feat: add topic example

examples/settings.gradle.kts

@@ -24,3 +24,4 @@ include("cache")
 include("cache-with-aws")
 include("lambda:docker")
 include("token")
+include("topic")

examples/topic/build.gradle.kts

@@ -0,0 +1,52 @@
+/*
+ * This file was generated by the Gradle 'init' task.
+ *
+ * This generated file contains a sample Java library project to get you started.
+ * For more details take a look at the 'Building Java & JVM projects' chapter in the Gradle
+ * User Manual available at https://docs.gradle.org/7.2/userguide/building_java_projects.html
+ */
+
+plugins {
+    application
+    id("com.diffplug.spotless") version "5.15.1"
+}
+
+repositories {
+    // Use Maven Central for resolving dependencies.
+    mavenCentral()
+}
+
+dependencies {
+    implementation("software.momento.java:sdk:1.7.0")
+
+    implementation("com.google.guava:guava:31.1-android")
+
+    // Logging framework to log and enable logging in the Momento client.
+    implementation("ch.qos.logback:logback-classic:1.4.7")
+
+    // Histogram for collecting stats in the load generator
+    implementation("org.hdrhistogram:HdrHistogram:2.1.12")
+
+    // Use JUnit Jupiter for testing.
+    testImplementation("org.junit.jupiter:junit-jupiter:5.9.2")
+}
+
+spotless {
+    java {
+        removeUnusedImports()
+        googleJavaFormat("1.11.0")
+    }
+}
+
+tasks.test {
+    // Use JUnit Platform for unit tests.
+    useJUnitPlatform()
+}
+
+task("topic", JavaExec::class) {
+    description = "Run the disposable token example"
+    classpath = sourceSets.main.get().runtimeClasspath
+    mainClass.set("momento.client.example.TopicExample")
+}
+
+task("prepareKotlinBuildScriptModel") {}

examples/topic/src/main/java/momento/client/example/TopicExample.java

@@ -0,0 +1,123 @@
+package momento.client.example;
+
+import java.time.Duration;
+import momento.sdk.CacheClient;
+import momento.sdk.ISubscriptionCallbacks;
+import momento.sdk.TopicClient;
+import momento.sdk.auth.CredentialProvider;
+import momento.sdk.auth.EnvVarCredentialProvider;
+import momento.sdk.config.Configurations;
+import momento.sdk.config.TopicConfigurations;
+import momento.sdk.exceptions.AlreadyExistsException;
+import momento.sdk.exceptions.SdkException;
+import momento.sdk.responses.cache.control.CacheCreateResponse;
+import momento.sdk.responses.topic.TopicMessage;
+import momento.sdk.responses.topic.TopicPublishResponse;
+import momento.sdk.responses.topic.TopicSubscribeResponse;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class TopicExample {
+
+  private static final String API_KEY_ENV_VAR = "MOMENTO_API_KEY";
+  private static final Duration DEFAULT_ITEM_TTL = Duration.ofSeconds(60);
+
+  private static final String CACHE_NAME = "topic-example-cache";
+  private static final String TOPIC_NAME = "example-topic";
+
+  private static final Logger logger = LoggerFactory.getLogger(TopicExample.class);
+
+  public static void main(String[] args) {
+    logStartBanner();
+
+    final CredentialProvider credentialProvider;
+    try {
+      credentialProvider = new EnvVarCredentialProvider(API_KEY_ENV_VAR);
+    } catch (SdkException e) {
+      logger.error("Unable to load credential from environment variable " + API_KEY_ENV_VAR, e);
+      throw e;
+    }
+
+    try (final CacheClient client =
+            CacheClient.create(
+                credentialProvider, Configurations.Laptop.latest(), DEFAULT_ITEM_TTL);
+        final TopicClient topicClient =
+            TopicClient.create(credentialProvider, TopicConfigurations.Laptop.latest())) {
+
+      // Create a cache
+      final CacheCreateResponse createResponse = client.createCache(CACHE_NAME).join();
+      if (createResponse instanceof CacheCreateResponse.Error error) {
+        if (error.getCause() instanceof AlreadyExistsException) {
+          logger.info("Cache with name '{}' already exists.", CACHE_NAME);
+        } else {
+          logger.error("Cache creation failed with error " + error.getErrorCode(), error);
+        }
+      }
+
+      // Subscribe to a topic
+      TopicSubscribeResponse.Subscription subscription = subscribeToTopic(topicClient);
+
+      // Publish messages to the topic
+      for (int i = 0; i < 100; i++) {
+        publishToTopic(topicClient, "message " + i);
+        Thread.sleep(1000);
+      }
+
+      subscription.unsubscribe();
+
+    } catch (Exception e) {
+      logger.error("An unexpected error occurred", e);
+      throw new RuntimeException(e);
+    }
+
+    logEndBanner();
+  }
+
+  private static TopicSubscribeResponse.Subscription subscribeToTopic(TopicClient topicClient) {
+    final TopicSubscribeResponse subscribeResponse =
+        topicClient
+            .subscribe(
+                TopicExample.CACHE_NAME,
+                TOPIC_NAME,
+                new ISubscriptionCallbacks() {
+                  @Override
+                  public void onItem(TopicMessage message) {
+                    logger.info("Received message on topic {}: {}", TOPIC_NAME, message.toString());
+                  }
+
+                  @Override
+                  public void onError(Throwable error) {
+                    logger.error("Subscription to topic {} failed with error", TOPIC_NAME, error);
+                  }
+
+                  @Override
+                  public void onCompleted() {
+                    logger.info("Subscription to topic {} completed", TOPIC_NAME);
+                  }
+                })
+            .join();
+    return subscribeResponse.orElseThrow(
+        () -> new RuntimeException("Unable to subscribe to topic " + TOPIC_NAME));
+  }
+
+  private static void publishToTopic(TopicClient topicClient, String message) {
+    final TopicPublishResponse publishResponse =
+        topicClient.publish(TopicExample.CACHE_NAME, TOPIC_NAME, message).join();
+    if (publishResponse instanceof TopicPublishResponse.Error error) {
+      logger.error(
+          "Topic {} publish failed with error {}", TOPIC_NAME, error.getErrorCode(), error);
+    }
+  }
+
+  private static void logStartBanner() {
+    logger.info("******************************************************************");
+    logger.info("Example Start");
+    logger.info("******************************************************************");
+  }
+
+  private static void logEndBanner() {
+    logger.info("******************************************************************");
+    logger.info("Example End");
+    logger.info("******************************************************************");
+  }
+}

examples/topic/src/main/resources/logback.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE configuration>
+
+<configuration>
+    <import class="ch.qos.logback.classic.encoder.PatternLayoutEncoder"/>
+    <import class="ch.qos.logback.core.ConsoleAppender"/>
+
+    <appender name="STDOUT" class="ConsoleAppender">
+        <encoder class="PatternLayoutEncoder">
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} -%kvp- %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="info">
+        <appender-ref ref="STDOUT"/>
+    </root>
+</configuration>

momento-sdk/src/main/java/momento/sdk/SubscriptionWrapper.java

@@ -201,11 +201,6 @@ public void close() {
     if (subscription != null) {
       subscription.onCompleted();
     }
-    if (scheduler != null) {
-      scheduler.shutdown();
-    }
-    if (grpcManager != null) {
-      grpcManager.close();
-    }
+    scheduler.shutdown();
   }
 }