filter name as the attribute name. This allows context external mechanism (eg JMX via ContextHandler.MANAGED_ATTRIBUTES) to manage the configuration of the filter.

字段摘要

protected int	_maxRequests
protected long	_suspendMs
protected long	_waitMs

构造方法摘要

QoSFilter()

方法摘要

void	destroy() Called by the web container to indicate to a filter that it is being taken out of service.
void	doFilter(ServletRequest request, ServletResponse response, FilterChain chain) The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain.
int	getMaxRequests() Get the maximum number of requests allowed to be processed at the same time.
protected int	getPriority(ServletRequest request) Get the request Priority.
long	getSuspendMs() Get the amount of time (in milliseconds) that the filter would suspend a request for while waiting for the semaphore to become available.
long	getWaitMs() Get the (short) amount of time (in milliseconds) that the filter would wait for the semaphore to become available before suspending a request.
void	init(FilterConfig filterConfig) Called by the web container to indicate to a filter that it is being placed into service.
void	setMaxRequests(int value) Set the maximum number of requests allowed to be processed at the same time.
void	setSuspendMs(long value) Set the amount of time (in milliseconds) that the filter would suspend a request for while waiting for the semaphore to become available.
void	setWaitMs(long value) Set the (short) amount of time (in milliseconds) that the filter would wait for the semaphore to become available before suspending a request.

从类 java.lang.Object 继承的方法

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

字段详细信息

_waitMs

protected long _waitMs

_suspendMs

protected long _suspendMs

_maxRequests

protected int _maxRequests

构造方法详细信息

QoSFilter

public QoSFilter()

方法详细信息

init

public void init(FilterConfig filterConfig)

从接口 Filter 复制的描述

Called by the web container to indicate to a filter that it is being placed into service.

The servlet container calls the init method exactly once after instantiating the filter. The init method must complete successfully before the filter is asked to do any filtering work.

The web container cannot place the filter into service if the init method either

1. Throws a ServletException
2. Does not return within a time period defined by the web container

指定者：

接口 Filter 中的 init

另请参见：

Filter.init(javax.servlet.FilterConfig)

doFilter

public void doFilter(ServletRequest request,
                     ServletResponse response,
                     FilterChain chain)
              throws IOException,
                     ServletException

从接口 Filter 复制的描述

The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain. The FilterChain passed in to this method allows the Filter to pass on the request and response to the next entity in the chain.

A typical implementation of this method would follow the following pattern:

1. Examine the request
2. Optionally wrap the request object with a custom implementation to filter content or headers for input filtering
3. Optionally wrap the response object with a custom implementation to filter content or headers for output filtering
4. • Either invoke the next entity in the chain using the FilterChain object (chain.doFilter()),
   • or not pass on the request/response pair to the next entity in the filter chain to block the request processing
5. Directly set headers on the response after invocation of the next entity in the filter chain.

指定者：

接口 Filter 中的 doFilter

抛出：

IOException

ServletException

另请参见：

Filter.doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)

getPriority

protected int getPriority(ServletRequest request)

Get the request Priority.

The default implementation assigns the following priorities:

• 2 - for a authenticated request
• 1 - for a request with valid /non new session
• 0 - for all other requests.

This method may be specialised to provide application specific priorities.

参数：

request -

返回：

the request priority

destroy

public void destroy()

从接口 Filter 复制的描述

Called by the web container to indicate to a filter that it is being taken out of service.

This method is only called once all threads within the filter's doFilter method have exited or after a timeout period has passed. After the web container calls this method, it will not call the doFilter method again on this instance of the filter.

This method gives the filter an opportunity to clean up any resources that are being held (for example, memory, file handles, threads) and make sure that any persistent state is synchronized with the filter's current state in memory.

指定者：

接口 Filter 中的 destroy

另请参见：

Filter.destroy()

getWaitMs

public long getWaitMs()

Get the (short) amount of time (in milliseconds) that the filter would wait for the semaphore to become available before suspending a request.

返回：

wait time (in milliseconds)

setWaitMs

public void setWaitMs(long value)

Set the (short) amount of time (in milliseconds) that the filter would wait for the semaphore to become available before suspending a request.

参数：

value - wait time (in milliseconds)

getSuspendMs

public long getSuspendMs()

Get the amount of time (in milliseconds) that the filter would suspend a request for while waiting for the semaphore to become available.

返回：

suspend time (in milliseconds)

setSuspendMs

public void setSuspendMs(long value)

Set the amount of time (in milliseconds) that the filter would suspend a request for while waiting for the semaphore to become available.

参数：

value - suspend time (in milliseconds)

getMaxRequests

public int getMaxRequests()

Get the maximum number of requests allowed to be processed at the same time.

返回：

maximum number of requests

setMaxRequests

public void setMaxRequests(int value)

Set the maximum number of requests allowed to be processed at the same time.

参数：

value - the number of requests