1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
// Copyright (c) 2018 The Jaeger Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package remote
import (
"fmt"
"net/url"
"sync"
"sync/atomic"
"time"
"github.com/pkg/errors"
"github.com/uber/jaeger-client-go"
"github.com/uber/jaeger-client-go/utils"
)
const (
// minimumCredits is the minimum amount of credits necessary to not be throttled.
// i.e. if currentCredits > minimumCredits, then the operation will not be throttled.
minimumCredits = 1.0
)
var (
errorUUIDNotSet = errors.New("Throttler UUID must be set")
)
type operationBalance struct {
Operation string `json:"operation"`
Balance float64 `json:"balance"`
}
type creditResponse struct {
Balances []operationBalance `json:"balances"`
}
type httpCreditManagerProxy struct {
hostPort string
}
func newHTTPCreditManagerProxy(hostPort string) *httpCreditManagerProxy {
return &httpCreditManagerProxy{
hostPort: hostPort,
}
}
// N.B. Operations list must not be empty.
func (m *httpCreditManagerProxy) FetchCredits(uuid, serviceName string, operations []string) (*creditResponse, error) {
params := url.Values{}
params.Set("service", serviceName)
params.Set("uuid", uuid)
for _, op := range operations {
params.Add("operations", op)
}
var resp creditResponse
if err := utils.GetJSON(fmt.Sprintf("http://%s/credits?%s", m.hostPort, params.Encode()), &resp); err != nil {
return nil, errors.Wrap(err, "Failed to receive credits from agent")
}
return &resp, nil
}
// Throttler retrieves credits from agent and uses it to throttle operations.
type Throttler struct {
options
mux sync.RWMutex
service string
uuid atomic.Value
creditManager *httpCreditManagerProxy
credits map[string]float64 // map of operation->credits
close chan struct{}
stopped sync.WaitGroup
}
// NewThrottler returns a Throttler that polls agent for credits and uses them to throttle
// the service.
func NewThrottler(service string, options ...Option) *Throttler {
opts := applyOptions(options...)
creditManager := newHTTPCreditManagerProxy(opts.hostPort)
t := &Throttler{
options: opts,
creditManager: creditManager,
service: service,
credits: make(map[string]float64),
close: make(chan struct{}),
}
t.stopped.Add(1)
go t.pollManager()
return t
}
// IsAllowed implements Throttler#IsAllowed.
func (t *Throttler) IsAllowed(operation string) bool {
t.mux.Lock()
defer t.mux.Unlock()
value, ok := t.credits[operation]
if !ok || value == 0 {
if !ok {
// NOTE: This appears to be a no-op at first glance, but it stores
// the operation key in the map. Necessary for functionality of
// Throttler#operations method.
t.credits[operation] = 0
}
if !t.synchronousInitialization {
t.metrics.ThrottledDebugSpans.Inc(1)
return false
}
// If it is the first time this operation is being checked, synchronously fetch
// the credits.
credits, err := t.fetchCredits([]string{operation})
if err != nil {
// Failed to receive credits from agent, try again next time
t.logger.Error("Failed to fetch credits: " + err.Error())
return false
}
if len(credits.Balances) == 0 {
// This shouldn't happen but just in case
return false
}
for _, opBalance := range credits.Balances {
t.credits[opBalance.Operation] += opBalance.Balance
}
}
return t.isAllowed(operation)
}
// Close stops the throttler from fetching credits from remote.
func (t *Throttler) Close() error {
close(t.close)
t.stopped.Wait()
return nil
}
// SetProcess implements ProcessSetter#SetProcess. It's imperative that the UUID is set before any remote
// requests are made.
func (t *Throttler) SetProcess(process jaeger.Process) {
if process.UUID != "" {
t.uuid.Store(process.UUID)
}
}
// N.B. This function must be called with the Write Lock
func (t *Throttler) isAllowed(operation string) bool {
credits := t.credits[operation]
if credits < minimumCredits {
t.metrics.ThrottledDebugSpans.Inc(1)
return false
}
t.credits[operation] = credits - minimumCredits
return true
}
func (t *Throttler) pollManager() {
defer t.stopped.Done()
ticker := time.NewTicker(t.refreshInterval)
defer ticker.Stop()
for {
select {
case <-ticker.C:
t.refreshCredits()
case <-t.close:
return
}
}
}
func (t *Throttler) operations() []string {
t.mux.RLock()
defer t.mux.RUnlock()
operations := make([]string, 0, len(t.credits))
for op := range t.credits {
operations = append(operations, op)
}
return operations
}
func (t *Throttler) refreshCredits() {
operations := t.operations()
if len(operations) == 0 {
return
}
newCredits, err := t.fetchCredits(operations)
if err != nil {
t.metrics.ThrottlerUpdateFailure.Inc(1)
t.logger.Error("Failed to fetch credits: " + err.Error())
return
}
t.metrics.ThrottlerUpdateSuccess.Inc(1)
t.mux.Lock()
defer t.mux.Unlock()
for _, opBalance := range newCredits.Balances {
t.credits[opBalance.Operation] += opBalance.Balance
}
}
func (t *Throttler) fetchCredits(operations []string) (*creditResponse, error) {
uuid := t.uuid.Load()
uuidStr, _ := uuid.(string)
if uuid == nil || uuidStr == "" {
return nil, errorUUIDNotSet
}
return t.creditManager.FetchCredits(uuidStr, t.service, operations)
}
|
