feat(metrics)!: expose identify metrics for connected peers only

examples/metrics/Cargo.toml

@@ -12,4 +12,4 @@ hyper = { version = "0.14", features = ["server", "tcp", "http1"] }
 libp2p = { path = "../../libp2p", features = ["async-std", "metrics", "ping", "noise", "identify", "tcp", "yamux", "macros"] }
 log = "0.4.0"
 tokio = { version = "1", features = ["rt-multi-thread"] }
-prometheus-client = "0.20.0"
+prometheus-client = "0.21.0"

examples/metrics/src/http_service.rs

@@ -33,7 +33,7 @@ const METRICS_CONTENT_TYPE: &str = "application/openmetrics-text;charset=utf-8;v
 
 pub(crate) async fn metrics_server(registry: Registry) -> Result<(), std::io::Error> {
     // Serve on localhost.
-    let addr = ([127, 0, 0, 1], 0).into();
+    let addr = ([127, 0, 0, 1], 8080).into();
 
     // Use the tokio runtime to run the hyper server.
     let rt = tokio::runtime::Runtime::new()?;

misc/metrics/CHANGELOG.md

@@ -1,9 +1,29 @@
 ## 0.13.0 - unreleased
 
+- Previously `libp2p-metrics::identify` would increase a counter / gauge / histogram on each
+  received identify information. These metrics are misleading, as e.g. they depend on the identify
+  interval and don't represent the set of currently connected peers. With this change, identify
+  information is tracked for the currently connected peers only. Instead of an increase on each
+  received identify information, metrics represent the status quo (Gauge).
+
+  Metrics removed:
+  - `libp2p_identify_protocols`
+  - `libp2p_identify_received_info_listen_addrs`
+  - `libp2p_identify_received_info_protocols`
+  - `libp2p_identify_listen_addresses`
+
+  Metrics added:
+  - `libp2p_identify_remote_protocols`
+  - `libp2p_identify_remote_listen_addresses`
+  - `libp2p_identify_local_observed_addresses`
+
+  See [PR 3325].
+
 - Raise MSRV to 1.65.
   See [PR 3715].
 
 [PR 3715]: https://github.com/libp2p/rust-libp2p/pull/3715
+[PR 3325]: https://github.com/libp2p/rust-libp2p/pull/3325
 
 ## 0.12.0
 

misc/metrics/Cargo.toml

@@ -27,7 +27,8 @@ libp2p-ping = { workspace = true, optional = true }
 libp2p-relay =  { workspace = true, optional = true }
 libp2p-swarm = { workspace = true }
 libp2p-identity = { workspace = true }
-prometheus-client = "0.20.0"
+prometheus-client = { version = "0.21.0" }
+once_cell = "1.16.0"
 
 [target.'cfg(not(target_os = "unknown"))'.dependencies]
 libp2p-gossipsub =  { workspace = true, optional = true }