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From "Oleg Kalnichevski (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (HTTPCORE-3) HttpParser triggers unfriendly OutOfMemoryError on challenging input
Date Mon, 15 May 2006 21:18:06 GMT
     [ http://issues.apache.org/jira/browse/HTTPCORE-3?page=all ]
     
Oleg Kalnichevski resolved HTTPCORE-3:
--------------------------------------

    Resolution: Invalid

Feel free to re-open the issue if you think the problem has not been adequately resolved

Oleg

> HttpParser triggers unfriendly OutOfMemoryError on challenging input
> --------------------------------------------------------------------
>
>          Key: HTTPCORE-3
>          URL: http://issues.apache.org/jira/browse/HTTPCORE-3
>      Project: Jakarta HttpCore
>         Type: Bug

>   Components: HttpCore
>     Reporter: Gordon Mohr

>
> Many users of HttpClient use it to connect to servers which generate challenging HTTP
responses, such as responses which include an arbitrarily large number of headers or headers
of arbitrarily large size. (Sometimes such headers are conformant with the spec, in that they
contain legal characters in plausible header formats; other times these are filled with binary
content that is a violation of the relevant specs. Even when technically legal, often such
giant headers are the inadvertent result of server-side bugs.)
> As a Java execution environment always has a hard cap on the available heap space, any
parsing code which can use an arbitrary amount of memory risks triggering an OutOfMemoryError,
either in its own thread or even another thread that happens to need memory after the parsing
thread has exhausted it all. 
> Such OutOfMemoryErrors are a particularly unfriendly way to indicate that a practical
limit has been exceeded, compared to other options. They can hide the thread of execution
which is most to blame. It is hard and awkward to set up handlers that catch and recover from
OOMEs wherever they are most likely to occur.  Even with such handlers, the actual allocation
triggering an OOME may occur in another critical thread, even if that thread has minimal and
well-controlled memory needs. 
> HttpClient ought to provide one or more ways for a user to protect against such OOMEs,
and instead receive a more convenient/recoverable indication of an HTTP response that is impossible
to process with the HttpClient library within the available resources. Many approaches are
possible; the easiest would be to allow a user of HttpClient to set their own optional, pragmatic
limits on header sizes and number. Then, just as a user may already cleanly cancel the stream-reading
of an arbitrarily-long content-body without fouling up their application state, they would
be able to cancel the parsing of oversized response headers. 
> Similar issues have been discussed before, for example in Bugzilla bug #25468 (http://issues.apache.org/bugzilla/show_bug.cgi?id=25468)
which was to "Provide HttpParser plug-in mechanism." Though that issue is marked resolved/fixed,
there is no such plug-in mechanism allowing an OOME workaround in the 3.x HttpClient, and
it is not clear that a mechanism/work-around exists in whatever 4.0 work has been completed.
> So my suggestion is that this new issue be used to uniquely track the OOME risk in HttpParser,
and only be considered "fixed" when some version of HttpClient offers an alternative to throwing
OOMEs as a way of dealing with challenging HTTP responses. Alternatively, this could simply
become the issue in the new system for collecting user-contributed workarounds/patches. 

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