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Scavenging

When you delete events or streams in Event Store, they aren’t removed immediately. In order for these events to be permanently deleted you will need to run a scavenge on your database.

Simply put, a scavenge reclaims disk space by rewriting your database chunks minus the events that should be deleted, and then deleting the old chunks. Once a scavenge has been run, any deleted events cannot be recovered.

Scavenges only affect completed chunks, so deleted events in the current chunk will still be there after you run a scavenge.

Starting a scavenge

Scavenges are not run automatically by Event Store. Our recommendation is that you set up a scheduled task, for example using cron or Windows Scheduler, to trigger a scavenge as often as you need.

A scavenge can be started by issuing an empty POST to the HTTP API with the credentials of an admin or ops user :

curl -i -d {} -X POST http://localhost:2113/admin/scavenge -u "admin:changeit"

Scavenges can also be started from the Admin page in the Admin UI.

Each node in a cluster has its own independant database. As such, when you run a scavenge, you will need to issue a scavenge request to each node.

How often should scavenges be run

How often you should run a scavenge depends on the following:

  • How often you delete streams
  • Depending on how you set $maxAge, $maxCount or $tb metadata on your streams

Scavenging while Event Store is online

It is safe to run a scavenge while Event Store is running and processing events; it is designed to be an online operation.

Keep in mind that scavenging will increase the number of reads/writes being made to your disk, and therefore it is not recommended to run it when your system is under heavy load.

Event Store docs are hosted on GitHub. The repository is public and it’s open to issues and pull requests. Contributions, corrections and feedback are all welcome.