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#pragma once
#include <Interpreters/DDLWorker.h>
#include <Common/ZooKeeper/ZooKeeper.h>
namespace DB
{
class DatabaseReplicated;
/// It's similar to DDLWorker, but has the following differences:
/// 1. DDL queue in ZooKeeper is not shared between multiple clusters and databases,
/// each DatabaseReplicated has its own queue in ZooKeeper and DatabaseReplicatedDDLWorker object.
/// 2. Shards and replicas are identified by shard_name and replica_name arguments of database engine,
/// not by address:port pairs. Cluster (of multiple database replicas) is identified by its zookeeper_path.
/// 3. After creation of an entry in DDL queue initiator tries to execute the entry locally
/// and other hosts wait for query to finish on initiator host.
/// If query succeed on initiator, then all hosts must execute it, so they will retry until query succeed.
/// We assume that cluster is homogeneous, so if replicas are in consistent state and query succeed on one host,
/// then all hosts can execute it (maybe after several retries).
/// 4. Each database replica stores its log pointer in ZooKeeper. Cleanup thread removes old entry
/// if its number < max_log_ptr - logs_to_keep.
class DatabaseReplicatedDDLWorker : public DDLWorker
{
public:
DatabaseReplicatedDDLWorker(DatabaseReplicated * db, ContextPtr context_);
String enqueueQuery(DDLLogEntry & entry) override;
String tryEnqueueAndExecuteEntry(DDLLogEntry & entry, ContextPtr query_context);
void shutdown() override;
bool waitForReplicaToProcessAllEntries(UInt64 timeout_ms);
static String enqueueQueryImpl(const ZooKeeperPtr & zookeeper, DDLLogEntry & entry,
DatabaseReplicated * const database, bool committed = false); /// NOLINT
UInt32 getLogPointer() const;
private:
bool initializeMainThread() override;
void initializeReplication();
void initializeLogPointer(const String & processed_entry_name);
DDLTaskPtr initAndCheckTask(const String & entry_name, String & out_reason, const ZooKeeperPtr & zookeeper) override;
bool canRemoveQueueEntry(const String & entry_name, const Coordination::Stat & stat) override;
DatabaseReplicated * const database;
mutable std::mutex mutex;
std::condition_variable wait_current_task_change;
String current_task;
std::atomic<UInt32> logs_to_keep = std::numeric_limits<UInt32>::max();
/// EphemeralNodeHolder has reference to ZooKeeper, it may become dangling
ZooKeeperPtr active_node_holder_zookeeper;
/// It will remove "active" node when database is detached
zkutil::EphemeralNodeHolderPtr active_node_holder;
};
}
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