feat(cmn): have BaseService expose a full server (#2725)

Updates BaseServiceV2 to expose a full server instead of simply exposing
the server for metrics. Services can now add new custom routes to this
server. Mainly useful because we're already running the metrics server,
so we might as well allow people to add more things to it.

.changeset/five-fireants-notice.md

+---
+'@eth-optimism/common-ts': minor
+---
+
+Minor upgrade to BaseServiceV2 to expose a full customizable server, instead of just metrics.

packages/common-ts/package.json

@@ -34,21 +34,26 @@
     "@eth-optimism/core-utils": "0.8.6",
     "@sentry/node": "^6.3.1",
     "bcfg": "^0.1.7",
+    "body-parser": "^1.20.0",
     "commander": "^9.0.0",
     "dotenv": "^16.0.0",
     "envalid": "^7.2.2",
     "ethers": "^5.6.8",
     "express": "^4.17.1",
+    "express-prom-bundle": "^6.4.1",
     "lodash": "^4.17.21",
+    "morgan": "^1.10.0",
     "pino": "^6.11.3",
     "pino-multi-stream": "^5.3.0",
     "pino-sentry": "^0.7.0",
-    "prom-client": "^13.1.0"
+    "prom-client": "^13.1.0",
+    "qs": "^6.10.5"
   },
   "devDependencies": {
     "@ethersproject/abstract-provider": "^5.6.1",
     "@ethersproject/abstract-signer": "^5.6.2",
-    "@types/express": "^4.17.12",
+    "@types/express": "^4.17.13",
+    "@types/morgan": "^1.9.3",
     "@types/pino": "^6.3.6",
     "@types/pino-multi-stream": "^5.1.1",
     "chai": "^4.3.4",

packages/common-ts/src/base-service/base-service-v2.ts

@@ -6,8 +6,11 @@ import { Command, Option } from 'commander'
 import { ValidatorSpec, Spec, cleanEnv } from 'envalid'
 import { sleep } from '@eth-optimism/core-utils'
 import snakeCase from 'lodash/snakeCase'
-import express from 'express'
+import express, { Router } from 'express'
 import prometheus, { Registry } from 'prom-client'
+import promBundle from 'express-prom-bundle'
+import bodyParser from 'body-parser'
+import morgan from 'morgan'
 
 import { Logger } from '../common/logger'
 import { Metric } from './metrics'
@@ -19,8 +22,8 @@ export type Options = {
 
 export type StandardOptions = {
   loopIntervalMs?: number
-  metricsServerPort?: number
-  metricsServerHostname?: string
+  port?: number
+  hostname?: string
 }
 
 export type OptionsSpec<TOptions extends Options> = {
@@ -43,6 +46,8 @@ export type MetricsSpec<TMetrics extends MetricsV2> = {
   }
 }
 
+export type ExpressRouter = Router
+
 /**
  * BaseServiceV2 is an advanced but simple base class for long-running TypeScript services.
  */
@@ -71,6 +76,11 @@ export abstract class BaseServiceV2<
    */
   protected done: boolean
 
+  /**
+   * Whether or not the service is currently healthy.
+   */
+  protected healthy: boolean
+
   /**
    * Logger class for this service.
    */
@@ -97,19 +107,19 @@ export abstract class BaseServiceV2<
   protected readonly metricsRegistry: Registry
 
   /**
-   * Metrics server.
+   * App server.
    */
-  protected metricsServer: Server
+  protected server: Server
 
   /**
-   * Port for the metrics server.
+   * Port for the app server.
    */
-  protected readonly metricsServerPort: number
+  protected readonly port: number
 
   /**
-   * Hostname for the metrics server.
+   * Hostname for the app server.
    */
-  protected readonly metricsServerHostname: string
+  protected readonly hostname: string
 
