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87f0b480bf
`ResponseExpirationCache` is using only `method` (or `command`) as a key, but responses might be different with different params. This may lead to a client getting incorrect response because of caching. This PR fixes it by caching only requests without any additional params.
132 lines
3.8 KiB
C++
132 lines
3.8 KiB
C++
#pragma once
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#include "util/Mutex.hpp"
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#include <boost/json/object.hpp>
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#include <chrono>
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#include <optional>
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#include <shared_mutex>
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#include <string>
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#include <unordered_map>
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#include <unordered_set>
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namespace util {
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/**
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* @brief Cache of requests' responses with TTL support and configurable cacheable commands
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*/
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class ResponseExpirationCache {
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/**
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* @brief A class to store a cache entry.
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*/
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class Entry {
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std::chrono::steady_clock::time_point lastUpdated_;
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std::optional<boost::json::object> response_;
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public:
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/**
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* @brief Put a response into the cache
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*
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* @param response The response to store
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*/
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void
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put(boost::json::object response);
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/**
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* @brief Get the response from the cache
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*
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* @return The response
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*/
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[[nodiscard]] std::optional<boost::json::object>
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get() const;
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/**
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* @brief Get the last time the cache was updated
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*
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* @return The last time the cache was updated
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*/
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[[nodiscard]] std::chrono::steady_clock::time_point
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lastUpdated() const;
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/**
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* @brief Invalidate the cache entry
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*/
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void
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invalidate();
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};
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std::chrono::steady_clock::duration cacheTimeout_;
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std::unordered_map<std::string, util::Mutex<Entry, std::shared_mutex>> cache_;
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bool
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shouldCache(std::string const& cmd);
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/**
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* @brief Check whether a request is "bare" (carries no response-customizing params).
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*
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* A request is bare iff every key it contains is one of: "command", "method", "id".
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* Any other key (e.g. "api_version", "hash", "counters", "ledger_index") makes the request
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* non-bare, and the cache must be bypassed for it.
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*
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* @param request The request object to inspect
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* @return true if the request is bare; false otherwise
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*/
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static bool
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isBareRequest(boost::json::object const& request);
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public:
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/**
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* @brief Construct a new Cache object
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*
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* @param cacheTimeout The time for cache entries to expire
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* @param cmds The commands that should be cached
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*/
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ResponseExpirationCache(
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std::chrono::steady_clock::duration cacheTimeout,
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std::unordered_set<std::string> const& cmds
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)
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: cacheTimeout_(cacheTimeout)
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{
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for (auto const& command : cmds) {
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cache_.emplace(command, Entry{});
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}
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}
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/**
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* @brief Get a response from the cache
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*
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* Only bare requests (those carrying no response-customizing params beyond "command", "method",
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* and "id") are served from the cache. Non-bare requests always return std::nullopt.
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*
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* @param cmd The command to get the response for
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* @param request The full request object; used to determine whether the request is bare
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* @return The cached response if available and not expired, or std::nullopt otherwise
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*/
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[[nodiscard]] std::optional<boost::json::object>
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get(std::string const& cmd, boost::json::object const& request) const;
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/**
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* @brief Put a response into the cache if the request should be cached
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*
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* Only bare requests (those carrying no response-customizing params beyond "command", "method",
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* and "id") are stored in the cache. Non-bare requests are silently ignored.
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*
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* @param cmd The command to store the response for
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* @param request The full request object; used to determine whether the request is bare
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* @param response The response to store
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*/
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void
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put(std::string const& cmd,
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boost::json::object const& request,
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boost::json::object const& response);
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/**
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* @brief Invalidate all entries in the cache
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*/
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void
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invalidate();
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};
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} // namespace util
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