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73 lines
3.1 KiB
C++
73 lines
3.1 KiB
C++
#ifndef SERVER_RATE_LIMITER_H
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#define SERVER_RATE_LIMITER_H
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#include <QDateTime>
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#include <QMap>
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#include <QString>
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/**
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* @class ServerRateLimiter
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* @ingroup Utility
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* @brief Tracks per-server backoff state triggered by HTTP 429 responses.
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*
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* Keeps a monotonic backoff deadline per host and a retry-round budget that
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* escalates once per backoff window (a burst of concurrent 429s counts as a
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* single round). The budget is refreshed after a long period without 429s so a
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* server is not permanently blacklisted after a past overload.
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*/
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class ServerRateLimiter
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{
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public:
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static constexpr int MAX_RETRIES = 5; ///< Max 429 rounds per host before the budget is exhausted
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static constexpr int MIN_429_BACKOFF_MS = 30000; ///< Minimum wait after a 429 (scryfall documented cool-down)
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static constexpr int MAX_BACKOFF_MS = 60000; ///< Cap for a single backoff period
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static constexpr int EXHAUSTED_BACKOFF_MS = 60000; ///< Cool-down once the retry budget is exhausted
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static constexpr qint64 RESET_GRACE_MS = 300000; ///< Idle time after which the retry budget refreshes
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/**
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* @brief Checks whether a host is currently in backoff.
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* @param host The host to check
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* @param now The current time
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* @return True if requests to the host should be paused
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*/
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[[nodiscard]] bool isRateLimited(const QString &host, const QDateTime &now) const;
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/** @return The number of consecutive 429 rounds recorded for the host. */
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[[nodiscard]] int rounds(const QString &host) const;
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/** @return The current backoff deadline for the host, or an invalid QDateTime. */
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[[nodiscard]] QDateTime deadline(const QString &host) const;
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/** @return The earliest active backoff deadline across all hosts, or an invalid QDateTime. */
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[[nodiscard]] QDateTime earliestDeadline(const QDateTime &now) const;
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/**
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* @brief Registers a 429 response for the given host.
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* @param host The host that returned 429
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* @param now The time the response was received
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* @param retryAfterMs A Retry-After hint in milliseconds, or 0 if absent
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* @return The new backoff deadline for the host
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*
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* The round counter only escalates once the previous backoff window has
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* fully passed, so concurrent 429s from a burst do not consume the whole
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* budget. The deadline is extended monotonically and never shortened.
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*/
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QDateTime on429(const QString &host, const QDateTime &now, qint64 retryAfterMs = 0);
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/** @brief Clears all penalty state for a host after a successful request. */
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void onSuccess(const QString &host);
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/**
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* @brief Removes expired backoffs, refreshing the round budget of hosts
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* that have been idle past the reset grace period.
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* @param now The current time
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*/
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void clearExpired(const QDateTime &now);
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private:
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QMap<QString, QDateTime> backoffUntil; ///< When each host may be contacted again
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QMap<QString, int> retryRounds; ///< Consecutive 429 rounds per host
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QMap<QString, QDateTime> last429; ///< When each host was last rate limited
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};
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#endif // SERVER_RATE_LIMITER_H
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