We need to free some of our MongoDB space, and we identified 100Gb + worth of documents that can be safely removed from a collection.
So we removed them from our test environment which has this setting:
- mongodb version 3.0.1
- no sharding
- 1 node, no replica
- wiredtiger engine
When done, we found out that the space on disk was still used and needed to be reclaimed. We found this post and it helped us: after running both
db.runCommand({repairDatabase: 1})
and
db.runCommand({compact: collection-name })
We freed 100Gb +.
We then proceeded in production, forgetting that the setting was different since we had 1 replica node:
- mongodb version 3.0.1
- no sharding
- 1 primary node, 1 replica node
- wiredtiger engine
After removing the documents, we run
db.runCommand({repairDatabase: 1})
and got the OK message (after a while, 10 min +). We tried running
db.runCommand({compact: collection-name })
and got this error:
will not run compact on an active replica set primary as this is a slow blocking operation. use force:true to force
So we run
db.runCommand({compact: collection-name, force: true })
and got the OK message (almost instantly), but the disk on space is still used, it wasn't freed.
we searched for solutions for running the repairDatabase and compact commands with replica-set but the advise was focused on avoiding downtime as if that was the only issue. However, we can schedule downtime and our problem is rather that the commands don't work as expected since the space is not actually reclaimed.
What did we do wrong?