com.signicat.hystrix.servlet

Class AsyncWrapperServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

com.signicat.hystrix.servlet.AsyncWrapperServlet

All Implemented Interfaces:

Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

@WebServlet(asyncSupported=true)
public class AsyncWrapperServlet
extends javax.servlet.http.HttpServlet

Wrapper class for executing any HttpServlet within a Hystrix thread pool. Subclass this, create a no-arg constructor in the subclass, and pass the HttpServlet to wrap to the superclass. Then configure the new subclass to run in web.xml, instead of the old (wrapped) servlet. If you want to control which thread pool a request ends up executing within, make the wrapped servlet implement HystrixAwareServlet.getCommandGroupKey(javax.servlet.http.HttpServletRequest).

Author:

Einar Rosenvinge <einarmr@gmail.com>

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_COMMAND_GROUP_KEY
static int	DEFAULT_CORE_POOL_SIZE
static long	DEFAULT_TIMEOUT

Constructor Summary

Constructors

Constructor and Description
AsyncWrapperServlet(javax.servlet.http.HttpServlet wrappedServlet)
AsyncWrapperServlet(javax.servlet.http.HttpServlet wrappedServlet, long timeoutMillis, int corePoolSize)

Method Summary

Modifier and Type	Method and Description
void	destroy()
protected String	getCommandGroupKey(javax.servlet.http.HttpServlet srv, javax.servlet.http.HttpServletRequest req)
void	init()
void	init(javax.servlet.ServletConfig config)
protected Runnable	onAfterCommandExecute() Note that this is called from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), i.e.
protected void	onAfterCommandSubmit() Useful? for subclasses, but really mostly for testing.
protected Runnable	onBeforeCommandSubmit() Note that this is called from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), i.e.
protected void	onHystrixCompleted(javax.servlet.AsyncContext asyncContext) Override this method if you want to do some extra work when Hystrix is notified that the processing of the request/response is done.
protected void	onHystrixError(javax.servlet.AsyncContext asyncContext, Throwable throwable) Override this method if you want to do some extra work when Hystrix has caught an exception from HystrixCommand.run(), or if the operation has timed out.
protected void	onHystrixNext(javax.servlet.AsyncContext asyncContext, Object o) Override this method if you want to do some extra work when Hystrix is notified that the processing of the request/response is done.
protected void	onServletCompleted(javax.servlet.AsyncEvent asyncEvent) Override this method if you want to do some extra work when AsyncContext.complete() has been called.
protected void	onServletError(javax.servlet.AsyncEvent asyncEvent) Override this method if you want to do some extra work when the servlet container has caught an exception from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse).
protected void	onServletTimeout(javax.servlet.AsyncEvent asyncEvent) Override this method if you want to do some extra work when the servlet container has timed out the request.
void	service(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse resp)

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service

Methods inherited from class javax.servlet.GenericServlet

getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, log, log

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_COMMAND_GROUP_KEY

public static final String DEFAULT_COMMAND_GROUP_KEY

See Also:

Constant Field Values

DEFAULT_TIMEOUT

public static final long DEFAULT_TIMEOUT

See Also:

Constant Field Values

DEFAULT_CORE_POOL_SIZE

public static final int DEFAULT_CORE_POOL_SIZE

See Also:

Constant Field Values

Constructor Detail

AsyncWrapperServlet

public AsyncWrapperServlet(javax.servlet.http.HttpServlet wrappedServlet)

AsyncWrapperServlet

public AsyncWrapperServlet(javax.servlet.http.HttpServlet wrappedServlet,
                           long timeoutMillis,
                           int corePoolSize)

Method Detail

init

public void init()
          throws javax.servlet.ServletException

Overrides:

init in class javax.servlet.GenericServlet

Throws:

javax.servlet.ServletException

init

public void init(javax.servlet.ServletConfig config)
          throws javax.servlet.ServletException

Specified by:

init in interface javax.servlet.Servlet

Overrides:

init in class javax.servlet.GenericServlet

Throws:

javax.servlet.ServletException

destroy

public void destroy()

