ensure max listener count before adding listeners

Author: marcuspoehls

lib/lifecycle-handler.js

@@ -21,6 +21,7 @@ class LifecycleHandler {
 
     this.server = server
     this.logger = logger
+    this.isStopping = null
     this.preShutdown = preShutdown
     this.preServerStop = preServerStop
     this.postServerStop = postServerStop
@@ -44,10 +45,27 @@ class LifecycleHandler {
    */
   addListeners () {
     this.signals.forEach(signal => {
+      this.ensureMaxListenerCountFor(signal)
       process.on(signal, this.shutdownListener)
     })
   }
 
+  /**
+   * Ensures that registering the event listener
+   * for hapi-pulse won’t exceed the max
+   * listener count.
+   *
+   * @param {String} event
+   */
+  ensureMaxListenerCountFor (event) {
+    const maxListeners = process.getMaxListeners()
+    const listenerCount = process.listenerCount(event)
+
+    if (listenerCount >= maxListeners) {
+      process.setMaxListeners(maxListeners + 1)
+    }
+  }
+
   /**
    * Remove all shutdown listeners.
    */

test/comply-event-listener-limit.js

@@ -0,0 +1,53 @@
+'use strict'
+
+const Lab = require('lab')
+const Code = require('code')
+const Hapi = require('hapi')
+const Hoek = require('hoek')
+const Sinon = require('sinon')
+
+const { describe, it, beforeEach, afterEach } = (exports.lab = Lab.script())
+
+describe('server stop with custom signals:', () => {
+  beforeEach(async () => {
+    // stub process.exit to keep the Node.js process alive while running the tests
+    // else it would actually EXIT the process
+    Sinon.stub(process, 'exit')
+  })
+
+  afterEach(() => {
+    process.exit.restore()
+  })
+
+  it('increases the max listeners count for the given signals', async () => {
+    process.setMaxListeners(1)
+
+    const server = new Hapi.Server()
+    await server.register({
+      plugin: require('../lib'),
+      options: {
+        signals: ['HAPIPULSE', 'HAPIPULSE']
+      }
+    })
+
+    Code.expect(process.getMaxListeners()).to.equal(2)
+
+    await server.start()
+
+    Code.expect(process.getMaxListeners()).to.equal(2)
+    Code.expect(process.listenerCount('HAPIPULSE')).to.equal(2)
+
+    // a stopped hapi server has a "started" timestamp of 0
+    Code.expect(server.info.started).to.not.equal(0)
+
+    process.emit('HAPIPULSE')
+
+    // wait for the server to stop
+    await Hoek.wait(100)
+
+    Sinon.assert.called(process.exit)
+
+    // a stopped hapi server has a "started" timestamp of 0
+    Code.expect(server.info.started).to.equal(0)
+  })
+})