SYSTEM STOP SWARM MODE command for graceful shutdown swarm node

docs/en/sql-reference/statements/system.md

@@ -206,6 +206,12 @@ SYSTEM RELOAD USERS [ON CLUSTER cluster_name]
 
 Normally shuts down ClickHouse (like `service clickhouse-server stop` / `kill {$pid_clickhouse-server}`)
 
+## PRESHUTDOWN {#preshutdown}
+
+<CloudNotSupportedBadge/>
+
+Prepare node for graceful shutdown. Unregister in autodiscovered clusters, stop accepting distributed requests to object storages (s3Cluster, icebergCluster, etc.).
+
 ## KILL {#kill}
 
 Aborts ClickHouse process (like `kill -9 {$ pid_clickhouse-server}`)

programs/server/Server.cpp

@@ -2292,6 +2292,8 @@ try
 
     }
 
+    global_context->startSwarmMode();
+
     {
         std::lock_guard lock(servers_lock);
         /// We should start interserver communications before (and more important shutdown after) tables.
@@ -2701,6 +2703,8 @@ try
 
             is_cancelled = true;
 
+            global_context->stopSwarmMode();
+
             LOG_DEBUG(log, "Waiting for current connections to close.");
 
             size_t current_connections = 0;

src/Access/Common/AccessType.h

@@ -200,6 +200,7 @@ enum class AccessType : uint8_t
     M(SYSTEM_TTL_MERGES, "SYSTEM STOP TTL MERGES, SYSTEM START TTL MERGES, STOP TTL MERGES, START TTL MERGES", TABLE, SYSTEM) \
     M(SYSTEM_FETCHES, "SYSTEM STOP FETCHES, SYSTEM START FETCHES, STOP FETCHES, START FETCHES", TABLE, SYSTEM) \
     M(SYSTEM_MOVES, "SYSTEM STOP MOVES, SYSTEM START MOVES, STOP MOVES, START MOVES", TABLE, SYSTEM) \
+    M(SYSTEM_SWARM, "SYSTEM STOP SWARM MODE, SYSTEM START SWARM MODE, STOP SWARM MODE, START SWARM MODE", GLOBAL, SYSTEM) \
     M(SYSTEM_PULLING_REPLICATION_LOG, "SYSTEM STOP PULLING REPLICATION LOG, SYSTEM START PULLING REPLICATION LOG", TABLE, SYSTEM) \
     M(SYSTEM_CLEANUP, "SYSTEM STOP CLEANUP, SYSTEM START CLEANUP", TABLE, SYSTEM) \
     M(SYSTEM_VIEWS, "SYSTEM REFRESH VIEW, SYSTEM START VIEWS, SYSTEM STOP VIEWS, SYSTEM START VIEW, SYSTEM STOP VIEW, SYSTEM CANCEL VIEW, REFRESH VIEW, START VIEWS, STOP VIEWS, START VIEW, STOP VIEW, CANCEL VIEW", VIEW, SYSTEM) \

src/Common/CurrentMetrics.cpp

@@ -430,6 +430,7 @@
     M(StartupScriptsExecutionState, "State of startup scripts execution: 0 = not finished, 1 = success, 2 = failure.") \
     \
     M(IsServerShuttingDown, "Indicates if the server is shutting down: 0 = no, 1 = yes") \
+    M(IsSwarmModeEnabled, "Indicates if the swarm mode enabled or not: 0 = disabled, 1 = enabled") \
     \
     M(TotalMergeFailures, "Number of all failed merges since startup, including the ones that were aborted") \
     M(NonAbortedMergeFailures, "Number of failed merges since startup, excluding the merges that were aborted") \

src/Interpreters/ClusterDiscovery.cpp

@@ -108,6 +108,13 @@ class ClusterDiscovery::Flags
         cv.notify_one();
     }
 
+    void wakeup()
+    {
+        std::unique_lock<std::mutex> lk(mu);
+        any_need_update = true;
+        cv.notify_one();
+    }
+
 private:
     std::condition_variable cv;
     std::mutex mu;
@@ -391,7 +398,9 @@ bool ClusterDiscovery::upsertCluster(ClusterInfo & cluster_info)
         return true;
     };
 
