pg doesn't invoke callback if server accepts the connection and immediately disconnects

[jess-sheneberger]

I've got a short repro of the issue: https://gist.github.com/jess-sheneberger/9532352

When I run the code in the gist, the output I get is:

server listening
client connecting
server connected
server socket destroyed.
server closed

...and then the program ends, meaning client.connect's callback was never invoked. I expected to see another line after "server closed", something like "Error on connect: " or "client connected".

Some context: I'm using postgres behind a HAProxy. Sometimes HAProxy accepts a connection, fails to connect to postgres and then disconnects. This causes my initialization scripts to fail consistently.

I can reproduce this on both my Ubuntu 12.04 VM and on OSX Mavericks.

[brianc]

Hey! thanks for the awesome example code. I'll try to get this fixed for the v3.0 release (this weekend). Cheers.

[jess-sheneberger]

No problem, thanks for responding so quickly. Let me know if I can be of any assistance.

[strk]

I might be experiencing this or a similar problem with [email protected] and pg@master (2.11.0+, 2716f95):
CartoDB/CartoDB-SQL-API#135

[strk]

2.4.0 is also affected

[strk]

The native module handles this better (although with obscure error):

server listening
client connecting
server connected
server socket destroyed.
server closed
Error on connect: Error: Unknown native driver error: 

[strk]

@brianc the Connection object only sends 'error' or 'end' events. When the other end closes the connection, an 'end' is received by the "stream" object, not an 'error'. How to turn that into an 'error' based on expectance ?

[strk]

Could we say, for example, that getting 'end' before getting 'readyForQuery' has to be considered an error ?

[strk]

This seems to fix this case for me:

diff --git a/lib/client.js b/lib/client.js
index 490e1d1..73f910a 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -170,9 +170,17 @@ Client.prototype.connect = function(callback) {
       return self.emit('error', error);
     }
     callback(error);
+    callback = null;
   });

   con.once('end', function() {
+    if ( callback ) {
+      // haven't received a connection message yet !
+      var err = new Error("Stream unexpectedly ended before getting ready for query execution");
+      callback(err);
+      callback = null;
+      return;
+    }
     if(self.activeQuery) {
       var disconnectError = new Error('Stream unexpectedly ended during query execution');
       self.activeQuery.handleError(disconnectError);

[strk]

Basically, if "callback" is still set, it means it wasn't called on "readyForQuery"

[strk]

The patch is meant for 2.11.1

[strk]

@jess-sheneberger could you test #546 ?

[jess-sheneberger]

I’ll try to take a look later today. Thanks for the fix!

[jess-sheneberger]

Works for me. Thanks again for fixing this!

[brianc]

Sweet - I'll get to these ASAP, test 'em and merge them in.

[jess-sheneberger]

@brianc Any idea when you'll be able to merge the fix to this one?