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	"context"
34	"time"
35)
36
37// A user defined call stub.
38type APICall func(context.Context, CallSettings) error
39
40// Invoke calls the given APICall,
41// performing retries as specified by opts, if any.
42func Invoke(ctx context.Context, call APICall, opts ...CallOption) error {
43	var settings CallSettings
44	for _, opt := range opts {
45		opt.Resolve(&settings)
46	}
47	return invoke(ctx, call, settings, Sleep)
48}
49
50// Sleep is similar to time.Sleep, but it can be interrupted by ctx.Done() closing.
51// If interrupted, Sleep returns ctx.Err().
52func Sleep(ctx context.Context, d time.Duration) error {
53	t := time.NewTimer(d)
54	select {
55	case <-ctx.Done():
56		t.Stop()
57		return ctx.Err()
58	case <-t.C:
59		return nil
60	}
61}
62
63type sleeper func(ctx context.Context, d time.Duration) error
64
65// invoke implements Invoke, taking an additional sleeper argument for testing.
66func invoke(ctx context.Context, call APICall, settings CallSettings, sp sleeper) error {
67	var retryer Retryer
68	for {
69		err := call(ctx, settings)
70		if err == nil {
71			return nil
72		}
73		if settings.Retry == nil {
74			return err
75		}
76		if retryer == nil {
77			if r := settings.Retry(); r != nil {
78				retryer = r
79			} else {
80				return err
81			}
82		}
83		if d, ok := retryer.Retry(err); !ok {
84			return err
85		} else if err = sp(ctx, d); err != nil {
86			return err
87		}
88	}
89}
90