Faster topic removal in MultiDC setup

hermes-common/src/main/java/pl/allegro/tech/hermes/infrastructure/zookeeper/ZookeeperBasedRepository.java

@@ -5,6 +5,8 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.commons.lang3.ArrayUtils;
 import org.apache.curator.framework.CuratorFramework;
+import org.apache.curator.framework.api.transaction.CuratorTransactionFinal;
+import org.apache.curator.utils.ZKPaths;
 import org.apache.zookeeper.data.Stat;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -18,6 +20,7 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.function.BiConsumer;
+import java.util.stream.Collectors;
 
 public abstract class ZookeeperBasedRepository {
 
@@ -75,6 +78,13 @@ protected List<String> childrenOf(String path) {
         }
     }
 
+    protected List<String> childrenPathsOf(String path) {
+        List<String> childNodes = childrenOf(path);
+        return childNodes.stream()
+                .map(child -> ZKPaths.makePath(path, child))
+                .collect(Collectors.toList());
+    }
+
     @SuppressWarnings("unchecked")
     protected byte[] readFrom(String path) {
         return readWithStatFrom(path, bytes -> bytes, (t, stat) -> {}, false).get();
@@ -156,6 +166,20 @@ protected void createInTransaction(String path, Object value, String childPath)
                 .commit();
     }
 
+    protected void deleteInTransaction(List<String> paths) throws Exception {
+        if (paths.isEmpty()) {
+            throw new InternalProcessingException("Attempting to remove empty set of paths from ZK");
+        }
+        ensureConnected();
+        CuratorTransactionFinal transaction = zookeeper.inTransaction().delete().forPath(paths.get(0)).and();
+
+        for (int i = 1; i < paths.size(); i++) {
+            transaction = transaction.delete().forPath(paths.get(i)).and();
+        }
+
+        transaction.commit();
+    }
+
     protected void create(String path, Object value) throws Exception {
         ensureConnected();
         zookeeper.create().forPath(path, mapper.writeValueAsBytes(value));

hermes-common/src/main/java/pl/allegro/tech/hermes/infrastructure/zookeeper/ZookeeperGroupRepository.java

@@ -7,6 +7,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import pl.allegro.tech.hermes.api.Group;
+import pl.allegro.tech.hermes.api.TopicName;
 import pl.allegro.tech.hermes.common.exception.InternalProcessingException;
 import pl.allegro.tech.hermes.domain.group.GroupAlreadyExistsException;
 import pl.allegro.tech.hermes.domain.group.GroupNotEmptyException;
@@ -65,14 +66,23 @@ public void updateGroup(Group group) {
         }
     }
 
+    /**
+     * Atomic removal of <code>group</code> and <code>group/topics</code>
+     * nodes is required to prevent lengthy loop during removal, see:
+     * {@link pl.allegro.tech.hermes.infrastructure.zookeeper.ZookeeperTopicRepository#removeTopic(TopicName)}.
+     */
     @Override
     public void removeGroup(String groupName) {
         ensureGroupExists(groupName);
         ensureGroupIsEmpty(groupName);
 
         logger.info("Removing group: {}", groupName);
+        List<String> pathsToDelete = List.of(
+                paths.topicsPath(groupName),
+                paths.groupPath(groupName)
+        );
         try {
-            remove(paths.groupPath(groupName));
+            deleteInTransaction(pathsToDelete);
         } catch (Exception e) {
             throw new InternalProcessingException(e);
         }

hermes-common/src/main/java/pl/allegro/tech/hermes/infrastructure/zookeeper/ZookeeperMessagePreviewRepository.java

@@ -28,7 +28,7 @@ public ZookeeperMessagePreviewRepository(CuratorFramework zookeeper, ObjectMappe
     @Override
     public List<MessagePreview> loadPreview(TopicName topicName) {
         try {
-            return Optional.of(paths.topicPath(topicName, ZookeeperPaths.PREVIEW_PATH))
+            return Optional.of(paths.topicPreviewPath(topicName))
                     .filter(this::pathExists)
                     .flatMap(p -> readFrom(p, new TypeReference<List<MessagePreview>>() {}, true))
                     .orElseGet(ArrayList::new);
@@ -50,7 +50,7 @@ private void persistMessage(TopicName topic, List<MessagePreview> messages) {
         logger.debug("Persisting {} messages for preview of topic: {}", messages.size(), topic.qualifiedName());
         try {
             if (pathExists(paths.topicPath(topic))) {
-                String previewPath = paths.topicPath(topic, ZookeeperPaths.PREVIEW_PATH);
+                String previewPath = paths.topicPreviewPath(topic);
                 ensurePathExists(previewPath);
                 overwrite(previewPath, messages);
             }

hermes-common/src/main/java/pl/allegro/tech/hermes/infrastructure/zookeeper/ZookeeperPaths.java

