minio/docs/metrics/healthcheck/README.md

MinIO Healthcheck

MinIO server exposes three un-authenticated, healthcheck endpoints liveness probe and a cluster probe at /minio/health/live, /minio/health/ready and /minio/health/cluster respectively.

Liveness probe

This probe always responds with '200 OK'. When liveness probe fails, Kubernetes like platforms restart the container.

          livenessProbe:
            httpGet:
              path: /minio/health/live
              port: 9000
              scheme: HTTP
            initialDelaySeconds: 120
            periodSeconds: 15
            timeoutSeconds: 10
            successThreshold: 1
            failureThreshold: 3

Cluster probe

This probe is not useful in almost all cases, this is meant for administrators to see if quorum is available in any given cluster. The reply is '200 OK' if cluster has quorum if not it returns '503 Service Unavailable'.

curl http://minio1:9001/minio/health/cluster
HTTP/1.1 503 Service Unavailable
Accept-Ranges: bytes
Content-Length: 0
Content-Security-Policy: block-all-mixed-content
Server: MinIO/GOGET.GOGET
Vary: Origin
X-Amz-Bucket-Region: us-east-1
X-Minio-Write-Quorum: 3
X-Amz-Request-Id: 16239D6AB80EBECF
X-Xss-Protection: 1; mode=block
Date: Tue, 21 Jul 2020 00:36:14 GMT

Checking cluster health for maintenance

You may query the cluster probe endpoint to check if the node which received the request can be taken down for maintenance, if the server replies back '412 Precondition Failed' this means you will lose HA. '200 OK' means you are okay to proceed.

curl http://minio1:9001/minio/health/cluster?maintenance=true
HTTP/1.1 412 Precondition Failed
Accept-Ranges: bytes
Content-Length: 0
Content-Security-Policy: block-all-mixed-content
Server: MinIO/GOGET.GOGET
Vary: Origin
X-Amz-Bucket-Region: us-east-1
X-Amz-Request-Id: 16239D63820C6E76
X-Xss-Protection: 1; mode=block
X-Minio-Write-Quorum: 3
Date: Tue, 21 Jul 2020 00:35:43 GMT