fix: bring back metrics file that got deleted during rebase

package.json

@@ -128,9 +128,8 @@
     "lodash.get": "^4.4.2",
     "lodash.sortby": "^4.7.0",
     "lodash.values": "^4.3.0",
-    "mime-types": "^2.1.13",
-    "mafmt": "^2.1.8",
     "mime-types": "^2.1.16",
+    "mafmt": "^2.1.8",
     "mkdirp": "~0.5.1",
     "multiaddr": "^2.3.0",
     "multihashes": "~0.4.9",

src/http/api/routes/debug.js

@@ -0,0 +1,31 @@
+'use strict'
+
+const register = require('prom-client').register
+const client = require('prom-client')
+
+// Endpoint for handling debug metrics
+module.exports = (server) => {
+  const api = server.select('API')
+  // Clear the register to make sure we're not registering multiple ones
+  register.clear()
+  const gauge = new client.Gauge({ name: 'number_of_peers', help: 'the_number_of_currently_connected_peers' })
+
+  api.route({
+    method: 'GET',
+    path: '/debug/metrics/prometheus',
+    handler: (request, reply) => {
+      if (!process.env.IPFS_MONITORING) {
+        return reply('Monitoring is disabled. Enable it by setting environment variable IPFS_MONITORING')
+          .code(501) // 501 = Not Implemented
+      }
+      server.app.ipfs.swarm.peers((err, res) => {
+        if (err) {
+          return reply(err).code(500)
+        }
+        const count = res.length
+        gauge.set(count)
+        reply(register.metrics()).header('Content-Type', register.contentType)
+      })
+    }
+  })
+}