Add /metrics endpoint for prometheus support (#512)

monitor/index.js

@@ -2,6 +2,7 @@ require('dotenv').config()
 const express = require('express')
 const cors = require('cors')
 const { readFile } = require('./utils/file')
+const { getPrometheusMetrics } = require('./prometheusMetrics')
 
 const app = express()
 const bridgeRouter = express.Router({ mergeParams: true })
@@ -11,10 +12,10 @@ app.use(cors())
 app.get('/favicon.ico', (req, res) => res.sendStatus(204))
 app.use('/:bridgeName', bridgeRouter)
 
-bridgeRouter.get('/:file(validators|eventsStats|alerts|mediators|stuckTransfers|failures)?', async (req, res, next) => {
+bridgeRouter.get('/:file(validators|eventsStats|alerts|mediators|stuckTransfers|failures)?', (req, res, next) => {
   try {
     const { bridgeName, file } = req.params
-    const results = await readFile(`./responses/${bridgeName}/${file || 'getBalances'}.json`)
+    const results = readFile(`./responses/${bridgeName}/${file || 'getBalances'}.json`)
     res.json(results)
   } catch (e) {
     // this will eventually be handled by your error handling middleware
@@ -22,6 +23,15 @@ bridgeRouter.get('/:file(validators|eventsStats|alerts|mediators|stuckTransfers|
   }
 })
 
+bridgeRouter.get('/metrics', (req, res, next) => {
+  try {
+    const metrics = getPrometheusMetrics(req.params.bridgeName)
+    res.type('text').send(metrics)
+  } catch (e) {
+    next(e)
+  }
+})
+
 const port = process.env.MONITOR_PORT || 3003
 app.set('port', port)
 app.listen(port, () => console.log(`Monitoring app listening on port ${port}!`))

monitor/prometheusMetrics.js

@@ -0,0 +1,104 @@
+const { readFile } = require('./utils/file')
+
+const {
+  MONITOR_HOME_TO_FOREIGN_ALLOWANCE_LIST,
+  MONITOR_HOME_TO_FOREIGN_BLOCK_LIST,
+  MONITOR_HOME_VALIDATORS_BALANCE_ENABLE,
+  MONITOR_FOREIGN_VALIDATORS_BALANCE_ENABLE
+} = process.env
+
+function BridgeConf(type, validatorsBalanceEnable, alertTargetFunc, failureDirection) {
+  this.type = type
+  this.validatorsBalanceEnable = validatorsBalanceEnable
+  this.alertTargetFunc = alertTargetFunc
+  this.failureDirection = failureDirection
+}
+
+const BRIDGE_CONFS = [
+  new BridgeConf('home', MONITOR_HOME_VALIDATORS_BALANCE_ENABLE, 'executeAffirmations', 'homeToForeign'),
+  new BridgeConf('foreign', MONITOR_FOREIGN_VALIDATORS_BALANCE_ENABLE, 'executeSignatures', 'foreignToHome')
+]
+
+function hasError(obj) {
+  return 'error' in obj
+}
+
+function getPrometheusMetrics(bridgeName) {
+  const responsePath = jsonName => `./responses/${bridgeName}/${jsonName}.json`
+
+  const metrics = {}
+
+  // Balance metrics
+  const balancesFile = readFile(responsePath('getBalances'))
+
+  if (!hasError(balancesFile)) {
+    const { home: homeBalances, foreign: foreignBalances, ...commonBalances } = balancesFile
+    metrics.balances_home_value = homeBalances.totalSupply
+    metrics.balances_home_txs_deposit = homeBalances.deposits
+    metrics.balances_home_txs_withdrawal = homeBalances.withdrawals
+
+    metrics.balances_foreign_value = foreignBalances.erc20Balance
+    metrics.balances_foreign_txs_deposit = foreignBalances.deposits
+    metrics.balances_foreign_txs_withdrawal = foreignBalances.withdrawals
+
+    metrics.balances_diff_value = commonBalances.balanceDiff
+    metrics.balances_diff_deposit = commonBalances.depositsDiff
+    metrics.balances_diff_withdrawal = commonBalances.withdrawalDiff
+    if (MONITOR_HOME_TO_FOREIGN_ALLOWANCE_LIST || MONITOR_HOME_TO_FOREIGN_BLOCK_LIST) {
+      metrics.balances_unclaimed_txs = commonBalances.unclaimedDiff
+      metrics.balances_unclaimed_value = commonBalances.unclaimedBalance
+    }
+  }
+
+  // Validator metrics
+  const validatorsFile = readFile(responsePath('validators'))
+
+  if (!hasError(validatorsFile)) {
+    for (const bridge of BRIDGE_CONFS) {
+      const allValidators = validatorsFile[bridge.type].validators
+      const validatorAddressesWithBalanceCheck =
+        typeof bridge.validatorsBalanceEnable === 'string'
+          ? bridge.validatorsBalanceEnable.split(' ')
+          : Object.keys(allValidators)
+
+      validatorAddressesWithBalanceCheck.forEach((addr, ind) => {
+        metrics[`validators_balances_${bridge.type}${ind}{address="${addr}"}`] = allValidators[addr].balance
+      })
+    }
+  }
+
+  // Alert metrics
+  const alertsFile = readFile(responsePath('alerts'))
+
+  if (!hasError(alertsFile)) {
+    for (const bridge of BRIDGE_CONFS) {
+      Object.entries(alertsFile[bridge.alertTargetFunc].misbehavior).forEach(([period, val]) => {
+        metrics[`misbehavior_${bridge.type}_${period}`] = val
+      })
+    }
+  }
+
+  // Failure metrics
+  const failureFile = readFile(responsePath('failures'))
+
+  if (!hasError(failureFile)) {
+    for (const bridge of BRIDGE_CONFS) {
+      const dir = bridge.failureDirection
+      const failures = failureFile[dir]
+      metrics[`failures_${dir}_total`] = failures.total
+      Object.entries(failures.stats).forEach(([period, count]) => {
+        metrics[`failures_${dir}_${period}`] = count
+      })
+    }
+  }
+
+  // Pack metrcis into a plain text
+  return Object.entries(metrics).reduceRight(
+    // Prometheus supports `Nan` and possibly signed `Infinity`
+    // in case cast to `Number` fails
+    (acc, [key, val]) => `${key} ${val ? Number(val) : 0}\n${acc}`,
+    ''
+  )
+}
+
+module.exports = { getPrometheusMetrics }

monitor/utils/file.js

@@ -1,9 +1,9 @@
 const fs = require('fs')
 const path = require('path')
 
-async function readFile(filePath) {
+function readFile(filePath) {
   try {
-    const content = await fs.readFileSync(filePath)
+    const content = fs.readFileSync(filePath)
     const json = JSON.parse(content)
     const timeDiff = Math.floor(Date.now() / 1000) - json.lastChecked
     return Object.assign({}, json, { timeDiff })