add Google App Engine deployment configuration and health check contr…

…oller

.gitignore

@@ -24,4 +24,9 @@
 .env
 
 # Log
-*.log
+*.log
+
+# Misc
+.gcloudignore
+gcloud.txt
+app.yaml

README.md

@@ -12,9 +12,11 @@ In this implementation, when a HEIC format attachment is uploaded in a text chan
 converts it to a JPEG image. The bot then posts the converted image in the same text channel.
 
 The project is developed with Java Spring Boot using Java Discord API and built with Gradle. 
+The app is deployed on Google App Engine.
+
 The image conversion service is separated from the app, developed as a Google Cloud Function written
 in Python with Flask and using Pillow for image processing. It communicates with the 
-app through HTTP requests.
+app via HTTP requests.
 
 ## Project Structure
 
@@ -25,9 +27,23 @@ app through HTTP requests.
 - `src/`: Contains the Java source code.
 - `build.gradle`: The Gradle build file.
 
-## Environment Variables
-Sensitive data for the project is specified as environment variables. In the Google Cloud Function, 
-they are set directly during initial deployment. In the Spring Boot application, they are loaded 
-from a `.env` file. The `application.properties` file contains the loading configuration and 
-variable placeholders for reference.
+## Deployment
+The deployment configuration for Google App Engine is specified in the app.yaml file. Manual instance 
+scaling is used to ensure continuous operation, as there is no direct traffic to the app (the app 
+does not have its own endpoints to serve). Google App Engine performs periodic health checks to
+assess the app's liveness, so a REST controller is implemented to respond to these health checks.
+
+## Sensitive Data Handling
+
+Sensitive data for the project is specified as environment variables. The handling of these variables 
+is as follows:
+
+- **Google Cloud Function:**
+  - Environment variables are set directly during the initial deployment process.
 
+- **Spring Boot Application:**
+  - Local Development:
+    - Environment variables are loaded from a `.env` file. The `application.properties` file contains 
+    the configuration to load these variables and placeholders for reference.
+  - Deployment:
+    - Environment variables are specified in the `app.yaml` file.

build.gradle

@@ -14,8 +14,11 @@ dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter:5.9.1'
 }
 
-sourceCompatibility = '18'
-targetCompatibility = '18'
+//sourceCompatibility = '18' // local development
+//targetCompatibility = '18' // local development
+
+sourceCompatibility = '17' // deploying on Google App Engine
+targetCompatibility = '17' // deploying on Google App Engine
 
 compileJava {
     options.encoding = "UTF-8"
@@ -33,3 +36,14 @@ test {
     useJUnitPlatform()
 }
 
+jar {
+    enabled = false
+}
+
+bootJar {
+    enabled = true
+    archiveBaseName = 'discord-bot'
+    archiveVersion = '1.0.0'
+}
+
+

src/main/java/com/my/discordbot/BotInitializer.java

@@ -8,7 +8,7 @@
 import org.springframework.stereotype.Component;
 
 @Component
-public class BotInitializer {
+class BotInitializer {
 
     @Autowired
     private EventListener eventListener;

src/main/java/com/my/discordbot/EventListener.java

@@ -12,7 +12,7 @@
 import org.springframework.stereotype.Component;
 
 @Component
-public class EventListener extends ListenerAdapter {
+class EventListener extends ListenerAdapter {
 
     private static final Logger logger = LoggerFactory.getLogger(EventListener.class);
 

src/main/java/com/my/discordbot/HealthCheckRestController.java

@@ -0,0 +1,16 @@
+package com.my.discordbot;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+class HealthCheckRestController {
+
+    @GetMapping("/")
+    public ResponseEntity<String> checkHealth() {
+        return new ResponseEntity<>("OK", HttpStatus.OK);
+    }
+
+}

src/main/java/com/my/discordbot/ProcessConversionToJpg.java

@@ -11,7 +11,6 @@
 import okhttp3.RequestBody;
 import okhttp3.Response;
 import okhttp3.ResponseBody;
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
 
@@ -20,7 +19,7 @@
 import java.nio.file.Files;
 
 @Component
-public class ProcessConversionToJpg {
+class ProcessConversionToJpg {
 
     @Value("${CLOUD_FUNCTION_URL}")
     private String cloudFunctionUrl;

src/main/resources/application.properties

@@ -1,6 +1,11 @@
 # sensitive properties, loaded from .env
-spring.config.import=optional:file:.env[.properties]
+# configuration for local development only!
+# spring.config.import=optional:file:.env[.properties]
 
+# for deployment on Google App Engine environment variables are
+# specified in app.yaml
+
+# environment variables used in this application (list for reference only)
 # DISCORD_BOT_TOKEN=${DISCORD_BOT_TOKEN}
 # OWNER_ID=${OWNER_ID}
 # CLOUD_FUNCTION_URL=${CLOUD_FUNCTION_URL}