Restart cluster tasks on connection lost

Author: ianton-ru

src/Core/Protocol.h

@@ -96,8 +96,10 @@ namespace Protocol
             MergeTreeReadTaskRequest = 16,  /// Request from a MergeTree replica to a coordinator
             TimezoneUpdate = 17,            /// Receive server's (session-wide) default timezone
             SSHChallenge = 18,              /// Return challenge for SSH signature signing
+
             MAX = SSHChallenge,
 
+            ConnectionLost = 255,           /// Exception that occurred on the client side.
         };
 
         /// NOTE: If the type of packet argument would be Enum, the comparison packet >= 0 && packet < 10

src/Core/Settings.cpp

@@ -6130,6 +6130,9 @@ Limit for hosts used for request in object storage cluster table functions - azu
 Possible values:
 - Positive integer.
 - 0 — All hosts in cluster.
+)", EXPERIMENTAL) \
+    DECLARE(Bool, allow_retries_in_cluster_requests, false, R"(
+Allow retries in cluster request, when one node goes offline
 )", EXPERIMENTAL) \
     \
     /** Experimental tsToGrid aggregate function. */ \

src/Core/SettingsChangesHistory.cpp

@@ -94,6 +94,8 @@ const VersionToSettingsChangesMap & getSettingsChangesHistory()
             {"iceberg_snapshot_id", 0, 0, "New setting."},
             {"parallel_replicas_for_cluster_engines", false, true, "New setting."},
             /// Release closed. Please use 25.4
+            {"use_object_storage_list_objects_cache", true, false, "New setting."},
+            {"allow_retries_in_cluster_requests", false, false, "New setting."},
         });
         addSettingsChanges(settings_changes_history, "24.12.2.20000",
         {

src/QueryPipeline/RemoteQueryExecutor.cpp

@@ -49,6 +49,7 @@ namespace Setting
     extern const SettingsOverflowMode timeout_overflow_mode;
     extern const SettingsBool use_hedged_requests;
     extern const SettingsBool push_external_roles_in_interserver_queries;
+    extern const SettingsBool allow_retries_in_cluster_requests;
 }
 
 namespace ErrorCodes
@@ -77,6 +78,7 @@ RemoteQueryExecutor::RemoteQueryExecutor(
     , extension(extension_)
     , priority_func(priority_func_)
     , read_packet_type_separately(context->canUseParallelReplicasOnInitiator() && !context->getSettingsRef()[Setting::use_hedged_requests])
+    , allow_retries_in_cluster_requests(context->getSettingsRef()[Setting::allow_retries_in_cluster_requests])
 {
 }
 
@@ -458,7 +460,8 @@ int RemoteQueryExecutor::sendQueryAsync()
         read_context = std::make_unique<ReadContext>(
             *this,
             /*suspend_when_query_sent*/ true,
-            read_packet_type_separately);
+            read_packet_type_separately,
+            allow_retries_in_cluster_requests);
 
     /// If query already sent, do nothing. Note that we cannot use sent_query flag here,
     /// because we can still be in process of sending scalars or external tables.
@@ -531,7 +534,8 @@ RemoteQueryExecutor::ReadResult RemoteQueryExecutor::readAsync()
         read_context = std::make_unique<ReadContext>(
             *this,
             /*suspend_when_query_sent*/ false,
-            read_packet_type_separately);
+            read_packet_type_separately,
+            allow_retries_in_cluster_requests);
         recreate_read_context = false;
     }
 
@@ -655,7 +659,11 @@ RemoteQueryExecutor::ReadResult RemoteQueryExecutor::processPacket(Packet packet
             /// We can actually return it, and the first call to RemoteQueryExecutor::read
             /// will return earlier. We should consider doing it.
             if (packet.block && (packet.block.rows() > 0))
+            {
+                if (extension && extension->replica_info)
+                    replica_has_processed_data.insert(extension->replica_info->number_of_current_replica);
                 return ReadResult(adaptBlockStructure(packet.block, header));
+            }
             break;  /// If the block is empty - we will receive other packets before EndOfStream.
 
         case Protocol::Server::Exception:
@@ -717,6 +725,22 @@ RemoteQueryExecutor::ReadResult RemoteQueryExecutor::processPacket(Packet packet
         case Protocol::Server::TimezoneUpdate:
             break;
 
