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transport.go
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transport.go
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// Copyright 2016 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License. See the AUTHORS file
// for names of contributors.
//
// Author: Ben Darnell
package kv
import (
"sort"
"time"
"golang.org/x/net/context"
"google.golang.org/grpc"
"github.com/cockroachdb/cockroach/pkg/internal/client"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/rpc"
"github.com/cockroachdb/cockroach/pkg/util/grpcutil"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/syncutil"
"github.com/cockroachdb/cockroach/pkg/util/timeutil"
"github.com/cockroachdb/cockroach/pkg/util/tracing"
"github.com/opentracing/opentracing-go"
)
// A SendOptions structure describes the algorithm for sending RPCs to one or
// more replicas, depending on error conditions and how many successful
// responses are required.
type SendOptions struct {
// SendNextTimeout is the duration after which RPCs are sent to
// other replicas in a set.
SendNextTimeout time.Duration
transportFactory TransportFactory
metrics *DistSenderMetrics
}
type batchClient struct {
remoteAddr string
conn *grpc.ClientConn
client roachpb.InternalClient
args roachpb.BatchRequest
healthy bool
pending bool
retryable bool
deadline time.Time
}
// BatchCall contains a response and an RPC error (note that the
// response contains its own roachpb.Error, which is separate from
// BatchCall.Err), and is analogous to the net/rpc.Call struct.
type BatchCall struct {
Reply *roachpb.BatchResponse
Err error
}
// TransportFactory encapsulates all interaction with the RPC
// subsystem, allowing it to be mocked out for testing. The factory
// function returns a Transport object which is used to send the given
// arguments to one or more replicas in the slice.
//
// In addition to actually sending RPCs, the transport is responsible
// for ordering replicas in accordance with SendOptions.Ordering and
// transport-specific knowledge such as connection health or latency.
//
// TODO(bdarnell): clean up this crufty interface; it was extracted
// verbatim from the non-abstracted code.
type TransportFactory func(
SendOptions, *rpc.Context, ReplicaSlice, roachpb.BatchRequest,
) (Transport, error)
// Transport objects can send RPCs to one or more replicas of a range.
// All calls to Transport methods are made from a single thread, so
// Transports are not required to be thread-safe.
type Transport interface {
// IsExhausted returns true if there are no more replicas to try.
IsExhausted() bool
// SendNextTimeout returns the timeout after which the next untried,
// or retryable, replica may be attempted. Returns a duration
// indicating when another replica should be tried, and a bool
// indicating whether one should be (if false, duration will be 0).
SendNextTimeout(time.Duration) (time.Duration, bool)
// SendNext sends the rpc (captured at creation time) to the next
// replica. May panic if the transport is exhausted. Should not
// block; the transport is responsible for starting other goroutines
// as needed.
SendNext(context.Context, chan<- BatchCall)
// NextReplica returns the replica descriptor of the replica to be tried in
// the next call to SendNext. MoveToFront will cause the return value to
// change. Returns a zero value if the transport is exhausted.
NextReplica() roachpb.ReplicaDescriptor
// MoveToFront locates the specified replica and moves it to the
// front of the ordering of replicas to try. If the replica has
// already been tried, it will be retried. If the specified replica
// can't be found, this is a noop.
MoveToFront(roachpb.ReplicaDescriptor)
// Close is called when the transport is no longer needed. It may
// cancel any pending RPCs without writing any response to the channel.
Close()
}
// grpcTransportFactoryImpl is the default TransportFactory, using GRPC.
// Do not use this directly - use grpcTransportFactory instead.
//
// During race builds, we wrap this to hold on to and read all obtained
// requests in a tight loop, exposing data races; see transport_race.go.
func grpcTransportFactoryImpl(
opts SendOptions, rpcContext *rpc.Context, replicas ReplicaSlice, args roachpb.BatchRequest,
) (Transport, error) {
clients := make([]batchClient, 0, len(replicas))
for _, replica := range replicas {
conn, err := rpcContext.GRPCDial(replica.NodeDesc.Address.String())
if err != nil {
return nil, err
}
argsCopy := args
argsCopy.Replica = replica.ReplicaDescriptor
remoteAddr := replica.NodeDesc.Address.String()
clients = append(clients, batchClient{
remoteAddr: remoteAddr,
conn: conn,
client: roachpb.NewInternalClient(conn),
args: argsCopy,
healthy: rpcContext.ConnHealth(remoteAddr) == nil,
})
}
// Put known-unhealthy clients last.
splitHealthy(clients)
return &grpcTransport{
opts: opts,
rpcContext: rpcContext,
orderedClients: clients,
}, nil
}
type grpcTransport struct {
opts SendOptions
rpcContext *rpc.Context
clientIndex int
orderedClients []batchClient
clientPendingMu syncutil.Mutex // protects access to all batchClient pending flags
}
// IsExhausted returns false if there are any untried replicas
// remaining. If there are none, it attempts to resurrect replicas
// which were tried but failed with a retryable error and have a
// deadline set which has elapsed. If any where resurrected, returns
// false; true otherwise.
