While working on a project with EdgeDB1 and FastAPI2, I wanted to perform health checks against the FastAPI server in the GitHub CI. This would notify me about the working state of the application. The idea is to:
- Run the server in the background.
- Run the commands against the server that’ll denote that the app is in a working state.
- Perform cleanup.
- Exit with code 0 if the check is successful, else exit with code 1.
The following shell script demonstrates a similar workflow with a Python HTTP server. This script:
- Runs a Python web server in the background.
- Makes an HTTP request against the server and checks if it returns HTTP 200 (OK). If the request fails or the server isn’t ready then waits for a second and makes the request again, and keeps retrying for the next 20 times before giving up.
- Performs cleanups and kills the Python processes.
- Exit with code 0 if the request is successful, else exit with code 1.
#!/bin/bash set -euo pipefail # Run the Python server in the background. nohup python3 -m http.server 5000 >> /dev/null & # Give the server enough time to be ready before accepting requests. c=20 while [[ $c != 0 ]] do # Run the healthcheck. if [[ $(curl -I http://localhost:5000/ 2>&1) =~ "200 OK" ]]; then echo "Health check passed!" # ...do additional cleanups if required. pkill -9 -i python exit 0 fi ((c--)) echo "Server isn't ready. Retrying..." $c sleep 1 done echo "Health check failed!" # ...do additional cleanups if required. pkill -9 -i python exit 1
nohup before the
python3 -m http.server 5000 makes sure that the
can’t reach the server and shut down the process. The ampersand
& after the command runs
the process in the background. Afterward, the script starts making requests to the
http://localhost:5000/ URL in a loop. If the server returns HTTP 200, the health check is
considered successful. This will break the loop and the script will be terminated with
exit 0 status. If the server doesn’t return HTTP 200 or isn’t ready yet, the script will
keep retrying 20 times with a 1 second interval between each subsequent request before
giving up. A failed health check will cause the script to terminate with
exit 1 status.