examples: add example for ORCA load reporting

examples/examples_test.sh

@@ -64,6 +64,7 @@ EXAMPLES=(
     "features/metadata_interceptor"
     "features/multiplex"
     "features/name_resolving"
+    "features/orca"
     "features/retry"
     "features/unix_abstract"
 )
@@ -75,6 +76,7 @@ declare -A SERVER_ARGS=(
 
 declare -A CLIENT_ARGS=(
     ["features/unix_abstract"]="-addr $UNIX_ADDR"
+    ["features/orca"]="-test=true"
     ["default"]="-addr localhost:$SERVER_PORT"
 )
 
@@ -114,6 +116,7 @@ declare -A EXPECTED_SERVER_OUTPUT=(
     ["features/metadata_interceptor"]="key1 from metadata: "
     ["features/multiplex"]=":50051"
     ["features/name_resolving"]="serving on localhost:50051"
+    ["features/orca"]="Server listening"
     ["features/retry"]="request succeeded count: 4"
     ["features/unix_abstract"]="serving on @abstract-unix-socket"
 )
@@ -134,6 +137,7 @@ declare -A EXPECTED_CLIENT_OUTPUT=(
     ["features/metadata_interceptor"]="BidiStreaming Echo:  hello world"
     ["features/multiplex"]="Greeting:  Hello multiplex"
     ["features/name_resolving"]="calling helloworld.Greeter/SayHello to \"example:///resolver.example.grpc.io\""
+    ["features/orca"]="Per-call load report received: map\[db_queries:10\]"
     ["features/retry"]="UnaryEcho reply: message:\"Try and Success\""
     ["features/unix_abstract"]="calling echo.Echo/UnaryEcho to unix-abstract:abstract-unix-socket"
 )

examples/features/orca/README.md

@@ -0,0 +1,48 @@
+# ORCA Load Reporting
+
+ORCA is a protocol for reporting load between servers and clients.  This
+example shows how to implement this from both the client and server side.  For
+more details, please see [gRFC
+A51](https://github.com/grpc/proposal/blob/master/A51-custom-backend-metrics.md)
+
+## Try it
+
+```
+go run server/main.go
+```
+
+```
+go run client/main.go
+```
+
+## Explanation
+
+gRPC ORCA support provides two different ways to report load data to clients
+from servers: out-of-band and per-RPC.  Out-of-band metrics are reported
+regularly at some interval on a stream, while per-RPC metrics are reported
+along with the trailers at the end of a call.  Both of these mechanisms are
+optional and work independently.
+
+The full ORCA API documentation is available here:
+https://pkg.go.dev/google.golang.org/grpc/orca
+
+### Out-of-band Metrics
+
+The server registers an ORCA service that is used for out-of-band metrics.  It
+does this by using `orca.Register()` and then setting metrics on the returned
+`orca.Service` using its methods.
+
+The client receives out-of-band metrics via the LB policy.  It receives
+callbacks to a listener by registering the listener on a `SubConn` via
+`orca.RegisterOOBListener`.
+
+### Per-RPC Metrics
+
+The server is set up to report query cost metrics in its RPC handler.  For
+per-RPC metrics to be reported, the gRPC server must be created with the
+`orca.CallMetricsServerOption()` option, and metrics are set by calling methods
+on the returned `orca.CallMetricRecorder` from
+`orca.CallMetricRecorderFromContext()`.
+
+The client performs one RPC per second.  Per-RPC metrics are available for each
+call via the `Done()` callback returned from the LB policy's picker.

