Golang RangeDescriptor.FindReplica方法代码示例

// Send implements the client.Sender interface. It verifies
// permissions and looks up the appropriate range based on the
// supplied key and sends the RPC according to the specified options.
//
// If the request spans multiple ranges (which is possible for Scan or
// DeleteRange requests), Send sends requests to the individual ranges
// sequentially and combines the results transparently.
//
// This may temporarily adjust the request headers, so the proto.Call
// must not be used concurrently until Send has returned.
func (ds *DistSender) Send(_ context.Context, call proto.Call) {
	args := call.Args
	finalReply := call.Reply

	// Verify permissions.
	if err := ds.verifyPermissions(call.Args); err != nil {
		call.Reply.Header().SetGoError(err)
		return
	}

	// In the event that timestamp isn't set and read consistency isn't
	// required, set the timestamp using the local clock.
	if args.Header().ReadConsistency == proto.INCONSISTENT && args.Header().Timestamp.Equal(proto.ZeroTimestamp) {
		// Make sure that after the call, args hasn't changed.
		defer func(timestamp proto.Timestamp) {
			args.Header().Timestamp = timestamp
		}(args.Header().Timestamp)
		args.Header().Timestamp = ds.clock.Now()
	}

	// If this is a bounded request, we will change its bound as we receive
	// replies. This undoes that when we return.
	boundedArgs, argsBounded := args.(proto.Bounded)

	if argsBounded {
		defer func(bound int64) {
			boundedArgs.SetBound(bound)
		}(boundedArgs.GetBound())
	}

	defer func(key proto.Key) {
		args.Header().Key = key
	}(args.Header().Key)

	// Retry logic for lookup of range by key and RPCs to range replicas.
	curReply := finalReply
	for {
		call.Reply = curReply
		curReply.Header().Reset()

		var desc, descNext *proto.RangeDescriptor
		var err error
		for r := retry.Start(ds.rpcRetryOptions); r.Next(); {
			// Get range descriptor (or, when spanning range, descriptors).
			// sendAttempt below may clear them on certain errors, so we
			// refresh (likely from the cache) on every retry.
			desc, descNext, err = ds.getDescriptors(call)
			// getDescriptors may fail retryably if the first range isn't
			// available via Gossip.
			if err != nil {
				if rErr, ok := err.(util.Retryable); ok && rErr.CanRetry() {
					if log.V(1) {
						log.Warning(err)
					}
					continue
				}
				break
			}
			err = func() error {
				// Truncate the request to our current range, making sure not to
				// touch it unless we have to (it is illegal to send EndKey on
				// commands which do not operate on ranges).
				if descNext != nil {
					defer func(endKey proto.Key) {
						args.Header().EndKey = endKey
					}(args.Header().EndKey)
					args.Header().EndKey = desc.EndKey
				}
				leader := ds.leaderCache.Lookup(proto.RaftID(desc.RaftID))

				// Try to send the call.
				replicas := newReplicaSlice(ds.gossip, desc)

				// Rearrange the replicas so that those replicas with long common
				// prefix of attributes end up first. If there's no prefix, this is a
				// no-op.
				order := ds.optimizeReplicaOrder(replicas)

				// If this request needs to go to a leader and we know who that is, move
				// it to the front.
				if !(proto.IsRead(args) && args.Header().ReadConsistency == proto.INCONSISTENT) &&
					leader.StoreID > 0 {
					if i := replicas.FindReplica(leader.StoreID); i >= 0 {
						replicas.MoveToFront(i)
						order = rpc.OrderStable
					}
				}

				return ds.sendRPC(desc.RaftID, replicas, order, args, curReply)
			}()
//.........这里部分代码省略.........

// sendAttempt is invoked by Send and handles retry logic and cache eviction
// for a call sent to a single range. It returns a retry status, which is Break
// on success and either Break, Continue or Reset depending on error condition.
// This method is expected to be invoked from within a backoff / retry loop to
// retry the send repeatedly (e.g. to continue processing after a critical node
// becomes available after downtime or the range descriptor is refreshed via
// lookup).
func (ds *DistSender) sendAttempt(desc *proto.RangeDescriptor, call proto.Call) (retry.Status, error) {
	leader := ds.leaderCache.Lookup(proto.RaftID(desc.RaftID))

	// Try to send the call.
	replicas := newReplicaSlice(ds.gossip, desc)

	// Rearrange the replicas so that those replicas with long common
	// prefix of attributes end up first. If there's no prefix, this is a
	// no-op.
	order := ds.optimizeReplicaOrder(replicas)

	args := call.Args
	reply := call.Reply

	// If this request needs to go to a leader and we know who that is, move
	// it to the front.
	if !(proto.IsRead(args) && args.Header().ReadConsistency == proto.INCONSISTENT) &&
		leader.StoreID > 0 {
		if i := replicas.FindReplica(leader.StoreID); i >= 0 {
			replicas.MoveToFront(i)
			order = rpc.OrderStable
		}
	}

	err := ds.sendRPC(desc.RaftID, replicas, order, args, reply)
	if err != nil {
		// For an RPC error to occur, we must've been unable to contact any
		// replicas. In this case, likely all nodes are down (or not getting back
		// to us within a reasonable amount of time).
		// We may simply not be trying to talk to the up-to-date replicas, so
		// clearing the descriptor here should be a good idea.
		// TODO(tschottdorf): If a replica group goes dead, this will cause clients
		// to put high read pressure on the first range, so there should be some
		// rate limiting here.
		ds.rangeCache.EvictCachedRangeDescriptor(args.Header().Key, desc)
	} else {
		err = reply.Header().GoError()
	}

	if err != nil {
		if log.V(1) {
			log.Warningf("failed to invoke %s: %s", call.Method(), err)
		}

