io.nats.examples.service.ServiceExample Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jnats Show documentation
Client library for working with the NATS messaging system.
The newest version!
// Copyright 2022 The NATS 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.nats.examples.service;

import io.nats.client.*;
import io.nats.client.support.JsonSerializable;
import io.nats.client.support.JsonValue;
import io.nats.client.support.JsonValueUtils;
import io.nats.service.*;

import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;

/**
 * This example demonstrates basic setup and use of the Service Framework
 */
public class ServiceExample {
    public static void main(String[] args) throws IOException {

        Options options = new Options.Builder()
            .server("nats://localhost:4222")
            .errorListener(new ErrorListener() {})
            .build();

        try (Connection nc = Nats.connect(options)) {
            // endpoints can be created ahead of time
            // or created directly by the ServiceEndpoint builder.
            Endpoint epEcho = Endpoint.builder()
                .name("EchoEndpoint")
                .subject("echo")
                .build();

            // Sort is going to be grouped. This will affect the actual subject
            Group sortGroup = new Group("sort");

            // 4 service endpoints. 3 in service 1, 1 in service 2
            // - We will reuse an endpoint definition, so we make it ahead of time
            // - For echo, we could have reused a handler as well, if we wanted to.
            ServiceEndpoint seEcho1 = ServiceEndpoint.builder()
                .endpoint(epEcho)
                .handler(msg -> handleEchoMessage(nc, msg, "S1E")) // see below: handleEchoMessage below
                .statsDataSupplier(new ExampleStatsDataSupplier()) // see below: ExampleStatsDataSupplier
                .build();

            ServiceEndpoint seEcho2 = ServiceEndpoint.builder()
                .endpoint(epEcho)
                .handler(msg -> handleEchoMessage(nc, msg, "S2E"))
                .build();

            // you can make the Endpoint directly on the Service Endpoint Builder
            ServiceEndpoint seSort1A = ServiceEndpoint.builder()
                .group(sortGroup)
                .endpointName("SortEndpointAscending")
                .endpointSubject("ascending")
                .handler(msg -> handleSortAscending(nc, msg, "S1A"))
                .build();

            // you can also make an endpoint with a constructor instead of a builder.
            Endpoint endSortD = new Endpoint("SortEndpointDescending", "descending");
            ServiceEndpoint seSort1D = ServiceEndpoint.builder()
                .group(sortGroup)
                .endpoint(endSortD)
                .handler(msg -> handlerSortDescending(nc, msg, "S1D"))
                .build();

            // Create the service from service endpoints.
            Service service1 = new ServiceBuilder()
                .connection(nc)
                .name("Service1")
                .description("Service1 Description") // optional
                .version("0.0.1")
                .addServiceEndpoint(seEcho1)
                .addServiceEndpoint(seSort1A)
                .addServiceEndpoint(seSort1D)
                .build();

            Service service2 = new ServiceBuilder()
                .connection(nc)
                .name("Service2")
                .version("0.0.1")
                .addServiceEndpoint(seEcho2) // another of the echo type
                .build();

            System.out.println("\n" + service1);
            System.out.println("\n" + service2);

            // ----------------------------------------------------------------------------------------------------
            // Start the services
            // ----------------------------------------------------------------------------------------------------
            CompletableFuture serviceStoppedFuture1 = service1.startService();
            CompletableFuture serviceStoppedFuture2 = service2.startService();

            // ----------------------------------------------------------------------------------------------------
            // Call the services
            // ----------------------------------------------------------------------------------------------------
            System.out.println();
            String request = null;
            for (int x = 1; x <= 9; x++) { // run ping a few times to see it hit different services
                request = randomText();
                String subject = "echo";
                CompletableFuture reply = nc.request(subject, request.getBytes());
                String response = new String(reply.get().getData());
                System.out.println(x + ". Called " + subject + " with [" + request + "] Received " + response);
            }

            // sort subjects are formed this way because the endpoints have groups
            String subject = "sort.ascending";
            CompletableFuture reply = nc.request(subject, request.getBytes());
            String response = new String(reply.get().getData());
            System.out.println("1. Called " + subject + " with [" + request + "] Received " + response);

            subject = "sort.descending";
            reply = nc.request(subject, request.getBytes());
            response = new String(reply.get().getData());
            System.out.println("1. Called " + subject + " with [" + request + "] Received " + response);

