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	"time"
34
35	"golang.org/x/net/context"
36)
37
38// A user defined call stub.
39type APICall func(context.Context, CallSettings) error
40
41// Invoke calls the given APICall,
42// performing retries as specified by opts, if any.
43func Invoke(ctx context.Context, call APICall, opts ...CallOption) error {
44	var settings CallSettings
45	for _, opt := range opts {
46		opt.Resolve(&settings)
47	}
48	return invoke(ctx, call, settings, Sleep)
49}
50
51// Sleep is similar to time.Sleep, but it can be interrupted by ctx.Done() closing.
52// If interrupted, Sleep returns ctx.Err().
53func Sleep(ctx context.Context, d time.Duration) error {
54	t := time.NewTimer(d)
55	select {
56	case <-ctx.Done():
57		t.Stop()
58		return ctx.Err()
59	case <-t.C:
60		return nil
61	}
62}
63
64type sleeper func(ctx context.Context, d time.Duration) error
65
66// invoke implements Invoke, taking an additional sleeper argument for testing.
67func invoke(ctx context.Context, call APICall, settings CallSettings, sp sleeper) error {
68	var retryer Retryer
69	for {
70		err := call(ctx, settings)
71		if err == nil {
72			return nil
73		}
74		if settings.Retry == nil {
75			return err
76		}
77		if retryer == nil {
78			if r := settings.Retry(); r != nil {
79				retryer = r
80			} else {
81				return err
82			}
83		}
84		if d, ok := retryer.Retry(err); !ok {
85			return err
86		} else if err = sp(ctx, d); err != nil {
87			return err
88		}
89	}
90}
91