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https://issues.apache.org/jira/browse/COUCHDB-1230?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Hirst updated COUCHDB-1230:
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Attachment: sequence_number.png
This is the last sequence number of a replication target graphed over ~20 hours.
It shows that restarting replication gives a speed boost and that after a while
the speed diminishes.
> Replication slows down over time
> --------------------------------
>
> Key: COUCHDB-1230
> URL: https://issues.apache.org/jira/browse/COUCHDB-1230
> Project: CouchDB
> Issue Type: Bug
> Components: Replication
> Affects Versions: 1.0.2, 1.1
> Environment: Ubuntu 10.04,
> Reporter: Paul Hirst
> Attachments: sequence_number.png
>
>
> I have two databases which were replicated in the past, one is running 1.0.2.
> I shall call this the source database. The other is running 1.1.0, I shall
> call this the target database.
> The source and target are bidirectionally replicated using a push and pull
> replication from the target (using a couple of documents in the new
> _replicator database).
> The source database is in production and is getting changes applied to it
> from live systems. The target is only participating in replication and it's
> being used directly by any production systems.
> The database has about 50 million documents many of these will have been
> updated a handful of times. The database is about 500G after compaction, but
> the source database is currently at about 900G as it hasn't been compacted
> for a while.
> The databases were replicated in the past however this replication was torn
> down when the target was upgraded from 1.0.2 to 1.1.0. When replication was
> reenabled the system wasn't able to pick up were it left off and had to
> reenumerate all the documents again. This process initially started quickly
> but after a while ground to a halt such that the target actually stopped
> making progress against the source database.
> I found that restarting replication starts the process running again at a
> decent speed for a while. I did this by deleting and recreating the
> appropriate document in the _replicator database on the target.
> I have graphed the last_seq of the target database against time for about a
> day, noting when replication was manually restarted. I shall try to attach
> the graph if possible. It shows a clear improvement in replication speed
> after restarting replication.
> I previously witnessed this behaviour between 1.0.2 databases but didn't grab
> any stats at the time but I don't think it's a new problem.
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