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examples: Health example (grpc#9991)
Provides a server with both a greet service and the health service.
Client has an example of using the health service directly through the unary call
<a href="https://github.com/grpc/grpc-java/blob/master/services/src/main/proto/grpc/health/v1/health.proto">check</a>
to get the current health. It also utilizes the health of the server's greet service
indirectly through the round robin load balancer, which uses the streaming rpc
<strong>watch</strong> (you can see how it is done in
{@link io.grpc.protobuf.services.HealthCheckingLoadBalancerFactory}).- Loading branch information
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examples/src/main/java/io/grpc/examples/healthservice/HealthServiceClient.java
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| /* | ||
| * Copyright 2023 The 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. | ||
| */ | ||
|
|
||
| package io.grpc.examples.healthservice; | ||
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|
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| import io.grpc.Channel; | ||
| import io.grpc.Grpc; | ||
| import io.grpc.InsecureChannelCredentials; | ||
| import io.grpc.LoadBalancerProvider; | ||
| import io.grpc.LoadBalancerRegistry; | ||
| import io.grpc.ManagedChannel; | ||
| import io.grpc.ManagedChannelBuilder; | ||
| import io.grpc.StatusRuntimeException; | ||
| import io.grpc.examples.helloworld.GreeterGrpc; | ||
| import io.grpc.examples.helloworld.HelloReply; | ||
| import io.grpc.examples.helloworld.HelloRequest; | ||
| import io.grpc.health.v1.HealthCheckRequest; | ||
| import io.grpc.health.v1.HealthCheckResponse; | ||
| import io.grpc.health.v1.HealthCheckResponse.ServingStatus; | ||
| import io.grpc.health.v1.HealthGrpc; | ||
| import java.util.Arrays; | ||
| import java.util.HashMap; | ||
| import java.util.Map; | ||
| import java.util.concurrent.TimeUnit; | ||
| import java.util.logging.Level; | ||
| import java.util.logging.Logger; | ||
|
|
||
| /** | ||
| * A client that requests a greeting from the {@link HelloWorldServer}. | ||
| */ | ||
| public class HealthServiceClient { | ||
| private static final Logger logger = Logger.getLogger(HealthServiceClient.class.getName()); | ||
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| private final GreeterGrpc.GreeterBlockingStub greeterBlockingStub; | ||
| private final HealthGrpc.HealthStub healthStub; | ||
| private final HealthGrpc.HealthBlockingStub healthBlockingStub; | ||
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| private final HealthCheckRequest healthRequest; | ||
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| /** Construct client for accessing HelloWorld server using the existing channel. */ | ||
| public HealthServiceClient(Channel channel) { | ||
| greeterBlockingStub = GreeterGrpc.newBlockingStub(channel); | ||
| healthStub = HealthGrpc.newStub(channel); | ||
| healthBlockingStub = HealthGrpc.newBlockingStub(channel); | ||
| healthRequest = HealthCheckRequest.getDefaultInstance(); | ||
| LoadBalancerProvider roundRobin = LoadBalancerRegistry.getDefaultRegistry() | ||
| .getProvider("round_robin"); | ||
|
|
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| } | ||
|
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| private ServingStatus checkHealth(String prefix) { | ||
| HealthCheckResponse response = | ||
| healthBlockingStub.check(healthRequest); | ||
| logger.info(prefix + ", current health is: " + response.getStatus()); | ||
| return response.getStatus(); | ||
| } | ||
|
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| /** Say hello to server. */ | ||
| public void greet(String name) { | ||
| logger.info("Will try to greet " + name + " ..."); | ||
| HelloRequest request = HelloRequest.newBuilder().setName(name).build(); | ||
| HelloReply response; | ||
| try { | ||
| response = greeterBlockingStub.sayHello(request); | ||
| } catch (StatusRuntimeException e) { | ||
| logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus()); | ||
| return; | ||
| } catch (Exception e) { | ||
| e.printStackTrace(); | ||
| return; | ||
| } | ||
| logger.info("Greeting: " + response.getMessage()); | ||
| } | ||
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| private static void runTest(String target, String[] users, boolean useRoundRobin) | ||
| throws InterruptedException { | ||
| ManagedChannelBuilder<?> builder = | ||
| Grpc.newChannelBuilder(target, InsecureChannelCredentials.create()); | ||
|
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| // Round Robin, when a healthCheckConfig is present in the default service configuration, runs | ||
| // a watch on the health service and when picking an endpoint will | ||
