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Date: Wed, 14 Jan 2015 16:10:39 +0000 (UTC)
From: "Mike Wallace (JIRA)" <jira@apache.org>
To: dev@couchdb.apache.org
Message-ID: <JIRA.12752048.1414784064000.81881.1421251839859@Atlassian.JIRA>
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 <JIRA.12752048.1414784064824@arcas>
Subject: [jira] [Commented] (COUCHDB-2425) Exceptions in
 couch_proc_manager:new_proc/1 leave dangling couch_query_servers
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    [ https://issues.apache.org/jira/browse/COUCHDB-2425?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14277130#comment-14277130 ] 

Mike Wallace commented on COUCHDB-2425:
---------------------------------------

Pondering whether this issue could be fixed by changing the timeout in {{case gen_server:call(couch_proc_manager, {get_proc, Lang}, infinity) of}} to something other than infinity [1]. That way the couch_query_server process will eventually die instead of hanging around until the next node reboot.

This approach would also fix COUCHDB-2426.

[1] https://github.com/apache/couchdb-couch/blob/master/src/couch_query_servers.erl#L363

> Exceptions in couch_proc_manager:new_proc/1 leave dangling couch_query_servers
> ------------------------------------------------------------------------------
>
>                 Key: COUCHDB-2425
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-2425
>             Project: CouchDB
>          Issue Type: Bug
>      Security Level: public(Regular issues) 
>          Components: JavaScript View Server
>    Affects Versions: 2.0.0
>            Reporter: Mike Wallace
>             Fix For: 2.0.0
>
>
> If an exception is thrown in the try blocks in either of the couch_proc_manager:new_proc/1 clauses [1] [2] then a spawn_error is returned which is handled by a specific handle_info clause [3] which does not reply to the calling process. When the caller is couch_query_servers:get_os_process/1 [4] there is an infinite timeout so that process will hang around until either the node reboots or someone intervenes.
> The user-facing symptom is an entry in _active_tasks that makes no progress and never goes away.
> The easiest way to reproduce this is to create a new view and then patch the code to force an exception in the appropriate place, e.g.: (assuming a live dev/run instance): 
>  1. Create DB, add a ddoc and a doc:
> {code}
> $ curl -X PUT http://localhost:15984/kitteh
> {"ok":true}
> $ curl -X POST http://localhost:15984/kitteh -d '{"_id":"_design/view", "views": {"test": {"map": "function(doc) { emit(doc.id, 1); }"}}}' -H 'Content-Type: application/json'
> {"ok":true,"id":"_design/view","rev":"1-ef10f980522d4c8e691e3c26d4c3fac5"}
> $ curl -X PUT http://localhost:15984/kitteh/ohai -d '{}'
> {"ok":true,"id":"ohai","rev":"1-967a00dff5e02add41819138abb3284d"}
> {code}
>  2. Apply https://gist.github.com/mikewallace1979/79f823da25f6a78e2725 then re-run make and dev/run.
>  3. Attempt to query the view:
> {code}
> $ curl -X GET http://localhost:15984/kitteh/_design/view/_view/test
> {"error":"timeout","reason":"The request could not be processed in a reasonable amount of time."}
> {code}
>  4. Observe index build tasks which never go away:
> {code}
> $ curl -X GET http://localhost:15986/_active_tasks
> [{"pid":"<0.2403.0>","changes_done":0,"database":"shards/40000000-5fffffff/kitteh.1414779043","design_document":"_design/view","progress":0,"started_on":1414779439,"total_changes":1,"type":"indexer","updated_on":1414779439},{"pid":"<0.2444.0>","changes_done":0,"database":"shards/00000000-1fffffff/kitteh.1414779043","design_document":"_design/view","progress":0,"started_on":1414779439,"total_changes":1,"type":"indexer","updated_on":1414779439}]
> {code}
> [1] https://github.com/apache/couchdb-couch/blob/master/src/couch_query_servers.erl#L354
> [2] https://github.com/apache/couchdb-couch/blob/master/src/couch_proc_manager.erl#L368-L384
> [3] https://github.com/apache/couchdb-couch/blob/master/src/couch_proc_manager.erl#L239-L245
> [4] https://github.com/apache/couchdb-couch/blob/master/src/couch_query_servers.erl#L354


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