[jira] Resolved: (AXIS2-4800) Http connection listener terminates when request executor full

["Samisa Abeysinghe (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AXIS2-4800?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Samisa Abeysinghe resolved AXIS2-4800.
--------------------------------------

       Resolution: Fixed
    Fix Version/s: 1.6

Applied patch 

> Http connection listener terminates when request executor full
> --------------------------------------------------------------
>
>                 Key: AXIS2-4800
>                 URL: https://issues.apache.org/jira/browse/AXIS2-4800
>             Project: Axis2
>          Issue Type: Bug
>          Components: transports
>    Affects Versions: 1.6, 1.5.2, 1.5.1, 1.5, nightly
>         Environment: Any
>            Reporter: Chuck Williams
>            Assignee: Samisa Abeysinghe
>             Fix For: 1.6
>
>         Attachments: DefaultConnectionListener.patch
>
>   Original Estimate: 0.5h
>  Remaining Estimate: 0.5h
>
> The DefaultConnectionListener of the built-in http server invokes the failure apparatus in the configured ConnectionListenerFailureHandler when exceptions arise handing off a new request connection to an HttpServiceProcessor.  The built-in failure apparatus in DefaultConnectionListenerFailureHandler retries (default 10 times) and then gives up, after which the DefaultConnectionListener shuts down.  This permanently closes the port, rendering the web service unreachable.  One can replace the DefaultConnectionListenerFailureHandler easily by overriding HttpFactory.newRequestConnectionListener(), however the failure processing methods do not have access to the request connection and thus cannot take any action that requires sending a response back to the client.
> A particularly important case arises when the http request executor's thread pool and backing queue are both full.  In this case the attempt to launch a thread to process the new http request gets RejectedExecutionException.  The server should return an http 503 Service Unavailable, since it has already accessed the new connection and so cannot refuse it.  This is impossible to achieve with the existing failure apparatus because it can't send a response.  The result is that the when the web service becomes overloaded the connection listener permanently shuts down!
> The failure apparatus is actually a patch of mine from a few years ago.  At the time any failure would immediately shut down the connection listener and I added some simple processing for the case of an intermittent issue.  The new case of RejectedExecutionException is clearly an important one and I've prepared a new patch (to be attached next) that fixes this by sending 503 Service Unavailable whenever the request executor cannot accept a new request after the connection listener has already accepted the request connection.
> I would have committed this, but since I've been inactive in axis2 development for some time that seemed unwise.  An active developer should probably first weigh in.  I have tested the patch successfully in an application that requires it.
> More should be done here.  Failure cases in the connection listener are important as the consequences of improper handling are dire, leaving your web service unreachable.  Probably there are additional cases that should be built in, and the extensible failure apparatus should be generalized so that it can send responses whenever a request has already been accepted but the normal processing fails back to the listener.

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