node-mysql pool experiences ETIMEDOUT - google-cloud-sql

Question

I have a node-mysql pool configuration of
var db_init={
host : 'ip_address_of_GCS_SQL',
user : 'user_name_of_GCS_SQL',
password : 'password here',
database : 'db here',
supportBigNumbers: true,
connectionLimit:100
};
Pool was created using
GLOBAL.db_foobar = mysql.createPool(db_init);
I basically just left the connection on for a couple of hours and I saw this error reported by my connection.query Request (after getConnection of course):
prodAPI-104 (out): { status: 'Error',
prodAPI-104 (out): details: '[foobar_function]Error in query',
prodAPI-104 (out): err: '{ [Error: read ETIMEDOUT]\n code: \'ETIMEDOUT\',\n errno: \'ETIMEDOUT\',\n syscall: \'read\',\n fatal: true }',
prodAPI-104 (out): query: 'SELECT * FROM `foobar_table`;' }
Why is this happening? The MySQL in Google-Cloud-SQL didn't report a query taking too long to create so I dunno why this happened.

Answer 1

I suspect the reason is that keepalive is not enabled on the connection to the MySQL server.
node-mysql does not have an option to enable keepalive and neither does node-mysql2, but node-mysql2 provides a way to supply a custom function for creating sockets which we can use to enable keepalive:
var mysql = require('mysql2');
var net = require('net');
var pool = mysql.createPool({
connectionLimit : 100,
host : '123.123.123.123',
user : 'foo',
password : 'bar',
database : 'baz',
stream : function(opts) {
var socket = net.connect(opts.config.port, opts.config.host);
socket.setKeepAlive(true);
return socket;
}
});