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d36f52502e
It's still hackish and dirty, but server and client compies. Server starts, but throwes meaningless exception on any query. Client seems to be working fine. Linux compilation might (but shouldn't) be broken (not tested).
58 lines
1.9 KiB
C++
58 lines
1.9 KiB
C++
#pragma once
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#include <zkutil/Common.h>
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#include <string>
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#include <functional>
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namespace zkutil
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{
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/// Implementation of a distributed single barrier for ZooKeeper.
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/// Consider a barrier with N slots. A node that wants to enter this barrier
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/// creates a uniquely identified token and puts it in a free slot, then waits
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/// until all of the N slots have been taken.
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/// This implementation allows entering a barrier more than once. This is done
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/// by prefixing tokens with a tag which is an integer number representing the
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/// number of times this barrier has already been crossed. When a node attempts
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/// to puts its token into a slot, first it looks for lingering obsolete tokens,
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/// then, if found, deletes them. If a node has put its token into the last free
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/// slot, it increments the tag value.
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class SingleBarrier final
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{
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public:
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using CancellationHook = std::function<void()>;
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public:
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SingleBarrier(GetZooKeeper get_zookeeper_, const std::string & path_, size_t counter_);
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SingleBarrier(const SingleBarrier &) = delete;
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SingleBarrier & operator=(const SingleBarrier &) = delete;
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SingleBarrier(SingleBarrier &&) = default;
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SingleBarrier & operator=(SingleBarrier &&) = default;
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/// Register a function that cancels barrier operations if requested.
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void setCancellationHook(CancellationHook cancellation_hook_);
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void enter(UInt64 timeout = 0);
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private:
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/// Cancel any ongoing operation if requested. Additionally perform cleanup.
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void abortIfRequested();
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private:
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/// Helper that acquires an alive ZooKeeper session.
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GetZooKeeper get_zookeeper;
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EventPtr event = std::make_shared<Poco::Event>();
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/// Function that cancels barrier operations if requested.
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CancellationHook cancellation_hook;
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/// Path to the barrier storage.
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std::string path;
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/// Token created by the node attempting to enter the barrier.
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std::string token;
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/// Number of available slots.
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size_t counter;
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};
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}
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