locust does not respond when the time to complete a single request is (very) long

Describe the bug

When running locust against a database with queries that needs long processing time (above 3 seconds) locust does not respond anymore:

Expected behavior

Locust should work as usual

Actual behavior

• run as local: stopping the test from the UI does not work. The runner keeps sending request to the database
• run as master/worker the master loose the worker, printing heartbeat not arrived.

Steps to reproduce

I have created a repository. It need docker and Unix tools, python packages: locust and pyscopg2.

1. git clone https://github.com/belloni-SAP/locust_sql
2. cd locust_sql
3. run ./prepare_test.sh
4. Al local:
   • locust -f postgres_test.py start test from UI and try to stop. In the terminal locust keeps sending request to the database.
   • distributed * master: locust -f postgres_test.py --master * worker: locust -f postgres_test.py --worker After few seconds in the master terminal an heartbeat problem will try to stop the test. Increasing the value of the heartbeat-related variables in locust.runnerhave no effect.

Environment

• OS: Linux - x86_64 GNU/Linux
• Python version: Python 3.7.1
• Locust version: locust 1.2.3
• Locust command line that you ran: see above
• Locust file contents (anonymized if necessary): see above

[belloni-SAP]

Many thanks. After using the correct driver, everything works fine. We are, however, using also another driver which is not gevent-friendly.

I was thinking if it could be useful for others to insert in https://docs.locust.io/en/stable/testing-other-systems.html a hint to this possible problematic.

[cyberw]

Cool!

For postgres, there are standard environment variables that are automatically used (PGHOST, PGPORT, etc https://www.postgresql.org/docs/current/libpq-envars.html), which is neat (and I use that approach for TimescaleListener in locust-plugins).

As long as you provide the ability to override them in code (using class-level variables on the User maybe?), especially if you want to use TimescaleListener AND your User 😃