Implement app restart on dynamic config change. Resolves #616

Author: Haarolean

api/src/main/java/io/kafbat/ui/service/app/ConfigReloadService.java

@@ -0,0 +1,114 @@
+package io.kafbat.ui.service.app;
+
+import io.kafbat.ui.util.ApplicationRestarter;
+import io.kafbat.ui.util.DynamicConfigOperations;
+import jakarta.annotation.PostConstruct;
+import jakarta.annotation.PreDestroy;
+import java.io.IOException;
+import java.nio.file.ClosedWatchServiceException;
+import java.nio.file.FileSystems;
+import java.nio.file.Path;
+import java.nio.file.StandardWatchEventKinds;
+import java.nio.file.WatchEvent;
+import java.nio.file.WatchKey;
+import java.nio.file.WatchService;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.stereotype.Service;
+
+@Service
+@ConditionalOnProperty(value = {"dynamic.config.enabled", "dynamic.config.autoreload"}, havingValue = "true")
+@RequiredArgsConstructor
+@Slf4j
+public class ConfigReloadService {
+
+  private static final String THREAD_NAME = "config-watcher-thread";
+  private static final long STARTUP_SUPPRESSION_MS = 1000;
+  private final long appStartedAt = System.currentTimeMillis();
+
+  private final DynamicConfigOperations dynamicConfigOperations;
+  private final ApplicationRestarter restarter;
+
+  private WatchService watchService;
+  private Thread watcherThread;
+
+  @PostConstruct
+  public void init() {
+    log.debug("Auto reload is enabled, will watch for config changes");
+
+    try {
+      registerWatchService();
+      startWatching();
+    } catch (IOException e) {
+      log.error("Error while registering watch service", e);
+    }
+  }
+
+  @PreDestroy
+  public void shutdown() {
+    try {
+      if (watchService != null) {
+        watchService.close();
+      }
+    } catch (IOException ignored) {
+    }
+    if (watcherThread != null) {
+      this.watcherThread.interrupt();
+    }
+  }
+
+  private void registerWatchService() throws IOException {
+    this.watchService = FileSystems.getDefault().newWatchService();
+    dynamicConfigOperations.dynamicConfigFilePath()
+        .getParent()
+        .register(watchService, StandardWatchEventKinds.ENTRY_MODIFY);
+  }
+
+  private void startWatching() {
+    watcherThread = new Thread(this::watchLoop, THREAD_NAME);
+    watcherThread.start();
+  }
+
+  private void watchLoop() {
+    final var watchedDir = dynamicConfigOperations.dynamicConfigFilePath().getParent();
+
+    while (true) {
+      try {
+        WatchKey key = watchService.take();
+        for (WatchEvent<?> event : key.pollEvents()) {
+          WatchEvent.Kind<?> kind = event.kind();
+          Path changed = watchedDir.resolve((Path) event.context());
+
+          if (kind != StandardWatchEventKinds.ENTRY_MODIFY) {
+            continue;
+          }
+          if (!changed.equals(dynamicConfigOperations.dynamicConfigFilePath())) {
+            continue;
+          }
+
+          var now = System.currentTimeMillis();
+          if (now - appStartedAt < STARTUP_SUPPRESSION_MS) {
+            continue;
+          }
+
+          restart();
+        }
+        key.reset();
+      } catch (ClosedWatchServiceException e) {
+        log.trace("Watch service closed, exiting watcher thread");
+        break;
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+        break;
+      }
+    }
+  }
+
+  private void restart() {
+    log.info("Application config change detected, restarting");
+    restarter.requestRestart();
+  }
+
+
+}

api/src/main/java/io/kafbat/ui/util/DynamicConfigOperations.java

@@ -30,9 +30,7 @@
 import org.springframework.http.codec.multipart.FilePart;
 import org.springframework.stereotype.Component;
 import org.yaml.snakeyaml.DumperOptions;
-import org.yaml.snakeyaml.LoaderOptions;
 import org.yaml.snakeyaml.Yaml;
-import org.yaml.snakeyaml.constructor.Constructor;
 import org.yaml.snakeyaml.introspector.BeanAccess;
 import org.yaml.snakeyaml.introspector.Property;
 import org.yaml.snakeyaml.introspector.PropertyUtils;
@@ -67,7 +65,7 @@ public boolean dynamicConfigEnabled() {
     return "true".equalsIgnoreCase(ctx.getEnvironment().getProperty(DYNAMIC_CONFIG_ENABLED_ENV_PROPERTY));
   }
 
-  private Path dynamicConfigFilePath() {
+  public Path dynamicConfigFilePath() {
     return Paths.get(
         Optional.ofNullable(ctx.getEnvironment().getProperty(DYNAMIC_CONFIG_PATH_ENV_PROPERTY))
             .orElse(DYNAMIC_CONFIG_PATH_ENV_PROPERTY_DEFAULT)