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Date: Fri, 27 May 2011 11:13:47 +0000 (UTC)
From: "Alexander Shorin (JIRA)" <jira@apache.org>
To: dev@couchdb.apache.org
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Subject: [jira] [Reopened] (COUCHDB-1171) Multiple requests to _changes feed
 causes {error, system_limit} "Too many processes"
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     [ https://issues.apache.org/jira/browse/COUCHDB-1171?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alexander Shorin reopened COUCHDB-1171:
---------------------------------------

    Skill Level: New Contributors Level (Easy)

> Multiple requests to _changes feed causes {error, system_limit} "Too many processes"
> ------------------------------------------------------------------------------------
>
>                 Key: COUCHDB-1171
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1171
>             Project: CouchDB
>          Issue Type: Bug
>    Affects Versions: 1.0.2, 1.0.3, 1.1
>            Reporter: Alexander Shorin
>         Attachments: couchdb-changes-stats-process-leak-test.js, couchdb-changes-stats-process-leak.patch
>
>
> Originally I have investigated of issue 182 of couchdb-python package where calling db.changes() function over 32768 times generates next messages in CouchDB log:
> [Thu, 19 May 2011 14:03:26 GMT] [info] [<0.2909.0>] 127.0.0.1 - - 'GET' /test/_changes 200
> [Thu, 19 May 2011 14:03:26 GMT] [error] [emulator] Too many processes
> [Thu, 19 May 2011 14:03:26 GMT] [error] [<0.2909.0>] Uncaught error in HTTP request: {error,system_limit}
> [Thu, 19 May 2011 14:03:26 GMT] [info] [<0.2909.0>] Stacktrace: [{erlang,spawn,
>                      [erlang,apply,
>                       [#Fun<couch_stats_collector.1.123391259>,[]]]},
>              {erlang,spawn,1},
>              {couch_httpd_db,handle_changes_req,2},
>              {couch_httpd_db,do_db_req,2},
>              {couch_httpd,handle_request_int,5},
>              {mochiweb_http,headers,5},
>              {proc_lib,init_p_do_apply,3}]
> [Thu, 19 May 2011 14:03:26 GMT] [info] [<0.2909.0>] 127.0.0.1 - - 'GET' /test/_changes 500
> More info about this issue could be found there: http://code.google.com/p/couchdb-python/issues/detail?id=182
> However, I still couldn't reproduce this error using only httplib module, but I've got that same behavior using feed=longpool option:
> from httplib import HTTPConnection
> def test2():
>     conn = HTTPConnection('localhost:5984')
>     conn.connect()
>     i = 0
>     while(True):
>         conn.putrequest('GET', '/test/_changes?feed=longpool')
>         conn.endheaders()
>         conn.getresponse().read()
>         i = i + 1
>         if i % 100 == 0:
>             print i
> When i get's around 32667 exception raises
> Traceback (most recent call last):
>   File "/home/kxepal/projects/couchdb-python/issue-182/test.py", line 259, in <module>
>     test2()
>   File "/home/kxepal/projects/couchdb-python/issue-182/test.py", line 239, in test2
>     resp.read()
>   File "/usr/lib/python2.6/httplib.py", line 522, in read
>     return self._read_chunked(amt)
>   File "/usr/lib/python2.6/httplib.py", line 565, in _read_chunked
>     raise IncompleteRead(''.join(value))
> httplib.IncompleteRead: IncompleteRead(0 bytes read)
> [Thu, 19 May 2011 14:10:20 GMT] [info] [<0.3240.4>] 127.0.0.1 - - 'GET' /test/_changes?feed=longpool 200
> [Thu, 19 May 2011 14:10:20 GMT] [error] [emulator] Too many processes
> [Thu, 19 May 2011 14:10:20 GMT] [error] [<0.3240.4>] Uncaught error in HTTP request: {error,system_limit}
> [Thu, 19 May 2011 14:10:20 GMT] [info] [<0.3240.4>] Stacktrace: [{erlang,spawn,
>                      [erlang,apply,
>                       [#Fun<couch_stats_collector.1.123391259>,[]]]},
>              {erlang,spawn,1},
>              {couch_httpd_db,handle_changes_req,2},
>              {couch_httpd_db,do_db_req,2},
>              {couch_httpd,handle_request_int,5},
>              {mochiweb_http,headers,5},
>              {proc_lib,init_p_do_apply,3}]
> [Thu, 19 May 2011 14:10:20 GMT] [info] [<0.3240.4>] 127.0.0.1 - - 'GET' /test/_changes?feed=longpool 500
> Same error. I know, that test function is quite outside from real use case, but is this correct behavior and couldn't it be used in malicious aims?
> This exception occurres only for multiple requests within single connection for changes feed, chunked lists or attachments are not affected, if I've done all right.
> Test environment:
> Gentoo Linux 2.6.38
> CouchDB 1.0.2 release
> couchdb-python@63feefd9e3b6
> Python 2.6.6
> If there is needed some additional information I could try to provide it.

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