examples/features/orca/client/main.go

@@ -0,0 +1,153 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Binary client is an example client.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/orca"
+
+	v3orcapb "github.com/cncf/xds/go/xds/data/orca/v3"
+	pb "google.golang.org/grpc/examples/features/proto/echo"
+)
+
+var addr = flag.String("addr", "localhost:50051", "the address to connect to")
+var test = flag.Bool("test", false, "if set, only 1 RPC is performed before exiting")
+
+func main() {
+	flag.Parse()
+
+	// Set up a connection to the server.  Configure to use our custom LB
+	// policy which will receive all the ORCA load reports.
+	conn, err := grpc.Dial(*addr,
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+		grpc.WithDefaultServiceConfig(`{"loadBalancingConfig": [{"orca_example":{}}]}`),
+	)
+	if err != nil {
+		log.Fatalf("did not connect: %v", err)
+	}
+	defer conn.Close()
+
+	c := pb.NewEchoClient(conn)
+
+	// Perform RPCs once per second.
+	ticker := time.NewTicker(time.Second)
+	for range ticker.C {
+		func() {
+			// Use an anonymous function to ensure context cancelation via defer.
+			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+			defer cancel()
+			if _, err := c.UnaryEcho(ctx, &pb.EchoRequest{Message: "test echo message"}); err != nil {
+				log.Fatalf("Error from UnaryEcho call: %v", err)
+			}
+		}()
+		if *test {
+			return
+		}
+	}
+
+}
+
+// Register an ORCA load balancing policy to receive per-call metrics and
+// out-of-band metrics.
+func init() {
+	balancer.Register(orcaLBBuilder{})
+}
+
+type orcaLBBuilder struct{}
+
+func (orcaLBBuilder) Name() string { return "orca_example" }
+func (orcaLBBuilder) Build(cc balancer.ClientConn, opts balancer.BuildOptions) balancer.Balancer {
+	return &orcaLB{cc: cc}
+}
+
+// orcaLB is an incomplete LB policy designed to show basic ORCA load reporting
+// functionality.  It collects per-call metrics in the `Done` callback returned
+// by its picker, and it collects out-of-band metrics by registering a listener
+// when its SubConn is created.  It does not follow general LB policy best
+// practices and makes assumptions about the simple test environment it is
+// designed to run within.
+type orcaLB struct {
+	cc balancer.ClientConn
+}
+
+func (o *orcaLB) UpdateClientConnState(ccs balancer.ClientConnState) error {
+	// We assume only one update, ever, containing exactly one address, given
+	// the use of the "passthrough" (default) name resolver.
+
+	addrs := ccs.ResolverState.Addresses
+	if len(addrs) != 1 {
+		return fmt.Errorf("orcaLB: expected 1 address; received: %v", addrs)
+	}
+
+	// Create one SubConn for the address and connect it.
+	sc, err := o.cc.NewSubConn(addrs, balancer.NewSubConnOptions{})
+	if err != nil {
+		return fmt.Errorf("orcaLB: error creating SubConn: %v", err)
+	}
+	sc.Connect()
+
+	// Register a simple ORCA OOB listener on the SubConn.  We request a 1
+	// second report interval, but in this example the server indicated the
+	// minimum interval it will allow is 3 seconds, so reports will only be
+	// sent that often.
+	orca.RegisterOOBListener(sc, orcaLis{}, orca.OOBListenerOptions{ReportInterval: time.Second})
+
+	return nil
+}
+
+func (o *orcaLB) ResolverError(error) {}
+
+func (o *orcaLB) UpdateSubConnState(sc balancer.SubConn, scs balancer.SubConnState) {
+	if scs.ConnectivityState == connectivity.Ready {
+		o.cc.UpdateState(balancer.State{ConnectivityState: connectivity.Ready, Picker: &picker{sc}})
+	}
+}
+
+func (o *orcaLB) Close() {}
+
+type picker struct {
+	sc balancer.SubConn
+}
+
+func (p *picker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
+	return balancer.PickResult{
+		SubConn: p.sc,
+		Done: func(di balancer.DoneInfo) {
+			fmt.Println("Per-call load report received:", di.ServerLoad.(*v3orcapb.OrcaLoadReport).GetRequestCost())
+		},
+	}, nil
+}
+
+// orcaLis is the out-of-band load report listener that we pass to
+// orca.RegisterOOBListener to receive periodic load report information.
+type orcaLis struct{}
+
+func (orcaLis) OnLoadReport(lr *v3orcapb.OrcaLoadReport) {
+	fmt.Println("Out-of-band load report received:", lr)
+}

