// These are static for all objects extracted.
	reqParams := extractReqParams(r)
	respElements := map[string]string{
		"requestId": w.Header().Get(xhttp.AmzRequestID),
		"nodeId":    w.Header().Get(xhttp.AmzRequestHostID),
	}
	if sc == "" {
		sc = storageclass.STANDARD
	}

	putObjectTar := func(reader io.Reader, info os.FileInfo, object string) error {
		size := info.Size()

	// first node. The following is required to serialize (the effects of)
	// concurrent rebalance-start commands.
	if ep := globalEndpoints[0].Endpoints[0]; !ep.IsLocal {
		for nodeIdx, proxyEp := range globalProxyEndpoints {
			if proxyEp.Host == ep.Host {
				if proxied, success := proxyRequestByNodeIndex(ctx, w, r, nodeIdx, false); proxied && success {
					return
				}
			}
		}

		}

		participants[i] = ps.Participating
	}
	z.rebalMu.RUnlock()

	for poolIdx, doRebalance := range participants {
		if !doRebalance {
			continue
		}
		// nothing to do if this node is not pool's first node (i.e pool's rebalance 'leader').
		if !globalEndpoints[poolIdx].Endpoints[0].IsLocal {
			continue
		}

		go func(idx int) {
			stopfn := globalRebalanceMetrics.log(rebalanceMetricRebalanceBuckets, idx)