@@ -77,6 +77,14 @@ public String topicPath(TopicName topicName, String... tail) {
         return Joiner.on(URL_SEPARATOR).join(topicsPath(topicName.getGroupName()), topicName.getName(), (Object[]) tail);
     }
 
+    public String topicPreviewPath(TopicName topicName) {
+        return topicPath(topicName, ZookeeperPaths.PREVIEW_PATH);
+    }
+
+    public String topicMetricsPath(TopicName topicName) {
+        return topicPath(topicName, METRICS_PATH);
+    }
+
     public String subscriptionPath(TopicName topicName, String subscriptionName, String... tail) {
         return Joiner.on(URL_SEPARATOR).join(subscriptionsPath(topicName), subscriptionName, (Object[]) tail);
     }

hermes-common/src/main/java/pl/allegro/tech/hermes/infrastructure/zookeeper/ZookeeperTopicRepository.java

@@ -13,6 +13,7 @@
 import pl.allegro.tech.hermes.domain.topic.TopicNotExistsException;
 import pl.allegro.tech.hermes.domain.topic.TopicRepository;
 
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
@@ -77,12 +78,67 @@ public void createTopic(Topic topic) {
         }
     }
 
+    /**
+     * To remove topic node, we must remove topic node and its children. The tree looks like this:
+     * <ul>
+     * <li>- topic
+     * <li>----- /subscriptions (required)
+     * <li>----- /preview (optional)
+     * <li>----- /metrics (optional)
+     * <li>--------------- /volume
+     * <li>--------------- /published
+     * </ul>
+     *
+     * <p>One way to remove the whole tree for topic that would be to use <code>deletingChildrenIfNeeded()</code>:
+     * e.g. <code>zookeeper.delete().deletingChildrenIfNeeded().forPath(topicPath)</code>.
+     * However, <code>deletingChildrenIfNeeded</code> is not atomic. It first tries to remove the node <code>topic</code>
+     * and upon receiving <code>KeeperException.NotEmptyException</code> it tries to remove children recursively
+     * and then retries the node removal. This means that there is a potentially large time gap between
+     * removal of <code>topic/subscriptions</code> node and <code>topic</code> node, especially when topic removal is being done
+     * in remote DC.
+     *
+     * <p>It turns out that <code>PathChildrenCache</code> used by <code>HierarchicalCacheLevel</code> in
+     * Consumers and Frontend listens for <code>topics/subscriptions</code> changes and recreates that node when deleted.
+     * If the recreation happens between the <code>topic/subscriptions</code> and <code>topic</code> node removal
+     * than the whole removal process must be repeated resulting in a lengthy loop that may even result in <code>StackOverflowException</code>.
+     * Example of that scenario would be
+     * <ol>
+     * <li> DELETE <code>topic</code> - issued by management, fails with KeeperException.NotEmptyException
+     * <li> DELETE <code>topic/subscriptions</code> - issued by management, succeeds
+     * <li> CREATE <code>topic/subscriptions</code> - issued by frontend, succeeds
+     * <li> DELETE <code>topic</code> - issued by management, fails with KeeperException.NotEmptyException
+     * <li> [...]
+     * </ol>
+     *
+     * <p>To solve this we must remove <code>topic</code> and <code>topic/subscriptions</code> atomically. However, we must also remove
+     * other <code>topic</code> children. Transaction API does not allow for optional deletes so we:
+     * <ol>
+     * <li> find all children paths
+     * <li> delete all children in one transaction
+     * </ol>
+     */
     @Override
     public void removeTopic(TopicName topicName) {
         ensureTopicExists(topicName);
         logger.info("Removing topic: " + topicName);
+
+        List<String> pathsForRemoval = new ArrayList<>();
+        String topicMetricsPath = paths.topicMetricsPath(topicName);
+        if (pathExists(topicMetricsPath)) {
+            pathsForRemoval.addAll(childrenPathsOf(topicMetricsPath));
+            pathsForRemoval.add(topicMetricsPath);
+        }
+
+        String topicPreviewPath = paths.topicPreviewPath(topicName);
+        if (pathExists(topicPreviewPath)) {
+            pathsForRemoval.add(topicPreviewPath);
+        }
+
+        pathsForRemoval.add(paths.subscriptionsPath(topicName));
+        pathsForRemoval.add(paths.topicPath(topicName));
+
         try {
-            remove(paths.topicPath(topicName));
+            deleteInTransaction(pathsForRemoval);
         } catch (Exception e) {
             throw new InternalProcessingException(e);
         }

