How to handle errors properly?

[DJDaveMark]

Is this still the correct way to handle errors?

We wrote this code back in January 2017 when we were using ^4.4.3 using pg.connect before refactoring it to use pool.connect when we upgraded to use ^7.11.0 back in June 2019

pool.connect(function (err, client, done) {
    if (err) {
        done(err); // done may be called multiple times with no side-effects
        console.error('could not connect to postgres', err);
        callback(err);
        return;
    }

    // do something
});

today we started getting the following error:

TypeError: done is not a function

pointing to the 3rd line of the code above.

I see from the current documentation that done is not called in case of an error:

pool.connect((err, client, done) => {
  if (err) throw err
  client.query('SELECT * FROM users WHERE id = $1', [1], (err, res) => {
    done()
    if (err) {
      console.log(err.stack)
    } else {
      console.log(res.rows[0])
    }
  })
})

But I can't find any guidelines in the current documentation on how are you supposed to handle errors (in ^7.11.0 at least).

Can anyone provide an example?

Note: we are using old-style callbacks

[sehrope]

You should not be getting that done is not a function error.

If the connection creation or acquisition encounters an error then the client arg is undefined and the done callback is a no-op function. Nothing happens if you call the no-op done function but you do not have to as there is no client to release back.

What's the exact version of node, pg, and pg-pool that you are using? And is the error a connection creation one or a timeout one?

I see from the current documentation that done is not called in case of an error:

Those examples need to be cleaned up anyway though as it looks like it's just throwing the error as an unhandled exception.

[charmander]

Correct, you aren’t supposed to call done in the case that pool.connect calls its callback with an error. Did that work once? It definitely looks like it doesn’t in the current pg-pool code.

Fixed example:

pool.connect(function (err, client, done) {
    if (err) {
        console.error('could not connect to postgres', err);
        callback(err);
        return;
    }

    // do something
});

Remember that you should still call done no matter what after that point, though, because then you have the client. When calling it because of a client error, or because of any error that leaves the client in a state where it shouldn’t be reused – or, for simplicity, because of any error at all – make sure to pass a truthy value, e.g. done(true) or done(err).

pool.connect(function (err, client, done) {
    if (err) {
        console.error('could not connect to postgres', err);
        callback(err);
        return;
    }

    client.query('SELECT * FROM users WHERE id = $1', [1], function (err, res) {
        done(err);
        if (err) {
            callback(err);
        } else {
            callback(res.rows[0]);
        }
    });
});

[budarin]

I'm not getting error.message in error in case connection errors (for an example: connection timeout)

try {
    const res = await pool.query(text, params);
    return res.rows[0];
} catch (error) {
    console.error(error.message);
}

error.message is undefined
we can get error text in stack only