fix: expose routing_http_client* metrics (#262)

* Expose routing_http_client* metrics

These metrics are using opencensus, so the part that plugs opencensus to prometheus was missing. Setup inspired by what Kubo does.

With this, the metrics will appear in the form `ipfs_routing_http_client_*`.

Verified that it works by hand.

Fixes #261

---------

Co-authored-by: Marcin Rataj <[email protected]>

Author: hsanjuan

CHANGELOG.md

@@ -19,6 +19,8 @@ The following emojis are used to highlight certain changes:
 
 ### Fixed
 
+* Fix exporting of routing http client metrics: the endpoint will now include `ipfs_routing_http_client_*` metrics routing clients are used. See [docs/metrics.md](https://github.com/ipfs/rainbow/blob/main/docs/metrics.md) for more details.
+
 ### Removed
 
 ### Security

docs/metrics.md

@@ -0,0 +1,19 @@
+## rainbow metrics
+
+By default, a prometheus endpoint is exposed by Rainbow at `http://127.0.0.1:8091/debug/metrics/prometheus`.
+
+It includes default [Prometheus Glient metrics](https://prometheus.io/docs/guides/go-application/) + rainbow-specific listed below.
+
+### Delegated HTTP Routing (`/routing/v1`) client
+
+Metrics from `boxo/routing/http/client` are exposed with `ipfs_` prefix:
+
+- Histogram: the latency of operations by the routing HTTP client:
+  - `ipfs_routing_http_client_latency_bucket{code,error,host,operation,le}`
+  - `ipfs_routing_http_client_latency_sum{code,error,host,operation}`
+  - `ipfs_routing_http_client_latency_count{code,error,host,operation}`
+- Histogram: the number of elements in a response collection
+  - `ipfs_routing_http_client_length_bucket{host,operation,le}`
+  - `ipfs_routing_http_client_length_sum{host,operation}`
+  - `ipfs_routing_http_client_length_count{host,operation}`
+

go.mod

@@ -3,6 +3,7 @@ module github.com/ipfs/rainbow
 go 1.24
 
 require (
+	contrib.go.opencensus.io/exporter/prometheus v0.4.2
 	github.com/cockroachdb/pebble v1.1.4
 	github.com/coreos/go-systemd/v22 v22.5.0
 	github.com/dgraph-io/badger/v4 v4.5.1
@@ -83,6 +84,8 @@ require (
 	github.com/gammazero/chanqueue v1.1.0 // indirect
 	github.com/gammazero/deque v1.0.0 // indirect
 	github.com/getsentry/sentry-go v0.27.0 // indirect
+	github.com/go-kit/log v0.2.1 // indirect
+	github.com/go-logfmt/logfmt v0.5.1 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-ole/go-ole v1.3.0 // indirect
@@ -183,6 +186,7 @@ require (
 	github.com/prometheus/client_model v0.6.1 // indirect
 	github.com/prometheus/common v0.62.0 // indirect
 	github.com/prometheus/procfs v0.15.1 // indirect
+	github.com/prometheus/statsd_exporter v0.22.7 // indirect
 	github.com/quic-go/qpack v0.5.1 // indirect
 	github.com/quic-go/quic-go v0.50.1 // indirect
 	github.com/quic-go/webtransport-go v0.8.1-0.20241018022711-4ac2c9250e66 // indirect
@@ -231,6 +235,7 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20241007155032-5fefd90f89a9 // indirect
 	google.golang.org/grpc v1.67.1 // indirect
 	google.golang.org/protobuf v1.36.5 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	lukechampine.com/blake3 v1.4.0 // indirect
 )