Store Compiled Packet Parsers in a global cache - Resolves #722

When a connection is closed, any compiled parser created for that will
be lost, as the connection is removed.

However, Node/V8 Internals appear to be holding onto any created function.

This can result in memory leaking based on connection cycling and new
parsers being created again.

This change creates a global cache store since everything around the generated
code is not connection specific.

This also completes a TODO to use an LRU cache, although I set a high value
as to avoid running into the leak if the LRU is too small.

An API is provided for anyone who does need to control the max value, as
well as an API to clear the parser cache.

Author: aikar

index.js

@@ -2,6 +2,7 @@ var SqlString = require('sqlstring');
 
 var Connection = require('./lib/connection.js');
 var ConnectionConfig = require('./lib/connection_config.js');
+var parserCache = require("./lib/parsers/parser_cache");
 
 module.exports.createConnection = function(opts) {
   return new Connection({ config: new ConnectionConfig(opts) });
@@ -61,3 +62,11 @@ exports.__defineGetter__('Charsets', function() {
 exports.__defineGetter__('CharsetToEncoding', function() {
   return require('./lib/constants/charset_encodings.js');
 });
+
+exports.setMaxParserCache = function (max) {
+  parserCache.setMaxCache(max);
+};
+
+exports.clearParserCache = function () {
+  parserCache.clearCache();
+};

lib/commands/execute.js

@@ -6,7 +6,7 @@ var Packets = require('../packets/index.js');
 
 var objectAssign = require('object-assign');
 
-var compileParser = require('../compile_binary_parser.js');
+var getBinaryParser = require('../parsers/binary_parser.js');
 
 function Execute(options, callback) {
   Command.call(this);
@@ -33,13 +33,7 @@ function Execute(options, callback) {
 util.inherits(Execute, Command);
 
 Execute.prototype.buildParserFromFields = function(fields, connection) {
-  var parserKey = connection.keyFromFields(fields, this.options);
-  var parser = connection.binaryProtocolParsers[parserKey];
-  if (!parser) {
-    parser = compileParser(fields, this.options, connection.config);
-    connection.binaryProtocolParsers[parserKey] = parser;
-  }
-  return parser;
+  return getBinaryParser(fields, this.options, connection.config);
 };
 
 Execute.prototype.start = function(packet, connection) {

lib/commands/query.js

@@ -7,7 +7,7 @@ var objectAssign = require('object-assign');
 
 var Command = require('./command.js');
 var Packets = require('../packets/index.js');
-var compileParser = require('../compile_text_parser.js');
+var getTextParser = require('../parsers/text_parser.js');
 var ServerStatus = require('../constants/server_status.js');
 var CharsetToEncoding = require('../constants/charset_encodings.js');
 
@@ -195,15 +195,10 @@ Query.prototype.readField = function(packet, connection) {
   }
 
   // last field received
-  if (this._receivedFieldsCount == this._fieldCount) {
+  if (this._receivedFieldsCount === this._fieldCount) {
     var fields = this._fields[this._resultIndex];
     this.emit('fields', fields);
-    var parserKey = connection.keyFromFields(fields, this.options);
-    this._rowParser = connection.textProtocolParsers[parserKey];
-    if (!this._rowParser) {
-      this._rowParser = compileParser(fields, this.options, connection.config);
-      connection.textProtocolParsers[parserKey] = this._rowParser;
-    }
+    this._rowParser = getTextParser(fields, this.options, connection.config);
     return Query.prototype.fieldsEOF;
   }
   return Query.prototype.readField;

lib/connection.js

@@ -58,19 +58,6 @@ function Connection(opts) {
     }
   });
 
-  // TODO: make it lru cache
-  // https://github.com/mercadolibre/node-simple-lru-cache
-  // or https://github.com/rsms/js-lru
-  // or https://github.com/monsur/jscache
-  // or https://github.com/isaacs/node-lru-cache
-  //
-  // key is field.name + ':' + field.columnType + ':' field.flags + '/'
-  this.textProtocolParsers = {};
-
-  // TODO: not sure if cache should be separate (same key as with textProtocolParsers)
-  // or part of prepared statements cache (key is sql query)
-  this.binaryProtocolParsers = {};
-
   this.serverCapabilityFlags = 0;
   this.authorized = false;
 
