Error: Global connection already exists. Call sql.close() first.

[braco]

I'm wrestling with an aws lambda and mssql.

It seems like there's some kind of error event that exits but doesn't close the connection, so the next request is met with:

Error: Global connection already exists. Call sql.close() first. From here

It seems important to be able to check for the existence of globalConnection, but there doesn't seem to be a getter, correct? Something like the following would help:

// Turn off this error and just return the existing globalConnection
sql.connect({ reuseConnection: true })
sql.connect()

// Just a getter for globalConnection
sql.getConnection()

if (sql.connectionStatus() === CONNECTED) { ... }

[johncade]

👍

[mnboos]

👍

[WeihanLi]

I got connectionStatus is not a function error, I use the code below instead:

let connectionPool;

var getConnection = async function(){
    if(!(connectionPool && connectionPool.connected)) {
        connectionPool = await mssql.connect(connConfig);
    }
    return connectionPool;
}

[dhensby]

@willmorgan any insight on this?

[willmorgan]

@WeihanLi - as I understand it, the the connectionStatus code was a proof of concept, not something concrete that's been shipped.

@braco I know this is an old issue but it does seem valid. If you fancy submitting a PR with something to that effect, that would be helpful.

In the interim, you will be able to access the globalConnection by trying to create a Request with no connection. The globalConnection is then used:

node-mssql/lib/base.js

Lines 969 to 985 in eb8fe7d

	class Request extends EventEmitter {
	/**
	* Create new Request.
	*
	* @param {Connection|ConnectionPool|Transaction|PreparedStatement} parent If ommited, global connection is used instead.
	*/
	constructor (parent) {
	super()
	IDS.add(this, 'Request')
	debug('request(%d): created', IDS.get(this))
	this.canceled = false
	this.parent = parent || globalConnection
	this.parameters = {}
	}

So something like this allows you to access it, albeit in a roundabout way:

const sql = require('mssql');
const fakeRequest = new sql.Request();
fakeRequest.parent.close();

[arvingopi]

The above suggestion is not working.

TypeError: Cannot read property 'close' of null

[arvingopi]

new msSQL.ConnectionPool(dbConfig).connect().then(pool => {
    pool.close();
});

This above code fixed the issue or more like a work-around. After this, one can setup the code to execute the requests using the pool normally. Remember to call sql.close() both when the record_set is received and at the catch block too.

[dhensby]

@arvnan52 yep, that's how I've had to do it too

[dhensby]

I'm really in two minds about this.

1. If AWS Lambda process is experiencing an error but not cleaning up the connection, then that sounds like bad AWS behaviour
2. You really should avoid using the global connection IMO because it's bad practice, you can maintain your own connection instead which will provide much better control
3. I really would rather not add a getConnection function for accessing the global connection for fear of making it appear acceptable to use.

However, I can see how it would be useful, maybe connect should just return the existing connection if it exists instead of erroring?