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From "Paul Joseph Davis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-1259) Replication ID is not stable if local server has a dynamic port number
Date Wed, 24 Aug 2011 03:07:29 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-1259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089973#comment-13089973
] 

Paul Joseph Davis commented on COUCHDB-1259:
--------------------------------------------

@Jason

URL's are nice and all, but they're fairly unstable. What's the URL for a couch on a phone?
Or after it changes networks? Or if its behind a proxy? And how would that couch figure out
what's URL is?

Randall's comment about copying files is why its not viable to just generate a UUID for each
database. Because its quite likely that a sysadmin would copy that file which would result
in to db's having the same UUID making the UUID not so UI.


> Replication ID is not stable if local server has a dynamic port number
> ----------------------------------------------------------------------
>
>                 Key: COUCHDB-1259
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1259
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Replication
>    Affects Versions: 1.1
>            Reporter: Jens Alfke
>
> I noticed that when Couchbase Mobile running on iOS replicates to/from a remote server
(on iriscouch in this case), the replication has to fetch the full _changes feed every time
it starts. Filipe helped me track down the problem -- the replication ID is coming out different
every time. The reason for this is that the local port number, which is one of the inputs
to the hash that generates the replication ID, is randomly assigned by the OS. (I.e. it uses
a port number of 0 when opening its listener socket.) This is because there could be multiple
apps using Couchbase Mobile running on the same device and we can't have their ports colliding.
> The underlying problem is that CouchDB is attempting to generate a unique ID for a particular
pair of {source, destination} databases, but it's basing it on attributes that aren't fundamental
to the database and can change, like the hostname or port number.
> One solution, proposed by Filipe and me, is to assign each database (or each server?)
a random UUID when it's created, and use that to generate replication IDs.
> Another solution, proposed by Damien, is to have CouchDB let the client work out the
replication ID on its own, and set it as a property in the replication document (or the JSON
body of a _replicate request.) This is even more flexible and will handle tricky scenarios
like full P2P replication where there may be no low-level way to uniquely identify the remote
database being synced with.

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