-
Notifications
You must be signed in to change notification settings - Fork 0
/
genserver.go
205 lines (176 loc) · 4.31 KB
/
genserver.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
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
package genserver
import (
"errors"
"fmt"
"io"
"log"
"net/rpc"
"reflect"
)
func Reply[T any](call *rpc.Call) T {
return *(call.Reply.(*T))
}
type Behaviour interface {
Handle(serviceMethod string, seq uint64, body any) (any, error)
}
type GenServer interface {
Listen(Behaviour)
Cast(serviceMethod string, args any, reply any, done chan *rpc.Call) *rpc.Call
Call(serviceMethod string, args any, reply any) error
Close() error
}
func Listen[T Behaviour](f func(GenServer) T) T {
serv := NewGenServer()
behaviour := f(serv)
go serv.Listen(behaviour)
return behaviour
}
func NewGenServer() *genServer {
return newGenServer(4096, 4096)
}
func newGenServer(incap uint, outcap uint) *genServer {
requests := make(chan request, incap)
responses := make(chan response, outcap)
codec := &genServerCodec{requests: requests, responses: responses}
client := rpc.NewClientWithCodec(codec)
return &genServer{codec: codec, client: client}
}
type genServer struct {
codec *genServerCodec
client *rpc.Client
}
var _ GenServer = (*genServer)(nil)
func (s *genServer) Cast(serviceMethod string, args any, reply any, done chan *rpc.Call) *rpc.Call {
return s.client.Go(serviceMethod, args, reply, done)
}
func (s *genServer) Call(serviceMethod string, args any, reply any) error {
return s.client.Call(serviceMethod, args, reply)
}
func (s *genServer) Close() error {
return s.client.Close()
}
func (s *genServer) Listen(behaviour Behaviour) {
s.codec.Listen(behaviour)
}
type genServerCodec struct {
requests chan request
responses chan response
current response
}
var _ rpc.ClientCodec = (*genServerCodec)(nil)
func (c *genServerCodec) WriteRequest(req *rpc.Request, body any) error {
var err error
tryCatch(func() {
c.requests <- request{seq: req.Seq, serviceMethod: req.ServiceMethod, body: body}
}, &err)
return err
}
func (c *genServerCodec) ReadResponseHeader(res *rpc.Response) error {
response, ok := <-c.responses
if !ok {
return io.EOF
}
c.current = response
res.Seq = response.seq
res.ServiceMethod = response.serviceMethod
if response.Err() != nil {
res.Error = response.Err().Error()
}
return response.Err()
}
func (c *genServerCodec) ReadResponseBody(body any) error {
// if `ReadResponseHeader` DOES NOT return error then `ReadResponseBody` will be called => c.current.result.Err == nil
if c.current.Err() != nil {
log.Fatal("must be unreachable")
}
v := c.current.Value()
if v == nil {
return nil
}
if body == nil { // should ignore nil `reply`
return nil
}
tbody := reflect.TypeOf(body)
if tbody.Kind() != reflect.Pointer { // should ignore if `reply` non-pointer type
return nil
}
if tbody.Elem() != reflect.TypeOf(v) { // should ignore if `reply` has wrong type
return nil
}
vbody := reflect.ValueOf(body)
vbody.Elem().Set(reflect.ValueOf(v))
return nil
}
/**
* Codec's `Close` method called by the `rpc.Client`
* `rpc.Client` provides the following guaranties:
* - called once
* - thread safety
*/
func (c *genServerCodec) Close() error {
close(c.requests)
close(c.responses)
return nil
}
// It's not part of `rpc.ClientCodec`
func (c *genServerCodec) Listen(behaviour Behaviour) {
for {
req, ok := <-c.requests
if !ok {
// rpc.Client.Close -> codec.Close() -> close(codec.requestsStream)
return
}
var v any
var err error
tryCatch(func() {
v, err = behaviour.Handle(req.serviceMethod, req.seq, req.body)
}, &err)
var crucialErr error
tryCatch(func() {
c.responses <- response{
seq: req.seq,
serviceMethod: req.serviceMethod,
result: result[any]{Value: v, Error: err},
}
}, &crucialErr)
if crucialErr != nil {
log.Print(crucialErr)
}
}
}
type request struct {
seq uint64
serviceMethod string
body any
}
type response struct {
seq uint64
serviceMethod string
result result[any]
}
func (r response) Value() any {
return r.result.Value
}
func (r response) Err() error {
return r.result.Error
}
type result[T any] struct {
Value T
Error error
}
func tryCatch(f func(), crucialErr *error) {
defer func() {
if info := recover(); info != nil {
if errorMessage, ok := info.(string); ok {
*crucialErr = errors.New(errorMessage)
return
}
if err, ok := info.(error); ok {
*crucialErr = err
return
}
*crucialErr = fmt.Errorf("%v", info)
}
}()
f()
}