clio/src/data/LedgerCache.hpp

#pragma once

#include "data/LedgerCacheInterface.hpp"
#include "data/Types.hpp"
#include "etl/Models.hpp"
#include "util/prometheus/Bool.hpp"
#include "util/prometheus/Counter.hpp"
#include "util/prometheus/Label.hpp"
#include "util/prometheus/Prometheus.hpp"

#include <xrpl/basics/base_uint.h>
#include <xrpl/basics/hardened_hash.h>

#include <condition_variable>
#include <cstddef>
#include <cstdint>
#include <functional>
#include <map>
#include <optional>
#include <shared_mutex>
#include <string>
#include <unordered_set>
#include <vector>

namespace data {

/**
 * @brief Cache for an entire ledger.
 */
class LedgerCache : public LedgerCacheInterface {
public:
    /** @brief An entry of the cache */
    struct CacheEntry {
        uint32_t seq = 0;
        Blob blob;
    };

    using CacheMap = std::map<xrpl::uint256, CacheEntry>;

private:
    // counters for fetchLedgerObject(s) hit rate
    std::reference_wrapper<util::prometheus::CounterInt> objectReqCounter_{
        PrometheusService::counterInt(
            "ledger_cache_counter_total_number",
            util::prometheus::Labels({{"type", "request"}, {"fetch", "ledger_objects"}}),
            "LedgerCache statistics"
        )
    };
    std::reference_wrapper<util::prometheus::CounterInt> objectHitCounter_{
        PrometheusService::counterInt(
            "ledger_cache_counter_total_number",
            util::prometheus::Labels({{"type", "cache_hit"}, {"fetch", "ledger_objects"}})
        )
    };

    // counters for fetchSuccessorKey hit rate
    std::reference_wrapper<util::prometheus::CounterInt> successorReqCounter_{
        PrometheusService::counterInt(
            "ledger_cache_counter_total_number",
            util::prometheus::Labels({{"type", "request"}, {"fetch", "successor_key"}}),
            "ledgerCache"
        )
    };
    std::reference_wrapper<util::prometheus::CounterInt> successorHitCounter_{
        PrometheusService::counterInt(
            "ledger_cache_counter_total_number",
            util::prometheus::Labels({{"type", "cache_hit"}, {"fetch", "successor_key"}})
        )
    };

    CacheMap map_;
    CacheMap deleted_;

    mutable std::shared_mutex mtx_;
    std::condition_variable_any cv_;
    uint32_t latestSeq_ = 0;
    util::prometheus::Bool full_{PrometheusService::boolMetric(
        "ledger_cache_full",
        util::prometheus::Labels{},
        "Whether ledger cache full or not"
    )};
    util::prometheus::Bool disabled_{PrometheusService::boolMetric(
        "ledger_cache_disabled",
        util::prometheus::Labels{},
        "Whether ledger cache is disabled or not"
    )};
    util::prometheus::Bool isCurrentlyLoading_{
        PrometheusService::boolMetric(
            "ledger_cache_is_currently_loading",
            util::prometheus::Labels{},
            "Whether ledger cache is currently loading or not"
        )

    };

    // temporary set to prevent background thread from writing already deleted data. not used when
    // cache is full
    std::unordered_set<xrpl::uint256, xrpl::HardenedHash<>> deletes_;

public:
    void
    update(std::vector<LedgerObject> const& objs, uint32_t seq, bool isBackground) override;

    void
    update(std::vector<etl::model::Object> const& objs, uint32_t seq) override;

    std::optional<Blob>
    get(xrpl::uint256 const& key, uint32_t seq) const override;

    std::optional<Blob>
    getDeleted(xrpl::uint256 const& key, uint32_t seq) const override;

    std::optional<LedgerObject>
    getSuccessor(xrpl::uint256 const& key, uint32_t seq) const override;

    std::optional<LedgerObject>
    getPredecessor(xrpl::uint256 const& key, uint32_t seq) const override;

    void
    setDisabled() override;

    bool
    isDisabled() const override;

    void
    setFull() override;

    uint32_t
    latestLedgerSequence() const override;

    bool
    isFull() const override;

    size_t
    size() const override;

    float
    getObjectHitRate() const override;

    float
    getSuccessorHitRate() const override;

    void
    waitUntilCacheContainsSeq(uint32_t seq) override;

    std::expected<void, std::string>
    saveToFile(std::string const& path) const override;

    std::expected<void, std::string>
    loadFromFile(std::string const& path, uint32_t minLatestSequence) override;

    void
    startLoading() override;

    [[nodiscard]] bool
    isCurrentlyLoading() const override;
};

}  // namespace data