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From "Oleg Kalnichevski (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HTTPCLIENT-1105) Built-in way to do auto-retry for certain status codes
Date Wed, 29 Jun 2011 13:16:29 GMT

     [ https://issues.apache.org/jira/browse/HTTPCLIENT-1105?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Oleg Kalnichevski resolved HTTPCLIENT-1105.
-------------------------------------------

    Resolution: Fixed

Patch committed with some changes. I changed the signature of the ServiceUnavailableRetryStrategy
to make it more consistent with HttpRequestRetryHandler. I also did not quite like recursive
invocation of the #callBackend method. I replaced recursive method call with a simple loop.

Please review.

I also noticed that the default ServiceUnavailableRetryStrategy implementation was not fully
thread safe. Ideally all instance variables in the DefaultServiceUnavailableRetryStrategy
should be made final and the class should be made immutable.

Otherwise, many thanks for the contribution.

Oleg

> Built-in way to do auto-retry for certain status codes
> ------------------------------------------------------
>
>                 Key: HTTPCLIENT-1105
>                 URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1105
>             Project: HttpComponents HttpClient
>          Issue Type: Wish
>          Components: HttpClient
>    Affects Versions: 4.1.1
>            Reporter: Dan Checkoway
>            Priority: Minor
>             Fix For: 4.2 Alpha1
>
>         Attachments: patch_auto_retry.diff, patch_auto_retry_v2.diff
>
>
> The HttpRequestRetryHandler mechanism is great.  It allows API users to plug in their
own logic to control whether or not a retry should automatically be done, how many times it
should be retried, etc.  That works perfectly in scenarios where an exception is caught while
issuing the request.  It falls short, however, in this scenario...
> If I'm hitting a service that returns a 503, I want to be able to retry that request
automatically as well.  As of right now, I need to write my own logic to accomplish that,
and it's clunky trying to integrate it with the httpClient.execute() call, since it's my ResponseHandler
impl that ends up getting the 503.  I can see use cases for auto-retrying upon getting other
HTTP statuses as well, not just 503.
> My request here is...I would love to be able to configure, either on the HttpClient itself
or on a wrapping class or something, that a request should automatically be retried if the
HTTP status code is among of a set of statuses that I configure.  It would be nice if you
could set the max # of retries, an optional sleep time in between retries (perhaps optional
incremental backoff if you want to get fancy).  I'm not sure if this is possible, but it would
be nice if -- when this type of status-based retry is enabled -- my ResponseHandler wouldn't
even get invoked until retry was successful.
> Here's an alternative suggestion, possibly simpler to build, but definitely not as elegant:
> In my ResponseHandler, you could throw a RetryRequestException or something like that,
and the calling code would catch that and do as expected.  That might simplify the mechanism
so to speak.
> Anyway, I would love not to have to roll my own retry code, since I suspect this is something
that hundreds (thousands?) of HttpClient users have had to code.  Seems like providing a standardized,
well-written way to do it would go a long way to helping many coders out there.
> Thanks!

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