| // consider a transport to a server whose service is not in SERVING state to be unavailable. | ||
| // Since we only have a single server we are connecting to, then the load balancer will | ||
| // return an error without sending the RPC. | ||
| if (useRoundRobin) { | ||
| builder = builder | ||
| .defaultLoadBalancingPolicy("round_robin") | ||
| .defaultServiceConfig(generateHealthConfig("")); | ||
| } | ||
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| ManagedChannel channel = builder.build(); | ||
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| System.out.println("\nDoing test with" + (useRoundRobin ? "" : "out") | ||
| + " the Round Robin load balancer\n"); | ||
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| try { | ||
| HealthServiceClient client = new HealthServiceClient(channel); | ||
| if (!useRoundRobin) { | ||
| client.checkHealth("Before call"); | ||
| } | ||
| client.greet(users[0]); | ||
| if (!useRoundRobin) { | ||
| client.checkHealth("After user " + users[0]); | ||
| } | ||
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| for (String user : users) { | ||
| client.greet(user); | ||
| Thread.sleep(100); // Since the health update is asynchronous give it time to propagate | ||
| } | ||
|
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| if (!useRoundRobin) { | ||
| client.checkHealth("After all users"); | ||
| Thread.sleep(10000); | ||
| client.checkHealth("After 10 second wait"); | ||
| } else { | ||
| Thread.sleep(10000); | ||
| } | ||
| client.greet("Larry"); | ||
| } finally { | ||
| // ManagedChannels use resources like threads and TCP connections. To prevent leaking these | ||
| // resources the channel should be shut down when it will no longer be used. If it may be used | ||
| // again leave it running. | ||
| channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS); | ||
| } | ||
| } | ||
| private static Map<String, Object> generateHealthConfig(String serviceName) { | ||
| Map<String, Object> config = new HashMap<>(); | ||
| Map<String, Object> serviceMap = new HashMap<>(); | ||
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| config.put("healthCheckConfig", serviceMap); | ||
| serviceMap.put("serviceName", serviceName); | ||
| return config; | ||
| } | ||
|
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| /** | ||
| * Uses a server with both a greet service and the health service. | ||
| * If provided, the first element of {@code args} is the name to use in the | ||
| * greeting. The second argument is the target server. | ||
| * This has an example of using the health service directly through the unary call | ||
| * <a href="https://github.com/grpc/grpc-java/blob/master/services/src/main/proto/grpc/health/v1/health.proto">check</a> | ||
| * to get the current health. It also utilizes the health of the server's greet service | ||
| * indirectly through the round robin load balancer, which uses the streaming rpc | ||
| * <strong>watch</strong> (you can see how it is done in | ||
| * {@link io.grpc.protobuf.services.HealthCheckingLoadBalancerFactory}). | ||
| */ | ||
| public static void main(String[] args) throws Exception { | ||
| System.setProperty("java.util.logging.SimpleFormatter.format", | ||
| "%1$tH:%1$tM:%1$tS %4$s %2$s: %5$s%6$s%n"); | ||
|
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| String[] users = {"world", "foo", "I am Grut"}; | ||
| // Access a service running on the local machine on port 50051 | ||
| String target = "localhost:50051"; | ||
| // Allow passing in the user and target strings as command line arguments | ||
| if (args.length > 0) { | ||
| if ("--help".equals(args[0])) { | ||
| System.err.println("Usage: [target [name] [name] ...]"); | ||
| System.err.println(""); | ||
| System.err.println(" target The server to connect to. Defaults to " + target); | ||
| System.err.println(" name The names you wish to be greeted by. Defaults to " + Arrays.toString(users)); | ||
| System.exit(1); | ||
| } | ||
| target = args[0]; | ||
| } | ||
| if (args.length > 1) { | ||
| users = new String[args.length-1]; | ||
| for (int i=0; i < users.length; i++) { | ||
| users[i] = args[i+1]; | ||
| } | ||
| } | ||
|
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| // Will see failures of rpc's sent while server service is not serving, where the failures come | ||
| // from the server | ||
| runTest(target, users, false); | ||
|
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| // The client will throw an error when sending the rpc to a non-serving service because the | ||
| // round robin load balancer uses the health service's watch rpc. | ||
| runTest(target, users, true); | ||
|
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||
| } | ||
| } |
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