-    if (!cluster_info.current_node_is_observer && !contains(node_uuids, current_node_name))
+    if (!cluster_info.current_node_is_observer
+        && context->isSwarmModeEnabled()
+        && !contains(node_uuids, current_node_name))
     {
         LOG_ERROR(log, "Can't find current node in cluster '{}', will register again", cluster_info.name);
         registerInZk(zk, cluster_info);
@@ -455,12 +464,30 @@ void ClusterDiscovery::registerInZk(zkutil::ZooKeeperPtr & zk, ClusterInfo & inf
         return;
     }
 
+    if (!context->isSwarmModeEnabled())
+    {
+        LOG_DEBUG(log, "STOP SWARM MODE called, skip self-registering current node {} in cluster {}", current_node_name, info.name);
+        return;
+    }
+
     LOG_DEBUG(log, "Registering current node {} in cluster {}", current_node_name, info.name);
 
     zk->createOrUpdate(node_path, info.current_node.serialize(), zkutil::CreateMode::Ephemeral);
     LOG_DEBUG(log, "Current node {} registered in cluster {}", current_node_name, info.name);
 }
 
+void ClusterDiscovery::unregisterFromZk(zkutil::ZooKeeperPtr & zk, ClusterInfo & info)
+{
+    if (info.current_node_is_observer)
+        return;
+
+    String node_path = getShardsListPath(info.zk_root) / current_node_name;
+    LOG_DEBUG(log, "Removing current node {} from cluster {}", current_node_name, info.name);
+
+    zk->remove(node_path);
+    LOG_DEBUG(log, "Current node {} removed from cluster {}", current_node_name, info.name);
+}
+
 void ClusterDiscovery::initialUpdate()
 {
     LOG_DEBUG(log, "Initializing");
@@ -506,6 +533,18 @@ void ClusterDiscovery::initialUpdate()
     is_initialized = true;
 }
 
+void ClusterDiscovery::registerAll()
+{
+    register_change_flag = RegisterChangeFlag::RCF_REGISTER_ALL;
+    clusters_to_update->wakeup();
+}
+
+void ClusterDiscovery::unregisterAll()
+{
+    register_change_flag = RegisterChangeFlag::RCF_UNREGISTER_ALL;
+    clusters_to_update->wakeup();
+}
+
 void ClusterDiscovery::findDynamicClusters(
     std::unordered_map<String, ClusterDiscovery::ClusterInfo> & info,
     std::unordered_set<size_t> * unchanged_roots)
@@ -729,6 +768,27 @@ bool ClusterDiscovery::runMainThread(std::function<void()> up_to_date_callback)
         {
             up_to_date_callback();
         }
+
+        RegisterChangeFlag flag = register_change_flag.exchange(RegisterChangeFlag::RCF_NONE);
+
+        if (flag == RegisterChangeFlag::RCF_REGISTER_ALL)
+        {
+            LOG_DEBUG(log, "Register in all dynamic clusters");
+            for (auto & [_, info] : clusters_info)
+            {
+                auto zk = context->getDefaultOrAuxiliaryZooKeeper(info.zk_name);
+                registerInZk(zk, info);
+            }
+        }
+        else if (flag == RegisterChangeFlag::RCF_UNREGISTER_ALL)
+        {
+            LOG_DEBUG(log, "Unregister in all dynamic clusters");
+            for (auto & [_, info] : clusters_info)
+            {
+                auto zk = context->getDefaultOrAuxiliaryZooKeeper(info.zk_name);
+                unregisterFromZk(zk, info);
+            }
+        }
     }
     LOG_DEBUG(log, "Worker thread stopped");
     return finished;

src/Interpreters/ClusterDiscovery.h

@@ -38,6 +38,9 @@ class ClusterDiscovery
 
     ~ClusterDiscovery();
 
+    void registerAll();
+    void unregisterAll();
+
 private:
     struct NodeInfo
     {
@@ -125,6 +128,7 @@ class ClusterDiscovery
     void initialUpdate();
 
     void registerInZk(zkutil::ZooKeeperPtr & zk, ClusterInfo & info);
+    void unregisterFromZk(zkutil::ZooKeeperPtr & zk, ClusterInfo & info);
 
     Strings getNodeNames(zkutil::ZooKeeperPtr & zk,
                          const String & zk_root,
@@ -207,6 +211,15 @@ class ClusterDiscovery
     std::shared_ptr<std::vector<std::shared_ptr<MulticlusterDiscovery>>> multicluster_discovery_paths;
 
