Golang BatchRequest.TraceContext方法代碼示例

//.........這裏部分代碼省略.........
			var distinct bool
			// The request might already be used by an outgoing goroutine, so
			// we can't safely mutate anything in-place (as MergeSpans does).
			et.IntentSpans = append([]roachpb.Span(nil), et.IntentSpans...)
			et.IntentSpans, distinct = roachpb.MergeSpans(et.IntentSpans)
			ba.Header.DistinctSpans = distinct && distinctSpans
			if len(et.IntentSpans) == 0 {
				// If there aren't any intents, then there's factually no
				// transaction to end. Read-only txns have all of their state
				// in the client.
				return roachpb.NewErrorf("cannot commit a read-only transaction")
			}
			if txnMeta != nil {
				txnMeta.keys = et.IntentSpans
			}
			return nil
		}(); pErr != nil {
			return nil, pErr
		}

		if hasET && log.V(1) {
			for _, intent := range et.IntentSpans {
				log.Eventf(ctx, "intent: [%s,%s)", intent.Key, intent.EndKey)
			}
		}
	}

	// Embed the trace metadata into the header for use by RPC recipients. We need
	// to do this after the maybeBeginTxn call above.
	// TODO(tschottdorf): To get rid of the spurious alloc below we need to
	// implement the carrier interface on ba.Header or make Span non-nullable,
	// both of which force all of ba on the Heap. It's already there, so may
	// not be a big deal, but ba should live on the stack. Also not easy to use
	// a buffer pool here since anything that goes into the RPC layer could be
	// used by goroutines we didn't wait for.
	if ba.TraceContext == nil {
		ba.TraceContext = &tracing.SpanContextCarrier{}
	} else {
		// We didn't make this object but are about to mutate it, so we
		// have to take a copy - the original might already have been
		// passed to the RPC layer.
		ba.TraceContext = protoutil.Clone(ba.TraceContext).(*tracing.SpanContextCarrier)
	}
	if err := tracer.Inject(sp.Context(), basictracer.Delegator, ba.TraceContext); err != nil {
		return nil, roachpb.NewError(err)
	}

	// Send the command through wrapped sender, taking appropriate measures
	// on error.
	var br *roachpb.BatchResponse
	{
		var pErr *roachpb.Error
		br, pErr = tc.wrapped.Send(ctx, ba)

		if _, ok := pErr.GetDetail().(*roachpb.OpRequiresTxnError); ok {
			// TODO(tschottdorf): needs to keep the trace.
			br, pErr = tc.resendWithTxn(ba)
		}

		if pErr = tc.updateState(ctx, startNS, ba, br, pErr); pErr != nil {
			log.Eventf(ctx, "error: %s", pErr)
			return nil, pErr
		}
	}

	if br.Txn == nil {
		return br, nil
	}

	if _, ok := ba.GetArg(roachpb.EndTransaction); !ok {
		return br, nil
	}
	// If the --linearizable flag is set, we want to make sure that
	// all the clocks in the system are past the commit timestamp
	// of the transaction. This is guaranteed if either
	// - the commit timestamp is MaxOffset behind startNS
	// - MaxOffset ns were spent in this function
	// when returning to the client. Below we choose the option
	// that involves less waiting, which is likely the first one
	// unless a transaction commits with an odd timestamp.
	if tsNS := br.Txn.Timestamp.WallTime; startNS > tsNS {
		startNS = tsNS
	}
	sleepNS := tc.clock.MaxOffset() -
		time.Duration(tc.clock.PhysicalNow()-startNS)
	if tc.linearizable && sleepNS > 0 {
		defer func() {
			if log.V(1) {
				log.Infof(ctx, "%v: waiting %s on EndTransaction for linearizability", br.Txn.Short(), util.TruncateDuration(sleepNS, time.Millisecond))
			}
			time.Sleep(sleepNS)
		}()
	}
	if br.Txn.Status != roachpb.PENDING {
		tc.Lock()
		tc.cleanupTxnLocked(ctx, *br.Txn)
		tc.Unlock()
	}
	return br, nil
}