Running a Locust Load Test

In this tutorial, we will show you how to use Neocortix Cloud Services Scalable Compute to run a large load test with potentially hundreds of devices using the Locust load testing package, using the command.

Preparing the Master Node

We assume you have already installed our git repository at on the machine that you will use as the Locust Master, and installed the python packages and ansible, according to the instructions "Preparing the Master Node" in the Locust Load Test Introduction tutorial. Note: this procedure was tested on newly-created VMs with 8 GB RAM, running Ubuntu 16.04.4 or 18.04.2.

In that repository in the subdirectory ~/ncscli/examples/loadtest you will find the command. Its –help option says:

usage: [-h] [--authToken AUTHTOKEN]
     [--masterUrl MASTERURL]
     [--nWorkers NWORKERS]
     [--sshClientKeyName SSHCLIENTKEYNAME]
     [--usersPerWorker USERSPERWORKER]
     [--startTimeLimit STARTTIMELIMIT]
     [--susTime SUSTIME]
     victimHostUrl masterHost

does distributed load testing using Locust on NCS instances

positional arguments:
          url of the host to target as victim
          hostname or ip addr of the Locust master

optional arguments:
     -h, --help
          show this help message and exit
     --authToken AUTHTOKEN
          the NCS authorization token to use
     --masterUrl MASTERURL
          url of the Locust master to control
     ` --nWorkers NWORKERS
          the # of worker instances to launch (or zero for all available)
     --sshClientKeyName SSHCLIENTKEYNAME
          the name of the uploaded ssh client key to use
     --usersPerWorker USERSPERWORKER
          # of simulated users per worker
     --startTimeLimit STARTTIMELIMIT
          time to wait for startup of workers (in seconds)
     --susTime SUSTIME
          time to sustain the test after startup (in seconds)

Example Command

This example command essentially does our large daily test, launching all available nodes (usually around 800), installing all prerequisites, installing the Locust client onto them, starting the Locust workers, running the load test for 4 minutes, retrieving the logs from the workers, shutting down the workers, terminating the instances, and formatting the final report: @myAuthToken --nWorkers 0 --startTimeLimit 90 --susTime 240 --usersPerWorker 35 --sshClientKeyName xxx@ltmaster-0 > runDist_out.txt

Example Output (Small Test)

Here we show an example output for a test run where 20 instances were requested, with 10 simulated users/worker.

19 of 20 workers showed up, 19 workers working
200 simulated users
Load Test started: 2019/06/07 20:34:26
Duration 0.5 minutes

# of worker devices: 19
# of requests satisfied: 13024
requests per second: 460.0
RPS per device: 24.21
# of requests failed: 0
failure rate: 0.0%
mean response time: 243.7 ms
response time range: 56.0-5987.7 ms


Example Output (Large Test)

Here is an example output from one of our large daily tests, in which 813 instances were available and requested; all 813 instances launched; 775 devices (95% of requested) installed all prerequisites and performed successfully as Locust workers. The total load delivered (with measured response times) was about 30,000 Requests Per Second for the 6-minute duration of the Load Test. The entire process took about 37 minutes.

Test Summary

ncs launch job ID: 1fd0e196-b0e0-4e9f-b8e9-494a83c13fb8

813 devices listed as available
Requested 813 instances
320 device-replacement operations occurred
Launch started 813 Instances; Counter({'started': 813})
startWorkers found 789 good, 8 unreachable, 9 failed
781 of 789 workers showed up, 775 workers working
peak RPS (nominal) 48.4
31438 simulated users

775 out of 813 = 95% success rate

Load Test started: 2019/06/08 01:14:17
Duration 5.7 minutes

# of worker devices: 778
# of requests satisfied: 10341697
requests per second: 30094.2
RPS per device: 38.68
# of requests failed: 39354
failure rate: 0.4%
mean response time: 476.7 ms
response time range: -149.2-200743.8 ms

2019-06-08T01:29:02.449684 testLocustSystem finished
elapsed time 36.9 minutes

Timing Summary (durations in minutes)
00:52:11 01:02:52 10.7 launch
01:02:52 01:06:53 4.0 installPrereqs
01:06:53 01:14:18 7.4 startWorkers
01:14:19 01:20:31 6.2 runLocust
01:20:31 01:21:49 1.3 killWorkerProcs
01:22:19 01:24:42 2.4 retrieveWorkerLogs
01:24:42 01:29:02 4.3 terminateInstances
00:52:10 01:29:02 36.9 testLoadtest