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` and `/minio/health/cluster` respectively.

### Liveness probe

This probe always responds with '200 OK'. Only fails if 'etcd' is configured and unreachable. This behavior is specific to gateway. When liveness probe fails, Kubernetes like platforms restart the container.

```
livenessProbe:
  httpGet:
    path: /minio/health/live
    port: 9000
    scheme: HTTP
  initialDelaySeconds: 120
  periodSeconds: 30
  timeoutSeconds: 10
  successThreshold: 1
  failureThreshold: 3
```

### Readiness probe

This probe always responds with '200 OK'. Only fails if 'etcd' is configured and unreachable. This behavior is specific to gateway. When readiness probe fails, Kubernetes like platforms turn-off routing to the container.

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

### Cluster probe
#### Cluster-writeable probe
This probe is not useful in almost all cases, this is meant for administrators to see if write quorum is available in any given cluster. The reply is '200 OK' if cluster has write 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
```

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

```
curl http://minio1:9001/minio/health/cluster/read
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
```