Couchbase server runs something every 1 hr 45 min?


#1

Hi,

Does anyone know what Couchbase server does every 1 hr 45 mins (i.e. 105 minutes)?

Looking at our monit graphs, our couchbase box’s load average shoots up exactly every 1 hr 45 mins. For example: 07:30, 09:15, 11:00, 12:45, 14:30…

Normally the load average floats around 0.25-0.50 on the box. At that point every 105 minutes, it shoots up to 0.75-1.00.

Thanks,

blui


#2

Couchbase has a few background tasks which run periodically, however nothing which by default is every 105 minutes. The main tasks are:

  • The Expiry Pager (Couchbase Admin Guide) which actually delete any items which have expired from disk. It runs by default every 60 minutes but can be adjusted.

  • Compaction (Database and View Compaction is performed to compact the on-disk files, essentially removing deleted / old versions of documents. By default this runs when fragmentation of data / views reaches a given threashold and so the exact time this is run will vary depending on your workload.

In your situation I would guess that your disk/index fragmentation is hitting 30% (the default threshold to start compaction) every 105 minutes, and this is contributing to the load average you see. This is a normal, automatic process and so shouldn’t be a concern. There’s more detail on compaction in the link above.