[GitHub] [couchdb] aalegriadg opened a new issue, #4195: Timeout when making query while purging

[GitBox <gi...@apache.org>]

aalegriadg opened a new issue, #4195:
URL: https://github.com/apache/couchdb/issues/4195

   I have tried to make a query during a purge of many documents from the database and I get the following timeout error:
   
   `Error running query. Reason: (timeout) The request could not be processed in a reasonable amount of time.`
   
   And the following couchdb log error:
   
   `
   [error] 2022-10-03T15:25:47.790110Z couchdb@127.0.0.1 <0.27022.0> aa85e646df fabric_worker_timeout map_view,'couchdb@127.0.0.1',<<"shards/00000000-7fffffff/database.1664801850">>`
   
   It catches my attention since I am querying a partition whose documents are not included in the purge. That is, I am purging documents from partition2 and querying a view on partition1 using the `get_partitioned_view_result` method.
   
   What is the cause of the error? Is it not possible to perform queries while documents are being purged? Is it due to couchdb configuration? 


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[GitHub] [couchdb] nickva commented on issue #4195: Timeout when making query while purging

[GitBox <gi...@apache.org>]

nickva commented on issue #4195:
URL: https://github.com/apache/couchdb/issues/4195#issuecomment-1265677839

   It's probably because the view shard is processing the purge requests and has to catch up. Processing a lot of purge requests is about same as the making a lot of db updates and waiting for the view to catch up. 
   
   Partition could be located on the same shard as the other partitions and views are built per-shard. So, if the shard hasn't caught up yet, it will block clients waiting the latest updates from the partitions on that shard. One way to handle it could be to [split he shard range](https://docs.couchdb.org/en/3.2.2-docs/cluster/sharding.html#splitting-shards) to hopefully isolate the partition to just one shard.


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