fastify · mcollina · Oct 5, 2022 · Oct 5, 2022 · Oct 5, 2022
diff --git a/index.js b/index.js
@@ -8,6 +8,8 @@ async function start (opts) {
 
   let listening = false
   let stopped = false
+  let handler
+
   const res = {
     app: await (spinUpFastify(opts, serverWrapper, restart, true).ready()),
     restart,
@@ -38,19 +40,35 @@ async function start (opts) {
     stop
   }
 
-  res.app.server.on('request', res.app.server.handler)
+  res.app.server.on('request', handler)
 
   return res
 
   async function restart (_opts = opts) {
     const old = res.app
-    const oldHandler = serverWrapper.server.handler
+    const oldHandler = handler
     const clientErrorListeners = old.server.listeners('clientError')
     const newApp = spinUpFastify(_opts, serverWrapper, restart)
-    await newApp.ready()
-    old.server.removeListener('request', oldHandler)
+    try {
+      await newApp.ready()
+    } catch (err) {
+      const listenersNow = newApp.server.listeners('clientError')
+      handler = oldHandler
+      // Creating a new Fastify apps adds one clientError listener
+      // Let's remove all the new ones
+      for (const listener of listenersNow) {
+        if (clientErrorListeners.indexOf(listener) === -1) {
+          old.server.removeListener('clientError', listener)
+        }
+      }
+      await newApp.close()
+      throw err
+    }
+
+    // Remove the old handler and add the new one
+    // the handler variable was updated in the spinUpFastify function
     old.server.removeListener('request', oldHandler)
-    newApp.server.on('request', newApp.server.handler)
+    newApp.server.on('request', handler)
     for (const listener of clientErrorListeners) {
       old.server.removeListener('clientError', listener)
     }
@@ -72,22 +90,22 @@ async function start (opts) {
     await Promise.all(toClose)
     res.app.log.info('server stopped')
   }
-}
 
-function spinUpFastify (opts, serverWrapper, restart, isStart = false) {
-  const server = serverWrapper.server
-  const _opts = Object.assign({}, opts)
-  _opts.serverFactory = function (handler) {
-    server.handler = handler
-    return server
-  }
-  const app = Fastify(_opts)
+  function spinUpFastify (opts, serverWrapper, restart, isStart = false) {
+    const server = serverWrapper.server
+    const _opts = Object.assign({}, opts)
+    _opts.serverFactory = function (_handler) {
+      handler = _handler
+      return server
+    }
+    const app = Fastify(_opts)
 
-  app.decorate('restart', restart)
-  app.decorate('restarted', !isStart)
-  app.register(opts.app, opts)
+    app.decorate('restart', restart)
+    app.decorate('restarted', !isStart)
+    app.register(opts.app, opts)
 
-  return app
+    return app
+  }
 }
 
 module.exports = {

diff --git a/test/test.js b/test/test.js
@@ -260,3 +260,56 @@ test('no warnings', async ({ pass, teardown, plan, same, equal, fail }) => {
     await restart()
   }
 })
+
+test('restart fastify after a failed start', async ({ pass, teardown, plan, same, equal, rejects }) => {
+  plan(11)
+
+  const _opts = {
+    port: 0,
+    app: myApp
+  }
+
+  let count = 0
+
+  async function myApp (app, opts) {
+    pass('application loaded')
+    equal(opts, _opts)
+
+    app.register(async function () {
+      if (count++ % 2) {
+        throw new Error('kaboom')
+      }
+    })
+    app.get('/', async () => {
+      return { hello: 'world' }
+    })
+  }
+
+  const server = await start(_opts)
+
+  same(server.app.restarted, false)
+
+  const { stop, restart, listen } = server
+  teardown(stop)
+
+  const { port } = await listen()
+
+  {
+    const res = await request(`http://127.0.0.1:${port}`)
+    same(await res.body.json(), { hello: 'world' })
+  }
+
+  await rejects(restart())
+
+  {
+    const res = await request(`http://127.0.0.1:${port}`)
+    same(await res.body.json(), { hello: 'world' })
+  }
+
+  await restart()
+
+  {
+    const res = await request(`http://127.0.0.1:${port}`)
+    same(await res.body.json(), { hello: 'world' })
+  }
+})