cardano-tracer: update docs

cardano-tracer/CHANGELOG.md

@@ -1,14 +1,17 @@
 # ChangeLog
 
-## 0.3 (September 20, 2024)
+## 0.3 (September 26, 2024)
 
 * Abondon `snap` webserver in favour of `wai`/`warp` for Prometheus and EKG Monitoring.
 * Add dynamic routing to EKG stores of all connected nodes.
 * Derive URL compliant routes from connected node names (instead of plain node names).
 * Remove the requirement of two distinct ports for the EKG backend (changing `hasEKG` config type).
+* Improved OpenMetrics compliance of Prometheus exposition; also addresses [issue#5140][i5140].
+* Prometheus help annotations can be provided via the new optional config value `metricsHelp`.
 * For optional RTView component only: Disable SSL/https connections. Force `snap-server`
   dependency to build with `-flag -openssl`.
 * Add JSON responses when listing connected nodes for both Prometheus and EKG Monitoring.
+* Fix: actually send `forHuman` rendering output to journald when specified.
 * Add consistency check for redundant port values in the config.
 
 ## 0.2.4 (August 13, 2024)
@@ -48,3 +51,7 @@
 ## 0.1.0
 
 Initial version.
+
+
+
+[i5140]: https://github.com/IntersectMBO/cardano-node/issues/5140

cardano-tracer/docs/cardano-tracer.md

@@ -4,21 +4,24 @@
 
 # Contents
 
-1. [Introduction](#Introduction)
-   1. [Motivation](#Motivation)
-   3. [Overview](#Overview)
-2. [Build and run](#Build-and-run)
-3. [Configuration](#Configuration)
-   1. [Distributed Scenario](#Distributed-scenario)
-   2. [Local Scenario](#Local-scenario)
-   3. [Network Magic](#Network-magic)
-   4. [Requests](#Requests)
-   5. [Logging](#Logging)
-   6. [Logs Rotation](#Logs-rotation)
-   7. [Prometheus](#Prometheus)
-   8. [EKG Monitoring](#EKG-monitoring)
-   9. [Verbosity](#Verbosity)
-   10. [RTView](#RTView)
+- [Cardano Tracer](#cardano-tracer)
+- [Contents](#contents)
+- [Introduction](#introduction)
+  - [Motivation](#motivation)
+  - [Overview](#overview)
+- [Build and run](#build-and-run)
+- [Configuration](#configuration)
+  - [Distributed Scenario](#distributed-scenario)
+    - [Important](#important)
+  - [Local Scenario](#local-scenario)
+  - [Network Magic](#network-magic)
+  - [Requests](#requests)
+  - [Logging](#logging)
+  - [Logs Rotation](#logs-rotation)
+  - [Prometheus](#prometheus)
+  - [EKG Monitoring](#ekg-monitoring)
+  - [Verbosity](#verbosity)
+  - [RTView](#rtview)
 
 # Introduction
 
@@ -390,20 +393,51 @@ $ curl --silent -H "Accept: application/json" '127.0.0.1:3200' | jq '.'
 }
 ```
 
-The Promethus output is a map from Prometheus metric to value:
+Prometheus uses the text-based exposition format, complete with `# TYPE` and `# HELP` annotations. The latter ones have to be provided by the `metricsHelp` config value (see below).  
+
+The output should be [OpenMetrics](https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#text-format) compliant. Example snippet:
 
