w.Header()[xhttp.ETag] = []string{"\"" + objInfo.ETag + "\""}
		}
	}
	// x-amz-copy-source-if-modified-since: Return the object only if it has been modified
	// since the specified time otherwise return 412 (precondition failed).
	ifModifiedSinceHeader := r.Header.Get(xhttp.AmzCopySourceIfModifiedSince)
	if ifModifiedSinceHeader != "" {
		if givenTime, err := amztime.ParseHeader(ifModifiedSinceHeader); err == nil {

```

### 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

	if c.TraceOutput != nil && resp.StatusCode != http.StatusOK {
		c.dumpHTTP(req, resp)
	}

	if resp.StatusCode != http.StatusOK {
		// If server returns 412 pre-condition failed, it would
		// mean that authentication succeeded, but another
		// side-channel check has failed, we shall take
		// the client offline in such situations.

func stack404()  { var buf [404]byte; use(buf[:]); C.callGoStackCheck() }
func stack408()  { var buf [408]byte; use(buf[:]); C.callGoStackCheck() }
func stack412()  { var buf [412]byte; use(buf[:]); C.callGoStackCheck() }
func stack416()  { var buf [416]byte; use(buf[:]); C.callGoStackCheck() }
func stack420()  { var buf [420]byte; use(buf[:]); C.callGoStackCheck() }

    assertCached(false, 408)
    assertCached(false, 409)
    // the HTTP spec permits caching 410s, but the RI doesn't.
    assertCached(true, 410)
    assertCached(false, 411)
    assertCached(false, 412)
    assertCached(false, 413)
    assertCached(true, 414)
    assertCached(false, 415)
    assertCached(false, 416)
    assertCached(false, 417)
    assertCached(false, 418)
    assertCached(false, 500)

// If-Unmodified-Since - Return the object only if it has not been modified since the specified time, else return a 412 (precondition failed).
func (s *TestSuiteCommon) TestHeadOnObjectLastModified(c *check) {
	// generate a random bucket name.
	bucketName := getRandomBucketName()
	// HTTP request to create the bucket.

pkg net/http, const StatusNotModified = 304
pkg net/http, const StatusOK = 200
pkg net/http, const StatusPartialContent = 206
pkg net/http, const StatusPaymentRequired = 402
pkg net/http, const StatusPreconditionFailed = 412
pkg net/http, const StatusProxyAuthRequired = 407
pkg net/http, const StatusRequestEntityTooLarge = 413
pkg net/http, const StatusRequestTimeout = 408
pkg net/http, const StatusRequestURITooLong = 414

pkg syscall (netbsd-arm64-cgo), const SYS__PSET_BIND = 415
pkg syscall (netbsd-arm64-cgo), const SYS__PSET_BIND ideal-int
pkg syscall (netbsd-arm64-cgo), const SYS_PSET_CREATE = 412
pkg syscall (netbsd-arm64-cgo), const SYS_PSET_CREATE ideal-int
pkg syscall (netbsd-arm64-cgo), const SYS_PSET_DESTROY = 413
pkg syscall (netbsd-arm64-cgo), const SYS_PSET_DESTROY ideal-int

pkg syscall (freebsd-riscv64), const SYS_EXTATTR_SET_FILE = 356 #53466
pkg syscall (freebsd-riscv64), const SYS_EXTATTR_SET_FILE ideal-int #53466
pkg syscall (freebsd-riscv64), const SYS_EXTATTR_SET_LINK = 412 #53466
pkg syscall (freebsd-riscv64), const SYS_EXTATTR_SET_LINK ideal-int #53466
pkg syscall (freebsd-riscv64), const SYS_FACCESSAT = 489 #53466
pkg syscall (freebsd-riscv64), const SYS_FACCESSAT ideal-int #53466

pkg syscall (darwin-arm64), const SYS_WRITE ideal-int
pkg syscall (darwin-arm64), const SYS_WRITEV = 121
pkg syscall (darwin-arm64), const SYS_WRITEV ideal-int
pkg syscall (darwin-arm64), const SYS_WRITEV_NOCANCEL = 412
pkg syscall (darwin-arm64), const SYS_WRITEV_NOCANCEL ideal-int
pkg syscall (darwin-arm64), const SYS_WRITE_NOCANCEL = 397
pkg syscall (darwin-arm64), const SYS_WRITE_NOCANCEL ideal-int