I've created a Lambda that connects inconsistently to a PostgreSQL database in RDS.
When it works, it connects and completes the query in a small amount of time. Less than 100ms, usually only 20ms. I can execute this lambda ten or twenty times and it will work fine. Eventually though, it gets stuck trying to connect to the database.
The connection will time out eventually. I have set the timeout to be thirty seconds. Extending it doesn't seem to make a difference.
When it does get stuck connecting, I can sometimes try it half an hour later or so and it will be fine. Sometimes it will still fail, even after a day.
It usually works for a while when I upload a new zip. Sometimes, when it doesn't connect to the database immediately after the upload of a new zip, I can get it to work by editing the lambda in the AWS Lambda console and clicking Deploy from there.
Has anyone seen this behaviour before? What am I doing wrong? I'm new to node and Lambdas. I created a lambda in C# as well and get the same behaviour.
The database instance is correctly provisioned and has only a small number of connections.
Here is a sample of the code. I don't use the dbConfig as I have stored them as environment variables. The zip uploaded to Lambda contains this file and the node_modules folder for 'pg' and its dependancies.
'use strict';
var pg = require('pg');
exports.handler = async (event, context, callback) => {
var dbConfig = {
username: '<username>',
password: '<password>',
database: '<database>',
host: '<database_endpoint>',
};
var client = new pg.Client(dbConfig);
console.log('Waiting to connect');
await client.connect();
console.log('Connected');
console.log('Querying the database');
var res = await client.query('SELECT COUNT(*) FROM books;'); // 'books' is a table in the database
console.log(res);
await client.end();
console.log('Connection closed');
};
Using pg.Pool instead of pg.Client hasn't helped.
Moving the connection code outside of the handler only seems to work with callbacks. Callbacks don't seem to work well with Lambdas anymore.
