Health Checks

Super goes beyond checking if a process ID (PID) exists. It actively probes the service to determine if it is truly operational.

Health checks are critical for:

1. Dependency resolution: Unblocking dependent services once upstream is healthy.
2. Operational visibility: Distinguishing “process running” from “service actually ready”.
3. OTA Validation: Verifying a new version before committing an update.

Types of Checks

1. TCP Check

The simplest check. Succeeds if Super can establish a TCP connection to the port.

[programs.health_check]
type = "tcp"
port = 8080
# host = "127.0.0.1" # Optional, defaults to localhost

2. HTTP Check

Performs an HTTP request. Succeeds if the response status code is 200-299.

[programs.health_check]
type = "http"
url = "http://127.0.0.1:8080/healthz"
method = "GET" # Optional

3. Exec Check

Runs a shell command. Succeeds if the command exits with code 0. Ideal for checking file existence, database queries, or custom scripts.

[programs.health_check]
type = "exec"
command = "grep 'ready' /tmp/app.state"

Behavior

• Interval: Checks are performed every 5 seconds (default).
• Startup: Super waits for the first successful check before marking a process as Healthy.
• Failure: If a check fails while running, status stays Running (unhealthy) until the next check passes. Dependents that use depends_on wait for Healthy.