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330 lines
11 KiB
Go
330 lines
11 KiB
Go
// Copyright 2016 Michal Witkowski. All Rights Reserved.
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// See LICENSE for licensing terms.
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package grpc_retry
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import (
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"context"
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"fmt"
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"io"
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"sync"
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"time"
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"github.com/grpc-ecosystem/go-grpc-middleware/util/metautils"
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"golang.org/x/net/trace"
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"google.golang.org/grpc"
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"google.golang.org/grpc/codes"
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"google.golang.org/grpc/metadata"
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"google.golang.org/grpc/status"
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)
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const (
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AttemptMetadataKey = "x-retry-attempty"
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)
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// UnaryClientInterceptor returns a new retrying unary client interceptor.
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//
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// The default configuration of the interceptor is to not retry *at all*. This behaviour can be
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// changed through options (e.g. WithMax) on creation of the interceptor or on call (through grpc.CallOptions).
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func UnaryClientInterceptor(optFuncs ...CallOption) grpc.UnaryClientInterceptor {
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intOpts := reuseOrNewWithCallOptions(defaultOptions, optFuncs)
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return func(parentCtx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
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grpcOpts, retryOpts := filterCallOptions(opts)
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callOpts := reuseOrNewWithCallOptions(intOpts, retryOpts)
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// short circuit for simplicity, and avoiding allocations.
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if callOpts.max == 0 {
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return invoker(parentCtx, method, req, reply, cc, grpcOpts...)
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}
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var lastErr error
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for attempt := uint(0); attempt < callOpts.max; attempt++ {
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if err := waitRetryBackoff(attempt, parentCtx, callOpts); err != nil {
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return err
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}
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callCtx := perCallContext(parentCtx, callOpts, attempt)
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lastErr = invoker(callCtx, method, req, reply, cc, grpcOpts...)
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// TODO(mwitkow): Maybe dial and transport errors should be retriable?
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if lastErr == nil {
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return nil
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}
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logTrace(parentCtx, "grpc_retry attempt: %d, got err: %v", attempt, lastErr)
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if isContextError(lastErr) {
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if parentCtx.Err() != nil {
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logTrace(parentCtx, "grpc_retry attempt: %d, parent context error: %v", attempt, parentCtx.Err())
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// its the parent context deadline or cancellation.
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return lastErr
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} else if callOpts.perCallTimeout != 0 {
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// We have set a perCallTimeout in the retry middleware, which would result in a context error if
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// the deadline was exceeded, in which case try again.
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logTrace(parentCtx, "grpc_retry attempt: %d, context error from retry call", attempt)
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continue
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}
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}
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if !isRetriable(lastErr, callOpts) {
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return lastErr
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}
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}
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return lastErr
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}
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}
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// StreamClientInterceptor returns a new retrying stream client interceptor for server side streaming calls.
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//
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// The default configuration of the interceptor is to not retry *at all*. This behaviour can be
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// changed through options (e.g. WithMax) on creation of the interceptor or on call (through grpc.CallOptions).
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//
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// Retry logic is available *only for ServerStreams*, i.e. 1:n streams, as the internal logic needs
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// to buffer the messages sent by the client. If retry is enabled on any other streams (ClientStreams,
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// BidiStreams), the retry interceptor will fail the call.
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func StreamClientInterceptor(optFuncs ...CallOption) grpc.StreamClientInterceptor {
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intOpts := reuseOrNewWithCallOptions(defaultOptions, optFuncs)
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return func(parentCtx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
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grpcOpts, retryOpts := filterCallOptions(opts)
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callOpts := reuseOrNewWithCallOptions(intOpts, retryOpts)
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// short circuit for simplicity, and avoiding allocations.
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if callOpts.max == 0 {
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return streamer(parentCtx, desc, cc, method, grpcOpts...)
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}
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if desc.ClientStreams {
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return nil, status.Errorf(codes.Unimplemented, "grpc_retry: cannot retry on ClientStreams, set grpc_retry.Disable()")
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}
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var lastErr error
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for attempt := uint(0); attempt < callOpts.max; attempt++ {
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if err := waitRetryBackoff(attempt, parentCtx, callOpts); err != nil {
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return nil, err
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}
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callCtx := perCallContext(parentCtx, callOpts, 0)
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var newStreamer grpc.ClientStream
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newStreamer, lastErr = streamer(callCtx, desc, cc, method, grpcOpts...)