Specified by:

destroy in interface javax.servlet.Servlet

Overrides:

destroy in class javax.servlet.GenericServlet

service

public void service(javax.servlet.http.HttpServletRequest req,
                    javax.servlet.http.HttpServletResponse resp)
             throws javax.servlet.ServletException,
                    IOException

Overrides:

service in class javax.servlet.http.HttpServlet

Throws:

javax.servlet.ServletException

IOException

getCommandGroupKey

protected String getCommandGroupKey(javax.servlet.http.HttpServlet srv,
                                    javax.servlet.http.HttpServletRequest req)

onBeforeCommandSubmit

protected Runnable onBeforeCommandSubmit()

Note that this is called from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), i.e. by the servlet container thread. The Runnable returned is called by the Hystrix thread (in a try-catch block, with logging), at the beginning of HystrixCommand.run().

Returns:

a Runnable called by a Hystrix thread, at the beginning of HystrixCommand.run().

onAfterCommandSubmit

protected void onAfterCommandSubmit()

Useful? for subclasses, but really mostly for testing. Note that this is called from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), i.e. by the servlet container thread.

onAfterCommandExecute

protected Runnable onAfterCommandExecute()

Note that this is called from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), i.e. by the servlet container thread. The Runnable returned is called by the Hystrix thread (in a try-catch block, with logging, inside a finally block), at the end of HystrixCommand.run().

Returns:

a Runnable called by a Hystrix thread, at the end of HystrixCommand.run().

onServletCompleted

protected void onServletCompleted(javax.servlet.AsyncEvent asyncEvent)
                           throws IOException

Override this method if you want to do some extra work when AsyncContext.complete() has been called.

Parameters:

asyncEvent - the AsyncEvent indicating that an asynchronous operation has been completed

Throws:

IOException - if an I/O related error has occurred during the processing of the given AsyncEvent

onServletTimeout

protected void onServletTimeout(javax.servlet.AsyncEvent asyncEvent)
                         throws IOException

Override this method if you want to do some extra work when the servlet container has timed out the request. It is HIGHLY recommended to call the implementation in this superclass as well, to be certain that AsyncContext.complete() is called. Failure to do so will result in strange errors.

Parameters:

asyncEvent - the AsyncEvent indicating that an asynchronous operation has timed out

Throws:

IOException - if an I/O related error has occurred during the processing of the given AsyncEvent

onServletError

protected void onServletError(javax.servlet.AsyncEvent asyncEvent)
                       throws IOException

Override this method if you want to do some extra work when the servlet container has caught an exception from service(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse). It is HIGHLY recommended to call the implementation in this superclass as well, to be certain that AsyncContext.complete() is called. Failure to do so will result in strange errors.

Parameters:

asyncEvent - the AsyncEvent indicating that an asynchronous operation has failed to complete

Throws:

IOException - if an I/O related error has occurred during the processing of the given AsyncEvent

onHystrixCompleted

protected void onHystrixCompleted(javax.servlet.AsyncContext asyncContext)

Override this method if you want to do some extra work when Hystrix is notified that the processing of the request/response is done. It is HIGHLY recommended to call the implementation in this superclass as well, to be certain that AsyncContext.complete() is called. Failure to do so will result in strange errors.

Parameters:

asyncContext - The AsyncContext to complete.

onHystrixError

protected void onHystrixError(javax.servlet.AsyncContext asyncContext,
                              Throwable throwable)

Override this method if you want to do some extra work when Hystrix has caught an exception from HystrixCommand.run(), or if the operation has timed out. It is HIGHLY recommended to call the implementation in this superclass as well, to be certain that AsyncContext.complete() is called. Failure to do so will result in strange errors.

Parameters:

asyncContext - The AsyncContext to complete.

throwable - The Throwable caught.

onHystrixNext

protected void onHystrixNext(javax.servlet.AsyncContext asyncContext,
                             Object o)

Override this method if you want to do some extra work when Hystrix is notified that the processing of the request/response is done. It is HIGHLY recommended to call the implementation in this superclass as well, to be certain that AsyncContext.complete() is called. Failure to do so will result in strange errors.

Parameters:

asyncContext - The AsyncContext to complete.

o - In our implementation, a dummy object that is not useful in any way.