Add concurrency option for outbound observation

Add `enableConcurrency` option, false by default.

If it's set as `true`, start probing outbounds concurrently in every
circle of observation. Wait `probeInterval` between observation circles.

app/observatory/observer.go

@@ -66,22 +66,45 @@ func (o *Observer) background() {
 		}
 
 		outbounds := hs.Select(o.config.SubjectSelector)
-		sort.Strings(outbounds)
 
 		o.updateStatus(outbounds)
 
+		sleepTime := time.Second * 10
+		if o.config.ProbeInterval != 0 {
+			sleepTime = time.Duration(o.config.ProbeInterval)
+		}
+
+		if !o.config.EnableConcurrency {
+			sort.Strings(outbounds)
+			for _, v := range outbounds {
+				result := o.probe(v)
+				o.updateStatusForResult(v, &result)
+				if o.finished.Done() {
+					return
+				}
+				time.Sleep(sleepTime)
+			}
+			continue
+		}
+
+		ch := make(chan struct{}, len(outbounds))
+
 		for _, v := range outbounds {
-			result := o.probe(v)
-			o.updateStatusForResult(v, &result)
-			if o.finished.Done() {
+			go func(v string) {
+				result := o.probe(v)
+				o.updateStatusForResult(v, &result)
+				ch <- struct{}{}
+			}(v)
+		}
+
+		for range outbounds {
+			select {
+			case <-ch:
+			case <-o.finished.Wait():
 				return
 			}
-			sleepTime := time.Second * 10
-			if o.config.ProbeInterval != 0 {
-				sleepTime = time.Duration(o.config.ProbeInterval)
-			}
-			time.Sleep(sleepTime)
 		}
+		time.Sleep(sleepTime)
 	}
 }
 

infra/conf/observatory.go

@@ -2,17 +2,18 @@ package conf
 
 import (
 	"github.com/golang/protobuf/proto"
-	
+
 	"github.com/xtls/xray-core/app/observatory"
 	"github.com/xtls/xray-core/infra/conf/cfgcommon/duration"
 )
 
 type ObservatoryConfig struct {
-	SubjectSelector []string          `json:"subjectSelector"`
-	ProbeURL        string            `json:"probeURL"`
-	ProbeInterval   duration.Duration `json:"probeInterval"`
+	SubjectSelector   []string          `json:"subjectSelector"`
+	ProbeURL          string            `json:"probeURL"`
+	ProbeInterval     duration.Duration `json:"probeInterval"`
+	EnableConcurrency bool              `json:"enableConcurrency"`
 }
 
 func (o *ObservatoryConfig) Build() (proto.Message, error) {
-	return &observatory.Config{SubjectSelector: o.SubjectSelector, ProbeUrl: o.ProbeURL, ProbeInterval: int64(o.ProbeInterval)}, nil
+	return &observatory.Config{SubjectSelector: o.SubjectSelector, ProbeUrl: o.ProbeURL, ProbeInterval: int64(o.ProbeInterval), EnableConcurrency: o.EnableConcurrency}, nil
 }