Pooling keeps incrementing connections and ends up in ER_CON_COUNT_ERROR - mysql

Question

I have a class called Connection like one below. This only executes select statements. I have non pooling connection for insert or update.
var _mysql = require('mysql');
function Connection()
{
//private variables and dependencies includes
//create mysql pool connection requires nodejs mysql this connection is used only for selects.
var _connectionSelect = _mysql.createPool({
host : _config.mySQLDB.select.dbHost,
user : _config.mySQLDB.select.dbUser,
password : _config.mySQLDB.select.dbPass,
database : _config.mySQLDB.select.dbName,
supportBigNumbers : true,
connectTimeout : 7000,
connectionLimit : 5,
queueLimit : 5
});
this.executeSelect = function(sql, callback, Message)
{
//connects to mysql.
_connectionSelect.getConnection(function(connectionError, Connection){
if(connectionError)
{
console.log(connectionError);
//throws error if connection or sql gone wrong
Message.add("error", 'serviceDown');
Message.add("devError", 'unknownError');
callback(false);
}
else
{
//executes the query passed
Connection.query(sql, function(error, rows) {
Message.incerementQuery();
if(error)
{
Connection.release();
console.log(error+sql);
//throws error if connection or sql gone wrong
Message.add("error", 'unknownError');
Message.add("devError", "seriousError", "Database errors at resource server side");
callback(false);
}
else
{
Connection.release();
//executes the callback function
callback(rows);
}
});
}
});
};
}
exports.Connection = Connection;
I created an instance of this class whenever I want to execute a query.
I am aware that the default concurrent connections in MySQL is 100 and I wanted to keep that number.
Whenever I try running my application, this connection pooling is incrementing every select and reaches 100 connections pretty soon.
As you can see I am releasing the connection on success or error states. I am pretty sure that I must be doing something wrong, but difficult to figure out.
Is it because how I create instances of this class? I was hoping that if I supply
connectionLimit : 5
even if I create many instances of this class it should only utilise 5 connection?
Note: I have only one instance of this app in my local machine.
Sorry to be so amateur, I am new to this streaming I/O business. I love the idea of pooling but if I cant sort this out, I may need to use traditional open and close connection for every query . Any help would be much appreciated.
Many thanks,
Karthik

Answer 1

Got the answer from Doug Wilson from git hub https://github.com/dougwilson.
I should have instantiated createPool outside of the function. Works like a charm.
The code goes like
var _mysql = require('mysql');
//create mysql pool connection requires nodejs mysql this connection is used only for selects.
var _connectionSelect = _mysql.createPool({
host : _config.mySQLDB.select.dbHost,
user : _config.mySQLDB.select.dbUser,
password : _config.mySQLDB.select.dbPass,
database : _config.mySQLDB.select.dbName,
supportBigNumbers : true,
connectTimeout : 7000,
connectionLimit : 5,
queueLimit : 5
}
function Connection()
{
//private variables and dependencies includes
);
this.executeSelect = function(sql, callback, Message)
{
//connects to mysql.
_connectionSelect.getConnection(function(connectionError, Connection){
if(connectionError)
{
console.log(connectionError);
//throws error if connection or sql gone wrong
Message.add("error", 'serviceDown');
Message.add("devError", 'unknownError');
callback(false);
}
else
{
//executes the query passed
Connection.query(sql, function(error, rows) {
Message.incerementQuery();
if(error)
{
Connection.release();
console.log(error+sql);
//throws error if connection or sql gone wrong
Message.add("error", 'unknownError');
Message.add("devError", "seriousError", "Database errors at resource server side");
callback(false);
}
else
{
Connection.release();
//executes the callback function
callback(rows);
}
});
}
});
};
}
exports.Connection = Connection;
Thanks a lot. Sorry to be so stupid.
Karthik