Allow compiling the polyglot micronaut chat app to a native image

Author: timfel

polyglot-chat-app/README.md

@@ -44,6 +44,26 @@ The application uses the Gradle build tool.
     [bob 💬] still loading the sentiment model I believe
     ```
 
+## Building a Native Image
+
+The application can be AOT compiled using GraalVM Native Image.
+The Python code has to be shipped in a _resources_ directory that is kept next to the native executable.
+
+1. Build a native executable with the Micronaut AOT support:
+   ```bash
+   ./gradlew nativeCompile
+   ```
+
+2. Copy the venv into the output _resources_ directory:
+   ```bash
+   cp -R src/main/resources/venv/ build/native/nativeCompile/resources/python/
+   ```
+
+3. Run the native executable:
+   ```bash
+   build/native/nativeCompile/websocket.chat
+   ```
+
 ### Learn More 
 
 Learn more about GraalVM polyglot capabilities [here](https://www.graalvm.org/latest/reference-manual/polyglot-programming/).

polyglot-chat-app/build.gradle

@@ -33,6 +33,7 @@ dependencies {
 
     implementation("org.graalvm.sdk:graal-sdk:23.1.1")
     implementation("org.graalvm.polyglot:python:23.1.1")
+    implementation("org.graalvm.sdk:nativeimage:23.1.1")
 }
 
 

polyglot-chat-app/src/main/java/websocket/chat/PolyglotContextFactories.java

@@ -52,11 +52,12 @@
 import java.net.URISyntaxException;
 import java.nio.file.Paths;
 
+import org.graalvm.nativeimage.ImageInfo;
+import org.graalvm.nativeimage.ProcessProperties;
 import org.graalvm.polyglot.Context;
 import org.graalvm.polyglot.Engine;
 import org.graalvm.polyglot.Source;
 
-
 /**
  * Defines bean factories for polyglot {@link Context} and {@link Engine}
  * so that they can be injected into other beans. All {@link Context}
@@ -68,10 +69,26 @@ public class PolyglotContextFactories {
     @Singleton
     @Bean(preDestroy = "close")
     Context createContext(ResourceResolver resolver, ScriptsConfig config) throws URISyntaxException {
-        var exe = Paths.get(resolver.getResource(config.pythonVenv).get().toURI()).resolveSibling("bin").resolve("exe");
+        String exe;
+        if (ImageInfo.inImageRuntimeCode()) {
+            if (ProcessProperties.getArgumentVectorBlockSize() > 0) {
+                exe = Paths.get(ProcessProperties.getArgumentVectorProgramName())
+                    .resolveSibling("resources")
+                    .resolve("python")
+                    .resolve("venv")
+                    .resolve("bin")
+                    .resolve("exe")
+                    .toAbsolutePath()
+                    .toString();
+            } else {
+                exe = "";
+            }
+        } else {
+            exe = Paths.get(resolver.getResource(config.pythonVenv).get().toURI()).resolveSibling("bin").resolve("exe").toString();
+        }
         var context = Context.newBuilder("python")
                 .option("python.ForceImportSite", "true")
-                .option("python.Executable", exe.toString())
+                .option("python.Executable", exe)
                 .allowAllAccess(true)
                 .build();
         loadScript(context, "python", config.pythonInit);

polyglot-chat-app/src/main/java/websocket/chat/PolyglotMessageHandlerFactory.java

@@ -54,6 +54,17 @@
 public class PolyglotMessageHandlerFactory {
     @Bean
     MessageHandler createPythonHandler(Context context) {
-        return context.getPolyglotBindings().getMember("ChatMessageHandler").as(MessageHandler.class);
+        var value = context.getPolyglotBindings().getMember("ChatMessageHandler");
+        // we could use value.as(MessageHandler.class), but then we need a proxy config for native
+        // image.
+        return new MessageHandler() {
+            public boolean isValid(String senderTopic, String receiverTopic) {
+                return value.invokeMember("isValid", senderTopic, receiverTopic).asBoolean();
+            }
+
+            public String createMessage(String sender, String message) {
+                return value.invokeMember("createMessage", sender, message).asString();
+            }
+        };
     }
 }