hermes-common/src/test/groovy/pl/allegro/tech/hermes/infrastructure/zookeeper/ZookeeperTopicRepositoryTest.groovy

@@ -185,17 +185,16 @@ class ZookeeperTopicRepositoryTest extends IntegrationTest {
         !repository.topicExists(new TopicName(GROUP, 'remove'))
     }
 
-    def "should remove topic with metrics but without subscriptions"() {
+    def "should remove topic with metrics and without preview"() {
         given:
         def topicName = "topicWithMetrics"
 
         repository.createTopic(topic(GROUP, topicName).build())
         wait.untilTopicCreated(GROUP, topicName)
 
-        def path = pathsCompiler.compile(BASE_ZOOKEEPER_PATH + ZookeeperCounterStorage.SUBSCRIPTION_DELIVERED, pathContext()
+        def path = pathsCompiler.compile(BASE_ZOOKEEPER_PATH + ZookeeperCounterStorage.TOPIC_VOLUME_COUNTER, pathContext()
                 .withGroup(GROUP)
                 .withTopic(topicName)
-                .withSubscription("sample")
                 .build())
         zookeeper().create().creatingParentsIfNeeded().forPath(path, '1'.bytes)
         wait.untilZookeeperPathIsCreated(path)
@@ -207,6 +206,29 @@ class ZookeeperTopicRepositoryTest extends IntegrationTest {
         !repository.topicExists(new TopicName(GROUP, topicName))
     }
 
+    def "should remove topic with metrics and preview"() {
+        given: "a topic"
+        Topic topic = topic(GROUP, "topicWithMetricsAndPreview").build()
+        repository.createTopic(topic)
+        wait.untilTopicCreated(GROUP, topic.getName().getName())
+
+        and: "volume metric in zk for that topic"
+        String metricPath = paths.topicMetricPath(topic.getName(), "volume")
+        zookeeper().create().creatingParentsIfNeeded().forPath(metricPath, '1'.bytes)
+        wait.untilZookeeperPathIsCreated(metricPath)
+
+        and: "preview in zk for that topic"
+        String previewPath = paths.topicPreviewPath(topic.getName())
+        zookeeper().create().creatingParentsIfNeeded().forPath(previewPath , '1'.bytes)
+        wait.untilZookeeperPathIsCreated(previewPath)
+
+        when:
+        repository.removeTopic(topic.getName())
+
+        then:
+        !repository.topicExists(topic.getName())
+    }
+
     def "should not throw exception on malformed topic when reading list of all topics"() {
         given:
         zookeeper().create().forPath(paths.topicPath(new TopicName(GROUP, 'malformed')), ''.bytes)

hermes-management/src/main/java/pl/allegro/tech/hermes/management/config/kafka/KafkaConfiguration.java

@@ -82,7 +82,7 @@ MultiDCAwareService multiDCAwareService(KafkaNamesMappers kafkaNamesMappers, Sch
             AdminClient brokerAdminClient = brokerAdminClient(kafkaProperties);
             BrokerStorage storage = brokersStorage(brokerAdminClient);
             BrokerTopicManagement brokerTopicManagement =
-                    new KafkaBrokerTopicManagement(topicProperties, brokerAdminClient, kafkaNamesMapper);
+                    new KafkaBrokerTopicManagement(topicProperties, brokerAdminClient, kafkaNamesMapper, kafkaProperties.getDatacenter());
             KafkaConsumerPool consumerPool = kafkaConsumersPool(kafkaProperties, storage, kafkaProperties.getBrokerList());
             KafkaRawMessageReader kafkaRawMessageReader =
                     new KafkaRawMessageReader(consumerPool, kafkaProperties.getKafkaConsumer().getPollTimeoutMillis());

hermes-management/src/main/java/pl/allegro/tech/hermes/management/domain/dc/MultiDatacenterRepositoryCommandExecutor.java

