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From "Benoit Chesneau (JIRA)" <>
Subject [jira] Updated: (COUCHDB-1046) support load of external erlang modules in couchdb.
Date Thu, 27 Jan 2011 17:02:43 GMT


Benoit Chesneau updated COUCHDB-1046:

    Attachment: couchdb-plugins-02.patch

Here is a second patch that use code:rehash. It forces erlang to reload code path cache. Also
it allows to dynamically reload modules on config changes.

The reason I use a daemon section here, is to allows a plugin to be loaded as a supervisor
or as a worker. So we can have different shutdown type in supervision. Which isn't handled
by couchdb. Maybe it could be addressed in daemons though.

> support load of external erlang modules in couchdb. 
> ----------------------------------------------------
>                 Key: COUCHDB-1046
>                 URL:
>             Project: CouchDB
>          Issue Type: New Feature
>          Components: Database Core
>            Reporter: Benoit Chesneau
>             Fix For: 1.2
>         Attachments: couchdb-plugins-01.patch, couchdb-plugins-02.patch
> If you want to add external modules in CouchDB and load them , you need to set the ERL_FLAGS
environnement variable to the path of a module. 
> The attached patch allows couchdb to load plugins from plugin key in couchdb section.
It add needed path to the code path, so the vm can find modules.
> ex:
>    [couchdb]
>    plugins = plugin1, plugin2
>  Each plugin can have its own section where it set the binaries patch, eventually if
a service need to be added to the supervision you can set the module and function to load
like in daemon section and tel if it's a supervisor or simple service.
> It also allows couchdb to load a plugin service (gen_server or such) to the supervision.
You can choose if the service is a simple daemon or a supervisor.
>  ex:
>    [plugin1]
>    code_path = /path/to/plugin1/ebin
>    daemon = {module, function, [Args]}
>    supervisor = false
> Let me know what you think about it. This patch is really useful here and allows me to
dynamically load modules I want. Also it eases the integration of external module. For ex
I can load my couchapp_ng modules with this lines in local.ini : 
>     [couchdb]
>     plugins = couchapp-ng
>     [couchapp-ng]
>     code_path=/Users/benoitc/work/couchapp_ng/ebin
>     daemon = {couchapp_ng_routes, start_link, []}
>     [httpd_design_handlers]
>     _app = {couchapp_ng_httpd, handle_app_req}
>     [couchapp_ng_handlers]
>     rewrite = {couchapp_ng_handlers, rewrite_handler}
>     proxy = {couchapp_ng_handlers, proxy_handler}
> and can do the same with geocouch etc. Tested here with these modules.

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