func (gt *grpcTransport) IsExhausted() bool {
gt.clientPendingMu.Lock()
defer gt.clientPendingMu.Unlock()
if gt.clientIndex < len(gt.orderedClients) {
return false
}
return !gt.maybeResurrectRetryables()
}
// maybeResurrectRetryables moves already-tried replicas which
// experienced a retryable error (currently this means a
// NotLeaseHolderError) into a newly-active state so that they can be
// retried. Returns true if any replicas were moved to active.
func (gt *grpcTransport) maybeResurrectRetryables() bool {
var resurrect []batchClient
for i := 0; i < gt.clientIndex; i++ {
if c := gt.orderedClients[i]; !c.pending && c.retryable && timeutil.Since(c.deadline) >= 0 {
resurrect = append(resurrect, c)
}
}
for _, c := range resurrect {
gt.moveToFrontLocked(c.args.Replica)
}
return len(resurrect) > 0
}
// SendNextTimeout returns the default SendOpts.SendNextTimeout if
// there are any untried replicas in the transport. Otherwise, it
// returns the earliest deadline of any replicas which experienced
// retryable errors.
func (gt *grpcTransport) SendNextTimeout(defaultTimeout time.Duration) (time.Duration, bool) {
gt.clientPendingMu.Lock()
defer gt.clientPendingMu.Unlock()
if gt.clientIndex < len(gt.orderedClients) {
return defaultTimeout, true
}
var deadline time.Time
for i := 0; i < gt.clientIndex; i++ {
if c := gt.orderedClients[i]; !c.pending && c.retryable {
if (deadline == time.Time{}) || c.deadline.Before(deadline) {
deadline = c.deadline
}
}
}
if (deadline == time.Time{}) {
return 0, false
}
// Returning a negative duration is legal.
return deadline.Sub(timeutil.Now()), true
}
// SendNext invokes the specified RPC on the supplied client when the
// client is ready. On success, the reply is sent on the channel;
// otherwise an error is sent.
func (gt *grpcTransport) SendNext(ctx context.Context, done chan<- BatchCall) {
client := gt.orderedClients[gt.clientIndex]
gt.clientIndex++
gt.setState(client.args.Replica, true /* pending */, false /* retryable */)
// Fork the original context as this async send may outlast the
// caller's context.
// TODO(andrei): We shouldn't have to fork the ctx here; it's sketchy that
// these spans can outlast the caller's context. Instead, DistSender should
// wait on all the RPCs that it sends and it should also have the ability to
// cancel them when it received the first result.
ctx, sp := tracing.ForkCtxSpan(ctx, "grpcTransport SendNext")
go func() {
gt.opts.metrics.SentCount.Inc(1)
reply, err := func() (*roachpb.BatchResponse, error) {
if localServer := gt.rpcContext.GetLocalInternalServerForAddr(client.remoteAddr); localServer != nil {
// Clone the request. At the time of writing, Replica may mutate it
// during command execution which can lead to data races.
//
// TODO(tamird): we should clone all of client.args.Header, but the
// assertions in protoutil.Clone fire and there seems to be no
// reasonable workaround.
origTxn := client.args.Txn
if origTxn != nil {
clonedTxn := origTxn.Clone()
client.args.Txn = &clonedTxn
}
// Create a new context from the existing one with the "local request" field set.
// This tells the handler that this is an in-procress request, bypassing ctx.Peer checks.
localCtx := grpcutil.NewLocalRequestContext(ctx)
gt.opts.metrics.LocalSentCount.Inc(1)
log.VEvent(localCtx, 2, "sending request to local server")
return localServer.Batch(localCtx, &client.args)
}
log.VEventf(ctx, 2, "sending request to %s", client.remoteAddr)
reply, err := client.client.Batch(ctx, &client.args)
if reply != nil {
for i := range reply.Responses {
if err := reply.Responses[i].GetInner().Verify(client.args.Requests[i].GetInner()); err != nil {
log.Error(ctx, err)
}
}
}
return reply, err
}()
// NotLeaseHolderErrors can be retried.
var retryable bool
if reply != nil && reply.Error != nil {
// TODO(spencer): pass the lease expiration when setting the state to
// set a more efficient deadline for retrying this replica.
