I am running htop on the same machine where locust is running. during the tests I have been running this morning, I see one CPU (of 4) hit 100% while the other CPUs are largely idle. I have also observed up to 8 locust tasks running. This is not running distributed. How does locust implement threading and multiprocessing to maximize the available capabilities of the machine?
using multi-CPU platforms with locust
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3 Answers
See https://docs.locust.io/en/stable/running-locust-distributed.html
This applies both for running distributed over multiple machines or just multiple cores.
You need one worker process per core in order to fully utilize the machine.
You can use this bash script for running locust in distributed mode:
echo -e "\nStart LOCUST MASTER\n"
locust -f locust_scenario.py --headless -L $LOG_LEVEL --logfile=$LOG --master-bind-port=$MASTER_PORT \
--master-bind-host=$MASTER_IP -u $COUNT_OF_USERS --print-stats --master --expect-workers=$cores --host=$SERVER_HOST&
PID_MASTER=$!
echo "LOCAST MASTER PID = $PID_MASTER"
sleep 5
# start SLAVE (clients)
echo -e "\nStart LOCUST SLAVES\n"
PID_SLAVES=( )
for ((i = 1; i <= $cores; i++));do
locust -f locust_scenario.py --worker --master-host=$MASTER_IP --master-port=$MASTER_PORT -L $LOG_LEVEL --logfile=$LOG &
PID_SLAVES+=( $! )
done
echo "LOCAST SLAVE PIDs = ${PID_SLAVES[@]}"
I think the best option to run locust on multiple cores locally is to run locust master and workers with docker and docker-compose file as described here https://docs.locust.io/en/stable/running-in-docker.html
Simply mount your locustfile.py inside containers and start it using docker compose command. The number of workers can be easily changed using this command:
docker-compose up --scale worker=4
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