 ```
 $ curl '127.0.0.1:3200/12700130004'
-blockNum_int 35
-rts_gc_init_cpu_ms 5
-rts_gc_par_tot_bytes_copied 0
-served_block_counter 31
-submissions_accepted_counter 2771
-density_real 5.7692307692307696e-2
-blocksForged_int 6
-
+# TYPE Mem_resident_int gauge
+# HELP Mem_resident_int Kernel-reported RSS (resident set size)
+Mem_resident_int 103792640
+# TYPE rts_gc_max_bytes_used gauge
+rts_gc_max_bytes_used 5811512
+# TYPE rts_gc_gc_cpu_ms counter
+rts_gc_gc_cpu_ms 50
+# TYPE RTS_gcMajorNum_int gauge
+# HELP RTS_gcMajorNum_int Major GCs
+RTS_gcMajorNum_int 4
+# TYPE rts_gc_par_avg_bytes_copied gauge
+rts_gc_par_avg_bytes_copied 0
+# TYPE rts_gc_num_bytes_usage_samples counter
+rts_gc_num_bytes_usage_samples 4
+# TYPE remainingKESPeriods_int gauge
+remainingKESPeriods_int 62
+# TYPE rts_gc_bytes_copied counter
+rts_gc_bytes_copied 17114384
+# TYPE nodeCannotForge_int gauge
+# HELP nodeCannotForge_int How many times was this node unable to forge [a block]?
+# EOF
+```
+
+Passing metric help annotations to the service can be done in the config file, either as a key-value map from metric name to help text, or as a seperate JSON file containing such a map.
+The system's internal metric names have to be used as keys (cf. [metrics documentation](https://github.com/input-output-hk/cardano-node-wiki/blob/main/docs/new-tracing/tracers_doc_generated.md#metrics)).
+```
+"metricsHelp": "path/to/key-value-map.json"
+```
+or
+```
+"metricsHelp": {
+  "Mem.resident": "Kernel-reported RSS (resident set size)",
+  "RTS.gcMajorNum": "Major GCs",
+  "nodeCannotForge": "How many times was this node unable to forge [a block]?"
+}
 ```
 
+
+
 ## EKG Monitoring
 
 At top-level route `/` EKG gives a list of connected nodes.

cardano-tracer/src/Cardano/Tracer/Handlers/Metrics/Prometheus.hs

@@ -35,24 +35,34 @@ import qualified System.Metrics as EKG
 import           System.Metrics (Sample, Value (..), sampleAll)
 import           System.Time.Extra (sleep)
 
--- | Runs simple HTTP server that listens host and port and returns
---   the list of currently connected nodes in such a format:
+-- | Runs a simple HTTP server that listens on @endpoint@.
 --
---   * relay-1
---   * relay-2
---   * core-1
+--   At the root, it lists the connected nodes, either as HTML or JSON, depending
+--   on the requests 'Accept: ' header.
 --
---  where 'relay-1', 'relay-2' and 'core-1' are nodes' names.
+--   Routing is dynamic, depending on the connected nodes. A valid URL is derived
+--   from the nodeName configured for the connecting node. E.g. a node name
+--   of `127.0.0.1:30004` will result in the route `/12700130004` which
+--   renders that node's Prometheus / OpenMetrics text exposition:
 --
---  Each of list items is a href. By clicking on it, the user will be
---  redirected to the page with the list of metrics received from that node,
---  in such a format:
---
---  rts_gc_par_tot_bytes_copied 0
---  rts_gc_num_gcs 17
---  rts_gc_max_bytes_slop 15888
---  rts_gc_bytes_copied 165952
---  ekg_server_timestamp_ms 1639569439623
+-- # TYPE Mem_resident_int gauge
+-- # HELP Mem_resident_int Kernel-reported RSS (resident set size)
+-- Mem_resident_int 103792640
+-- # TYPE rts_gc_max_bytes_used gauge
+-- rts_gc_max_bytes_used 5811512
+-- # TYPE rts_gc_gc_cpu_ms counter
+-- rts_gc_gc_cpu_ms 50
+-- # TYPE RTS_gcMajorNum_int gauge
+-- # HELP RTS_gcMajorNum_int Major GCs
+-- RTS_gcMajorNum_int 4
+-- # TYPE rts_gc_num_bytes_usage_samples counter
+-- rts_gc_num_bytes_usage_samples 4
+-- # TYPE remainingKESPeriods_int gauge
+-- remainingKESPeriods_int 62
+-- # TYPE rts_gc_bytes_copied counter
+-- rts_gc_bytes_copied 17114384
+-- # TYPE nodeCannotForge_int gauge
+-- # HELP nodeCannotForge_int How many times was this node unable to forge [a block]?
 --
 runPrometheusServer
   :: TracerEnv