-
Notifications
You must be signed in to change notification settings - Fork 888
/
rtt_monitor.go
165 lines (135 loc) · 3.67 KB
/
rtt_monitor.go
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
// Copyright (C) MongoDB, Inc. 2017-present.
//
// 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
package topology
import (
"context"
"sync"
"time"
"go.mongodb.org/mongo-driver/x/mongo/driver"
"go.mongodb.org/mongo-driver/x/mongo/driver/operation"
)
const (
rttAlphaValue = 0.2
)
type rttConfig struct {
interval time.Duration
createConnectionFn func() (*connection, error)
createOperationFn func(driver.Connection) *operation.IsMaster
}
type rttMonitor struct {
sync.Mutex
conn *connection
averageRTT time.Duration
averageRTTSet bool
closeWg sync.WaitGroup
cfg *rttConfig
ctx context.Context
cancelFn context.CancelFunc
}
func newRttMonitor(cfg *rttConfig) *rttMonitor {
ctx, cancel := context.WithCancel(context.Background())
return &rttMonitor{
cfg: cfg,
ctx: ctx,
cancelFn: cancel,
}
}
func (r *rttMonitor) connect() {
r.closeWg.Add(1)
go r.start()
}
func (r *rttMonitor) disconnect() {
// Signal for the routine to stop.
r.cancelFn()
var conn *connection
r.Lock()
conn = r.conn
r.Unlock()
if conn != nil {
// If the connection exists, we need to wait for it to be connected. We can ignore the error from conn.wait().
// If the connection wasn't successfully opened, its state was set back to disconnected, so calling conn.close()
// will be a noop.
conn.closeConnectContext()
_ = conn.wait()
_ = conn.close()
}
r.closeWg.Wait()
}
func (r *rttMonitor) start() {
defer r.closeWg.Done()
ticker := time.NewTicker(r.cfg.interval)
defer ticker.Stop()
for {
// The context is only cancelled in disconnect() so if there's an error on it, the monitor is shutting down.
if r.ctx.Err() != nil {
return
}
r.pingServer()
select {
case <-ticker.C:
case <-r.ctx.Done():
// Shutting down
return
}
}
}
// reset sets the average RTT to 0. This should only be called from the server monitor when an error occurs during a
// server check. Errors in the RTT monitor should not reset the average RTT.
func (r *rttMonitor) reset() {
r.Lock()
defer r.Unlock()
r.averageRTT = 0
r.averageRTTSet = false
}
func (r *rttMonitor) setupRttConnection() error {
conn, err := r.cfg.createConnectionFn()
if err != nil {
return err
}
r.Lock()
r.conn = conn
r.Unlock()
r.conn.connect(r.ctx)
return r.conn.wait()
}
func (r *rttMonitor) pingServer() {
if r.conn == nil || r.conn.closed() {
if err := r.setupRttConnection(); err != nil {
return
}
// Add the initial connection handshake time as an RTT sample.
r.addSample(r.conn.isMasterRTT)
return
}
// We're using an already established connection. Issue an isMaster command to get a new RTT sample.
rttConn := initConnection{r.conn}
start := time.Now()
err := r.cfg.createOperationFn(rttConn).Execute(r.ctx)
if err != nil {
// Errors from the RTT monitor do not reset the average RTT or update the topology, so we close the existing
// connection and recreate it on the next check.
_ = r.conn.close()
return
}
r.addSample(time.Since(start))
}
func (r *rttMonitor) addSample(rtt time.Duration) {
// Lock for the duration of this method. We're doing compuationally inexpensive work very infrequently, so lock
// contention isn't expected.
r.Lock()
defer r.Unlock()
if !r.averageRTTSet {
r.averageRTT = rtt
r.averageRTTSet = true
return
}
r.averageRTT = time.Duration(rttAlphaValue*float64(rtt) + (1-rttAlphaValue)*float64(r.averageRTT))
}
func (r *rttMonitor) getRTT() time.Duration {
r.Lock()
defer r.Unlock()
return r.averageRTT
}