Add basics-kotlin (#189)

.tools/run_jvm_tests.sh

@@ -11,6 +11,7 @@ pushd $PROJECT_ROOT/templates/kotlin-gradle && ./gradlew check && popd
 pushd $PROJECT_ROOT/templates/kotlin-gradle-lambda-cdk/lambda && ./gradlew check && popd
 
 pushd $PROJECT_ROOT/basics/basics-java && ./gradlew check && popd
+pushd $PROJECT_ROOT/basics/basics-kotlin && ./gradlew check && popd
 
 pushd $PROJECT_ROOT/patterns-use-cases/sagas/sagas-java && ./gradlew check && popd
 pushd $PROJECT_ROOT/patterns-use-cases/payment-state-machine/payment-state-machine-java && ./gradlew check && popd

.tools/update_jvm_examples.sh

@@ -18,6 +18,7 @@ search_and_replace_version_gradle $PROJECT_ROOT/templates/kotlin-gradle
 search_and_replace_version_gradle $PROJECT_ROOT/templates/kotlin-gradle-lambda-cdk/lambda
 
 search_and_replace_version_gradle $PROJECT_ROOT/basics/basics-java
+search_and_replace_version_gradle $PROJECT_ROOT/basics/basics-kotlin
 
 search_and_replace_version_gradle $PROJECT_ROOT/patterns-use-cases/sagas/sagas-java
 search_and_replace_version_gradle $PROJECT_ROOT/patterns-use-cases/async-signals-payment/async-signals-payment-java

README.md

@@ -63,11 +63,12 @@ challenges.
 
 ### Kotlin
 
-| Type       | Name / Link                                                       |
-|------------|-------------------------------------------------------------------|
-| Templates  | [Template using Gradle](templates/kotlin-gradle)                  |
-| Use Cases  | [Sagas](patterns-use-cases/sagas/sagas-kotlin)                    |
-| End-to-End | [Food Ordering App](end-to-end-applications/kotlin/food-ordering) |
+| Type       | Name / Link                                                             |
+|------------|-------------------------------------------------------------------------|
+| Templates  | [Template using Gradle](templates/kotlin-gradle)                        |
+| Basics     | [Durable Execution, Event-processing, Virtual Objects](basics/basics-kotlin) |
+| Use Cases  | [Sagas](patterns-use-cases/sagas/sagas-kotlin)                          |
+| End-to-End | [Food Ordering App](end-to-end-applications/kotlin/food-ordering)       |
 
 
 ### Python

basics/basics-java/README.md

@@ -1,4 +1,4 @@
-# Examples of the basic concepts for Restate in TypeScript / JavaScript
+# Examples of the basic concepts for Restate in Java
 
 The examples here showcase the most basic building blocks of Restate. **Durable Execution**,
 **Durable Promises**, and **Virtual Objects**, and the **Workflows** abstraction built on top

basics/basics-kotlin/.gitignore

@@ -0,0 +1,35 @@
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# Ignore Gradle project-specific cache directory
+.gradle
+
+# Ignore Gradle build output directory
+build
+
+.idea
+*.iml
+
+# Unignore the gradle wrapper
+!gradle/wrapper/gradle-wrapper.jar

basics/basics-kotlin/README.md

@@ -0,0 +1,66 @@
+# Examples of the basic concepts for Restate in Kotlin
+
+The examples here showcase the most basic building blocks of Restate. **Durable Execution**,
+**Durable Promises**, and **Virtual Objects**, and the **Workflows** abstraction built on top
+of them.
+
+The individual example files contain code snippets with comments and a brief descriptions
+about how they work and how they can be run.
+
+### Examples
+
+* **[Basic Durable Execution:](durable_execution/RoleUpdateService.java):** Running code cleanly
+  to the end in the presence of failures. Automatic retries and recovery of previously
+  finished actions. The example applies a series of updates and permission setting changes
+  to user's profile.
+    ```shell
+    ./gradlew -PmainClass=durable_execution.RoleUpdateServiceKt run
+    ```
+
+* **[Durable Execution with Compensations](durable_execution_compensation/RoleUpdateService.java):**
+  Reliably compensating / undoing previous actions upon unrecoverable errors halfway
+  through multi-step change. This is the same example as above, extended for cases where
+  a part of the change cannot be applied (conflict) and everything has to roll back.
+    ```shell
+    ./gradlew -PmainClass=durable_execution_compensation.RoleUpdateServiceKt run
+    ```
+
+* **[Workflows](workflows/SignupWorkflow.java):** Workflows are durable execution tasks that can
+  be submitted and awaited. They have an identity and can be signaled and queried
+  through durable promises. The example is a user-signup flow that takes multiple
+  operations, including verifying the email address.
+
+* **[Virtual Objects](virtual_objects/GreeterObject.java):** Stateful serverless objects
+  to manage durable consistent state and state-manipulating logic.
+    ```shell
+    ./gradlew -PmainClass=virtual_objects.GreeterObjectKt run
+    ```
+
+* **[Kafka Event-processing](events_processing/UserUpdatesService.java):** Processing events to
+  update various downstream systems with durable event handlers, event-delaying,
+  in a strict-per-key order.
+    ```shell
+    ./gradlew -PmainClass=events_processing.UserUpdatesServiceKt run
+    ```
+
+* **[Stateful Event-processing](events_state/ProfileService.java):** Populating state from
+  events and making is queryable via RPC handlers.
+    ```shell
+    ./gradlew -PmainClass=events_state.ProfileServiceKt run
+    ```
+
+
+### Running the examples
+
+1. Start Restate Server in a separate shell: `npx restate-server`
+
+2. Start the relevant example. The commands are listed above for each example.
+
+3. Register the example at Restate server by calling
+   `npx restate -y deployment register --force localhost:9080`.
+
+   _Note: the '--force' flag here is to circumvent all checks related to graceful upgrades, because it is only a playground, not a production setup._
+
+4. Check the comments in the example for how to interact with the example.
+
+**NOTE:** When you get an error of the type `{"code":"not_found","message":"Service 'greeter' not found. ...}`, then you forgot step (3) for that example.

basics/basics-kotlin/build.gradle.kts

@@ -0,0 +1,45 @@
+plugins {
+  application
+  kotlin("jvm") version "2.0.0"
+  // Kotlinx serialization (optional)
+  kotlin("plugin.serialization") version "2.0.0"
+
+  id("com.google.devtools.ksp") version "2.0.0-1.0.21"
+}
+
+repositories {
+  mavenCentral()
+}
+
+val restateVersion = "1.0.1"
+
+dependencies {
+  // Annotation processor
+  ksp("dev.restate:sdk-api-kotlin-gen:$restateVersion")
+
+  // Restate SDK
+  implementation("dev.restate:sdk-api-kotlin:$restateVersion")
+  implementation("dev.restate:sdk-http-vertx:$restateVersion")
+
+  // Logging (optional)
+  implementation("org.apache.logging.log4j:log4j-core:2.23.0")
+
+  // Kotlinx serialization (optional)
+  implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.2")
+}
+
+// Setup Java/Kotlin compiler target
+java {
+  toolchain {
+    languageVersion.set(JavaLanguageVersion.of(17))
+  }
+}
+
+// Set main class
+application {
+  if (project.hasProperty("mainClass")) {
+    mainClass.set(project.property("mainClass") as String)
+  } else {
+    mainClass.set("durable_execution.RoleUpdateServiceKt")
+  }
+}

basics/basics-kotlin/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.2-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists