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From Jan Lehnardt <>
Subject Re: [jira] [Commented] (COUCHDB-1259) Replication ID is not stable if local server has a dynamic port number
Date Tue, 06 Nov 2012 12:47:29 GMT
Benoit & Jens,

can I ask you both to keep a civil tone?

I understand that it can be frustrating when the other party 
seemlingly doesn’t understand your point of view, but I believe
that the resulting energy is better put towards trying harder to 
understand the other side and making myself more clear. (which 
you did later on, so thanks :)

I know you’ve both been around the block enough to understand :)

With relaxing regards

On Nov 5, 2012, at 05:43 , Benoit Chesneau (JIRA) <> wrote:

>    [
> Benoit Chesneau commented on COUCHDB-1259:
> ------------------------------------------
> Hello.... are you understanding that this isn't only about your application? Some may
have different uses. And different routing policy. And this is not the role of couchdb to
fix them.
>> Replication ID is not stable if local server has a dynamic port number
>> ----------------------------------------------------------------------
>>                Key: COUCHDB-1259
>>                URL:
>>            Project: CouchDB
>>         Issue Type: Bug
>>         Components: Replication
>>   Affects Versions: 1.1
>>           Reporter: Jens Alfke
>>           Assignee: Robert Newson
>>           Priority: Blocker
>>            Fix For: 1.3
>>        Attachments: couchdb-1259.patch, couchdb-1259.patch
>> 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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