Callback passed to 'database.query' in some situations is called twice about node-firebird

[mariuz]

I will take a look do you have a test case that you can send it to me ?

[piotr-przebieracz]

Hi!

First of all, I would like to apologise that I didn't write to you earlier.
As I said, this situation is not easy to reproduce, but I managed to prepare sample simulating this situation. I wrote shortest possible Node.js server updating some data in Firebird database and corresponding load test for this server. Whole sample is available as a gist here:
https://gist.github.com/piotr-przebieracz/f7949bfb89654213fa2a
After downloading my sample, just install npm packages and replace path to test database in server.js file. I ran load test on 3 machines - in some cases the error occurred right after first execution, sometimes - a little bit later.

It is also important that I used forked version of 'node-firebird' package (https://github.com/ela-compil/node-firebird). As you can see, the only change is default isolation level. Me and my colleagues needed NO WAIT behaviour in case of a situation when two or more simultaneous updates occur, because it was important for us to receive an error immediately without waiting.
The default behaviour (waiting for the other transaction to finish) resulted in very long response times when two or more users modified the same data.

[petersirka]

You should use fb.attach() for each request. I added a connection pooling into new version, try it with new version v0.2.0:

A small modification:
https://www.online-clipboard.com/1413307914875304f8b589e205ebx28/

Everything works but server gets too many requests.