How to use the command 'locust' (with examples)
The ’locust’ command is a load-testing tool used to determine the number of concurrent users a system can handle. It allows you to simulate user behavior and generate load on a web application. With ’locust’, you can test the performance and scalability of your system.
Use case 1: Load-test “example.com” with web interface using locustfile.py
Code:
locust --host=http://example.com
Motivation:
Using the ’locust’ command, you can load-test a web application hosted on “example.com” with the default locust file named ’locustfile.py’. This test will simulate user behavior and generate load on the web application, allowing you to measure its performance under various scenarios.
Explanation:
--host: Specifies the target host to load-test. In this example, the target host is set to “example.com”.
Example Output:
The ’locust’ command will start running and display the web interface on the console. The interface will show various statistics and allow you to monitor the load-testing progress in real-time.
Use case 2: Use a different test file
Code:
locust --locustfile=test_file.py --host=http://example.com
Motivation:
In some cases, you may want to use a custom test file instead of the default ’locustfile.py’. This allows you to define your own user behavior and scenarios to suit your specific testing needs.
Explanation:
--locustfile: Specifies a different test file to use. In this example, we use ’test_file.py'.--host: Specifies the target host to load-test. In this case, it is “example.com”.
Example Output:
The ’locust’ command will load the specified test file and start load-testing the target host according to the defined user behavior and scenarios.
Use case 3: Run test without web interface, spawning 1 user a second until there are 100 users
Code:
locust --no-web --clients=100 --hatch-rate=1 --host=http://example.com
Motivation:
In certain scenarios, you may want to run the load test without the web interface. The ’locust’ command allows you to do this, configuring the number of clients and the rate at which new users are spawned.
Explanation:
--no-web: Starts the load test without the web interface.--clients: Specifies the number of clients (users) to simulate. In this example, it is set to 100.--hatch-rate: Configures the rate at which new users are spawned. In this case, 1 user per second.--host: Specifies the target host to load-test. Here, it is “example.com”.
Example Output:
The ’locust’ command will start running the load test without the web interface. It will spawn 1 user per second until there are 100 users, generating load on the target host.
Use case 4: Start Locust in master mode
Code:
locust --master --host=http://example.com
Motivation:
In distributed load-testing scenarios, you may want to set up a Locust master node to manage multiple slave nodes. The master node coordinates the distribution of load and collects results from the slaves.
Explanation:
--master: Starts Locust in master mode.--host: Specifies the target host to load-test. In this case, it is “example.com”.
Example Output:
The ’locust’ command will start running in master mode, waiting for slave nodes to connect. It will display the web interface on the console to monitor the load-testing progress and collect results from the connected slaves.
Use case 5: Connect Locust slave to master
Code:
locust --slave --host=http://example.com
Motivation:
In a distributed load-testing setup with Locust, you can connect one or more slave nodes to a master node. The slave nodes generate load and send the results to the master node for aggregation.
Explanation:
--slave: Starts Locust in slave mode.--host: Specifies the target host to load-test. In this case, it is “example.com”.
Example Output:
The ’locust’ command will start running in slave mode and connect to a Locust master node. It will generate load on the target host as instructed by the master node and send the results back for aggregation.
Use case 6: Connect Locust slave to master on a different machine
Code:
locust --slave --master-host=master_hostname --host=http://example.com
Motivation:
In distributed load-testing scenarios, you may have the Locust master and slave nodes running on different machines. This use case demonstrates how to connect a slave node to a master node on a different machine.
Explanation:
--slave: Starts Locust in slave mode.--master-host: Specifies the hostname or IP address of the master node. In this example, it is “master_hostname”.--host: Specifies the target host to load-test. Here, it is “example.com”.
Example Output:
The ’locust’ command will start running in slave mode and connect to a Locust master node running on a different machine. It will generate load on the target host as instructed by the master node and send the results back for aggregation.
Conclusion:
The ’locust’ command is a powerful load-testing tool that allows you to simulate user behavior and measure the performance and scalability of your web application. You can use it with various configurations to suit your testing needs, whether it’s load-testing a single host, setting up a distributed load-testing environment, or customizing user behavior and scenarios.
