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https://issues.apache.org/jira/browse/COUCHDB-1259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089935#comment-13089935
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Jason Smith commented on COUCHDB-1259:
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Couch already has a unique identifier: its URL. I'm not sure another per-server 
UUID buys you much. With a second unique identifier, you can determine that 
(this couch has moved on the Internet || this couch has a configuration error). 
Maybe the first condition is more likely. Meh.

Couch already has a per-server UUID: _config/couch_httpd_auth/secret. Hashing 
this value can produce a public unique ID.

Normal users may not read the config, so you have to expose this value to them 
somehow. Is that a new global handler? Or is it added to the 
{"couchdb":"Welcome"} response?

For these reasons, I'm not sure the solution is to assign a random UUID to the 
Couch.

> 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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