+        case Protocol::Server::ConnectionLost:
+            if (allow_retries_in_cluster_requests)
+            {
+                if (extension && extension->task_iterator && extension->task_iterator->supportRerunTask() && extension->replica_info)
+                {
+                    if (!replica_has_processed_data.contains(extension->replica_info->number_of_current_replica))
+                    {
+                        finished = true;
+                        extension->task_iterator->rescheduleTasksFromReplica(extension->replica_info->number_of_current_replica);
+                        return ReadResult(Block{});
+                    }
+                }
+            }
+            packet.exception->rethrow();
+            break;
+
         default:
             got_unknown_packet_from_replica = true;
             throw Exception(

src/QueryPipeline/RemoteQueryExecutor.h

@@ -27,8 +27,22 @@ class RemoteQueryExecutorReadContext;
 
 class ParallelReplicasReadingCoordinator;
 
-/// This is the same type as StorageS3Source::IteratorWrapper
-using TaskIterator = std::function<String(size_t)>;
+namespace ErrorCodes
+{
+    extern const int NOT_IMPLEMENTED;
+};
+
+class TaskIterator
+{
+public:
+    virtual ~TaskIterator() = default;
+    virtual bool supportRerunTask() const { return false; }
+    virtual void rescheduleTasksFromReplica(size_t /* number_of_current_replica */)
+    {
+        throw Exception(ErrorCodes::NOT_IMPLEMENTED, "Method rescheduleTasksFromReplica is not implemented");
+    }
+    virtual std::string operator()(size_t number_of_current_replica) const = 0;
+};
 
 /// This class allows one to launch queries on remote replicas of one shard and get results
 class RemoteQueryExecutor
@@ -320,6 +334,10 @@ class RemoteQueryExecutor
 
     const bool read_packet_type_separately = false;
 
+    const bool allow_retries_in_cluster_requests = false;
+
+    std::unordered_set<size_t> replica_has_processed_data;
+
     /// Send all scalars to remote servers
     void sendScalars();
 

src/QueryPipeline/RemoteQueryExecutorReadContext.cpp

@@ -19,11 +19,15 @@ namespace ErrorCodes
 }
 
 RemoteQueryExecutorReadContext::RemoteQueryExecutorReadContext(
-    RemoteQueryExecutor & executor_, bool suspend_when_query_sent_, bool read_packet_type_separately_)
+    RemoteQueryExecutor & executor_,
+    bool suspend_when_query_sent_,
+    bool read_packet_type_separately_,
+    bool allow_retries_in_cluster_requests_)
     : AsyncTaskExecutor(std::make_unique<Task>(*this))
     , executor(executor_)
     , suspend_when_query_sent(suspend_when_query_sent_)
     , read_packet_type_separately(read_packet_type_separately_)
+    , allow_retries_in_cluster_requests(allow_retries_in_cluster_requests_)
 {
     if (-1 == pipe2(pipe_fd, O_NONBLOCK))
         throw ErrnoException(ErrorCodes::CANNOT_OPEN_FILE, "Cannot create pipe");
@@ -54,18 +58,29 @@ void RemoteQueryExecutorReadContext::Task::run(AsyncCallback async_callback, Sus
     if (read_context.executor.needToSkipUnavailableShard())
         return;
 
-    while (true)
+    try
     {
-        read_context.has_read_packet_part = PacketPart::None;
-
-        if (read_context.read_packet_type_separately)
+        while (true)
         {
-            read_context.packet.type = read_context.executor.getConnections().receivePacketTypeUnlocked(async_callback);
-            read_context.has_read_packet_part = PacketPart::Type;
+            read_context.has_read_packet_part = PacketPart::None;
+
+            if (read_context.read_packet_type_separately)
+            {
+                read_context.packet.type = read_context.executor.getConnections().receivePacketTypeUnlocked(async_callback);
+                read_context.has_read_packet_part = PacketPart::Type;
+                suspend_callback();
+            }
+            read_context.packet = read_context.executor.getConnections().receivePacketUnlocked(async_callback);
+            read_context.has_read_packet_part = PacketPart::Body;
             suspend_callback();
         }
-        read_context.packet = read_context.executor.getConnections().receivePacketUnlocked(async_callback);
-        read_context.has_read_packet_part = PacketPart::Body;
+    }
+    catch (const Exception &)
+    {
+        if (!read_context.allow_retries_in_cluster_requests)
+            throw;
+        read_context.packet.type = Protocol::Server::ConnectionLost;
+        read_context.packet.exception = std::make_unique<Exception>(getCurrentExceptionMessageAndPattern(true), getCurrentExceptionCode());
         suspend_callback();
     }
 }