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if lastErr == nil {
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retryingStreamer := &serverStreamingRetryingStream{
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ClientStream: newStreamer,
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callOpts: callOpts,
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parentCtx: parentCtx,
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streamerCall: func(ctx context.Context) (grpc.ClientStream, error) {
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return streamer(ctx, desc, cc, method, grpcOpts...)
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},
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}
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return retryingStreamer, nil
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}
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logTrace(parentCtx, "grpc_retry attempt: %d, got err: %v", attempt, lastErr)
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if isContextError(lastErr) {
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if parentCtx.Err() != nil {
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logTrace(parentCtx, "grpc_retry attempt: %d, parent context error: %v", attempt, parentCtx.Err())
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// its the parent context deadline or cancellation.
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return nil, lastErr
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} else if callOpts.perCallTimeout != 0 {
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// We have set a perCallTimeout in the retry middleware, which would result in a context error if
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// the deadline was exceeded, in which case try again.
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logTrace(parentCtx, "grpc_retry attempt: %d, context error from retry call", attempt)
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continue
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}
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}
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if !isRetriable(lastErr, callOpts) {
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return nil, lastErr
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}
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}
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return nil, lastErr
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}
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}
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// type serverStreamingRetryingStream is the implementation of grpc.ClientStream that acts as a
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// proxy to the underlying call. If any of the RecvMsg() calls fail, it will try to reestablish
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// a new ClientStream according to the retry policy.
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type serverStreamingRetryingStream struct {
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grpc.ClientStream
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bufferedSends []interface{} // single message that the client can sen
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receivedGood bool // indicates whether any prior receives were successful
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wasClosedSend bool // indicates that CloseSend was closed
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parentCtx context.Context
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callOpts *options
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streamerCall func(ctx context.Context) (grpc.ClientStream, error)
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mu sync.RWMutex
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}
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func (s *serverStreamingRetryingStream) setStream(clientStream grpc.ClientStream) {
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s.mu.Lock()
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s.ClientStream = clientStream
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s.mu.Unlock()
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}
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func (s *serverStreamingRetryingStream) getStream() grpc.ClientStream {
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s.mu.RLock()
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defer s.mu.RUnlock()
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return s.ClientStream
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}
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func (s *serverStreamingRetryingStream) SendMsg(m interface{}) error {
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s.mu.Lock()
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s.bufferedSends = append(s.bufferedSends, m)
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s.mu.Unlock()
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return s.getStream().SendMsg(m)
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}
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func (s *serverStreamingRetryingStream) CloseSend() error {
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s.mu.Lock()
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s.wasClosedSend = true
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s.mu.Unlock()
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return s.getStream().CloseSend()
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}
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func (s *serverStreamingRetryingStream) Header() (metadata.MD, error) {
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return s.getStream().Header()
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}
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func (s *serverStreamingRetryingStream) Trailer() metadata.MD {
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return s.getStream().Trailer()
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}
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func (s *serverStreamingRetryingStream) RecvMsg(m interface{}) error {
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attemptRetry, lastErr := s.receiveMsgAndIndicateRetry(m)
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if !attemptRetry {
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return lastErr // success or hard failure
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}
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// We start off from attempt 1, because zeroth was already made on normal SendMsg().
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for attempt := uint(1); attempt < s.callOpts.max; attempt++ {
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if err := waitRetryBackoff(attempt, s.parentCtx, s.callOpts); err != nil {
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return err
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}
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callCtx := perCallContext(s.parentCtx, s.callOpts, attempt)
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newStream, err := s.reestablishStreamAndResendBuffer(callCtx)
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if err != nil {
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// Retry dial and transport errors of establishing stream as grpc doesn't retry.
