ClickHouse/src/Coordination/NuKeeperStateMachine.h

#pragma once

#include <Coordination/TestKeeperStorage.h>
#include <libnuraft/nuraft.hxx>
#include <common/logger_useful.h>

namespace DB
{

class NuKeeperStateMachine : public nuraft::state_machine
{
public:
    NuKeeperStateMachine();

    nuraft::ptr<nuraft::buffer> pre_commit(const size_t /*log_idx*/, nuraft::buffer & /*data*/) override { return nullptr; }

    nuraft::ptr<nuraft::buffer> commit(const size_t log_idx, nuraft::buffer & data) override;

    void rollback(const size_t /*log_idx*/, nuraft::buffer & /*data*/) override {}

    size_t last_commit_index() override { return last_committed_idx; }

    bool apply_snapshot(nuraft::snapshot & s) override;

    nuraft::ptr<nuraft::snapshot> last_snapshot() override;

    void create_snapshot(
        nuraft::snapshot & s,
        nuraft::async_result<bool>::handler_type & when_done) override;

    void save_logical_snp_obj(
        nuraft::snapshot & s,
        size_t & obj_id,
        nuraft::buffer & data,
        bool is_first_obj,
        bool is_last_obj) override;

    int read_logical_snp_obj(
        nuraft::snapshot & s,
        void* & user_snp_ctx,
        ulong obj_id,
        nuraft::ptr<nuraft::buffer> & data_out,
        bool & is_last_obj) override;

    TestKeeperStorage & getStorage()
    {
        return storage;
    }

    TestKeeperStorage::ResponsesForSessions processReadRequest(const TestKeeperStorage::RequestForSession & requests);

private:
    struct StorageSnapshot
    {
        StorageSnapshot(const nuraft::ptr<nuraft::snapshot> & s, const TestKeeperStorage & storage_)
            : snapshot(s)
            , storage(storage_)
        {}

        nuraft::ptr<nuraft::snapshot> snapshot;
        TestKeeperStorage storage;
    };

    using StorageSnapshotPtr = std::shared_ptr<StorageSnapshot>;

    StorageSnapshotPtr createSnapshotInternal(nuraft::snapshot & s);

    static StorageSnapshotPtr readSnapshot(nuraft::snapshot & s, nuraft::buffer & in);

    static void writeSnapshot(const StorageSnapshotPtr & snapshot, nuraft::ptr<nuraft::buffer> & out);

    TestKeeperStorage storage;
    /// Mutex for snapshots
    std::mutex snapshots_lock;

    /// Lock for storage
    std::mutex storage_lock;

    /// Fake snapshot storage
    std::map<uint64_t, StorageSnapshotPtr> snapshots;

    /// Last committed Raft log number.
    std::atomic<size_t> last_committed_idx;
    Poco::Logger * log;
};

}