[targets.example] Add targets extensions example. (#742)

examples/extensions/myprober/myprobe/myprobe.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/cloudprober/cloudprober/logger"
 	"github.com/cloudprober/cloudprober/metrics"
+	"github.com/cloudprober/cloudprober/probes"
 	"github.com/cloudprober/cloudprober/probes/options"
 	"github.com/cloudprober/cloudprober/targets/endpoint"
 	"github.com/hoisie/redis"
@@ -133,3 +134,10 @@ func (p *Probe) runProbe(ctx context.Context) {
 
 	wg.Wait()
 }
+
+func Init() {
+	// Register stubby probe type
+	fmt.Println("Registering probe type")
+	extNumber := int(E_RedisProbe.TypeDescriptor().Number())
+	probes.RegisterProbeType(extNumber, func() probes.Probe { return &Probe{} })
+}

examples/extensions/myprober/myprober.cfg

@@ -12,3 +12,16 @@ probe {
     value: "testval"
   }
 }
+
+probe {
+  name: "targets_ext_demo"
+  type: HTTP
+  interval_msec: 10000
+  timeout_msec: 5000
+  targets {
+    [myprober.mytargets] {
+      hostname: "localhost"
+      port: 9313
+    }
+  }
+}

examples/extensions/myprober/myprober.go

@@ -6,8 +6,8 @@ import (
 
 	"github.com/cloudprober/cloudprober"
 	"github.com/cloudprober/cloudprober/examples/extensions/myprober/myprobe"
+	"github.com/cloudprober/cloudprober/examples/extensions/myprober/mytargets"
 	"github.com/cloudprober/cloudprober/logger"
-	"github.com/cloudprober/cloudprober/probes"
 	"github.com/cloudprober/cloudprober/web"
 )
 
@@ -16,9 +16,8 @@ func main() {
 
 	var log = logger.New()
 
-	// Register stubby probe type
-	probes.RegisterProbeType(int(myprobe.E_RedisProbe.TypeDescriptor().Number()),
-		func() probes.Probe { return &myprobe.Probe{} })
+	myprobe.Init()
+	mytargets.Init()
 
 	if err := cloudprober.Init(); err != nil {
 		log.Criticalf("Error initializing cloudprober. Err: %v", err)

examples/extensions/myprober/mytargets/mytargets.go

@@ -0,0 +1,41 @@
+package mytargets
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/cloudprober/cloudprober/logger"
+	"github.com/cloudprober/cloudprober/targets"
+	"github.com/cloudprober/cloudprober/targets/endpoint"
+	"github.com/cloudprober/cloudprober/targets/resolver"
+)
+
+var globalResolver = resolver.New()
+
+type myTargets struct {
+	c *MyTargetsConf
+}
+
+func (ut *myTargets) ListEndpoints() []endpoint.Endpoint {
+	return []endpoint.Endpoint{{
+		Name: ut.c.GetHostname(),
+		Port: int(ut.c.GetPort()),
+	}}
+}
+
+func (ut *myTargets) Resolve(name string, ipVer int) (net.IP, error) {
+	return globalResolver.Resolve(name, ipVer)
+}
+
+func Init() {
+	extensionNumber := int(E_Mytargets.TypeDescriptor().Number())
+	targets.RegisterTargetsType(extensionNumber, func(c interface{}, l *logger.Logger) (targets.Targets, error) {
+		utConf, ok := c.(*MyTargetsConf)
+		if !ok {
+			return nil, fmt.Errorf("invalid target config type: %T", c)
+		}
+		return &myTargets{
+			c: utConf,
+		}, nil
+	})
+}

examples/extensions/myprober/mytargets/mytargets.proto

@@ -0,0 +1,16 @@
+syntax = "proto2";
+
+package myprober;
+
+option go_package="github.com/cloudprober/cloudprober/examples/extensions/myprober/mytargets";
+
+import "github.com/cloudprober/cloudprober/targets/proto/targets.proto";
+
+message MyTargetsConf {
+    optional string hostname = 1;
+    optional int32 port = 2;
+}
+
+extend cloudprober.targets.TargetsDef {
+    optional MyTargetsConf mytargets = 200;
+}