src/QueryPipeline/RemoteQueryExecutorReadContext.h

@@ -26,7 +26,10 @@ class RemoteQueryExecutorReadContext : public AsyncTaskExecutor
 {
 public:
     explicit RemoteQueryExecutorReadContext(
-        RemoteQueryExecutor & executor_, bool suspend_when_query_sent_, bool read_packet_type_separately_);
+        RemoteQueryExecutor & executor_,
+        bool suspend_when_query_sent_,
+        bool read_packet_type_separately_,
+        bool allow_retries_in_cluster_requests_);
 
     ~RemoteQueryExecutorReadContext() override;
 
@@ -108,6 +111,7 @@ class RemoteQueryExecutorReadContext : public AsyncTaskExecutor
     bool suspend_when_query_sent = false;
     bool is_query_sent = false;
     const bool read_packet_type_separately = false;
+    const bool allow_retries_in_cluster_requests = false;
 };
 
 }

src/Storages/ObjectStorage/StorageObjectStorageCluster.cpp

@@ -363,6 +363,28 @@ void StorageObjectStorageCluster::updateQueryToSendIfNeeded(
         args.insert(args.end(), object_storage_type_arg);
 }
 
+class TaskDistributor : public TaskIterator
+{
+public:
+    TaskDistributor(std::shared_ptr<IObjectIterator> iterator,
+        const std::vector<std::string> & ids_of_hosts)
+        : task_distributor(iterator, ids_of_hosts) {}
+    ~TaskDistributor() override = default;
+    bool supportRerunTask() const override { return true; }
+    void rescheduleTasksFromReplica(size_t number_of_current_replica) override
+    {
+        task_distributor.rescheduleTasksFromReplica(number_of_current_replica);
+    }
+
+    std::string operator()(size_t number_of_current_replica) const override
+    {
+        return task_distributor.getNextTask(number_of_current_replica).value_or("");
+    }
+
+private:
+    mutable StorageObjectStorageStableTaskDistributor task_distributor;
+};
+
 RemoteQueryExecutor::Extension StorageObjectStorageCluster::getTaskIteratorExtension(
     const ActionsDAG::Node * predicate,
     const std::optional<ActionsDAG> & filter_actions_dag,
@@ -386,12 +408,7 @@ RemoteQueryExecutor::Extension StorageObjectStorageCluster::getTaskIteratorExten
         }
     }
 
-    auto task_distributor = std::make_shared<StorageObjectStorageStableTaskDistributor>(iterator, ids_of_hosts);
-
-    auto callback = std::make_shared<TaskIterator>(
-        [task_distributor](size_t number_of_current_replica) mutable -> String {
-            return task_distributor->getNextTask(number_of_current_replica).value_or("");
-        });
+    auto callback = std::make_shared<TaskDistributor>(iterator, ids_of_hosts);
 
     return RemoteQueryExecutor::Extension{ .task_iterator = std::move(callback) };
 }

src/Storages/ObjectStorage/StorageObjectStorageStableTaskDistributor.cpp

@@ -6,6 +6,12 @@
 namespace DB
 {
 
+namespace ErrorCodes
+{
+    extern const int LOGICAL_ERROR;
+    extern const int CANNOT_READ_ALL_DATA;
+};
+
 StorageObjectStorageStableTaskDistributor::StorageObjectStorageStableTaskDistributor(
     std::shared_ptr<IObjectIterator> iterator_,
     std::vector<std::string> ids_of_nodes_)
@@ -14,6 +20,9 @@ StorageObjectStorageStableTaskDistributor::StorageObjectStorageStableTaskDistrib
     , ids_of_nodes(ids_of_nodes_)
     , iterator_exhausted(false)
 {
+    size_t nodes = ids_of_nodes.size();
+    for (size_t i = 0; i < nodes; ++i)
+        replica_to_files_to_be_processed[i] = std::list<String>{};
 }
 
 std::optional<String> StorageObjectStorageStableTaskDistributor::getNextTask(size_t number_of_current_replica)
@@ -24,16 +33,27 @@ std::optional<String> StorageObjectStorageStableTaskDistributor::getNextTask(siz
         number_of_current_replica
     );
 