@@ -46,9 +46,12 @@ private <T> void execute(RepositoryCommand<T> command, boolean isRollbackEnabled
         List<DatacenterBoundRepositoryHolder<T>> executedRepoHolders = new ArrayList<>();
 
         for (DatacenterBoundRepositoryHolder<T> repoHolder : repoHolders) {
+            long start = System.currentTimeMillis();
             try {
                 executedRepoHolders.add(repoHolder);
+                logger.info("Executing repository command: {} in ZK dc: {}", command, repoHolder.getDatacenterName());
                 command.execute(repoHolder);
+                logger.info("Successfully executed repository command: {} in ZK dc: {} in: {} ms", command, repoHolder.getDatacenterName(), System.currentTimeMillis() - start);
             } catch (RepositoryNotAvailableException e) {
                 logger.warn("Execute failed with an RepositoryNotAvailableException error", e);
                 if (isRollbackEnabled) {
@@ -58,7 +61,7 @@ private <T> void execute(RepositoryCommand<T> command, boolean isRollbackEnabled
                     throw ExceptionWrapper.wrapInInternalProcessingExceptionIfNeeded(e, command.toString(), repoHolder.getDatacenterName());
                 }
             } catch (Exception e) {
-                logger.warn("Execute failed with an error", e);
+                logger.warn("Failed to execute repository command: {} in ZK dc: {} in: {} ms", command, repoHolder.getDatacenterName(), System.currentTimeMillis() - start, e);
                 if (isRollbackEnabled) {
                     rollback(executedRepoHolders, command);
                 }
@@ -68,9 +71,12 @@ private <T> void execute(RepositoryCommand<T> command, boolean isRollbackEnabled
     }
 
     private <T> void rollback(List<DatacenterBoundRepositoryHolder<T>> repoHolders, RepositoryCommand<T> command) {
+        long start = System.currentTimeMillis();
         for (DatacenterBoundRepositoryHolder<T> repoHolder : repoHolders) {
+            logger.info("Executing rollback of repository command: {} in ZK dc: {}", command, repoHolder.getDatacenterName());
             try {
                 command.rollback(repoHolder);
+                logger.info("Successfully executed rollback of repository command: {} in ZK dc: {} in: {} ms", command, repoHolder.getDatacenterName(), System.currentTimeMillis() - start);
             } catch (Exception e) {
                 logger.error("Rollback procedure failed for command {} on DC {}", command, repoHolder.getDatacenterName(), e);
             }

hermes-management/src/main/java/pl/allegro/tech/hermes/management/domain/subscription/SubscriptionRemover.java

@@ -43,9 +43,11 @@ public void removeSubscription(TopicName topicName, String subscriptionName, Req
 
     public void removeSubscriptionRelatedToTopic(Topic topic, RequestUser removedBy) {
         List<Subscription> subscriptions = subscriptionRepository.listSubscriptions(topic.getName());
-
         ensureSubscriptionsHaveAutoRemove(subscriptions, topic.getName());
+        logger.info("Removing subscriptions of topic: {}, subscriptions: {}", topic.getName(), subscriptions);
+        long start = System.currentTimeMillis();
         subscriptions.forEach(sub -> removeSubscription(topic.getName(), sub.getName(), removedBy));
+        logger.info("Removed subscriptions of topic: {} in {} ms", topic.getName(), System.currentTimeMillis() - start);
     }
 
 

hermes-management/src/main/java/pl/allegro/tech/hermes/management/domain/topic/TopicService.java

