I am using a postgres database for my express web server. I am using the 'pg' library to execute queries on this database.
Here is my connection method :
const db = new Client({
user: 'xxx',
host: 'xxx',
database: 'xxx',
password: 'xxx',
port: xxx,
})
db.connect(err => {
if (err) {
console.error('connection error', err.stack)
} else {
console.log('connected')
}
Then to execute a request I do this:
db.query(MY_REQUEST, function (err, data) {
if (err) throw err;
res.render('hello/world', {
title: 'Hello',
data: data.rows
});
});`
It all works perfectly. But after several minutes without using my website, my connection to the db times out, and I get the following error:
node:events:355
throw er; // Unhandled 'error' event
^
Error: Connection terminated unexpectedly
at Connection.<anonymous> (/usr/src/app/node_modules/pg/lib/client.js:132:73)
at Object.onceWrapper (node:events:484:28)
at Connection.emit (node:events:378:20)
at Socket.<anonymous> (/usr/src/app/node_modules/pg/lib/connection.js:58:12)
at Socket.emit (node:events:378:20)
at TCP.<anonymous> (node:net:665:12)
Emitted 'error' event on Client instance at:
at Client._handleErrorEvent (/usr/src/app/node_modules/pg/lib/client.js:319:10)
at Connection.<anonymous> (/usr/src/app/node_modules/pg/lib/client.js:149:16)
at Object.onceWrapper (node:events:484:28)
[... lines matching original stack trace ...]
at TCP.<anonymous> (node:net:665:12)
How could I do to reconnect automatically when the connection is cut or when a request fails?
You should attach an error-handler in order to prevent the unhandled error crashing your app. It's as simple as:
db.on('error', e => {
console.error('DB error', e);
});
As to why the error happens we need more details, looks like it could be a connection reset due to idle-timeout?
You can create a function to control if you're connected to database or not, before you continue with your main function.
Create a function for controlling database connection status, reconnecting etc. and before you run a database related function, first start that middle function and wait for result, after that you can continue using database again.
If you want(which should be prefered way mostly), create that middle function as an async function and return a promise, when using that function wait for that function.