I'm trying to test connectivity between my Lambda and an RDS instance. I have them both on the same private subnets with all ports open in the security group. When I trigger the Lambda I do see a connection opened on the RDS instance. However, the Lambda times out after 4 minutes, 40 seconds. The PG environment variables are set in the Lambda configuration.
const { Client } = require('pg');
const client = new Client();
var hello = [
{ name: 'test', description: 'testerface' }
];
exports.handler = async (event, context, callback) => {
// Postgres Connect
client.connect();
const res = client.query('SELECT $1::text as message', ['Hello world!']);
console.log(res);
var response = {
"statusCode": 200,
"headers": {
"Content-Type" : "application/json"
},
"body": JSON.stringify(hello),
"isBase64Encoded": false
};
callback(null, response);
};
How can I get back the response from the connection in the Lambda's logs - or even better in the response body?
You can configure Lambda to access your RDS instance. You can enable this using Lambda management console. Select Lambda function which need access to RDS instance and then go to Configuration -> Advanced settings and select the VPC (which is your RDS instance is in) you need it to access.
Sign in to the AWS Management Console and open the Amazon RDS console at https://console.aws.amazon.com/rds/ . Open the RDS console and then choose Databases to display a list of your DB instances. Choose the PostgreSQL DB instance name to display its details. On the Connectivity & security tab, copy the endpoint.
Lambda can work seamlessly with RDS instances, as long as you remember the specific requirements for this particular setup. Since RDS instances are running in your VPC and Lambda by default does not have access to those resources, you'll need to configure the VPC connection when creating a Lambda function.
You need to handle the client connection better. That means catching any exceptions that the client may through and releasing the connection properly. This code will return the output of the query to the response body:
const pg = require('pg')
const pool = new pg.Pool()
async function query (q) {
const client = await pool.connect()
let res
try {
await client.query('BEGIN')
try {
res = await client.query(q)
await client.query('COMMIT')
} catch (err) {
await client.query('ROLLBACK')
throw err
}
} finally {
client.release()
}
return res
}
exports.handler = async (event, context, callback) => {
try {
const { rows } = await query("select * from pg_tables")
console.log(JSON.stringify(rows[0]))
var response = {
"statusCode": 200,
"headers": {
"Content-Type" : "application/json"
},
"body": JSON.stringify(rows),
"isBase64Encoded": false
};
callback(null, response);
} catch (err) {
console.log('Database ' + err)
callback(null, 'Database ' + err);
}
};
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