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88 lines
4.0 KiB
C++
88 lines
4.0 KiB
C++
#pragma once
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#include <Poco/Util/ServerApplication.h>
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#include <daemon/BaseDaemon.h>
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/* clickhouse cluster copier util
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* Copies tables data from one cluster to new tables of other (possibly the same) cluster in distributed fault-tolerant manner.
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*
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* See overview in the docs: docs/en/utils/clickhouse-copier.md
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*
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* Implementation details:
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*
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* cluster-copier workers pull each partition of each shard of the source cluster and push it to the destination cluster through
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* Distributed table (to preform data resharding). So, worker job is a partition of a source shard.
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* A job has three states: Active, Finished and Abandoned. Abandoned means that worker died and did not finish the job.
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*
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* If an error occurred during the copying (a worker failed or a worker did not finish the INSERT), then the whole partition (on
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* all destination servers) should be dropped and refilled. So, copying entity is a partition of all destination shards.
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* If a failure is detected a special /is_dirty node is created in ZooKeeper signalling that other workers copying the same partition
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* should stop, after a refilling procedure should start.
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*
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* ZooKeeper task node has the following structure:
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* /task/path_root - path passed in --task-path parameter
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* /description - contains user-defined XML config of the task
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* /task_active_workers - contains ephemeral nodes of all currently active workers, used to implement max_workers limitation
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* /server_fqdn#PID_timestamp - cluster-copier worker ID
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* ...
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* /tables - directory with table tasks
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* /cluster.db.table1 - directory of table_hits task
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* /partition1 - directory for partition1
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* /shards - directory for source cluster shards
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* /1 - worker job for the first shard of partition1 of table test.hits
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* Contains info about current status (Active or Finished) and worker ID.
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* /2
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* ...
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* /partition_active_workers
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* /1 - for each job in /shards a corresponding ephemeral node created in /partition_active_workers
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* It is used to detect Abandoned jobs (if there is Active node in /shards and there is no node in
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* /partition_active_workers).
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* Also, it is used to track active workers in the partition (when we need to refill the partition we do
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* not DROP PARTITION while there are active workers)
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* /2
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* ...
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* /is_dirty - the node is set if some worker detected that an error occurred (the INSERT is failed or an Abandoned node is
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* detected). If the node appeared workers in this partition should stop and start cleaning and refilling
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* partition procedure.
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* During this procedure a single 'cleaner' worker is selected. The worker waits for stopping all partition
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* workers, removes /shards node, executes DROP PARTITION on each destination node and removes /is_dirty node.
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* /cleaner- An ephemeral node used to select 'cleaner' worker. Contains ID of the worker.
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* /cluster.db.table2
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* ...
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*/
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namespace DB
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{
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class ClusterCopierApp : public BaseDaemon
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{
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public:
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void initialize(Poco::Util::Application & self) override;
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void handleHelp(const std::string &, const std::string &);
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void defineOptions(Poco::Util::OptionSet & options) override;
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int main(const std::vector<std::string> &) override;
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private:
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using Base = BaseDaemon;
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void mainImpl();
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std::string config_xml_path;
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std::string task_path;
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std::string log_level = "trace";
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bool is_safe_mode = false;
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double copy_fault_probability = 0;
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bool is_help = false;
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std::string base_dir;
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std::string process_path;
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std::string process_id;
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std::string host_id;
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};
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}
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