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Manual flow-control and back-pressure demo

This commit is contained in:
Ryan Michela 2017-09-26 10:01:42 -07:00 committed by Eric Anderson
parent 63c660b29c
commit 589da070f2
4 changed files with 405 additions and 0 deletions
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1
examples/pom.xml
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@ -10,6 +10,7 @@
<name>examples</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<grpc.version>1.7.0-SNAPSHOT</grpc.version><!-- CURRENT_GRPC_VERSION -->
</properties>
<dependencies>

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examples/src/main/java/io/grpc/examples/manualflowcontrol/ManualFlowControlClient.java Normal file
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/*
* Copyright 2017, gRPC Authors All rights reserved.
*
* 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.
*/
package io.grpc.examples.manualflowcontrol;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.examples.helloworld.HelloReply;
import io.grpc.examples.helloworld.HelloRequest;
import io.grpc.examples.helloworld.StreamingGreeterGrpc;
import io.grpc.stub.ClientCallStreamObserver;
import io.grpc.stub.ClientResponseObserver;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.logging.Logger;
public class ManualFlowControlClient {
private static final Logger logger =
Logger.getLogger(ManualFlowControlClient.class.getName());
public static void main(String[] args) throws InterruptedException {
final CountDownLatch done = new CountDownLatch(1);
// Create a channel and a stub
ManagedChannel channel = ManagedChannelBuilder
.forAddress("localhost", 50051)
.usePlaintext(true)
.build();
StreamingGreeterGrpc.StreamingGreeterStub stub = StreamingGreeterGrpc.newStub(channel);
// When using manual flow-control and back-pressure on the client, the ClientResponseObserver handles both
// request and response streams.
ClientResponseObserver<HelloRequest, HelloReply> clientResponseObserver =
new ClientResponseObserver<HelloRequest, HelloReply>() {
ClientCallStreamObserver<HelloRequest> requestStream;
@Override
public void beforeStart(final ClientCallStreamObserver<HelloRequest> requestStream) {
this.requestStream = requestStream;
// Set up manual flow control for the response stream. It feels backwards to configure the response
// stream's flow control using the request stream's observer, but this is the way it is.
requestStream.disableAutoInboundFlowControl();
// Set up a back-pressure-aware producer for the request stream. The onReadyHandler will be invoked
// when the consuming side has enough buffer space to receive more messages.
//
// Messages are serialized into a transport-specific transmit buffer. Depending on the size of this buffer,
// MANY messages may be buffered, however, they haven't yet been sent to the server. The server must call
// request() to pull a buffered message from the client.
//
// Note: the onReadyHandler's invocation is serialized on the same thread pool as the incoming
// StreamObserver'sonNext(), onError(), and onComplete() handlers. Blocking the onReadyHandler will prevent
// additional messages from being processed by the incoming StreamObserver. The onReadyHandler must return
// in a timely manor or else message processing throughput will suffer.
requestStream.setOnReadyHandler(new Runnable() {
// An iterator is used so we can pause and resume iteration of the request data.
Iterator<String> iterator = names().iterator();
@Override
public void run() {
// Start generating values from where we left off on a non-gRPC thread.
while (requestStream.isReady()) {
if (iterator.hasNext()) {
// Send more messages if there are more messages to send.
String name = iterator.next();
logger.info("--> " + name);
HelloRequest request = HelloRequest.newBuilder().setName(name).build();
requestStream.onNext(request);
} else {
// Signal completion if there is nothing left to send.
requestStream.onCompleted();
}
}
}
});
}
@Override
public void onNext(HelloReply value) {
logger.info("<-- " + value.getMessage());
// Signal the sender to send one message.
requestStream.request(1);
}
@Override
public void onError(Throwable t) {
t.printStackTrace();
done.countDown();
}
@Override
public void onCompleted() {
logger.info("All Done");
done.countDown();
}
};
// Note: clientResponseObserver is handling both request and response stream processing.
stub.sayHelloStreaming(clientResponseObserver);
done.await();
channel.shutdown();
channel.awaitTermination(1, TimeUnit.SECONDS);
}
private static List<String> names() {
return Arrays.asList(
"Sophia",
"Jackson",
"Emma",
"Aiden",
"Olivia",
"Lucas",
"Ava",
"Liam",
"Mia",
"Noah",
"Isabella",
"Ethan",
"Riley",
"Mason",
"Aria",
"Caden",
"Zoe",
"Oliver",
"Charlotte",
"Elijah",
"Lily",
"Grayson",
"Layla",
"Jacob",
"Amelia",
"Michael",
"Emily",
"Benjamin",
"Madelyn",
"Carter",
"Aubrey",
"James",
"Adalyn",
"Jayden",
"Madison",
"Logan",
"Chloe",
"Alexander",
"Harper",
"Caleb",
"Abigail",
"Ryan",
"Aaliyah",
"Luke",
"Avery",
"Daniel",
"Evelyn",
"Jack",
"Kaylee",
"William",
"Ella",
"Owen",
"Ellie",
"Gabriel",
"Scarlett",
"Matthew",
"Arianna",
"Connor",
"Hailey",
"Jayce",
"Nora",
"Isaac",
"Addison",
"Sebastian",
"Brooklyn",
"Henry",
"Hannah",
"Muhammad",
"Mila",
"Cameron",
"Leah",
"Wyatt",
"Elizabeth",
"Dylan",
"Sarah",
"Nathan",
"Eliana",
"Nicholas",
"Mackenzie",
"Julian",
"Peyton",
"Eli",
"Maria",
"Levi",
"Grace",
"Isaiah",
"Adeline",
"Landon",
"Elena",
"David",
"Anna",
"Christian",
"Victoria",
"Andrew",
"Camilla",
"Brayden",
"Lillian",
"John",
"Natalie",
"Lincoln"
);
}
}