     MultiVersion<Macros>::Version macros;
+
+    enum RegisterChangeFlag
+    {
+        RCF_NONE,
+        RCF_REGISTER_ALL,
+        RCF_UNREGISTER_ALL,
+    };
+
+    std::atomic<RegisterChangeFlag> register_change_flag = RegisterChangeFlag::RCF_NONE;
 };
 
 }

src/Interpreters/Context.cpp

@@ -188,6 +188,7 @@ namespace CurrentMetrics
     extern const Metric IcebergCatalogThreads;
     extern const Metric IcebergCatalogThreadsActive;
     extern const Metric IcebergCatalogThreadsScheduled;
+    extern const Metric IsSwarmModeEnabled;
 }
 
 
@@ -579,6 +580,7 @@ struct ContextSharedPart : boost::noncopyable
     std::map<String, UInt16> server_ports;
 
     std::atomic<bool> shutdown_called = false;
+    std::atomic<bool> swarm_mode_enabled = true;
 
     Stopwatch uptime_watch TSA_GUARDED_BY(mutex);
 
@@ -747,6 +749,8 @@ struct ContextSharedPart : boost::noncopyable
       */
     void shutdown() TSA_NO_THREAD_SAFETY_ANALYSIS
     {
+        swarm_mode_enabled = false;
+        CurrentMetrics::set(CurrentMetrics::IsSwarmModeEnabled, 0);
         bool is_shutdown_called = shutdown_called.exchange(true);
         if (is_shutdown_called)
             return;
@@ -4644,7 +4648,6 @@ std::shared_ptr<Cluster> Context::getCluster(const std::string & cluster_name) c
     throw Exception(ErrorCodes::CLUSTER_DOESNT_EXIST, "Requested cluster '{}' not found", cluster_name);
 }
 
-
 std::shared_ptr<Cluster> Context::tryGetCluster(const std::string & cluster_name) const
 {
     std::shared_ptr<Cluster> res = nullptr;
@@ -4663,6 +4666,21 @@ std::shared_ptr<Cluster> Context::tryGetCluster(const std::string & cluster_name
     return res;
 }
 
+void Context::unregisterInAutodiscoveryClusters()
+{
+    std::lock_guard lock(shared->clusters_mutex);
+    if (!shared->cluster_discovery)
+        return;
+    shared->cluster_discovery->unregisterAll();
+}
+
+void Context::registerInAutodiscoveryClusters()
+{
+    std::lock_guard lock(shared->clusters_mutex);
+    if (!shared->cluster_discovery)
+        return;
+    shared->cluster_discovery->registerAll();
+}
 
 void Context::reloadClusterConfig() const
 {
@@ -5540,12 +5558,35 @@ void Context::stopServers(const ServerType & server_type) const
     shared->stop_servers_callback(server_type);
 }
 
-
 void Context::shutdown() TSA_NO_THREAD_SAFETY_ANALYSIS
 {
     shared->shutdown();
 }
 
+bool Context::stopSwarmMode()
+{
+    bool expected_is_enabled = true;
+    bool is_stopped_now = shared->swarm_mode_enabled.compare_exchange_strong(expected_is_enabled, false);
+    if (is_stopped_now)
+        CurrentMetrics::set(CurrentMetrics::IsSwarmModeEnabled, 0);
+    // return true if stop successful
+    return is_stopped_now;
+}
+
+bool Context::startSwarmMode()
+{
+    bool expected_is_enabled = false;
+    bool is_started_now = shared->swarm_mode_enabled.compare_exchange_strong(expected_is_enabled, true);
+    if (is_started_now)
+        CurrentMetrics::set(CurrentMetrics::IsSwarmModeEnabled, 1);
+    // return true if start successful
+    return is_started_now;
+}
+
+bool Context::isSwarmModeEnabled() const
+{
+    return shared->swarm_mode_enabled;
+}
 
 Context::ApplicationType Context::getApplicationType() const
 {

src/Interpreters/Context.h

@@ -1296,6 +1296,8 @@ class Context: public ContextData, public std::enable_shared_from_this<Context>
     size_t getClustersVersion() const;
 
     void startClusterDiscovery();
+    void registerInAutodiscoveryClusters();
+    void unregisterInAutodiscoveryClusters();
 