            // ----------------------------------------------------------------------------------------------------
            // discovery
            // ----------------------------------------------------------------------------------------------------
            Discovery discovery = new Discovery(nc, 1000, 3);

            // ----------------------------------------------------------------------------------------------------
            // ping discover variations
            // ----------------------------------------------------------------------------------------------------
            List pingResponses = discovery.ping();
            printDiscovery("Ping", "[All]", pingResponses);

            pingResponses = discovery.ping("Service1");
            printDiscovery("Ping", "Service1", pingResponses);

            pingResponses = discovery.ping("Service2");
            printDiscovery("Ping", "Service2", pingResponses);

            // ----------------------------------------------------------------------------------------------------
            // info discover variations
            // ----------------------------------------------------------------------------------------------------
            List infoResponses = discovery.info();
            printDiscovery("Info", "[All]", infoResponses);

            infoResponses = discovery.info("Service1");
            printDiscovery("Info", "Service1", infoResponses);

            infoResponses = discovery.info("Service2");
            printDiscovery("Info", "Service2", infoResponses);

            // ----------------------------------------------------------------------------------------------------
            // stats discover variations
            // ----------------------------------------------------------------------------------------------------
            List statsResponseList = discovery.stats();
            printDiscovery("Stats", "[All]", statsResponseList);

            statsResponseList = discovery.stats("Service1");
            printDiscovery("Stats", "Service1", statsResponseList); // will show echo without data decoder

            statsResponseList = discovery.stats("Service2");
            printDiscovery("Stats", "Service2", statsResponseList);

            // ----------------------------------------------------------------------------------------------------
            // stop the service
            // ----------------------------------------------------------------------------------------------------
            service1.stop();
            service2.stop();

            // stopping the service will complete the futures received when starting the service
            System.out.println("\nService 1 stopped ? " + serviceStoppedFuture1.get(1, TimeUnit.SECONDS));
            System.out.println("Service 2 stopped ? " + serviceStoppedFuture2.get(2, TimeUnit.SECONDS));
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static JsonValue replyBody(String label, byte[] data, String handlerId) {
        return JsonValueUtils.mapBuilder()
            .put(label, new String(data))
            .put("hid", handlerId)
            .toJsonValue();
    }

    private static void handlerSortDescending(Connection nc, ServiceMessage smsg, String handlerId) {
        byte[] data = smsg.getData();
        Arrays.sort(data);
        int len = data.length;
        byte[] descending = new byte[len];
        for (int x = 0; x < len; x++) {
            descending[x] = data[len - x - 1];
        }
        smsg.respond(nc, replyBody("sort_descending", descending, handlerId));
    }

    private static void handleSortAscending(Connection nc, ServiceMessage smsg, String handlerId) {
        byte[] ascending = smsg.getData();
        Arrays.sort(ascending);
        smsg.respond(nc, replyBody("sort_ascending", ascending, handlerId));
    }

    private static void handleEchoMessage(Connection nc, ServiceMessage smsg, String handlerId) {
        smsg.respond(nc, replyBody("echo", smsg.getData(), handlerId));
    }

    @SuppressWarnings("rawtypes")
    private static void printDiscovery(String action, String label, List objects) {
        System.out.println("\n" + action + " " + label);
        for (Object o : objects) {
            System.out.println("  " + o);
        }
    }

    static class ExampleStatsData implements JsonSerializable {
        public String sData;
        public int iData;

        public ExampleStatsData(String sData, int iData) {
            this.sData = sData;
            this.iData = iData;
        }

        @Override
        public String toJson() {
            return toJsonValue().toJson();
        }

        @Override
        public JsonValue toJsonValue() {
            Map map = new HashMap<>();
            map.put("sdata", new JsonValue(sData));
            map.put("idata", new JsonValue(iData));
            return new JsonValue(map);
        }

        @Override
        public String toString() {
            return toJsonValue().toString(getClass());
        }
    }

    static class ExampleStatsDataSupplier implements Supplier {
        int x = 0;
        @Override
        public JsonValue get() {
            ++x;
            return new ExampleStatsData("s-" + hashCode(), x).toJsonValue();
        }
    }

    static String randomText() {
        return Long.toHexString(System.currentTimeMillis()) + Long.toHexString(System.nanoTime());
    }
}