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From Robert Newson <rnew...@apache.org>
Subject Re: Compaction Best Practices
Date Thu, 14 Jun 2012 12:54:00 GMT
Do you eventually delete every document you add?

If so, consider using a rolling database scheme instead. At some
point, perhaps daily, start a new database and write new transaction
logs there. Continue deleting old logs from the previous database(s)
until they're empty (doc_count:0) and then delete the database.

B.

On 14 June 2012 13:44, Nicolas Peeters <nicolists@gmail.com> wrote:
> I'd like some advice from the community regarding compaction.
>
> *Scenario:*
>
> We have a large-ish CouchDB database that is being used for transactional
> logs (very write heavy). Once in a while, we delete some of the records in
> large batches and we have scheduled compaction (not automatic (yet)) every
> 12hours.
>
> From what I can see, the DB is being hammered significantly every 12 hours
> and the compaction is taking 4 hours (with a size of 50-100GB of log data).
>
> *The problem:*
>
> The problem is that compaction takes a very long time and reduces the
> performance of the stack. It seems that it's hard for the compaction
> process to "keep up" with the insertions, hence why it takes so long. Also,
> what I'm not sure is how "incremental" the compaction is...
>
>   1. In this case, would it make sense to run the compaction more often
>   (every 10 minutes); since we're write-heavy.
>      1. Should we just run more often? (so hopefully it doesn't do
>      unnecessary work too often). Actually, in our case, we should probably
>      never have automatic compaction if there has been no "termination".
>      2. Or actually only once in a while? (bigger batch, but less
>      "useless" overhead)
>      3. Or should we just wait that a given size (which is the problem
>      really) is hit and use the auto compaction (in CouchDB 1.2.0) for this?
>   2. In CouchDB 1.2.0 there's a new feature: auto
> compaction<http://wiki.apache.org/couchdb/Compaction#Automatic_Compaction>
> which
>   may be useful for us. There's the "strict_window" feature to give a max
>   amount of time to compact and cancel the compaction after that (in order
>   not to have it running for 4h+…). I'm wondering what the impact of that is
>   on the long run. What if the compaction cannot be completed in that window?
>
> Thanks a lot!
>
> Nicolas

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