feat(metrics): add delegated routing client metrics to prometheus (#113)

* Add delegated routing client metrics to prometheus

* docs: document metrics.md

---------

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

Author: hsanjuan

CHANGELOG.md

@@ -15,6 +15,17 @@ The following emojis are used to highlight certain changes:
 
 ### Added
 
+- Added exporting of routing http client metrics: the endpoint will now include `someguy_routing_http_client_*` metrics when delegated routing clients are used:
+  - Histogram: the latency of operations by the routing HTTP client:
+    - `someguy_routing_http_client_latency_bucket{code,error,host,operation,le}`
+    - `someguy_routing_http_client_latency_sum{code,error,host,operation}`
+    - `someguy_routing_http_client_latency_count{code,error,host,operation}`
+  - Histogram: the number of elements in a response collection
+    - `someguy_routing_http_client_length_bucket{host,operation,le}`
+    - `someguy_routing_http_client_length_sum{host,operation}`
+    - `someguy_routing_http_client_length_count{host,operation}`
+  - See [docs/metrics.md](https://github.com/ipfs/someguy/blob/main/docs/metrics.md) for more details.
+
 ### Changed
 
 ### Removed

docs/metrics.md

@@ -0,0 +1,27 @@
+## someguy metrics
+
+By default, a prometheus endpoint is exposed by someguy at `http://127.0.0.1:8190/debug/metrics/prometheus`.
+
+It includes default [Prometheus Glient metrics](https://prometheus.io/docs/guides/go-application/) + someguy-specific listed below.
+
+### Delegated HTTP Routing (`/routing/v1`) server
+
+Metric from `boxo/routing/http/server` (used for `/routing/v1` handler) are exposed with `delegated_routing_server_` prefix:
+
+- `delegated_routing_server_http_request_duration_seconds_[bucket|sum|count]{code,handler,method}` - histogram: the latency of the HTTP requests
+- `delegated_routing_server_http_response_size_bytes_[bucket|sum|count]{code,handler,method}` - histogram: the size of the HTTP responses
+
+### Delegated HTTP Routing (`/routing/v1`) client
+
+If someguy is set up as an aggregating proxy for multiple other `/routing/v1` endpoints,
+metrics from `boxo/routing/http/client` are exposed with `someguy_` prefix:
+
+- `someguy_routing_http_client_latency_[bucket|sum|count]{code,error,host,operation}` - Histogram: the latency of operations by the routing HTTP client:
+- `someguy_routing_http_client_length_[bucket|sum|count]{host,operation}` - Histogram: the number of elements in a response collection
+
+### Someguy Caches
+
+- `someguy_cached_addr_book_probe_duration_seconds_[bucket|sum|count]` - Histogram: duration of peer probing operations in seconds
+- `someguy_cached_router_peer_addr_lookups{cache,origin}` - Counter: number of peer addr info lookups per origin and cache state
+- `someguy_cached_addr_book_peer_state_size` - Gauge: number of peers object currently in the peer state
+

go.mod

@@ -3,6 +3,7 @@ module github.com/ipfs/someguy
 go 1.23.0
 
 require (
+	contrib.go.opencensus.io/exporter/prometheus v0.4.2
 	github.com/CAFxX/httpcompression v0.0.9
 	github.com/coreos/go-systemd/v22 v22.5.0
 	github.com/dustin/go-humanize v1.0.1
@@ -22,6 +23,7 @@ require (
 	github.com/rs/cors v1.11.0
 	github.com/stretchr/testify v1.10.0
 	github.com/urfave/cli/v2 v2.27.3
+	go.opencensus.io v0.24.0
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.56.0
 	go.opentelemetry.io/contrib/propagators/autoprop v0.57.0
 	go.opentelemetry.io/otel v1.35.0
@@ -47,11 +49,14 @@ require (
 	github.com/filecoin-project/go-clock v0.1.0 // indirect
 	github.com/flynn/noise v1.1.0 // indirect
 	github.com/francoispqt/gojay v1.2.13 // indirect
+	github.com/go-kit/log v0.2.1 // indirect
+	github.com/go-logfmt/logfmt v0.6.0 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-task/slim-sprig/v3 v3.0.0 // indirect
 	github.com/godbus/dbus/v5 v5.1.0 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/google/gopacket v1.1.19 // indirect
 	github.com/google/pprof v0.0.0-20250208200701-d0013a598941 // indirect
 	github.com/google/uuid v1.6.0 // indirect
@@ -121,6 +126,7 @@ require (
 	github.com/prometheus/client_model v0.6.2 // indirect
 	github.com/prometheus/common v0.63.0 // indirect
 	github.com/prometheus/procfs v0.16.1 // indirect
+	github.com/prometheus/statsd_exporter v0.26.1 // 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
@@ -133,7 +139,6 @@ require (
 	github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1 // indirect
 	github.com/wlynxg/anet v0.0.5 // indirect
 	github.com/xrash/smetrics v0.0.0-20240521201337-686a1a2994c1 // indirect
-	go.opencensus.io v0.24.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/contrib/propagators/aws v1.32.0 // indirect
 	go.opentelemetry.io/contrib/propagators/b3 v1.32.0 // indirect
@@ -163,6 +168,7 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20241104194629-dd2ea8efbc28 // indirect
 	google.golang.org/grpc v1.67.1 // indirect
 	google.golang.org/protobuf v1.36.6 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	lukechampine.com/blake3 v1.4.0 // indirect
 )