micro-server-http/subscriber.go

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package http
import (
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"bytes"
"context"
"fmt"
"reflect"
"strings"
"unicode"
"unicode/utf8"
"github.com/micro/go-micro/broker"
"github.com/micro/go-micro/codec"
"github.com/micro/go-micro/metadata"
"github.com/micro/go-micro/registry"
"github.com/micro/go-micro/server"
)
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const (
subSig = "func(context.Context, interface{}) error"
)
var typeOfError = reflect.TypeOf((*error)(nil)).Elem()
type handler struct {
method reflect.Value
reqType reflect.Type
ctxType reflect.Type
}
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type httpSubscriber struct {
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topic string
rcvr reflect.Value
typ reflect.Type
subscriber interface{}
handlers []*handler
endpoints []*registry.Endpoint
opts server.SubscriberOptions
}
// Is this an exported - upper case - name?
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(rune)
}
// Is this type exported or a builtin?
func isExportedOrBuiltinType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
// PkgPath will be non-empty even for an exported type,
// so we need to check the type name as well.
return isExported(t.Name()) || t.PkgPath() == ""
}
func newSubscriber(topic string, sub interface{}, opts ...server.SubscriberOption) server.Subscriber {
var options server.SubscriberOptions
for _, o := range opts {
o(&options)
}
var endpoints []*registry.Endpoint
var handlers []*handler
if typ := reflect.TypeOf(sub); typ.Kind() == reflect.Func {
h := &handler{
method: reflect.ValueOf(sub),
}
switch typ.NumIn() {
case 1:
h.reqType = typ.In(0)
case 2:
h.ctxType = typ.In(0)
h.reqType = typ.In(1)
}
handlers = append(handlers, h)
endpoints = append(endpoints, &registry.Endpoint{
Name: "Func",
Request: extractSubValue(typ),
Metadata: map[string]string{
"topic": topic,
"subscriber": "true",
},
})
} else {
hdlr := reflect.ValueOf(sub)
name := reflect.Indirect(hdlr).Type().Name()
for m := 0; m < typ.NumMethod(); m++ {
method := typ.Method(m)
h := &handler{
method: method.Func,
}
switch method.Type.NumIn() {
case 2:
h.reqType = method.Type.In(1)
case 3:
h.ctxType = method.Type.In(1)
h.reqType = method.Type.In(2)
}
handlers = append(handlers, h)
endpoints = append(endpoints, &registry.Endpoint{
Name: name + "." + method.Name,
Request: extractSubValue(method.Type),
Metadata: map[string]string{
"topic": topic,
"subscriber": "true",
},
})
}
}
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return &httpSubscriber{
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rcvr: reflect.ValueOf(sub),
typ: reflect.TypeOf(sub),
topic: topic,
subscriber: sub,
handlers: handlers,
endpoints: endpoints,
opts: options,
}
}
func validateSubscriber(sub server.Subscriber) error {
typ := reflect.TypeOf(sub.Subscriber())
var argType reflect.Type
if typ.Kind() == reflect.Func {
name := "Func"
switch typ.NumIn() {
case 2:
argType = typ.In(1)
default:
return fmt.Errorf("subscriber %v takes wrong number of args: %v required signature %s", name, typ.NumIn(), subSig)
}
if !isExportedOrBuiltinType(argType) {
return fmt.Errorf("subscriber %v argument type not exported: %v", name, argType)
}
if typ.NumOut() != 1 {
return fmt.Errorf("subscriber %v has wrong number of outs: %v require signature %s",
name, typ.NumOut(), subSig)
}
if returnType := typ.Out(0); returnType != typeOfError {
return fmt.Errorf("subscriber %v returns %v not error", name, returnType.String())
}
} else {
hdlr := reflect.ValueOf(sub.Subscriber())
name := reflect.Indirect(hdlr).Type().Name()
for m := 0; m < typ.NumMethod(); m++ {
method := typ.Method(m)
switch method.Type.NumIn() {
case 3:
argType = method.Type.In(2)
default:
return fmt.Errorf("subscriber %v.%v takes wrong number of args: %v required signature %s",
name, method.Name, method.Type.NumIn(), subSig)
}
if !isExportedOrBuiltinType(argType) {
return fmt.Errorf("%v argument type not exported: %v", name, argType)
}
if method.Type.NumOut() != 1 {
return fmt.Errorf(
"subscriber %v.%v has wrong number of outs: %v require signature %s",
name, method.Name, method.Type.NumOut(), subSig)
}
if returnType := method.Type.Out(0); returnType != typeOfError {
return fmt.Errorf("subscriber %v.%v returns %v not error", name, method.Name, returnType.String())
}
}
}
return nil
}
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func (s *httpServer) createSubHandler(sb *httpSubscriber, opts server.Options) broker.Handler {
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return func(p broker.Event) error {
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msg := p.Message()
ct := msg.Header["Content-Type"]
cf, err := s.newCodec(ct)
if err != nil {
return err
}
hdr := make(map[string]string)
for k, v := range msg.Header {
hdr[k] = v
}
delete(hdr, "Content-Type")
ctx := metadata.NewContext(context.Background(), hdr)
results := make(chan error, len(sb.handlers))
for i := 0; i < len(sb.handlers); i++ {
handler := sb.handlers[i]
var isVal bool
var req reflect.Value
if handler.reqType.Kind() == reflect.Ptr {
req = reflect.New(handler.reqType.Elem())
} else {
req = reflect.New(handler.reqType)
isVal = true
}
if isVal {
req = req.Elem()
}
b := &buffer{bytes.NewBuffer(msg.Body)}
co := cf(b)
defer co.Close()
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if err := co.ReadHeader(&codec.Message{}, codec.Event); err != nil {
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return err
}
if err := co.ReadBody(req.Interface()); err != nil {
return err
}
fn := func(ctx context.Context, msg server.Message) error {
var vals []reflect.Value
if sb.typ.Kind() != reflect.Func {
vals = append(vals, sb.rcvr)
}
if handler.ctxType != nil {
vals = append(vals, reflect.ValueOf(ctx))
}
vals = append(vals, reflect.ValueOf(msg.Payload()))
returnValues := handler.method.Call(vals)
if err := returnValues[0].Interface(); err != nil {
return err.(error)
}
return nil
}
for i := len(opts.SubWrappers); i > 0; i-- {
fn = opts.SubWrappers[i-1](fn)
}
go func() {
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results <- fn(ctx, &httpMessage{
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topic: sb.topic,
contentType: ct,
payload: req.Interface(),
})
}()
}
var errors []string
for i := 0; i < len(sb.handlers); i++ {
if err := <-results; err != nil {
errors = append(errors, err.Error())
}
}
if len(errors) > 0 {
return fmt.Errorf("subscriber error: %s", strings.Join(errors, "\n"))
}
return nil
}
}
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func (s *httpSubscriber) Topic() string {
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return s.topic
}
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func (s *httpSubscriber) Subscriber() interface{} {
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return s.subscriber
}
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func (s *httpSubscriber) Endpoints() []*registry.Endpoint {
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return s.endpoints
}
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func (s *httpSubscriber) Options() server.SubscriberOptions {
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return s.opts
}