Loki with three scalable targets: read write and backend

mihailblip · September 20, 2023, 2:50pm

The current documentation (v2.9) is quite ambiguous and doesn’t give many details.
It doesn’t cover the scalable deployment with 3 targets, only 2: read and write. Loki deployment modes | Grafana Loki documentation.
There is a migration document to 3 target deployment but it doesn’t go much in explaining.
Migrate to three scalable targets | Grafana Loki documentation
My questions is: How are the roles spread in 3 target deployment comparing it to a 2 target one (aka legacy)? What is the exact role of the backend? Why it was decided to go with 3 target instead of 2 one.
Thanks in advance

tonyswumac · September 20, 2023, 5:55pm

There is a open issue on the github repo to add documentation. It has some details in the issue in terms of what components each of the target has:

github.com/grafana/loki

[Docs] Missing backend component(ssd model)

opened 07:46PM - 21 Jun 23 UTC

marcusteixeira

help wanted type/docs

**Describe the bug** As of release 2.8.0, a new component for Simple Scalable M…ode known as `backend` target was included, however there is no document that refers to this new component. "Notable changes": - New backend target: A new, third target was added to Loki's scalable configuration, which is the default configuration used in the Loki helm chart. This allows Loki to be run as 3 targets (read, write, and backend) and makes the read target stateless and therefore able to be run as a Kubernetes deployment that can be scaled automatically. **Expected behavior** A documentation containing this new component, to help new users understand and new implementation options. **Ref** - Slack Thread: https://grafana.slack.com/archives/CEPJRLQNL/p1687369520468689 - Components(code): https://github.com/grafana/loki/blob/806674fdaa6d68157019b00534edf3f04f0755d3/pkg/loki/loki.go#L672-L674

mihailblip · September 21, 2023, 8:44am

Thanks for quick reply. Looking forward to check out new documentation.