examples/features/orca/server/main.go

@@ -0,0 +1,92 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Binary server is an example server.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/orca"
+	"google.golang.org/grpc/status"
+
+	pb "google.golang.org/grpc/examples/features/proto/echo"
+)
+
+var port = flag.Int("port", 50051, "the port to serve on")
+
+type server struct {
+	pb.UnimplementedEchoServer
+}
+
+func (s *server) UnaryEcho(ctx context.Context, in *pb.EchoRequest) (*pb.EchoResponse, error) {
+	// Report a sample cost for this query.
+	cmr := orca.CallMetricRecorderFromContext(ctx)
+	if cmr == nil {
+		return nil, status.Errorf(codes.Internal, "unable to retrieve call metric recorder (missing ORCA ServerOption?)")
+	}
+	cmr.SetRequestCost("db_queries", 10)
+
+	return &pb.EchoResponse{Message: in.Message}, nil
+}
+
+func main() {
+	flag.Parse()
+
+	lis, err := net.Listen("tcp", fmt.Sprintf("localhost:%d", *port))
+	if err != nil {
+		log.Fatalf("Failed to listen: %v", err)
+	}
+	fmt.Printf("Server listening at %v\n", lis.Addr())
+
+	// Create the gRPC server with the orca.CallMetricsServerOption() option,
+	// which will enable per-call metric recording.
+	s := grpc.NewServer(orca.CallMetricsServerOption())
+	pb.RegisterEchoServer(s, &server{})
+
+	// Register the orca service for out-of-band metric reporting, and set the
+	// minimum reporting interval to 3 seconds.  Note that, by default, the
+	// minimum interval must be at least 30 seconds, but 3 seconds is set via
+	// an internal-only option for illustration purposes only.
+	opts := orca.ServiceOptions{MinReportingInterval: 3 * time.Second}
+	internal.ORCAAllowAnyMinReportingInterval.(func(so *orca.ServiceOptions))(&opts)
+	orcaSvc, err := orca.Register(s, opts)
+	if err != nil {
+		log.Fatalf("Failed to register ORCA service: %v", err)
+	}
+
+	// Simulate CPU utilization reporting.
+	go func() {
+		for {
+			orcaSvc.SetCPUUtilization(.5)
+			time.Sleep(2 * time.Second)
+			orcaSvc.SetCPUUtilization(.9)
+			time.Sleep(2 * time.Second)
+		}
+	}()
+
+	s.Serve(lis)
+}

examples/go.mod

@@ -3,6 +3,7 @@ module google.golang.org/grpc/examples
 go 1.17
 
 require (
+	github.com/cncf/xds/go v0.0.0-20230105202645-06c439db220b
 	github.com/golang/protobuf v1.5.2
 	golang.org/x/oauth2 v0.4.0
 	google.golang.org/genproto v0.0.0-20230110181048-76db0878b65f
@@ -16,7 +17,6 @@ require (
 	github.com/census-instrumentation/opencensus-proto v0.4.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/cncf/udpa/go v0.0.0-20220112060539-c52dc94e7fbe // indirect
-	github.com/cncf/xds/go v0.0.0-20230105202645-06c439db220b // indirect
 	github.com/envoyproxy/go-control-plane v0.10.3 // indirect
 	github.com/envoyproxy/protoc-gen-validate v0.9.1 // indirect
 	golang.org/x/net v0.8.0 // indirect

internal/internal.go

@@ -137,6 +137,9 @@ var (
 	//
 	// TODO: Remove this function once the RBAC env var is removed.
 	UnregisterRBACHTTPFilterForTesting func()
+
+	// ORCAAllowAnyMinReportingInterval is for examples/orca use ONLY.
+	ORCAAllowAnyMinReportingInterval interface{} // func(so *orca.ServiceOptions)
 )
 
 // HealthChecker defines the signature of the client-side LB channel health checking function.

orca/service.go

@@ -24,7 +24,8 @@ import (
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/orca/internal"
+	"google.golang.org/grpc/internal"
+	ointernal "google.golang.org/grpc/orca/internal"
 	"google.golang.org/grpc/status"
 
 	v3orcapb "github.com/cncf/xds/go/xds/data/orca/v3"
@@ -33,9 +34,10 @@ import (
 )
 
 func init() {
-	internal.AllowAnyMinReportingInterval = func(so *ServiceOptions) {
+	ointernal.AllowAnyMinReportingInterval = func(so *ServiceOptions) {
 		so.allowAnyMinReportingInterval = true
 	}
+	internal.ORCAAllowAnyMinReportingInterval = ointernal.AllowAnyMinReportingInterval
 }
 
 // minReportingInterval is the absolute minimum value supported for