feat(BaseServiceV2):End immediately when looping (#2731)

* end immediately when looping

* changeset

* improvements based on comments

* add logging

* add logging ect. to main loop

* stop main loop

* get rid of this.running for this.loop

* Revert "get rid of this.running for this.loop"

This reverts commit 18e6fe88c61eb154bc76418b0bf39914438d57a5.

* lower-case
Co-authored-by: Will Cory <willcory@Wills-MacBook-Pro.local>

.changeset/tasty-drinks-rhyme.md

+---
+'@eth-optimism/common-ts': minor
+---
+
+More gracefully shut down base service

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

@@ -4,7 +4,6 @@ import Config from 'bcfg'
 import * as dotenv from 'dotenv'
 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, { Router } from 'express'
 import prometheus, { Registry } from 'prom-client'
@@ -62,6 +61,17 @@ export abstract class BaseServiceV2<
   TMetrics extends MetricsV2,
   TServiceState
 > {
+  /**
+   * The timeout that controls the polling interval
+   * If clearTimeout(this.pollingTimeout) is called the timeout will stop
+   */
+  private pollingTimeout: NodeJS.Timeout
+
+  /**
+   * The promise representing this.main
+   */
+  private mainPromise: ReturnType<typeof this.main>
+
   /**
    * Whether or not the service will loop.
    */
@@ -77,11 +87,6 @@ export abstract class BaseServiceV2<
    */
   protected running: boolean
 
-  /**
-   * Whether or not the service has run to completion.
-   */
-  protected done: boolean
-
   /**
    * Whether or not the service is currently healthy.
    */
@@ -373,8 +378,6 @@ export abstract class BaseServiceV2<
    * main function. Will also catch unhandled errors.
    */
   public async run(): Promise<void> {
-    this.done = false
-
     // Start the app server if not yet running.
     if (!this.server) {
       this.logger.info('starting app server')
@@ -446,9 +449,11 @@ export abstract class BaseServiceV2<
     if (this.loop) {
       this.logger.info('starting main loop')
       this.running = true
-      while (this.running) {
+
+      const doLoop = async () => {
         try {
-          await this.main()
+          this.mainPromise = this.main()
+          await this.mainPromise
         } catch (err) {
           this.metrics.unhandledErrors.inc()
           this.logger.error('caught an unhandled exception', {
@@ -460,15 +465,14 @@ export abstract class BaseServiceV2<
 
         // Sleep between loops if we're still running (service not stopped).
         if (this.running) {
-          await sleep(this.loopIntervalMs)
+          this.pollingTimeout = setTimeout(doLoop, this.loopIntervalMs)
         }
       }
+      doLoop()
     } else {
       this.logger.info('running main function')
       await this.main()
     }
-
-    this.done = true
   }
 
   /**
@@ -476,13 +480,13 @@ export abstract class BaseServiceV2<
    * iteration is finished and will then stop looping.
    */
   public async stop(): Promise<void> {
+    this.logger.info('stopping main loop...')
     this.running = false
-
-    // Wait until the main loop has finished.
-    this.logger.info('stopping service, waiting for main loop to finish')
-    while (!this.done) {
-      await sleep(1000)
-    }
+    clearTimeout(this.pollingTimeout)
+    this.logger.info('waiting for main to complete')
+    // if main is in the middle of running wait for it to complete
+    await this.mainPromise
+    this.logger.info('main loop stoped.')
 
     // Shut down the metrics server if it's running.
     if (this.server) {