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| 1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 package wrapper | |
| 6 | |
| 7 import ( | |
| 8 "errors" | |
| 9 "fmt" | |
| 10 "runtime" | |
| 11 "strings" | |
| 12 "sync" | |
| 13 "unicode" | |
| 14 "unicode/utf8" | |
| 15 ) | |
| 16 | |
| 17 // FeatureBreaker allows a fake implementation to set and unset broken features. | |
| 18 // A feature is the Name of some method on the fake. So if you had: | |
| 19 // var fake interface{ FeatureBreaker, MCSingleReadWriter } = ... | |
| 20 // | |
| 21 // you could do: | |
| 22 // fake.BreakFeatures(memcache.ErrServerError, "Add", "Set") | |
| 23 // | |
| 24 // and then | |
| 25 // fake.Add(...) and fake.Set(...) | |
| 26 // | |
| 27 // would return the error. | |
| 28 // | |
| 29 // You may also pass nil as the error for BreakFeatures, and the fake will | |
| 30 // provide some suitable (but generic) error for those features (like a | |
| 31 // BAD_REQUEST or something like that). | |
| 32 type FeatureBreaker interface { | |
| 33 BreakFeatures(err error, feature ...string) | |
| 34 UnbreakFeatures(feature ...string) | |
| 35 } | |
| 36 | |
| 37 // ErrBrokenFeaturesBroken is returned from IsBroken when BrokenFeatures itself | |
| 38 // isn't working correctly. | |
| 39 var ErrBrokenFeaturesBroken = errors.New("brokenFeatures: Unable to retrieve cal
ler information") | |
| 40 | |
| 41 // BrokenFeatures implements the FeatureBreaker interface, and is suitable for | |
| 42 // embedding within a fake service. | |
| 43 type BrokenFeatures struct { | |
| 44 lock sync.Mutex | |
| 45 | |
| 46 broken map[string]error | |
| 47 | |
| 48 // DefaultError is the default error to return when you call | |
| 49 // BreakFeatures(nil, ...). If this is unset and the user calls BreakFea
tures | |
| 50 // with nil, BrokenFeatures will return a generic error. | |
| 51 DefaultError error | |
| 52 } | |
| 53 | |
| 54 // BreakFeatures allows you to specify an MCSingleReadWriter function name | |
| 55 // to cause it to return memcache.ErrServerError. e.g. | |
| 56 // | |
| 57 // m.SetBrokenFeatures("Add") | |
| 58 // | |
| 59 // would return memcache.ErrServerError. You can reverse this by calling | |
| 60 // UnbreakFeatures("Add"). | |
| 61 func (b *BrokenFeatures) BreakFeatures(err error, feature ...string) { | |
| 62 b.lock.Lock() | |
| 63 defer b.lock.Unlock() | |
| 64 if b.broken == nil { | |
| 65 b.broken = map[string]error{} | |
| 66 } | |
| 67 | |
| 68 for _, f := range feature { | |
| 69 b.broken[f] = err | |
| 70 } | |
| 71 } | |
| 72 | |
| 73 // UnbreakFeatures is the inverse of BreakFeatures, and will return the named | |
| 74 // features back to their original functionality. | |
| 75 func (b *BrokenFeatures) UnbreakFeatures(feature ...string) { | |
| 76 b.lock.Lock() | |
| 77 defer b.lock.Unlock() | |
| 78 | |
| 79 for _, f := range feature { | |
| 80 delete(b.broken, f) | |
| 81 } | |
| 82 } | |
| 83 | |
| 84 // IsBroken is to be called internally by the fake service on every | |
| 85 // publically-facing method. If it returns an error, the fake should return | |
| 86 // the error. | |
| 87 // | |
| 88 // Example: | |
| 89 // type MyService struct { BrokenFeatures } | |
| 90 // func (ms *MyService) Thingy() error { | |
| 91 // if err := ms.IsBroken(); err != nil { | |
| 92 // return err | |
| 93 // } | |
| 94 // ... | |
| 95 // } | |
| 96 // | |
| 97 // You can now do ms.SetBrokenFeatures("Thingy"), and Thingy will return an | |
| 98 // error. | |
| 99 // | |
| 100 // Note that IsBroken will keep walking the stack until it finds the first | |
| 101 // publically-exported method, which will allow you to put the IsBroken call | |
| 102 // in an internal helper method of your service implementation. | |
| 103 // | |
| 104 // Additionaly, IsBroken allows a very primitive form of overriding; it walks | |
| 105 // the stack until it finds the first method which is not called "IsBroken". | |
| 106 // This allows the embedding struct to call into BrokenFeatures.IsBroken from | |
| 107 // another IsBroken function, and still have it behave correctly. | |
| 108 func (b *BrokenFeatures) IsBroken() error { | |
| 109 if b.noBrokenFeatures() { | |
| 110 return nil | |
| 111 } | |
| 112 | |
| 113 var name string | |
| 114 for off := 1; ; off++ { // offset of 1 skips ourselves by default | |
| 115 // TODO(riannucci): Profile this to see if it's having an advers
e | |
| 116 // performance impact ont tests. | |
| 117 fn, _, _, ok := runtime.Caller(off) | |
| 118 if !ok { | |
| 119 return ErrBrokenFeaturesBroken | |
| 120 } | |
| 121 toks := strings.Split(runtime.FuncForPC(fn).Name(), ".") | |
| 122 name = toks[len(toks)-1] | |
| 123 firstRune, _ := utf8.DecodeRuneInString(name) | |
| 124 if !unicode.IsUpper(firstRune) { | |
| 125 // unexported method, keep walking till we find the firs
t exported | |
| 126 // method. Do !IsUpper, since exported is defined by IsU
pper and not | |
| 127 // !IsLower, and afaik, in unicode-land they're not dire
ct opposites. | |
| 128 continue | |
| 129 } | |
| 130 if name == "IsBroken" { | |
| 131 // Allow users to override IsBroken, keep walking until
we see a function | |
| 132 // which is named differently than IsBroken. | |
| 133 continue | |
| 134 } | |
| 135 break | |
| 136 } | |
| 137 | |
| 138 b.lock.Lock() | |
| 139 defer b.lock.Unlock() | |
| 140 if err, ok := b.broken[name]; ok { | |
| 141 if err != nil { | |
| 142 return err | |
| 143 } | |
| 144 if b.DefaultError != nil { | |
| 145 return b.DefaultError | |
| 146 } | |
| 147 return fmt.Errorf("feature %q is broken", name) | |
| 148 } | |
| 149 | |
| 150 return nil | |
| 151 } | |
| 152 | |
| 153 func (b *BrokenFeatures) noBrokenFeatures() bool { | |
| 154 b.lock.Lock() | |
| 155 defer b.lock.Unlock() | |
| 156 return len(b.broken) == 0 | |
| 157 } | |
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Chromium Code Reviews
Issue 1240573002:
Reland: Refactor current GAE abstraction library to be free of the SDK* (Closed)
Base URL: https://chromium.googlesource.com/infra/infra.git@master