HTTP/1.1 503 Service Unavailable
Accept-Ranges: bytes
Content-Length: 0
Server: MinIO
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

The reply is '200 OK' if cluster has read quorum if not it returns '503 Service Unavailable'.

```

    ImmutableSet<String> uppercaseAcronyms =
        ImmutableSet.of(
            "CH", "ID", "DNT", "DNS", "DPR", "ECT", "GPC", "HTTP2", "IP", "MD5", "P3P", "RTT", "TE",
            "UA", "UID", "URL", "WWW", "XSS");

    for (Field field : httpHeadersFields()) {
      assertEquals(
          upperToHttpHeaderName(field.getName(), specialCases, uppercaseAcronyms), field.get(null));
    }
  }

	commonInitialismsReplacer *strings.Replacer
)

func init() {
	commonInitialismsForReplacer := make([]string, 0, len(commonInitialisms))
	for _, initialism := range commonInitialisms {