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fanouthandler.go
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fanouthandler.go
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package resolver
import (
"context"
"reflect"
"sync"
"google.golang.org/grpc/status"
"google.golang.org/protobuf/proto"
)
type FanoutResult struct {
Messages []proto.Message
Err error
}
func NewFanoutResult(pbSlice interface{}, err error) FanoutResult {
return FanoutResult{
Messages: MessageSlice(pbSlice),
Err: err,
}
}
func NewSingleFanoutResult(message proto.Message, err error) FanoutResult {
return FanoutResult{
Messages: []proto.Message{message},
Err: err,
}
}
type FanoutHandler interface {
Add(delta int)
Done()
Cancelled() <-chan struct{}
Channel() chan<- FanoutResult
Results(limit uint32) (*Results, error)
}
type fanoutHandler struct {
ctx context.Context
cancel context.CancelFunc
wg sync.WaitGroup
ch chan FanoutResult
}
func (r *fanoutHandler) Add(delta int) { r.wg.Add(delta) }
func (r *fanoutHandler) Done() { r.wg.Done() }
func (r *fanoutHandler) Cancelled() <-chan struct{} { return r.ctx.Done() }
func (r *fanoutHandler) Channel() chan<- FanoutResult { return r.ch }
func (r *fanoutHandler) Results(limit uint32) (*Results, error) {
results := make([]proto.Message, 0, limit)
var failures []*status.Status
done := make(chan struct{})
go func() {
r.wg.Wait()
close(done)
}()
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer wg.Done()
for limit == 0 || len(results) < int(limit) {
select {
case <-done:
return
case result := <-r.ch:
if result.Err != nil {
failures = append(failures, status.Convert(result.Err))
} else {
results = append(results, result.Messages...)
}
}
}
r.cancel()
}()
wg.Wait()
return &Results{Messages: results, PartialFailures: failures}, nil
}
func NewFanoutHandler(ctx context.Context) (context.Context, FanoutHandler) {
ctx, cancel := context.WithCancel(ctx)
return ctx, &fanoutHandler{
ctx: ctx,
ch: make(chan FanoutResult),
cancel: cancel,
}
}
// MessageSlice takes a slice of protobuf objects and converts them to a slice of generic protobuf Messages.
func MessageSlice(s interface{}) []proto.Message {
rs := reflect.ValueOf(s)
ret := make([]proto.Message, rs.Len())
for i := 0; i < rs.Len(); i++ {
ret[i] = rs.Index(i).Interface().(proto.Message)
}
return ret
}