Merge pull request 'doc: Added observability.md.' (#477) from jpds/garage:observability-doc into main

Reviewed-on: Deuxfleurs/garage#477

doc/book/connect/_index.md

@@ -10,11 +10,12 @@ Garage implements the Amazon S3 protocol, which makes it compatible with many ex
 
 In particular, you will find here instructions to connect it with:
 
-  - [Browsing tools](@/documentation/connect/cli.md)
   - [Applications](@/documentation/connect/apps/index.md)
-  - [Website hosting](@/documentation/connect/websites.md)
-  - [Software repositories](@/documentation/connect/repositories.md)
+  - [Browsing tools](@/documentation/connect/cli.md)
   - [FUSE](@/documentation/connect/fs.md)
+  - [Observability](@/documentation/connect/observability.md)
+  - [Software repositories](@/documentation/connect/repositories.md)
+  - [Website hosting](@/documentation/connect/websites.md)
 
 ### Generic instructions
 

doc/book/connect/observability.md

@@ -0,0 +1,57 @@
++++
+title = "Observability"
+weight = 25
++++
+
+An object store can be used as data storage location for metrics, and logs which
+can then be leveraged for systems observability.
+
+## Metrics
+
+### Prometheus
+
+Prometheus itself has no object store capabilities, however two projects exist
+which support storing metrics in an object store:
+
+ - [Cortex](https://cortexmetrics.io/)
+ - [Thanos](https://thanos.io/)
+
+## System logs
+
+### Vector
+
+[Vector](https://vector.dev/) natively supports S3 as a
+[data sink](https://vector.dev/docs/reference/configuration/sinks/aws_s3/)
+(and [source](https://vector.dev/docs/reference/configuration/sources/aws_s3/)).
+
+This can be configured with Garage with the following:
+
+```bash
+garage key new --name vector-system-logs
+garage bucket create system-logs
+garage bucket allow system-logs --read --write --key vector-system-logs
+```
+
+The `vector.toml` can then be configured as follows:
+
+```toml
+[sources.journald]
+type = "journald"
+current_boot_only = true
+
+[sinks.out]
+encoding.codec = "json"
+type = "aws_s3"
+inputs = [ "journald" ]
+bucket = "system-logs"
+key_prefix = "%F/"
+compression = "none"
+region = "garage"
+endpoint = "https://my-garage-instance.mydomain.tld"
+auth.access_key_id = ""
+auth.secret_access_key = ""
+```
+
+This is an example configuration - please refer to the Vector documentation for
+all configuration and transformation possibilities. Also note that Garage
+performs its own compression, so this should be disabled in Vector.