couchdb-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Paul Joseph Davis (JIRA)" <j...@apache.org>
Subject [jira] Updated: (COUCHDB-755) use exported functions when registering for config changes / db updates to allow hot upgrading
Date Sat, 09 Oct 2010 19:45:02 GMT

     [ https://issues.apache.org/jira/browse/COUCHDB-755?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Paul Joseph Davis updated COUCHDB-755:
--------------------------------------

    Skill Level: Regular Contributors Level (Easy to Medium)

> use exported functions when registering for config changes / db updates to allow hot
upgrading
> ----------------------------------------------------------------------------------------------
>
>                 Key: COUCHDB-755
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-755
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: Database Core
>    Affects Versions: 0.11
>            Reporter: Adam Kocoloski
>             Fix For: 1.1
>
>
> This is a common idiom in our current codebase:
> couch_config:register(fun("couchdb", "os_process_timeout", NewTimeout) ->
>     couch_os_process:set_timeout(Pid, list_to_integer(NewTimeout))
> end),
> It proves problematic for hot code upgrades.  The issue is that the anonymous fun is
held by the couch_config process but belongs to the module in which it is defined (here, couch_external_server.erl).
 If an expert user loads a new version of couch_external_server, the anonymous fun will belong
to the 'old' version of the module.  If she upgrades the module again, couch_config will be
killed.  That's no good.
> The solution is to export the function that handles the configuration change or db update
event.  For instance
> -export(config_change/3).
> ...
> couch_config:register(fun ?MODULE:config_change/3),
> ...
> config_change("couchdb", "os_process_timeout", NewTimeout) ->
>     couch_os_process:set_timeout(Pid, list_to_integer(NewTimeout)).
> I have a patch for this that we've been using for some time in Cloudant, just need to
clean it up and apply it to trunk.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message