if _, ok := reply.Error.GetDetail().(*roachpb.NotLeaseHolderError); ok {
retryable = true
}
}
gt.setState(client.args.Replica, false /* pending */, retryable)
tracing.FinishSpan(sp)
done <- BatchCall{Reply: reply, Err: err}
}()
}
func (gt *grpcTransport) NextReplica() roachpb.ReplicaDescriptor {
if gt.IsExhausted() {
return roachpb.ReplicaDescriptor{}
}
return gt.orderedClients[gt.clientIndex].args.Replica
}
func (gt *grpcTransport) MoveToFront(replica roachpb.ReplicaDescriptor) {
gt.clientPendingMu.Lock()
defer gt.clientPendingMu.Unlock()
gt.moveToFrontLocked(replica)
}
func (gt *grpcTransport) moveToFrontLocked(replica roachpb.ReplicaDescriptor) {
for i := range gt.orderedClients {
if gt.orderedClients[i].args.Replica == replica {
// If a call to this replica is active, don't move it.
if gt.orderedClients[i].pending {
return
}
// Clear the retryable bit and deadline, as this replica is being made available.
gt.orderedClients[i].retryable = false
gt.orderedClients[i].deadline = time.Time{}
// If we've already processed the replica, decrement the current
// index before we swap.
if i < gt.clientIndex {
gt.clientIndex--
}
// Swap the client representing this replica to the front.
gt.orderedClients[i], gt.orderedClients[gt.clientIndex] =
gt.orderedClients[gt.clientIndex], gt.orderedClients[i]
return
}
}
}
func (*grpcTransport) Close() {
// TODO(bdarnell): Save the cancel functions of all pending RPCs and
// call them here. (it's fine to ignore them for now since they'll
// time out anyway)
}
// NB: this method's callers may have a reference to the client they wish to
// mutate, but the clients reside in a slice which is shuffled via
// MoveToFront, making it unsafe to mutate the client through a reference to
// the slice.
func (gt *grpcTransport) setState(replica roachpb.ReplicaDescriptor, pending, retryable bool) {
gt.clientPendingMu.Lock()
defer gt.clientPendingMu.Unlock()
for i := range gt.orderedClients {
if gt.orderedClients[i].args.Replica == replica {
gt.orderedClients[i].pending = pending
gt.orderedClients[i].retryable = retryable
if retryable {
gt.orderedClients[i].deadline = timeutil.Now().Add(gt.opts.SendNextTimeout)
}
return
}
}
}
// splitHealthy splits the provided client slice into healthy clients and
// unhealthy clients, based on their connection state. Healthy clients will
// be rearranged first in the slice, and unhealthy clients will be rearranged
// last. Within these two groups, the rearrangement will be stable. The function
// will then return the number of healthy clients.
func splitHealthy(clients []batchClient) int {
var nHealthy int
sort.Stable(byHealth(clients))
for _, client := range clients {
if client.healthy {
nHealthy++
}
}
return nHealthy
}
// byHealth sorts a slice of batchClients by their health with healthy first.
type byHealth []batchClient
func (h byHealth) Len() int { return len(h) }
func (h byHealth) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
func (h byHealth) Less(i, j int) bool { return h[i].healthy && !h[j].healthy }
// SenderTransportFactory wraps a client.Sender for use as a KV
// Transport. This is useful for tests that want to use DistSender
// without a full RPC stack.
func SenderTransportFactory(tracer opentracing.Tracer, sender client.Sender) TransportFactory {
return func(
_ SendOptions, _ *rpc.Context, _ ReplicaSlice, args roachpb.BatchRequest,
) (Transport, error) {
return &senderTransport{tracer, sender, args, false}, nil
}
}
type senderTransport struct {
tracer opentracing.Tracer
sender client.Sender
args roachpb.BatchRequest
called bool
}
func (s *senderTransport) IsExhausted() bool {
return s.called
}
func (s *senderTransport) SendNextTimeout(defaultTimeout time.Duration) (time.Duration, bool) {
if s.IsExhausted() {
return 0, false
}
return defaultTimeout, true
}
func (s *senderTransport) SendNext(ctx context.Context, done chan<- BatchCall) {
if s.called {
panic("called an exhausted transport")
}
s.called = true
sp := s.tracer.StartSpan("node")
defer sp.Finish()
ctx = opentracing.ContextWithSpan(ctx, sp)
log.Event(ctx, s.args.String())
br, pErr := s.sender.Send(ctx, s.args)
if br == nil {
br = &roachpb.BatchResponse{}
}
if br.Error != nil {
panic(roachpb.ErrorUnexpectedlySet(s.sender, br))
}
br.Error = pErr
if pErr != nil {
log.Event(ctx, "error: "+pErr.String())
}
done <- BatchCall{Reply: br}
}
func (s *senderTransport) NextReplica() roachpb.ReplicaDescriptor {
if s.IsExhausted() {
return roachpb.ReplicaDescriptor{}
}
return s.args.Replica
}
func (s *senderTransport) MoveToFront(replica roachpb.ReplicaDescriptor) {
}
func (s *senderTransport) Close() {
}