RHQ AS7 plugin with httpclient (important if you rely on this plugin for your development)

Thomas Segismont tsegismo at redhat.com
Mon Jan 21 13:16:21 UTC 2013


Hi all,

Following my email on BZ 887320 ( Agent raises OutOfMemoryError when 
adding new Deployment child resource on AS7 ).

A fix has been made and the AS7 plugin in master branch now uses commons 
httpclient to upload content.

All httpclient code is encapsulated in the ASUploadConnection so if 
you're a simple user of the class your code should not be broken (but 
please read the new documentation as some methods are now deprecated).

Some package protected fields which are no longer relevant have been 
removed but this should not impact your code (unless you extended the 
class in same package).

This change was very important as RHQ agents generally run with less 
resources than other Java programs (128M max heap) and we cannot rely on 
a tool which holds full EARs in memory.

If you have any concern with this changeset please email me.

Thanks and regards
Thomas Segismont

Le 18/12/2012 15:13, Thomas Segismont a écrit :
> Hi all,
>
> I'm writing to you about this bug:
> https://bugzilla.redhat.com/show_bug.cgi?id=887320
>
> For those not aware of it, an OutOfMemoryError is raised on the agent
> when you try to add a child resource of type deployment to a managed AS7
> instance.
>
> It happens because the AS7 plugin uses HttpUrlConnection to communicate
> with AS7 HTTP management interface.
>
> Basically, HttpUrlConnection waits for the request payload to be fully
> loaded in memory before it tries to contact the server. It does that to
> be able to resend the request payload if the server ask for redirection
> or start an authentication challenge.
>
> While this is acceptable for small payloads, it's not suitable for large
> file uploads (in our case a 42M WAR upload triggers the OutOfMemoryError).
>
> For large file uploads, HttpUrlConnection provides a streaming mode. But
> in streaming mode it does neither support redirection nor
> authentication. I tried to use streaming mode to make a fix yesterday
> and it's really not working (BTW, sorry for the patch revert waltz).
>
> I can see two options:
>
> #1 Keep HttpUrlConnection as communication layer
> In this case, the streaming mode is mandatory. This means we should
> maintain our own authentication challenge code and set authentication
> headers manually.
> #2 Use HttpClient as communication layer
>
> Personally, I prefer #2
>
> Importing HttpClient in AS7 plugin will increase the plugin dependencies
> list. But I think it's a small price to pay compared to the efforts we
> would spend maintaining our own authentication and redirection code.
>
> What do you think?
>
> Thanks
> Thomas
>



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