[server/logger] downgrade EPIPE errors to debug level (#9041)

Backports PR #9023

**Commit 1:**
[server/logger] downgrade EPIPE errors to debug level

* Original sha: 4703b367aa
* Authored by spalger <email@spalger.com> on 2016-11-09T23:48:48Z

**Commit 2:**
fix variable naming

* Original sha: fd272c5b3b
* Authored by spalger <email@spalger.com> on 2016-11-11T01:06:55Z

src/server/logging/__tests__/log_interceptor.js

@@ -2,9 +2,9 @@ import expect from 'expect.js';
 
 import { LogInterceptor } from '../log_interceptor';
 
-function stubEconnresetEvent() {
+function stubClientErrorEvent(errno) {
   const error = new Error();
-  error.errno = 'ECONNRESET';
+  error.errno = errno;
 
   return {
     event: 'error',
@@ -15,6 +15,9 @@ function stubEconnresetEvent() {
   };
 }
 
+const stubEconnresetEvent = () => stubClientErrorEvent('ECONNRESET');
+const stubEpipeEvent = () => stubClientErrorEvent('EPIPE');
+
 function assertDowngraded(transformed) {
   expect(!!transformed).to.be(true);
   expect(transformed).to.have.property('event', 'log');
@@ -30,6 +33,12 @@ describe('server logging LogInterceptor', () => {
       assertDowngraded(interceptor.downgradeIfEconnreset(event));
     });
 
+    it('transforms EPIPE events', () => {
+      const interceptor = new LogInterceptor();
+      const event = stubEpipeEvent();
+      assertDowngraded(interceptor.downgradeIfEpipe(event));
+    });
+
     it('does not match if the tags are not in order', () => {
       const interceptor = new LogInterceptor();
       const event = stubEconnresetEvent();
@@ -39,8 +48,7 @@ describe('server logging LogInterceptor', () => {
 
     it('ignores non ECONNRESET events', () => {
       const interceptor = new LogInterceptor();
-      const event = stubEconnresetEvent();
-      event.data.errno = 'not ECONNRESET';
+      const event = stubClientErrorEvent('not ECONNRESET');
       expect(interceptor.downgradeIfEconnreset(event)).to.be(null);
     });
 

src/server/logging/log_interceptor.js

@@ -38,8 +38,33 @@ export class LogInterceptor extends Stream.Transform {
     };
   }
 
+  /**
+   *  Since the upgrade to hapi 14, any socket write
+   *  error is surfaced as a generic "client error"
+   *  but "EPIPE" specifically is not useful for the
+   *  logs unless you are trying to debug edge-case behaviors.
+   *
+   *  For that reason, we downgrade this from error to debug level
+   *
+   *  @param {object} - log event
+   */
+  downgradeIfEpipe(event) {
+    const isClientError = doTagsMatch(event, ['connection', 'client', 'error']);
+    const isEpipe = isClientError && get(event, 'data.errno') === 'EPIPE';
+
+    if (!isEpipe) return null;
+
+    return {
+      event: 'log',
+      pid: event.pid,
+      timestamp: event.timestamp,
+      tags: ['debug', 'connection', 'epipe'],
+      data: 'EPIPE: Socket was closed by the client (probably the browser) before the response could be completed'
+    };
+  }
+
   _transform(event, enc, next) {
-    const downgraded = this.downgradeIfEconnreset(event);
+    const downgraded = this.downgradeIfEconnreset(event) || this.downgradeIfEpipe(event);
 
     this.push(downgraded || event);
     next();

tasks/config/simplemocha.js

@@ -13,7 +13,8 @@ module.exports = {
       'test/**/__tests__/**/*.js',
       'src/**/__tests__/**/*.js',
       'test/fixtures/__tests__/*.js',
-      '!src/**/public/**'
+      '!src/**/public/**',
+      '!**/_*.js'
     ]
   }
 };