callbackMutex.Lock()
	callbackToken++
	i := callbackToken
	callbackFuncs[i] = f
	callbackMutex.Unlock()

	// Pass the address of i because the C function was written to
	// take a pointer.  We could pass an int if we felt like
	// rewriting the C code.
	C.callback(unsafe.Pointer(&i))

	callbackMutex.Lock()
	delete(callbackFuncs, i)
	callbackMutex.Unlock()
}

//export goCallback

				rec := reqRec.rec
				// HTTP request used to call the handler.
				req := reqRec.req
				// HTTP request type string for V4/V2 requests.
				reqType := reqRec.reqType

				// Clone so we don't retain values we do not want.
				req.Header = req.Header.Clone()

				// introduce faults in the request.
				// deliberately introducing the invalid value to be able to assert the response with the expected error response.

		// successfully, we need to send a response to the client with
		// some details - FIXME: the disks on this cluster would need to
		// be cleaned to recover.
		partial := madmin.ReplicateAddStatus{
			Status:    madmin.ReplicateAddStatusPartial,
			ErrDetail: peerAddErr.Error(),
		}

		return partial, nil
	}

	// Other than handling existing buckets, we can now save the cluster

	for {
		select {
		case <-mTimer.C:
			saveMRFToDisk()
			mTimer.Reset(mrfSaveInterval)
		case <-p.ctx.Done():
			p.mrfStopCh <- struct{}{}
			xioutil.SafeClose(p.mrfSaveCh)
			// We try to save if possible, but we don't care beyond that.
			saveMRFToDisk()
			return
		case e, ok := <-p.mrfSaveCh:
			if !ok {
				return
			}
			entries[e.versionID] = e

						w.WriteHeader(ci.StatusCode)
						return
					}

					// We did not satisfy any requirement from the cache, update the cache.
					// this basically means that we do not have the Data for the object
					// cached yet
					update = true
				})
				if !update {
					// No update is needed means we have written already to the client just return here.
					return
				}
			}
		}

	response, err = s.client.Get(getGetObjectURL(s.endPoint, bucketName, objectName+".1"))
	c.Assert(err, nil)
	// assert the http response status code.
	verifyError(c, response, "AccessDenied", "Access Denied.", http.StatusForbidden)

	// initiate anonymous HTTP request to fetch the object which does exist. We need to return AccessDenied.

		enc := expfmt.NewEncoder(w, contentType)
		for _, mf := range mfs {
			if err := enc.Encode(mf); err != nil {
				// client may disconnect for any reasons
				// we do not have to log this.
				return
			}
		}
		if closer, ok := enc.(expfmt.Closer); ok {
			closer.Close()
		}
	})
}

func metricsBucketHandler() http.Handler {