fix(server): Add error handler for webserver socket.

Some times connection arrive, are given 404 responses, then disconnect,
resulting in ECONNRESET errors on the socket.  After we began monitoring
UncaughtExceptions, these errors show up. Suppress them with a handler
that ignores errors.

lib/server.js

@@ -123,6 +123,13 @@ class Server extends KarmaEventEmitter {
         BundleUtils.bundleResourceIfNotExist('context/main.js', 'static/context.js')
       ])
       this._boundServer = await NetUtils.bindAvailablePort(config.port, config.listenAddress)
+      this._boundServer.on('connection', (socket) => {
+        // Attach an error handler to avoid UncaughtException errors.
+        socket.on('error', (err) => {
+          // Errors on this socket are retried, ignore them
+          this.log.debug('Ignoring error on webserver connection: ' + err)
+        })
+      })
       config.port = this._boundServer.address().port
       this._injector.invoke(this._start, this)
     } catch (err) {
@@ -228,6 +235,10 @@ class Server extends KarmaEventEmitter {
 
       socket.on('complete', (data, ack) => ack())
 
+      socket.on('error', (err) => {
+        this.log.debug('karma server socket error: ' + err)
+      })
+
       socket.on('register', (info) => {
         let newBrowser = info.id ? (capturedBrowsers.getById(info.id) || singleRunBrowsers.getById(info.id)) : null
 
@@ -372,14 +383,19 @@ class Server extends KarmaEventEmitter {
     processWrapper.on('SIGINT', () => disconnectBrowsers(process.exitCode))
     processWrapper.on('SIGTERM', disconnectBrowsers)
 
-    processWrapper.on('uncaughtException', (error) => {
-      this.log.error(error)
+    const reportError = (error) => {
+      process.emit('infrastructure_error', error)
       disconnectBrowsers(1)
-    })
+    }
 
     processWrapper.on('unhandledRejection', (error) => {
-      this.log.error(error)
-      disconnectBrowsers(1)
+      this.log.error('UnhandledRejection')
+      reportError(error)
+    })
+
+    processWrapper.on('uncaughtException', (error) => {
+      this.log.error('UncaughtException')
+      reportError(error)
     })
   }
 

test/unit/server.spec.js

@@ -91,7 +91,7 @@ describe('server', () => {
     }
 
     mockBoundServer = {
-      on: sinon.spy((event, callback) => callback && callback()),
+      on: sinon.spy((event, callback) => callback && callback(mockServerSocket)),
       listen: sinon.spy((port, listenAddress, callback) => callback && callback()),
       close: sinon.spy((callback) => callback && callback()),
       address: () => { return { port: 9876 } }
@@ -148,6 +148,7 @@ describe('server', () => {
       server.start().then(() => {
         expect(NetUtils.bindAvailablePort).to.have.been.calledWith(9876, '127.0.0.1')
         expect(mockBoundServer.address).to.have.been.called
+        expect(typeof mockSocketEventListeners.get('error')).to.be.equal('function')
         done()
       })
     })