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97f2a2213e
* Move some code outside dbms/src folder * Fix paths
65 lines
1.6 KiB
C++
65 lines
1.6 KiB
C++
#pragma once
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#include <unordered_map>
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#include <unordered_set>
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#include <mutex>
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#include <memory>
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#include <optional>
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#include <Poco/Event.h>
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#include "ZooKeeper.h"
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#include "Common.h"
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namespace DB
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{
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namespace ErrorCodes
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{
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}
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}
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namespace zkutil
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{
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/// This class allows querying the contents of ZooKeeper nodes and caching the results.
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/// Watches are set for cached nodes and for nodes that were nonexistent at the time of query.
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/// After a watch fires, the callback or event that was passed by the user is notified.
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///
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/// NOTE: methods of this class are not thread-safe.
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///
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/// Intended use case: if you need one thread to watch changes in several nodes.
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/// If instead you use simple a watch event for this, watches will accumulate for nodes that do not change
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/// or change rarely.
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class ZooKeeperNodeCache
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{
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public:
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ZooKeeperNodeCache(GetZooKeeper get_zookeeper);
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ZooKeeperNodeCache(const ZooKeeperNodeCache &) = delete;
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ZooKeeperNodeCache(ZooKeeperNodeCache &&) = default;
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struct ZNode
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{
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bool exists = false;
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std::string contents;
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Coordination::Stat stat{};
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};
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ZNode get(const std::string & path, EventPtr watch_event);
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ZNode get(const std::string & path, Coordination::WatchCallback watch_callback);
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private:
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GetZooKeeper get_zookeeper;
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struct Context
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{
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std::mutex mutex;
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std::unordered_set<std::string> invalidated_paths;
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bool all_paths_invalidated = false;
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};
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std::shared_ptr<Context> context;
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std::unordered_map<std::string, ZNode> path_to_cached_znode;
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};
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}
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