   /**
    * @param params Options for the construction of the service.
@@ -122,8 +132,8 @@ export abstract class BaseServiceV2<
    * @param params.options Options to pass to the service.
    * @param params.loops Whether or not the service should loop. Defaults to true.
    * @param params.loopIntervalMs Loop interval in milliseconds. Defaults to zero.
-   * @param params.metricsServerPort Port for the metrics server. Defaults to 7300.
-   * @param params.metricsServerHostname Hostname for the metrics server. Defaults to 0.0.0.0.
+   * @param params.port Port for the app server. Defaults to 7300.
+   * @param params.hostname Hostname for the app server. Defaults to 0.0.0.0.
    */
   constructor(params: {
     name: string
@@ -132,8 +142,8 @@ export abstract class BaseServiceV2<
     options?: Partial<TOptions>
     loop?: boolean
     loopIntervalMs?: number
-    metricsServerPort?: number
-    metricsServerHostname?: string
+    port?: number
+    hostname?: string
   }) {
     this.loop = params.loop !== undefined ? params.loop : true
     this.state = {} as TServiceState
@@ -148,15 +158,15 @@ export abstract class BaseServiceV2<
         desc: 'Loop interval in milliseconds',
         default: params.loopIntervalMs || 0,
       },
-      metricsServerPort: {
+      port: {
         validator: validators.num,
-        desc: 'Port for the metrics server',
-        default: params.metricsServerPort || 7300,
+        desc: 'Port for the app server',
+        default: params.port || 7300,
       },
-      metricsServerHostname: {
+      hostname: {
         validator: validators.str,
-        desc: 'Hostname for the metrics server',
-        default: params.metricsServerHostname || '0.0.0.0',
+        desc: 'Hostname for the app server',
+        default: params.hostname || '0.0.0.0',
       },
     }
 
@@ -268,12 +278,13 @@ export abstract class BaseServiceV2<
 
     // Create the metrics server.
     this.metricsRegistry = prometheus.register
-    this.metricsServerPort = this.options.metricsServerPort
-    this.metricsServerHostname = this.options.metricsServerHostname
+    this.port = this.options.port
+    this.hostname = this.options.hostname
 
     // Set up everything else.
     this.loopIntervalMs = this.options.loopIntervalMs
     this.logger = new Logger({ name: params.name })
+    this.healthy = true
 
     // Gracefully handle stop signals.
     const maxSignalCount = 3
@@ -307,30 +318,69 @@ export abstract class BaseServiceV2<
   public async run(): Promise<void> {
     this.done = false
 
-    // Start the metrics server if not yet running.
-    if (!this.metricsServer) {
-      this.logger.info('starting metrics server')
+    // Start the app server if not yet running.
+    if (!this.server) {
+      this.logger.info('starting app server')
 
-      await new Promise((resolve) => {
+      // Start building the app.
       const app = express()
 
-        app.get('/metrics', async (_, res) => {
-          res.status(200).send(await this.metricsRegistry.metrics())
+      // Body parsing.
+      app.use(bodyParser.json())
+      app.use(bodyParser.urlencoded({ extended: true }))
+
+      // Logging.
+      app.use(
+        morgan((tokens, req, res) => {
+          return [
+            tokens.method(req, res),
+            tokens.url(req, res),
+            tokens.status(req, res),
+            JSON.stringify(req.body),
+            '\n',
+            tokens.res(req, res, 'content-length'),
+            '-',
+            tokens['response-time'](req, res),
+            'ms',
+          ].join(' ')
         })
+      )
 
-        this.metricsServer = app.listen(
-          this.metricsServerPort,
-          this.metricsServerHostname,
-          () => {
-            resolve(null)
-          }
+      // Metrics.
+      // Will expose a /metrics endpoint by default.
+      app.use(
+        promBundle({
+          promRegistry: this.metricsRegistry,
+          includeMethod: true,
+          includePath: true,
+          includeStatusCode: true,
+        })
       )
+
+      // Health status.
+      app.get('/healthz', async (req, res) => {
+        return res.json({
+          ok: this.healthy,
+        })
       })
 
-      this.logger.info(`metrics started`, {
-        port: this.metricsServerPort,
-        hostname: this.metricsServerHostname,
-        route: '/metrics',
+      // Registery user routes.
+      if (this.routes) {
+        const router = express.Router()
+        this.routes(router)
+        app.use('/api', router)
+      }
+
+      // Wait for server to come up.
+      await new Promise((resolve) => {
+        this.server = app.listen(this.port, this.hostname, () => {
+          resolve(null)
+        })
+      })
+
+      this.logger.info(`app server started`, {
+        port: this.port,
+        hostname: this.hostname,
       })
     }
 
@@ -381,15 +431,15 @@ export abstract class BaseServiceV2<
     }
 
     // Shut down the metrics server if it's running.
-    if (this.metricsServer) {
+    if (this.server) {
       this.logger.info('stopping metrics server')
       await new Promise((resolve) => {
-        this.metricsServer.close(() => {
+        this.server.close(() => {
           resolve(null)
         })
       })
       this.logger.info('metrics server stopped')
-      this.metricsServer = undefined
+      this.server = undefined
     }
   }
 
@@ -398,6 +448,13 @@ export abstract class BaseServiceV2<
    */
   protected init?(): Promise<void>
 
+  /**
+   * Initialization function for router.
+   *
+   * @param router Express router.
+   */
+  protected routes?(router: ExpressRouter): Promise<void>
+
   /**
    * Main function. Runs repeatedly when run() is called.
    */