1// Copyright 2016, Google Inc.
2// All rights reserved.
3//
4// Redistribution and use in source and binary forms, with or without
5// modification, are permitted provided that the following conditions are
6// met:
7//
8//     * Redistributions of source code must retain the above copyright
9// notice, this list of conditions and the following disclaimer.
10//     * Redistributions in binary form must reproduce the above
11// copyright notice, this list of conditions and the following disclaimer
12// in the documentation and/or other materials provided with the
13// distribution.
14//     * Neither the name of Google Inc. nor the names of its
15// contributors may be used to endorse or promote products derived from
16// this software without specific prior written permission.
17//
18// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30package gax
31
32import (
33	"math/rand"
34	"time"
35
36	"google.golang.org/grpc"
37	"google.golang.org/grpc/codes"
38	"google.golang.org/grpc/status"
39)
40
41// CallOption is an option used by Invoke to control behaviors of RPC calls.
42// CallOption works by modifying relevant fields of CallSettings.
43type CallOption interface {
44	// Resolve applies the option by modifying cs.
45	Resolve(cs *CallSettings)
46}
47
48// Retryer is used by Invoke to determine retry behavior.
49type Retryer interface {
50	// Retry reports whether a request should be retriedand how long to pause before retrying
51	// if the previous attempt returned with err. Invoke never calls Retry with nil error.
52	Retry(err error) (pause time.Duration, shouldRetry bool)
53}
54
55type retryerOption func() Retryer
56
57func (o retryerOption) Resolve(s *CallSettings) {
58	s.Retry = o
59}
60
61// WithRetry sets CallSettings.Retry to fn.
62func WithRetry(fn func() Retryer) CallOption {
63	return retryerOption(fn)
64}
65
66// OnCodes returns a Retryer that retries if and only if
67// the previous attempt returns a GRPC error whose error code is stored in cc.
68// Pause times between retries are specified by bo.
69//
70// bo is only used for its parameters; each Retryer has its own copy.
71func OnCodes(cc []codes.Code, bo Backoff) Retryer {
72	return &boRetryer{
73		backoff: bo,
74		codes:   append([]codes.Code(nil), cc...),
75	}
76}
77
78type boRetryer struct {
79	backoff Backoff
80	codes   []codes.Code
81}
82
83func (r *boRetryer) Retry(err error) (time.Duration, bool) {
84	st, ok := status.FromError(err)
85	if !ok {
86		return 0, false
87	}
88	c := st.Code()
89	for _, rc := range r.codes {
90		if c == rc {
91			return r.backoff.Pause(), true
92		}
93	}
94	return 0, false
95}
96
97// Backoff implements exponential backoff.
98// The wait time between retries is a random value between 0 and the "retry envelope".
99// The envelope starts at Initial and increases by the factor of Multiplier every retry,
100// but is capped at Max.
101type Backoff struct {
102	// Initial is the initial value of the retry envelope, defaults to 1 second.
103	Initial time.Duration
104
105	// Max is the maximum value of the retry envelope, defaults to 30 seconds.
106	Max time.Duration
107
108	// Multiplier is the factor by which the retry envelope increases.
109	// It should be greater than 1 and defaults to 2.
110	Multiplier float64
111
112	// cur is the current retry envelope
113	cur time.Duration
114}
115
116func (bo *Backoff) Pause() time.Duration {
117	if bo.Initial == 0 {
118		bo.Initial = time.Second
119	}
120	if bo.cur == 0 {
121		bo.cur = bo.Initial
122	}
123	if bo.Max == 0 {
124		bo.Max = 30 * time.Second
125	}
126	if bo.Multiplier < 1 {
127		bo.Multiplier = 2
128	}
129	// Select a duration between zero and the current max. It might seem counterintuitive to
130	// have so much jitter, but https://www.awsarchitectureblog.com/2015/03/backoff.html
131	// argues that that is the best strategy.
132	d := time.Duration(rand.Int63n(int64(bo.cur)))
133	bo.cur = time.Duration(float64(bo.cur) * bo.Multiplier)
134	if bo.cur > bo.Max {
135		bo.cur = bo.Max
136	}
137	return d
138}
139
140type grpcOpt []grpc.CallOption
141
142func (o grpcOpt) Resolve(s *CallSettings) {
143	s.GRPC = o
144}
145
146func WithGRPCOptions(opt ...grpc.CallOption) CallOption {
147	return grpcOpt(append([]grpc.CallOption(nil), opt...))
148}
149
150type CallSettings struct {
151	// Retry returns a Retryer to be used to control retry logic of a method call.
152	// If Retry is nil or the returned Retryer is nil, the call will not be retried.
153	Retry func() Retryer
154
155	// CallOptions to be forwarded to GRPC.
156	GRPC []grpc.CallOption
157}
158