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examples/src/main/java/io/grpc/examples/manualflowcontrol/ManualFlowControlServer.java Normal file
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/*
* Copyright 2017, gRPC Authors All rights reserved.
*
* 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.
*/
package io.grpc.examples.manualflowcontrol;
import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.Status;
import io.grpc.examples.helloworld.HelloReply;
import io.grpc.examples.helloworld.HelloRequest;
import io.grpc.examples.helloworld.StreamingGreeterGrpc;
import io.grpc.stub.ServerCallStreamObserver;
import io.grpc.stub.StreamObserver;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.logging.Logger;
public class ManualFlowControlServer {
private static final Logger logger =
Logger.getLogger(ManualFlowControlServer.class.getName());
public static void main(String[] args) throws InterruptedException, IOException {
// Service class implementation
StreamingGreeterGrpc.StreamingGreeterImplBase svc = new StreamingGreeterGrpc.StreamingGreeterImplBase() {
@Override
public StreamObserver<HelloRequest> sayHelloStreaming(final StreamObserver<HelloReply> responseObserver) {
// Set up manual flow control for the request stream. It feels backwards to configure the request
// stream's flow control using the response stream's observer, but this is the way it is.
final ServerCallStreamObserver<HelloReply> serverCallStreamObserver =
(ServerCallStreamObserver<HelloReply>) responseObserver;
serverCallStreamObserver.disableAutoInboundFlowControl();
// Guard against spurious onReady() calls caused by a race between onNext() and onReady(). If the transport
// toggles isReady() from false to true while onNext() is executing, but before onNext() checks isReady(),
// request(1) would be called twice - once by onNext() and once by the onReady() scheduled during onNext()'s
// execution.
final AtomicBoolean wasReady = new AtomicBoolean(false);
// Set up a back-pressure-aware consumer for the request stream. The onReadyHandler will be invoked
// when the consuming side has enough buffer space to receive more messages.
//
// Note: the onReadyHandler's invocation is serialized on the same thread pool as the incoming StreamObserver's
// onNext(), onError(), and onComplete() handlers. Blocking the onReadyHandler will prevent additional messages
// from being processed by the incoming StreamObserver. The onReadyHandler must return in a timely manor or else
// message processing throughput will suffer.
serverCallStreamObserver.setOnReadyHandler(new Runnable() {
public void run() {
if (serverCallStreamObserver.isReady() && wasReady.compareAndSet(false, true)) {
logger.info("READY");
// Signal the request sender to send one message. This happens when isReady() turns true, signaling that
// the receive buffer has enough free space to receive more messages. Calling request() serves to prime
// the message pump.
serverCallStreamObserver.request(1);
}
}
});
// Give gRPC a StreamObserver that can observe and process incoming requests.
return new StreamObserver<HelloRequest>() {
@Override
public void onNext(HelloRequest request) {
// Process the request and send a response or an error.
try {
// Accept and enqueue the request.
String name = request.getName();
logger.info("--> " + name);
// Simulate server "work"
Thread.sleep(100);
// Send a response.
String message = "Hello " + name;
logger.info("<-- " + message);
HelloReply reply = HelloReply.newBuilder().setMessage(message).build();
responseObserver.onNext(reply);
// Check the provided ServerCallStreamObserver to see if it is still ready to accept more messages.
if (serverCallStreamObserver.isReady()) {
// Signal the sender to send another request. As long as isReady() stays true, the server will keep
// cycling through the loop of onNext() -> request()...onNext() -> request()... until either the client
// runs out of messages and ends the loop or the server runs out of receive buffer space.
//
// If the server runs out of buffer space, isReady() will turn false. When the receive buffer has
// sufficiently drained, isReady() will turn true, and the serverCallStreamObserver's onReadyHandler
// will be called to restart the message pump.
serverCallStreamObserver.request(1);
} else {
// If not, note that back-pressure has begun.
wasReady.set(false);
}
} catch (Throwable throwable) {
throwable.printStackTrace();
responseObserver.onError(Status.UNKNOWN.withCause(throwable).asException());
}
}
@Override
public void onError(Throwable t) {
// End the response stream if the client presents an error.
t.printStackTrace();
responseObserver.onCompleted();
}
@Override
public void onCompleted() {
// Signal the end of work when the client ends the request stream.
logger.info("COMPLETED");
responseObserver.onCompleted();
}
};
}
};
final Server server = ServerBuilder
.forPort(50051)
.addService(svc)
.build()
.start();
logger.info("Listening on " + server.getPort());
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
logger.info("Shutting down");
server.shutdown();
}
});
server.awaitTermination();
}
}

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examples/src/main/proto/helloworld_streaming.proto Normal file
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// Copyright 2015, gRPC Authors
// All rights reserved.
//
// 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.
syntax = "proto3";
option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldStreamingProto";
option objc_class_prefix = "HLWS";
import "helloworld.proto";
package helloworld;
// The greeting service definition.
service StreamingGreeter {
// Streams a many greetings
rpc SayHelloStreaming (stream HelloRequest) returns (stream HelloReply) {}
}