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if isRetriable(err, s.callOpts) {
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continue
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}
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return err
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}
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s.setStream(newStream)
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attemptRetry, lastErr = s.receiveMsgAndIndicateRetry(m)
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//fmt.Printf("Received message and indicate: %v %v\n", attemptRetry, lastErr)
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if !attemptRetry {
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return lastErr
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}
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}
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return lastErr
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}
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func (s *serverStreamingRetryingStream) receiveMsgAndIndicateRetry(m interface{}) (bool, error) {
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s.mu.RLock()
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wasGood := s.receivedGood
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s.mu.RUnlock()
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err := s.getStream().RecvMsg(m)
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if err == nil || err == io.EOF {
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s.mu.Lock()
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s.receivedGood = true
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s.mu.Unlock()
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return false, err
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} else if wasGood {
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// previous RecvMsg in the stream succeeded, no retry logic should interfere
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return false, err
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}
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if isContextError(err) {
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if s.parentCtx.Err() != nil {
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logTrace(s.parentCtx, "grpc_retry parent context error: %v", s.parentCtx.Err())
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return false, err
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} else if s.callOpts.perCallTimeout != 0 {
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// We have set a perCallTimeout in the retry middleware, which would result in a context error if
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// the deadline was exceeded, in which case try again.
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logTrace(s.parentCtx, "grpc_retry context error from retry call")
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return true, err
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}
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}
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return isRetriable(err, s.callOpts), err
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}
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func (s *serverStreamingRetryingStream) reestablishStreamAndResendBuffer(
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callCtx context.Context,
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) (grpc.ClientStream, error) {
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s.mu.RLock()
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bufferedSends := s.bufferedSends
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s.mu.RUnlock()
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newStream, err := s.streamerCall(callCtx)
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if err != nil {
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logTrace(callCtx, "grpc_retry failed redialing new stream: %v", err)
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return nil, err
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}
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for _, msg := range bufferedSends {
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if err := newStream.SendMsg(msg); err != nil {
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logTrace(callCtx, "grpc_retry failed resending message: %v", err)
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return nil, err
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}
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}
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if err := newStream.CloseSend(); err != nil {
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logTrace(callCtx, "grpc_retry failed CloseSend on new stream %v", err)
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return nil, err
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}
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return newStream, nil
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}
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func waitRetryBackoff(attempt uint, parentCtx context.Context, callOpts *options) error {
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var waitTime time.Duration = 0
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if attempt > 0 {
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waitTime = callOpts.backoffFunc(parentCtx, attempt)
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}
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if waitTime > 0 {
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logTrace(parentCtx, "grpc_retry attempt: %d, backoff for %v", attempt, waitTime)
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timer := time.NewTimer(waitTime)
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select {
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case <-parentCtx.Done():
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timer.Stop()
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return contextErrToGrpcErr(parentCtx.Err())
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case <-timer.C:
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}
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}
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return nil
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}
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func isRetriable(err error, callOpts *options) bool {
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errCode := status.Code(err)
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if isContextError(err) {
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// context errors are not retriable based on user settings.
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return false
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}
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for _, code := range callOpts.codes {
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if code == errCode {
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return true
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}
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}
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return false
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}
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func isContextError(err error) bool {
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code := status.Code(err)
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return code == codes.DeadlineExceeded || code == codes.Canceled
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}
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func perCallContext(parentCtx context.Context, callOpts *options, attempt uint) context.Context {
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ctx := parentCtx
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if callOpts.perCallTimeout != 0 {
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ctx, _ = context.WithTimeout(ctx, callOpts.perCallTimeout)
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}
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if attempt > 0 && callOpts.includeHeader {
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mdClone := metautils.ExtractOutgoing(ctx).Clone().Set(AttemptMetadataKey, fmt.Sprintf("%d", attempt))
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ctx = mdClone.ToOutgoing(ctx)
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}
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return ctx
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}
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func contextErrToGrpcErr(err error) error {
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switch err {
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case context.DeadlineExceeded:
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return status.Error(codes.DeadlineExceeded, err.Error())
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case context.Canceled:
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return status.Error(codes.Canceled, err.Error())
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default:
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return status.Error(codes.Unknown, err.Error())
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}
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}
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func logTrace(ctx context.Context, format string, a ...interface{}) {
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tr, ok := trace.FromContext(ctx)
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if !ok {
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return
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}
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tr.LazyPrintf(format, a...)
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}
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