How do I use node-postgres in a server?

Question

I'm writing a Node.js web server that uses a Postgres database. I used to connect on each new request like this:

app.get('/', function (req, res) {
  pg.connect(pgconnstring, function (err, client) {
    // ...
  });
});

But after a few requests, I noticed 'out of memory' errors on Heroku when trying to connect. My database has only 10 rows, so I don't see how this could be happening. All of my database access is of this form:

client.query('SELECT * FROM table', function (err, result) {
  if (err) {
    res.send(500, 'database error');
    return;
  }

  res.set('Content-Type', 'application/json');
  res.send(JSON.stringify({ data: result.rows.map(makeJSON) }));
});

Assuming that the memory error was due to having several persistent connections to the database, I switched to a style I saw in several node-postgres examples of connecting only once at the top of the file:

var client = new pg.Client(pgconnstring);
client.connect();

app.get('/', function (req, res) {
  // ...
});

But now my requests hang (indefinitely?) when I try to execute a query after the connection is disrupted. (I simulated it by killing a Postgres server and bringing it back up.)

So how do I do one of these?

Properly pool Postgres connections so that I can 'reconnect' every time without running out of memory.
Have the global client automatically reconnect after a network failure.

Jonathan Hall · Accepted Answer · 2014-11-05 12:25:12Z

16

I'm assuming you're using the latest version of node-postgres, in which the connection pooling has been greatly improved. You must now check the connection back into the pool, or you'll bleed the connections:

app.get('/', function (req, res) {
  pg.connect(pgconnstring, function (err, client, done) {
    // do some stuff
    done();
  });
});

As for error handling on a global connection (#2, but I'd use the pool):

client.on('error', function(e){
  client.connect(); // would check the error, etc in a production app
});

The "missing" docs for all this is on the GitHub wiki.

edited Nov 5, 2014 at 12:25

Jonathan Hall

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answered Mar 26, 2013 at 5:47

Krut

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