Deploy Locust to Multiple Linode Regions using Terraform

What is Locust?

Locust is a scalable, modern load / performance testing tool, written in Python. It can be deployed as single instance or across multiple nodes, following the leader-worker pattern.

When it's deployed, a Flask-based web app starts automatically for users to manage tests, view statstics and download reports.

Locust by default looks for a test file named locustfile.py. The following is an example of that.

import time
from locust import HttpUser, task, between

class Quickstart(HttpUser):
    wait_time = between(1, 5)

    @task
    def google(self):
        self.client.request_name = "google"
        self.client.get("https://google.com/")

What is Linode?

Linode is one of the best, affordable, and flexible cloud providers, powered by Akamai Connected Cloud. It currently has 20+ core data centers across the globe. The Terraform script in this repository will deploy a Locust leader instance and however many worker instances per different regions (i.e. data centers). Thus, when test runs, requests would be generated from multiple regions simultaneously.

Getting Started

Once terraform is installed on your local machine, you can pull the repository.

$ git clone [email protected]:yosepkim/terraform-linode-locust.git

In order to interact with Linode API, an API access token needs to be acquired. Follow the article to do so.

A Terraform variable file needs to be created in the root directoy of the repository. First, go to the directory:

$ cd terraform-linode-locust

Then, create and save a file named terraform.tfvars in the root directory with the following content after replacing YOUR_ACCESS_TOKEN and YOUR_UNCRACKABLE_PASSWORD with your values:

token = "YOUR_ACCESS_TOKEN"
root_password = "YOUR_UNCRACKABLE_PASSWORD"

Make sure the script is ready to by running terraform plan command. Once everything checks out, then run terraform apply.

Once Terraform finishes its job, IP address of the leader and the worker instances will be printed out:

Apply complete! Resources: 8 added, 0 changed, 0 destroyed.

Outputs:

leader_public_ip = "172.233.161.95"
workers_public_ip = [
  "172.233.130.128",
]

Copy the leader's IP address, then paste into the address bar of your favorite browser of choice. Populate fields with desired values and start the test by clicking on Start swarming:

Multiple Region Deployment

To deploy worker instances across multiple regions of Linode, define node_regions variable in your terraform.tfvars. The following example deploys a worker instance to LA, Osaka, Paris, Milan, Chicago, and Washing DC regions.

token = "YOUR_ACCESS_TOKEN"
root_password = "YOUR_UNCRACKABLE_PASSWORD"
node_regions = ["us-lax", "jp-osa", "fr-par", "it-mil", "us-ord", "us-iad"]

Testing against Endpoint Requiring mutual TLS

The Terraform script supports testinga against target endpoints that require mutual TLS. To enable it, first set uses_mtls variable to true in the variable file, as shown below.

token = "YOUR_ACCESS_TOKEN"
root_password = "YOUR_UNCRACKABLE_PASSWORD"
node_regions = ["us-lax", "jp-osa", "fr-par", "it-mil", "us-ord", "us-iad"]
uses_mtls = true

Second, create a directory named certs under the plan directory, then add the server certificate (CA bundle), client certificate and client key files. Check the variable definition file variables.tf for default names of the files, which can be overriden by using appropriate variables.

Lastly, use mtls_locustfile.py as a base to build your test file. Basically, you need to tweak values of url, headers, and payload varible (if POST is being tested).

url = ""

payload = json.dumps({})

headers = {
  'Pragma': 'akamai-x-ew-debug, akamai-x-cache-on, akamai-x-cache-remote-on, akamai-x-check-cacheable, akamai-x-get-cache-key, akamai-x-get-true-cache-key, akamai-x-serial-no, akamai-x-get-request-id, akamai-x-get-client-ip, akamai-x-im-trace, X-Akamai-Scan-status, x-akamai-edgescape',
  'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/113.0.0.0 Safari/537.36',
  'Content-Type': 'application/json'
}

When Terraform applies the changes, it would copy the certs and key files into each instance and replace server certificate, client certificate, and the key placeholders with the actual file names using sed.