		// If retryable, allow retry. For range not found or range
		// key mismatch errors, we don't backoff on the retry,
		// but reset the backoff loop so we can retry immediately.
		switch tErr := err.(type) {
		case *proto.RangeNotFoundError, *proto.RangeKeyMismatchError:
			// Range descriptor might be out of date - evict it.
			ds.rangeCache.EvictCachedRangeDescriptor(args.Header().Key, desc)
			// On addressing errors, don't backoff; retry immediately.
			return retry.Reset, err
		case *proto.NotLeaderError:
			newLeader := tErr.GetLeader()
			// Verify that leader is a known replica according to the
			// descriptor. If not, we've got a stale replica; evict cache.
			// Next, cache the new leader.
			if newLeader != nil {
				if i, _ := desc.FindReplica(newLeader.StoreID); i == -1 {
					if log.V(1) {
						log.Infof("error indicates unknown leader %s, expunging descriptor %s", newLeader, desc)
					}
					ds.rangeCache.EvictCachedRangeDescriptor(args.Header().Key, desc)
				}
			} else {
				newLeader = &proto.Replica{}
			}
			ds.updateLeaderCache(proto.RaftID(desc.RaftID), *newLeader)
			return retry.Reset, err
		case util.Retryable:
			if tErr.CanRetry() {
				return retry.Continue, err
			}
		}
		return retry.Break, err
	}
	return retry.Break, nil
}

//.........这里部分代码省略.........
				// any replicas. In this case, likely all nodes are down (or
				// not getting back to us within a reasonable amount of time).
				// We may simply not be trying to talk to the up-to-date
				// replicas, so clearing the descriptor here should be a good
				// idea.
				// TODO(tschottdorf): If a replica group goes dead, this
				// will cause clients to put high read pressure on the first
				// range, so there should be some rate limiting here.
				evictDesc()
				if tErr.CanRetry() {
					continue
				}
			case *proto.RangeNotFoundError, *proto.RangeKeyMismatchError:
				trace.Event(fmt.Sprintf("reply error: %T", err))
				// Range descriptor might be out of date - evict it.
				evictDesc()
				// On addressing errors, don't backoff; retry immediately.
				r.Reset()
				if log.V(1) {
					log.Warning(err)
				}
				// For the remainder of this call, we'll assume that intents
				// are fair game. This replaces more complex logic based on
				// the type of request.
				options.considerIntents = true
				continue
			case *proto.NotLeaderError:
				trace.Event(fmt.Sprintf("reply error: %T", err))
				newLeader := tErr.GetLeader()
				// Verify that leader is a known replica according to the
				// descriptor. If not, we've got a stale replica; evict cache.
				// Next, cache the new leader.
				if newLeader != nil {
					if i, _ := desc.FindReplica(newLeader.StoreID); i == -1 {
						if log.V(1) {
							log.Infof("error indicates unknown leader %s, expunging descriptor %s", newLeader, desc)
						}
						evictDesc()
					}
				} else {
					newLeader = &proto.Replica{}
				}
				ds.updateLeaderCache(proto.RangeID(desc.RangeID), *newLeader)
				if log.V(1) {
					log.Warning(err)
				}
				r.Reset()
				continue
			case retry.Retryable:
				if tErr.CanRetry() {
					if log.V(1) {
						log.Warning(err)
					}
					trace.Event(fmt.Sprintf("reply error: %T", err))
					continue
				}
			}
			break
		}

		// Immediately return if querying a range failed non-retryably.
		if err != nil {
			return nil, err
		}

		first := br == nil

//.........这里部分代码省略.........
			} else {
				err = curReply.Header().GoError()
			}

			if err == nil {
				break
			}

			if log.V(1) {
				log.Warningf("failed to invoke %s: %s", call.Method(), err)
			}

			// If retryable, allow retry. For range not found or range
			// key mismatch errors, we don't backoff on the retry,
			// but reset the backoff loop so we can retry immediately.
			switch tErr := err.(type) {
			case *proto.RangeNotFoundError, *proto.RangeKeyMismatchError:
				trace.Event(fmt.Sprintf("reply error: %T", err))
				// Range descriptor might be out of date - evict it.
				ds.rangeCache.EvictCachedRangeDescriptor(descKey, desc, isReverseScan)
				// On addressing errors, don't backoff; retry immediately.
				r.Reset()
				if log.V(1) {
					log.Warning(err)
				}
				continue
			case *proto.NotLeaderError:
				trace.Event(fmt.Sprintf("reply error: %T", err))
				newLeader := tErr.GetLeader()
				// Verify that leader is a known replica according to the
				// descriptor. If not, we've got a stale replica; evict cache.
				// Next, cache the new leader.
				if newLeader != nil {
					if i, _ := desc.FindReplica(newLeader.StoreID); i == -1 {
						if log.V(1) {
							log.Infof("error indicates unknown leader %s, expunging descriptor %s", newLeader, desc)
						}
						ds.rangeCache.EvictCachedRangeDescriptor(descKey, desc, isReverseScan)
					}
				} else {
					newLeader = &proto.Replica{}
				}
				ds.updateLeaderCache(proto.RangeID(desc.RangeID), *newLeader)
				if log.V(1) {
					log.Warning(err)
				}
				r.Reset()
				continue
			case retry.Retryable:
				if tErr.CanRetry() {
					if log.V(1) {
						log.Warning(err)
					}
					trace.Event(fmt.Sprintf("reply error: %T", err))
					continue
				}
			}
			break
		}

		// Immediately return if querying a range failed non-retryably.
		// For multi-range requests, we return the failing range's reply.
		if err != nil {
			call.Reply.Header().SetGoError(err)
			return
		}