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From "Paul Joseph Davis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COUCHDB-393) Cannot discover currently running http port if ini file specifies port 0
Date Tue, 23 Jun 2009 15:08:07 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723103#action_12723103
] 

Paul Joseph Davis commented on COUCHDB-393:
-------------------------------------------

As was pointed out, reading the port from a log file is probably not the best solution. The
other alternative would be to make it available with something like `couchdb -s` which would
require some other voodoo magic. Another alternative would be to update the couchdb -s command
to actually be a couchdbctl command that uses Erlang RPC similar to how rabbitmqctl works.
The setup isn't without problems though as it requires coordination of erlang cookies and
other bits.

Any one else have thoughts on how to accomplish this better than the log style?

> Cannot discover currently running http port if ini file specifies port 0
> ------------------------------------------------------------------------
>
>                 Key: COUCHDB-393
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-393
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: HTTP Interface
>    Affects Versions: 0.9
>         Environment: Ubuntu 9.04
>            Reporter: Stuart Langridge
>
> It is currently not possible, if the ini file specifies port 0 as the http port (so that
the OS chooses a random port) to discover which port the OS actually chose.
> It would be nice if the currently running port was made available in the statusline output
(couchdb -s), but a log statement would be adequate; some way that an external script can
discover which port a running CouchDB is listening on.
> Edited discussion from #couchdb:
> <bitdiddle> aquarius: well at a glance it appears couch_http passes the 0 to mochiweb_http
which passes it to the mochiweb_socket_server, which passes it to gen_tcp, an erlang module
that lets the underlying OS assign it. mochiweb_socket_server then grabs that port and stores
it. It has a get method to retrieve properties but that needs to be exposed to mochiweb_http
so it would take a little work to do it. It's probably a JIRA ticket, unless someone else
sees a quicker approach
> <davisp> bitdiddle: you got that far and didn't find it?
> <aquarius> davisp: is there a better way to find the port?
> <davisp> oh, is that not the bind port?
>  I was just thinking a log statement
> <aquarius> davisp: the problem is if you specify 0 as the bind port (so the OS
chooses a port), how do you find out what was chosen?
> <davisp> aquarius: you have to look at the port returned by the socket
>  aquarius: in other words, CouchDB was never written to do that
> <davisp> AFAIK
> <bitdiddle> davisp: I found it, just needs some work to expose it
> <davisp> aquarius: and by do that, I mean, we never put in a statement to log that
> <bitdiddle> mochiweb_http is the module that needs to bubble it up
> <aquarius> davisp: I don't really mind whether it's a log statement or it's exposed
to couchdb -s (the latter seems tidier to me, but whichever), I just want to be able to start
couch on port 0 and then later find out which port got chosen :)
> <davisp> aquarius: for the time being you can use something like netstat or lsof,
but we'll get a log statement in there or something

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