@@ -382,8 +382,14 @@ private void removeSchema(Topic topic) {
     }
 
     private void removeTopic(Topic topic, RequestUser removedBy) {
+        logger.info("Removing topic: {} from ZK clusters", topic.getQualifiedName());
+        long start = System.currentTimeMillis();
         multiDcExecutor.executeByUser(new RemoveTopicRepositoryCommand(topic.getName()), removedBy);
+        logger.info("Removed topic: {} from ZK clusters in: {} ms", topic.getQualifiedName(), System.currentTimeMillis() - start);
+        logger.info("Removing topic: {} from Kafka clusters", topic.getQualifiedName());
+        start = System.currentTimeMillis();
         multiDCAwareService.manageTopic(brokerTopicManagement -> brokerTopicManagement.removeTopic(topic));
+        logger.info("Removed topic: {} from Kafka clusters in: {} ms", topic.getQualifiedName(), System.currentTimeMillis() - start);
         auditor.objectRemoved(removedBy.getUsername(), topic);
         topicOwnerCache.onRemovedTopic(topic);
     }

hermes-management/src/main/java/pl/allegro/tech/hermes/management/domain/topic/schema/SchemaService.java

@@ -1,5 +1,7 @@
 package pl.allegro.tech.hermes.management.domain.topic.schema;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
 import pl.allegro.tech.hermes.api.RawSchema;
@@ -24,6 +26,8 @@ public class SchemaService {
     private final SchemaValidatorProvider validatorProvider;
     private final TopicProperties topicProperties;
 
+    private static final Logger logger = LoggerFactory.getLogger(SchemaService.class);
+
     @Autowired
     public SchemaService(RawSchemaClient rawSchemaClient,
                          SchemaValidatorProvider validatorProvider,
@@ -68,7 +72,10 @@ public void deleteAllSchemaVersions(String qualifiedTopicName) {
         if (!topicProperties.isRemoveSchema()) {
             throw new SchemaRemovalDisabledException();
         }
+        logger.info("Removing all schema versions for topic: {}", qualifiedTopicName);
+        long start = System.currentTimeMillis();
         rawSchemaClient.deleteAllSchemaVersions(fromQualifiedName(qualifiedTopicName));
+        logger.info("Removed all schema versions for topic: {} in {} ms", qualifiedTopicName, System.currentTimeMillis() - start);
     }
 
     public void validateSchema(Topic topic, String schema) {

hermes-management/src/main/java/pl/allegro/tech/hermes/management/infrastructure/kafka/service/KafkaBrokerTopicManagement.java

@@ -9,6 +9,8 @@
 import org.apache.kafka.common.KafkaFuture;
 import org.apache.kafka.common.config.ConfigResource;
 import org.apache.kafka.common.config.TopicConfig;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import pl.allegro.tech.hermes.api.Topic;
 import pl.allegro.tech.hermes.common.kafka.KafkaNamesMapper;
 import pl.allegro.tech.hermes.common.kafka.KafkaTopic;
@@ -32,10 +34,16 @@ public class KafkaBrokerTopicManagement implements BrokerTopicManagement {
 
     private final KafkaNamesMapper kafkaNamesMapper;
 
-    public KafkaBrokerTopicManagement(TopicProperties topicProperties, AdminClient kafkaAdminClient, KafkaNamesMapper kafkaNamesMapper) {
+    private final String datacenterName;
+
+    private static final Logger logger = LoggerFactory.getLogger(KafkaBrokerTopicManagement.class);
+
+
+    public KafkaBrokerTopicManagement(TopicProperties topicProperties, AdminClient kafkaAdminClient, KafkaNamesMapper kafkaNamesMapper, String datacenterName) {
         this.topicProperties = topicProperties;
         this.kafkaAdminClient = kafkaAdminClient;
         this.kafkaNamesMapper = kafkaNamesMapper;
+        this.datacenterName = datacenterName;
     }
 
     @Override
@@ -59,7 +67,12 @@ public void removeTopic(Topic topic) {
         kafkaNamesMapper.toKafkaTopics(topic).stream()
                 .map(k -> kafkaAdminClient.deleteTopics(Collections.singletonList(k.name().asString())))
                 .map(DeleteTopicsResult::all)
-                .forEach(this::waitForKafkaFuture);
+                .forEach(future -> {
+                    logger.info("Removing topic: {} from Kafka dc: {}", topic, datacenterName);
+                    long start = System.currentTimeMillis();
+                    waitForKafkaFuture(future);
+                    logger.info("Removed topic: {} from Kafka dc: {} in {} ms", topic, datacenterName, System.currentTimeMillis() - start);
+                });
     }
 
     @Override