Add trace flag for configuring long stack traces

Author: dougwilson

Readme.md

@@ -158,6 +158,9 @@ issue [#501](https://github.com/felixge/node-mysql/issues/501). (Default: `'fals
 * `dateStrings`: Force date types (TIMESTAMP, DATETIME, DATE) to be returned as strings rather then
    inflated into JavaScript Date objects. (Default: `false`)
 * `debug`: Prints protocol details to stdout. (Default: `false`)
+* `trace`: Generates stack traces on `Error` to include call site of library
+   entrance ("long stack traces"). Slight performance penalty for most calls.
+   (Default: `true`)
 * `multipleStatements`: Allow multiple mysql statements per query. Be careful
   with this, it exposes you to SQL injection attacks. (Default: `false`)
 * `flags`: List of connection flags to use other than the default ones. It is

lib/ConnectionConfig.js

@@ -20,6 +20,7 @@ function ConnectionConfig(options) {
   this.bigNumberStrings   = options.bigNumberStrings || false;
   this.dateStrings        = options.dateStrings || false;
   this.debug              = options.debug;
+  this.trace              = options.trace !== false;
   this.stringifyObjects   = options.stringifyObjects || false;
   this.timezone           = options.timezone || 'local';
   this.flags              = options.flags || '';

lib/protocol/Protocol.js

@@ -105,6 +105,11 @@ Protocol.prototype._enqueue = function(sequence) {
     return sequence;
   }
 
+  if (this._config.trace) {
+    // Long stack trace support
+    sequence._callSite = new Error;
+  }
+
   this._queue.push(sequence);
 
   var self = this;

lib/protocol/sequences/Sequence.js

@@ -9,10 +9,8 @@ function Sequence(callback) {
   EventEmitter.call(this);
 
   this._callback         = callback;
+  this._callSite         = null;
   this._ended            = false;
-
-  // Experimental: Long stack trace support
-  this._callSite = new Error;
 }
 
 Sequence.determinePacket = function(byte) {
@@ -38,7 +36,12 @@ Sequence.prototype._packetToError = function(packet) {
 };
 
 Sequence.prototype._addLongStackTrace = function(err) {
+  if (!this._callSite) {
+    return;
+  }
+
   var delimiter = '\n    --------------------\n' ;
+
   if (err.stack.indexOf(delimiter) > -1) {
     return;
   }
@@ -62,7 +65,7 @@ Sequence.prototype.end = function(err) {
   // causes a cyclic reference that the GC does not detect properly, but I was
   // unable to produce a standalone version of this leak. This would be a great
   // challenge for somebody interested in difficult problems : )!
-  delete this._callSite;
+  this._callSite = null;
 
   // try...finally for exception safety
   try {

test/integration/connection/test-long-stack-traces-disabled.js

@@ -0,0 +1,14 @@
+var common     = require('../../common');
+var connection = common.createConnection({trace: false});
+var assert     = require('assert');
+
+var err;
+connection.query('invalid sql', function(_err) {
+  err = _err;
+});
+
+connection.end();
+
+process.on('exit', function() {
+  assert.ok(err.stack.indexOf(__filename) < 0);
+});

test/integration/connection/test-long-stack-traces.js

@@ -1,5 +1,3 @@
-// Experimental: https://github.com/felixge/node-mysql/issues/198
-
 var common     = require('../../common');
 var connection = common.createConnection();
 var assert     = require('assert');