[GitHub] [druid] clintropolis commented on a change in pull request #11144: Make sure updating coordinator config is protected against race condition

[GitBox <gi...@apache.org>]

clintropolis commented on a change in pull request #11144:
URL: https://github.com/apache/druid/pull/11144#discussion_r629623614



##########
File path: core/src/main/java/org/apache/druid/common/config/ConfigManager.java
##########
@@ -168,64 +171,99 @@ private void poll()
     return holder.getReference();
   }
 
-
   public <T> SetResult set(final String key, final ConfigSerde<T> serde, final T obj)
   {
-    if (obj == null || !started) {
-      if (obj == null) {
-        return SetResult.fail(new IllegalAccessException("input obj is null"));
+    return set(key, serde, null, obj);
+  }
+
+  public <T> SetResult set(final String key, final ConfigSerde<T> serde, @Nullable final T oldObject, final T newObject)
+  {
+    if (newObject == null || !started) {
+      if (newObject == null) {
+        return SetResult.fail(new IllegalAccessException("input obj is null"), false);

Review comment:
       super nitpick: i know this isn't new or your fault, but "obj" doesn't seem to need to be shortened

##########
File path: server/src/main/java/org/apache/druid/server/http/CoordinatorCompactionConfigsResource.java
##########
@@ -162,27 +165,68 @@ public Response deleteCompactionConfig(
       @Context HttpServletRequest req
   )
   {
-    final CoordinatorCompactionConfig current = CoordinatorCompactionConfig.current(manager);
-    final Map<String, DataSourceCompactionConfig> configs = current
-        .getCompactionConfigs()
-        .stream()
-        .collect(Collectors.toMap(DataSourceCompactionConfig::getDataSource, Function.identity()));
+    Callable<SetResult> callable = () -> {
+      final CoordinatorCompactionConfig current = CoordinatorCompactionConfig.current(manager);
+      final Map<String, DataSourceCompactionConfig> configs = current
+          .getCompactionConfigs()
+          .stream()
+          .collect(Collectors.toMap(DataSourceCompactionConfig::getDataSource, Function.identity()));
+
+      final DataSourceCompactionConfig config = configs.remove(dataSource);
+      if (config == null) {
+        return SetResult.fail(new NoSuchElementException("datasource not found"), false);
+      }
+
+      return manager.set(
+          CoordinatorCompactionConfig.CONFIG_KEY,
+          // Do database insert without swap if the current config is empty as this means the config may be null in the database
+          CoordinatorCompactionConfig.empty().equals(current) ? null : current,
+          CoordinatorCompactionConfig.from(current, ImmutableList.copyOf(configs.values())),
+          new AuditInfo(author, comment, req.getRemoteAddr())
+      );
+    };
+    return updateConfigHelper(callable);
+  }
 
-    final DataSourceCompactionConfig config = configs.remove(dataSource);
-    if (config == null) {
-      return Response.status(Response.Status.NOT_FOUND).build();
+  @VisibleForTesting
+  Response updateConfigHelper(Callable<SetResult> updateMethod)
+  {
+    int attemps = 0;
+    SetResult setResult = null;
+    try {
+      while (attemps < UPDATE_NUM_RETRY) {
+        setResult = updateMethod.call();
+        if (setResult.isOk() || !setResult.isRetryable()) {
+          break;
+        }
+        attemps++;
+        updateRetryDelay();
+      }
+    }

Review comment:
       Does RetryUtils not suitable for some reason?




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