     /// Sets custom cluster, but doesn't update configuration
     void setCluster(const String & cluster_name, const std::shared_ptr<Cluster> & cluster);
@@ -1408,6 +1410,15 @@ class Context: public ContextData, public std::enable_shared_from_this<Context>
 
     void shutdown();
 
+    /// Stop some works to allow graceful shutdown later.
+    /// Returns true if stop successful.
+    bool stopSwarmMode();
+    /// Resume some works if we change our mind.
+    /// Returns true if start successful.
+    bool startSwarmMode();
+    /// Return current swarm mode state.
+    bool isSwarmModeEnabled() const;
+
     bool isInternalQuery() const { return is_internal_query; }
     void setInternalQuery(bool internal) { is_internal_query = internal; }
 

src/Interpreters/InterpreterSystemQuery.cpp

@@ -715,6 +715,20 @@ BlockIO InterpreterSystemQuery::execute()
         case Type::START_MOVES:
             startStopAction(ActionLocks::PartsMove, true);
             break;
+        case Type::STOP_SWARM_MODE:
+        {
+            getContext()->checkAccess(AccessType::SYSTEM_SWARM);
+            if (getContext()->stopSwarmMode())
+                getContext()->unregisterInAutodiscoveryClusters();
+            break;
+        }
+        case Type::START_SWARM_MODE:
+        {
+            getContext()->checkAccess(AccessType::SYSTEM_SWARM);
+            if (getContext()->startSwarmMode())
+                getContext()->registerInAutodiscoveryClusters();
+            break;
+        }
         case Type::STOP_FETCHES:
             startStopAction(ActionLocks::PartsFetch, false);
             break;
@@ -1623,6 +1637,12 @@ AccessRightsElements InterpreterSystemQuery::getRequiredAccessForDDLOnCluster()
                 required_access.emplace_back(AccessType::SYSTEM_MOVES, query.getDatabase(), query.getTable());
             break;
         }
+        case Type::STOP_SWARM_MODE:
+        case Type::START_SWARM_MODE:
+        {
+            required_access.emplace_back(AccessType::SYSTEM_SWARM);
+            break;
+        }
         case Type::STOP_PULLING_REPLICATION_LOG:
         case Type::START_PULLING_REPLICATION_LOG:
         {

src/Parsers/ASTSystemQuery.cpp

@@ -495,6 +495,8 @@ void ASTSystemQuery::formatImpl(WriteBuffer & ostr, const FormatSettings & setti
         case Type::DROP_PAGE_CACHE:
         case Type::STOP_REPLICATED_DDL_QUERIES:
         case Type::START_REPLICATED_DDL_QUERIES:
+        case Type::STOP_SWARM_MODE:
+        case Type::START_SWARM_MODE:
             break;
         case Type::UNKNOWN:
         case Type::END:

src/Parsers/ASTSystemQuery.h

@@ -82,6 +82,8 @@ class ASTSystemQuery : public IAST, public ASTQueryWithOnCluster
         START_FETCHES,
         STOP_MOVES,
         START_MOVES,
+        STOP_SWARM_MODE,
+        START_SWARM_MODE,
         STOP_REPLICATED_SENDS,
         START_REPLICATED_SENDS,
         STOP_REPLICATION_QUEUES,

src/QueryPipeline/RemoteQueryExecutor.cpp

@@ -1034,6 +1034,11 @@ void RemoteQueryExecutor::setProfileInfoCallback(ProfileInfoCallback callback)
     profile_info_callback = std::move(callback);
 }
 
+bool RemoteQueryExecutor::skipUnavailableShards() const
+{
+    return context->getSettingsRef()[Setting::skip_unavailable_shards];
+}
+
 bool RemoteQueryExecutor::needToSkipUnavailableShard() const
 {
     return context->getSettingsRef()[Setting::skip_unavailable_shards] && (0 == connections->size());

src/QueryPipeline/RemoteQueryExecutor.h

@@ -241,6 +241,8 @@ class RemoteQueryExecutor
 
     IConnections & getConnections() { return *connections; }
 
+    bool skipUnavailableShards() const;
+
     bool needToSkipUnavailableShard() const;
 
     bool isReplicaUnavailable() const { return extension && extension->parallel_reading_coordinator && connections->size() == 0; }