opensource-portal/docs/healthChecks.md

Health checks

To help improve the experience of worldwide deployment and make load balancers happy, there are configuration values that can be used to allow for endpoint probes.

As of October 2022, no health probes are exposed by default, but they're easy enough to opt-in.

The file ./middleware/healthCheck.ts implements these currently. You can allow as many types of checks you like. The first check type that "matches" will be sent a generic HTTP 200 response (consider always just using HEAD to save on bandwidth), or a HTTP 500.

General probe configuration:

• ENABLE_WEB_HEALTH_PROBES: '1' by default - ready to provide probes, but no-op without any allowed probes
• WEB_HEALTH_LIVENESS_DELAY: initial delay at startup before attempting to expose liveness, defaults to 5 seconds
• WEB_HEALTH_READINESS_DELAY: initial delay at startup before exposing readiness, defaults to 10 seconds

"External" un-gated probe:

Expose an endpoint to any user, no check for headers, at /health/[endpoint suffix]

• EXTERNAL_HEALTH_PROBES: '1' to enable
• EXTERNAL_HEALTH_PROBE_ENDPOINT_SUFFIX: suffix added for the check's name; defaults to external to expose /health/external

Kubernetes pod health checks:

• KUBERNETES_HEALTH_PROBES: '1' to enable
• KUBERNETES_HEALTH_CHECK_KEY: header to check, default is x-health-check that our team uses
• KUBERNETES_HEALTH_CHECK_VALUE: header value to check, default is check that our team uses

Azure Front Door check:

• AZURE_FRONTDOOR_HEALTH_PROBES: set to '1' to expose /health/liveness and /health/readiness probes for Front Door
• AFD is gated on the user-agent "Edge Health Probe". AZURE_FRONTDOOR_HEALTH_CHECK_KEY and AZURE_FRONTDOOR_HEALTH_CHECK_VALUE can override.