[jira] [Created] (HTTPCLIENT-2033) Connection manager shutdown flushes output buffer without synchronization

["Aapo Laitinen (Jira)" <ji...@apache.org>]

Aapo Laitinen created HTTPCLIENT-2033:
-----------------------------------------

             Summary: 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


We've observed cases of garbled data sent over the wire that seem to correlate with calling {{HttpClientConnectionManager#shutdown()}} while request 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}+*}}.

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}}).



--
This message was sent by Atlassian Jira
(v8.3.4#803005)

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@hc.apache.org
For additional commands, e-mail: dev-help@hc.apache.org