Cannot call method 'ReleaseConnection' of null

[babsonmatt]

I've had no problems with using pool so far but the other night I received this error, any ideas?

[dougwilson]

What does the call to release look like on that line? It means the variable you are calling release on has been swapped to null in your code, perhaps because you are using a global variable, an object property, or manually set it to null at some point.

[tomislav]

I'm getting the same thing. Definitely not setting the connection to null before calling release(). Actually release() is the first function called after query(). It doesn't occur every time, maybe once every few days. MySQL problem?

TypeError: Cannot call method 'releaseConnection' of null
    at PoolConnection.release (/home/ec2-user/track-server/releases/20131002182733/node_modules/mysql/lib/PoolConnection.js:19:21)
    at Query._callback (/home/ec2-user/track-server/releases/20131002182733/server.js:419:28)
    at Query.Sequence.end (/home/ec2-user/track-server/releases/20131002182733/node_modules/mysql/lib/protocol/sequences/Sequence.js:75:24)
    at Protocol.handleNetworkError (/home/ec2-user/track-server/releases/20131002182733/node_modules/mysql/lib/protocol/Protocol.js:238:14)
    at PoolConnection.Connection._handleNetworkError (/home/ec2-user/track-server/releases/20131002182733/node_modules/mysql/lib/Connection.js:155:18)
    at Socket.EventEmitter.emit (events.js:117:20)
    at onwriteError (_stream_writable.js:233:10)
    at onwrite (_stream_writable.js:251:5)
    at WritableState.onwrite (_stream_writable.js:97:5)
    at fireErrorCallbacks (net.js:438:13)
    at Socket._destroy (net.js:472:3)
    at Object.afterWrite (net.js:718:10)

[dougwilson]

Can you show your code calling release where this happens, including where the connection variable is being declared so we can see that it is not a global variable?

[tomislav]

I'm using connection pooling, and it looks like this. "pool" is global variable

var pool;

pool = mysql.createPool({
   user: 'xxx',
   password: 'xxx',
   database: 'track'
});

appsecure.post('/api/update', function(req, res) {
    /* process request and generate db query */
    pool.getConnection(function(err, connection) {
        connection.query('INSERT INTO locations (track,latitude,longitude,horizontalaccuracy,timestamp) VALUES ' + dbvalues, function(err, results, fields) {
            connection.release();
            if (err) {
              /* do something */
            } else {
              /* do something good */
            }
        });
    });
});

[dougwilson]

It looks like the issue is that when a connection ends or encounters a fatal error, it is removed from the pool, but the release method doesn't check that before trying to release it (it doesn't have to do anything if already removed from the pool).