@@ -639,25 +626,6 @@ Connection.prototype.resume = function resume() {
   this.stream.resume();
 };
 
-Connection.prototype.keyFromFields = function keyFromFields(fields, options) {
-  var res =
-    typeof options.nestTables +
-    '/' +
-    options.nestTables +
-    '/' +
-    options.rowsAsArray +
-    options.supportBigNumbers +
-    '/' +
-    options.bigNumberStrings +
-    '/' +
-    typeof options.typeCast;
-  for (var i = 0; i < fields.length; ++i) {
-    res +=
-      '/' + fields[i].name + ':' + fields[i].columnType + ':' + fields[i].flags;
-  }
-  return res;
-};
-
 Connection.statementKey = function(options) {
   return (
     typeof options.nestTables +

lib/compile_binary_parser.js renamed to lib/parsers/binary_parser.js

@@ -1,10 +1,10 @@
-var FieldFlags = require('./constants/field_flags.js');
-var Charsets = require('./constants/charsets.js');
-var CharsetToEncoding = require('./constants/charset_encodings.js');
-var Types = require('./constants/types.js');
-var srcEscape = require('./helpers').srcEscape;
+var FieldFlags = require('../constants/field_flags.js');
+var Charsets = require('../constants/charsets.js');
+var CharsetToEncoding = require('../constants/charset_encodings.js');
+var Types = require('../constants/types.js');
+var srcEscape = require('../helpers').srcEscape;
 var genFunc = require('generate-function');
-
+var parserCache = require('./parser_cache.js');
 var typeNames = [];
 for (var t in Types) {
   typeNames[Types[t]] = t;
@@ -181,4 +181,8 @@ function readCodeFor(field, config, options, fieldNum) {
   }
 }
 
-module.exports = compile;
+function getBinaryParser(fields, options, config) {
+  return parserCache.getParser('binary', fields, options, config, compile);
+}
+
+module.exports = getBinaryParser;

lib/parsers/parser_cache.js

@@ -0,0 +1,53 @@
+var LRU = require('lru-cache');
+
+var parserCache = new LRU({
+  max: 15000
+});
+
+function keyFromFields(type, fields, options) {
+  var res =
+    type +
+    '/' +
+    typeof options.nestTables +
+    '/' +
+    options.nestTables +
+    '/' +
+    options.rowsAsArray +
+    options.supportBigNumbers +
+    '/' +
+    options.bigNumberStrings +
+    '/' +
+    typeof options.typeCast;
+  for (var i = 0; i < fields.length; ++i) {
+    res +=
+      '/' + fields[i].name + ':' + fields[i].columnType + ':' + fields[i].flags;
+  }
+  return res;
+}
+
+function getParser(type, fields, options, config, compiler) {
+  var key = keyFromFields(type, fields, options);
+  var parser = parserCache.get(key);
+
+  if (parser) {
+    return parser;
+  }
+
+  parser = compiler(fields, options, config);
+  parserCache.set(key, parser);
+  return parser;
+}
+
+function setMaxCache(max) {
+  parserCache.max = max;
+}
+
+function clearCache() {
+  parserCache.reset();
+}
+
+module.exports = {
+  getParser: getParser,
+  setMaxCache: setMaxCache,
+  clearCache: clearCache
+};

lib/compile_text_parser.js renamed to lib/parsers/text_parser.js

@@ -1,8 +1,9 @@
-var Types = require('./constants/types.js');
-var Charsets = require('./constants/charsets.js');
-var CharsetToEncoding = require('./constants/charset_encodings.js');
-var srcEscape = require('./helpers').srcEscape;
+var Types = require('../constants/types.js');
+var Charsets = require('../constants/charsets.js');
+var CharsetToEncoding = require('../constants/charset_encodings.js');
+var srcEscape = require('../helpers').srcEscape;
 var genFunc = require('generate-function');
+var parserCache = require('./parser_cache.js');
 
 var typeNames = [];
 for (var t in Types) {
@@ -189,4 +190,7 @@ function readCodeFor(type, charset, encodingExpr, config, options) {
   }
 }
 
-module.exports = compile;
+function getTextParser(fields, options, config) {
+  return parserCache.getParser('text', fields, options, config, compile);
+}
+module.exports = getTextParser;