/
picker.go
74 lines (59 loc) · 1.82 KB
/
picker.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
package loadbalance
import (
"strings"
"sync"
"sync/atomic"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/base"
)
var _ base.PickerBuilder = (*Picker)(nil)
// Picker handle the RPC balancing logic by
// picking a server from the servers discovered
// by the resolver to handel each RPC.
type Picker struct {
mu sync.RWMutex
leader balancer.SubConn
followers []balancer.SubConn
current uint64
}
// Build sets up a Picker using the map of sub connections given in buildInfo.
func (p *Picker) Build(buildInfo base.PickerBuildInfo) balancer.Picker {
p.mu.Lock()
defer p.mu.Unlock()
var followers []balancer.SubConn
for sc, scInfo := range buildInfo.ReadySCs {
if isLeader := scInfo.Address.Attributes.Value("is_leader").(bool); isLeader {
p.leader = sc
continue
}
followers = append(followers, sc)
}
p.followers = followers
return p
}
var _ balancer.Picker = (*Picker)(nil)
// Pick gets info containing the RPC's name and context from gRPC to help the picker know
// what subconnection to pick, and returns the subconnection to handle the call in the result.
func (p *Picker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
p.mu.RLock()
defer p.mu.RUnlock()
var result balancer.PickResult
if strings.Contains(info.FullMethodName, "Produce") || len(p.followers) == 0 {
result.SubConn = p.leader
} else if strings.Contains(info.FullMethodName, "Consume") {
result.SubConn = p.nextFollower()
}
if result.SubConn == nil {
return result, balancer.ErrNoSubConnAvailable
}
return result, nil
}
func (p *Picker) nextFollower() balancer.SubConn {
cur := atomic.AddUint64(&p.current, uint64(1))
len := uint64(len(p.followers))
idx := int(cur % len)
return p.followers[idx]
}
func init() {
balancer.Register(base.NewBalancerBuilder(Name, &Picker{}, base.Config{}))
}