-    // 1. Check pre-queued files first
-    if (auto file = getPreQueuedFile(number_of_current_replica))
-        return file;
+    auto processed_file_list_ptr = replica_to_files_to_be_processed.find(number_of_current_replica);
+    if (processed_file_list_ptr == replica_to_files_to_be_processed.end())
+        throw Exception(
+            ErrorCodes::LOGICAL_ERROR,
+            "Replica number {} was marked as lost, can't set task for it anymore",
+            number_of_current_replica
+        );
 
+    // 1. Check pre-queued files first
+    std::optional<String> file = getPreQueuedFile(number_of_current_replica);
     // 2. Try to find a matching file from the iterator
-    if (auto file = getMatchingFileFromIterator(number_of_current_replica))
-        return file;
-
+    if (!file.has_value())
+        file = getMatchingFileFromIterator(number_of_current_replica);
     // 3. Process unprocessed files if iterator is exhausted
-    return getAnyUnprocessedFile(number_of_current_replica);
+    if (!file.has_value())
+        file = getAnyUnprocessedFile(number_of_current_replica);
+
+    if (file.has_value())
+        processed_file_list_ptr->second.push_back(*file);
+
+    return file;
 }
 
 size_t StorageObjectStorageStableTaskDistributor::getReplicaForFile(const String & file_path)
@@ -179,4 +199,28 @@ std::optional<String> StorageObjectStorageStableTaskDistributor::getAnyUnprocess
     return std::nullopt;
 }
 
+void StorageObjectStorageStableTaskDistributor::rescheduleTasksFromReplica(size_t number_of_current_replica)
+{
+    LOG_INFO(log, "Replica {} is marked as lost, tasks are returned to queue", number_of_current_replica);
+    std::lock_guard lock(mutex);
+
+    auto processed_file_list_ptr = replica_to_files_to_be_processed.find(number_of_current_replica);
+    if (processed_file_list_ptr == replica_to_files_to_be_processed.end())
+        throw Exception(
+            ErrorCodes::LOGICAL_ERROR,
+            "Replica number {} was marked as lost already",
+            number_of_current_replica
+        );
+
+    if (replica_to_files_to_be_processed.size() < 2)
+        throw Exception(
+            ErrorCodes::CANNOT_READ_ALL_DATA,
+            "All replicas were marked as lost"
+        );
+
+    for (const auto & file_path : processed_file_list_ptr->second)
+        unprocessed_files.insert(file_path);
+    replica_to_files_to_be_processed.erase(number_of_current_replica);
+}
+
 }

src/Storages/ObjectStorage/StorageObjectStorageStableTaskDistributor.h

@@ -6,6 +6,8 @@
 #include <Storages/ObjectStorage/StorageObjectStorageSource.h>
 #include <Storages/ObjectStorageQueue/ObjectStorageQueueSource.h>
 #include <unordered_set>
+#include <unordered_map>
+#include <list>
 #include <vector>
 #include <mutex>
 #include <memory>
@@ -22,6 +24,9 @@ class StorageObjectStorageStableTaskDistributor
 
     std::optional<String> getNextTask(size_t number_of_current_replica);
 
+    /// Insert objects back to unprocessed files
+    void rescheduleTasksFromReplica(size_t number_of_current_replica);
+
 private:
     size_t getReplicaForFile(const String & file_path);
     std::optional<String> getPreQueuedFile(size_t number_of_current_replica);
@@ -34,6 +39,7 @@ class StorageObjectStorageStableTaskDistributor
     std::unordered_set<String> unprocessed_files;
 
     std::vector<std::string> ids_of_nodes;
+    std::unordered_map<size_t, std::list<String>> replica_to_files_to_be_processed;
 
     std::mutex mutex;
     bool iterator_exhausted = false;