feat: Handle termination signals

This patch adds handling of SIGINT and SIGTERM so that the server
is closed gracefully. It also moves the code that starts the server into
a function (in `server.ts`), separate from the command-line entrypoint
(in newly-added `main.ts`). This way, each code part's responsibilities
are clearer than if the process exit logic was conflated with running
Fastify.

Dockerfile

@@ -37,4 +37,4 @@ EXPOSE 8080
 
 # use tini as init process since Node.js isn't designed to be run as PID 1
 ENTRYPOINT ["/sbin/tini", "--"]
-CMD ["node", "--disable-proto=delete", "dist/server.js"]
+CMD ["node", "--disable-proto=delete", "dist/main.js"]

package.json

@@ -15,7 +15,7 @@
     "build": "npm run build --workspaces && node -e \"fs.rmSync('./dist',{force:true,recursive:true})\" && tsc",
     "lint": "npm run lint --workspaces && tsc --noEmit -p tsconfig.lint.json && eslint --ignore-path .gitignore src",
     "test": "npm run test --workspaces --if-present && mocha --require tsx --recursive \"test/**/*.ts\"",
-    "start": "node --disable-proto=delete dist/server.js"
+    "start": "node --disable-proto=delete dist/main.js"
   },
   "repository": {
     "type": "git",

src/main.ts

@@ -0,0 +1,89 @@
+import path from 'node:path'
+import { Config, readConfigDirectory } from './config.js'
+import { StructError } from 'superstruct'
+import pino from 'pino'
+import { startServer } from './server.js'
+import { getPort } from './environment.js'
+import { KubeConfig } from '@kubernetes/client-node'
+import { loadKubeConfig } from './kube-config.js'
+
+const log = pino({
+  level: 'info',
+  // do not log pid and hostname
+  base: undefined,
+  // use ISO strings for timestamps instead of milliseconds
+  timestamp: pino.stdTimeFunctions.isoTime,
+  // use string levels (e.g., "info") instead of level numbers (e.g., 30)
+  formatters: {
+    level: (label) => ({ level: label }),
+    log: (object) => {
+      if (object instanceof Error) {
+        return pino.stdSerializers.errWithCause(object)
+      }
+      return object
+    }
+  }
+})
+
+log.info('process_start')
+
+let config: Config
+try {
+  config = await readConfigDirectory(path.join(process.cwd(), 'config'))
+} catch (error) {
+  if (error instanceof StructError) {
+    // the value may contain secrets, so don't log it
+    error.value = undefined
+    error.branch = []
+  }
+  log.fatal(error, 'config_error')
+  process.exit(1)
+}
+
+let port: number
+try {
+  port = getPort()
+} catch (error) {
+  log.fatal(error, 'config_error')
+  process.exit(1)
+}
+
+let kubeConfig: KubeConfig
+try {
+  kubeConfig = loadKubeConfig(log, config)
+} catch (error) {
+  log.fatal(error, 'config_error')
+  process.exit(1)
+}
+
+const abortController = new AbortController()
+for (const signal of ['SIGINT', 'SIGTERM'] as const) {
+  process.once(signal, () => {
+    log.info({ signal }, 'process_signal')
+    abortController.abort()
+  })
+}
+
+try {
+  const close = await startServer({
+    log,
+    config,
+    port,
+    kubeConfig
+  })
+
+  if (abortController.signal.aborted) {
+    await close()
+  } else {
+    abortController.signal.addEventListener('abort', () => {
+      close().then(() => {
+        log.info('server_closed')
+      }).catch((error) => {
+        log.error(error, 'server_close_error')
+      })
+    })
+  }
+} catch (error) {
+  log.fatal(error, 'uncaught_error')
+  process.exit(1)
+}

src/server.ts

@@ -4,49 +4,20 @@ import { backend, notFound } from 'backend'
 import { fastifyStatic } from '@fastify/static'
 import path from 'node:path'
 import { fastify } from 'fastify'
-import { Config, readConfigDirectory } from './config.js'
-import { getPort } from './environment.js'
-import { loadKubeConfig } from './kube-config.js'
-import { StructError } from 'superstruct'
+import { Config } from './config.js'
+import { KubeConfig } from '@kubernetes/client-node'
 import { handleError } from './handle-error.js'
-import pino from 'pino'
+import { BaseLogger } from 'pino'
 
-const log = pino({
-  level: 'info',
-  // do not log pid and hostname
-  base: undefined,
-  // use ISO strings for timestamps instead of milliseconds
-  timestamp: pino.stdTimeFunctions.isoTime,
-  // use string levels (e.g., "info") instead of level numbers (e.g., 30)
-  formatters: {
-    level: (label) => ({ level: label }),
-    log: (object) => {
-      if (object instanceof Error) {
-        return pino.stdSerializers.errWithCause(object)
-      }
-      return object
-    }
-  }
-})
-
-log.info('process_start')
-
-let config: Config
-try {
-  config = await readConfigDirectory(path.join(process.cwd(), 'config'))
-} catch (error) {
-  if (error instanceof StructError) {
-    // the value may contain secrets, so don't log it
-    error.value = undefined
-    error.branch = []
-  }
-  log.fatal(error, 'config_error')
-  process.exit(1)
-}
+type CloseFunction = () => Promise<void>
 
-try {
-  const port = getPort()
-  const kubeConfig = loadKubeConfig(log, config)
+export async function startServer (options: {
+  log: BaseLogger
+  config: Config
+  port: number
+  kubeConfig: KubeConfig
+}): Promise<CloseFunction> {
+  const { log, config, port, kubeConfig } = options
 
   const app = fastify({
     logger: log
@@ -85,7 +56,8 @@ try {
   })
 
   await app.listen({ port, host: '::' })
-} catch (error) {
-  log.fatal(error, 'uncaught_error')
-  process.exit(1)
+
+  return async () => {
+    await app.close()
+  }
 }