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