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- // Copyright 2016, Google Inc.
- // All rights reserved.
- //
- // Redistribution and use in source and binary forms, with or without
- // modification, are permitted provided that the following conditions are
- // met:
- //
- // * Redistributions of source code must retain the above copyright
- // notice, this list of conditions and the following disclaimer.
- // * Redistributions in binary form must reproduce the above
- // copyright notice, this list of conditions and the following disclaimer
- // in the documentation and/or other materials provided with the
- // distribution.
- // * Neither the name of Google Inc. nor the names of its
- // contributors may be used to endorse or promote products derived from
- // this software without specific prior written permission.
- //
- // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
- package gax
-
- import (
- "math/rand"
- "time"
-
- "google.golang.org/grpc"
- "google.golang.org/grpc/codes"
- "google.golang.org/grpc/status"
- )
-
- // CallOption is an option used by Invoke to control behaviors of RPC calls.
- // CallOption works by modifying relevant fields of CallSettings.
- type CallOption interface {
- // Resolve applies the option by modifying cs.
- Resolve(cs *CallSettings)
- }
-
- // Retryer is used by Invoke to determine retry behavior.
- type Retryer interface {
- // Retry reports whether a request should be retriedand how long to pause before retrying
- // if the previous attempt returned with err. Invoke never calls Retry with nil error.
- Retry(err error) (pause time.Duration, shouldRetry bool)
- }
-
- type retryerOption func() Retryer
-
- func (o retryerOption) Resolve(s *CallSettings) {
- s.Retry = o
- }
-
- // WithRetry sets CallSettings.Retry to fn.
- func WithRetry(fn func() Retryer) CallOption {
- return retryerOption(fn)
- }
-
- // OnCodes returns a Retryer that retries if and only if
- // the previous attempt returns a GRPC error whose error code is stored in cc.
- // Pause times between retries are specified by bo.
- //
- // bo is only used for its parameters; each Retryer has its own copy.
- func OnCodes(cc []codes.Code, bo Backoff) Retryer {
- return &boRetryer{
- backoff: bo,
- codes: append([]codes.Code(nil), cc...),
- }
- }
-
- type boRetryer struct {
- backoff Backoff
- codes []codes.Code
- }
-
- func (r *boRetryer) Retry(err error) (time.Duration, bool) {
- st, ok := status.FromError(err)
- if !ok {
- return 0, false
- }
- c := st.Code()
- for _, rc := range r.codes {
- if c == rc {
- return r.backoff.Pause(), true
- }
- }
- return 0, false
- }
-
- // Backoff implements exponential backoff.
- // The wait time between retries is a random value between 0 and the "retry envelope".
- // The envelope starts at Initial and increases by the factor of Multiplier every retry,
- // but is capped at Max.
- type Backoff struct {
- // Initial is the initial value of the retry envelope, defaults to 1 second.
- Initial time.Duration
-
- // Max is the maximum value of the retry envelope, defaults to 30 seconds.
- Max time.Duration
-
- // Multiplier is the factor by which the retry envelope increases.
- // It should be greater than 1 and defaults to 2.
- Multiplier float64
-
- // cur is the current retry envelope
- cur time.Duration
- }
-
- // Pause returns the next time.Duration that the caller should use to backoff.
- func (bo *Backoff) Pause() time.Duration {
- if bo.Initial == 0 {
- bo.Initial = time.Second
- }
- if bo.cur == 0 {
- bo.cur = bo.Initial
- }
- if bo.Max == 0 {
- bo.Max = 30 * time.Second
- }
- if bo.Multiplier < 1 {
- bo.Multiplier = 2
- }
- // Select a duration between 1ns and the current max. It might seem
- // counterintuitive to have so much jitter, but
- // https://www.awsarchitectureblog.com/2015/03/backoff.html argues that
- // that is the best strategy.
- d := time.Duration(1 + rand.Int63n(int64(bo.cur)))
- bo.cur = time.Duration(float64(bo.cur) * bo.Multiplier)
- if bo.cur > bo.Max {
- bo.cur = bo.Max
- }
- return d
- }
-
- type grpcOpt []grpc.CallOption
-
- func (o grpcOpt) Resolve(s *CallSettings) {
- s.GRPC = o
- }
-
- // WithGRPCOptions allows passing gRPC call options during client creation.
- func WithGRPCOptions(opt ...grpc.CallOption) CallOption {
- return grpcOpt(append([]grpc.CallOption(nil), opt...))
- }
-
- // CallSettings allow fine-grained control over how calls are made.
- type CallSettings struct {
- // Retry returns a Retryer to be used to control retry logic of a method call.
- // If Retry is nil or the returned Retryer is nil, the call will not be retried.
- Retry func() Retryer
-
- // CallOptions to be forwarded to GRPC.
- GRPC []grpc.CallOption
- }
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