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https://issues.apache.org/jira/browse/HTTPCLIENT-2033?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aapo Laitinen closed HTTPCLIENT-2033.
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> Connection manager shutdown flushes output buffer without synchronization
> -------------------------------------------------------------------------
>
> Key: HTTPCLIENT-2033
> URL: https://issues.apache.org/jira/browse/HTTPCLIENT-2033
> Project: HttpComponents HttpClient
> Issue Type: Bug
> Components: HttpClient (classic)
> Affects Versions: 4.5.10
> Environment: Linux
> Reporter: Aapo Laitinen
> Priority: Major
> Fix For: 4.5.11
>
>
> We've observed cases of garbled data sent over the wire that seem to
> correlate with calling {{HttpClientConnectionManager#shutdown()}} while
> requests are in progress. For example, a PUT request with entity {{ABCD}}
> (each letter corresponding to 4 kilobytes of data) may be received as
> {{ABC{color:#172b4d}B{color}}} (the last block replaced with the second
> block).
> Omitting some intermediate layers, {{HttpClientConnectionManager#shutdown()}}
> proceeds to call {{AbstractConnPool#shutdown()}},
> {{BHttpConnectionBase#close()}}, {{SessionOutputBufferImpl#flush()}} and
> finally {{SessionOutputBufferImpl#flushBuffer()}}. As far as I can tell,
> there is nothing to stop the thread that is performing the shutdown from
> invoking {{flushBuffer()}} while another thread is writing data to the buffer
> and/or flushing it.
> *How to reproduce*
> I haven't been able to reliably reproduce the garbled data, but I confirmed
> the lack of synchronization as follows:
> 1. Modified {{flushBuffer()}} so that it will try to a acquire and release a
> shared lock before proceeding and will report any cases of two threads
> attempting to flush the same buffer at the same time.
> 2. Acquired the lock while another thread was making requests, making the
> other thread block inside {{flushBuffer()}}.
> 3. Called {{HttpClientConnectionManager#shutdown()}}
> 4. Observed that the thread doing the shutdown entered {{flushBuffer()}}
> while the thread that was making requests hadn't exited it yet.
> *What I was expecting to happen*
> I'm not sure what the expected behavior of calling
> {{HttpClientConnectionManager#shutdown()}} is, but either of flushing the
> buffer with proper synchronization or abruptly closing the connection
> ({{BHttpConnectionBase#shutdown()}} instead of {{close()}}) strike me as
> acceptable. Basically, I'd expect that the received data might be truncated
> (e.g. {{AB}} or {{ABC}} instead of {{ABCD}}) but never garbled (e.g. {{ABCB}}
> or {{ABCC}} instead of {{ABCD}}).
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