expose own metrics (#14)

index.js

@@ -15,6 +15,7 @@ const DEFAULT_PROM_TARGETS_LOC = './targets.json'
 class PrometheusDhtBridge extends ReadyResource {
   constructor (dht, server, sharedSecret, {
     keyPairSeed,
+    ownPromClient,
     _forceFlushOnClientReady = false,
     prometheusTargetsLoc = DEFAULT_PROM_TARGETS_LOC,
     entryExpiryMs = 3 * 60 * 60 * 1000,
@@ -44,6 +45,18 @@ class PrometheusDhtBridge extends ReadyResource {
       this._handleGet.bind(this)
     )
 
+    ownPromClient = ownPromClient || null
+    if (ownPromClient) {
+      this.server.get(
+        '/metrics',
+        { logLevel: serverLogLevel },
+        async function (req, reply) {
+          const metrics = await ownPromClient.register.metrics()
+          reply.send(metrics)
+        }
+      )
+    }
+
     this.promTargetsLoc = prometheusTargetsLoc
     this.aliasRpcServer = new AliasRpcServer(this.swarm, this.secret, this.putAlias.bind(this))
 

package.json

@@ -33,7 +33,6 @@
     "hypercore-crypto": "^3.4.2",
     "hyperdht": "^6.15.1",
     "newline-decoder": "^1.0.2",
-    "prom-client": "^15.1.2",
     "standard": "^17.1.0",
     "test-tmp": "^1.2.1",
     "z32": "^1.1.0"
@@ -48,6 +47,7 @@
     "hypercore-id-encoding": "^1.3.0",
     "hyperswarm": "^4.7.15",
     "pino": "^9.2.0",
+    "prom-client": "^15.1.3",
     "protomux-rpc": "^1.5.2",
     "ready-resource": "^1.1.1",
     "safety-catch": "^1.0.2"

prometheus/prometheus.yml

@@ -1,8 +1,8 @@
 # This is an example config.
 
 global:
-  scrape_interval: 1s
-  evaluation_interval: 1s
+  scrape_interval: 5s
+  evaluation_interval: 5s
 
 # Source for relabeling approach: https://stackoverflow.com/questions/59866342/prometheus-dynamic-metrics-path
 scrape_configs:

run.js

@@ -6,6 +6,7 @@ const pino = require('pino')
 const fastify = require('fastify')
 const idEnc = require('hypercore-id-encoding')
 const goodbye = require('graceful-goodbye')
+const promClient = require('prom-client')
 
 function loadConfig () {
   const config = {
@@ -59,13 +60,16 @@ async function main () {
     _forceFlushOnClientReady
   } = loadConfig()
 
+  promClient.collectDefaultMetrics()
+
   const logger = pino({ level: logLevel })
   logger.info('Starting up Prometheus DHT bridge')
 
   const dht = new HyperDHT({ bootstrap })
   const server = fastify({ logger })
   const bridge = new PrometheusDhtBridge(dht, server, sharedSecret, {
     keyPairSeed,
+    ownPromClient: promClient,
     prometheusTargetsLoc,
     _forceFlushOnClientReady,
     serverLogLevel

test/integration.js

@@ -12,6 +12,7 @@ const promClient = require('prom-client')
 const DhtPromClient = require('dht-prom-client')
 const HyperDHT = require('hyperdht')
 const z32 = require('z32')
+const axios = require('axios')
 
 const BRIDGE_EXECUTABLE = path.join(path.dirname(__dirname), 'run.js')
 const PROMETHEUS_EXECUTABLE = path.join(path.dirname(__dirname), 'prometheus', 'prometheus')
@@ -163,6 +164,10 @@ test('Integration test, happy path', async t => {
 
   await tAliasReq
 
+  const res = await axios.get(`${bridgeHttpAddress}/metrics`)
+  t.is(res.status, 200, 'can scrape own metrics')
+  t.is(res.data.includes('nodejs_eventloop_lag_mean_seconds'), true, 'sanity check')
+
   // 3) Setup prometheus
   const promConfigFileLoc = path.join(tmpDir, 'prometheus.yml')
   await writePromConfig(promConfigFileLoc, bridgeHttpAddress, promTargetsLoc)