hook.hpp

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#pragma once
 
/// @file userver/error_injection/hook.hpp
/// @brief @copybrief error_injection::Hook
 
#include <userver/engine/deadline.hpp>
#include <userver/engine/sleep.hpp>
#include <userver/error_injection/settings.hpp>
#include <userver/logging/log.hpp>
#include <userver/tracing/span.hpp>
 
USERVER_NAMESPACE_BEGIN
 
/// Artificial errors injection framework
namespace error_injection {
 
/// @brief Single-operation error injection: call PreHook(), run work, then PostHook()
class Hook final {
public:
    explicit Hook(const Settings& settings, engine::Deadline deadline);
 
    /// Must be called just before actual operation. May sleep for some time,
    /// throw an exception, or do nothing.
    /// @throws TimeoutException in case of artificial timeout
    /// @throws ErrorException in case of artificial error
    template <typename TimeoutException, typename ErrorException>
    void PreHook() {
        if (verdict_ == Verdict::kSkip) {
            // fast path
            return;
        }
 
        switch (verdict_) {
            case Verdict::kError:
                LOG_ERROR() << "Error injection hook triggered verdict: error";
                throw ErrorException{"error injection"};
 
            case Verdict::kTimeout:
                LOG_ERROR() << "Error injection hook triggered verdict: timeout";
                {
                    auto scope_time = tracing::Span::CurrentSpan().CreateScopeTime("error_injection_timeout");
                    engine::InterruptibleSleepUntil(deadline_);
                }
                throw TimeoutException{"error injection"};
 
            case Verdict::kMaxDelay:
            case Verdict::kRandomDelay:
            case Verdict::kSkip:
                // pass
                ;
        }
    }
 
    /// Must be called just after operation. May sleep for some time,
    /// or do nothing.
    void PostHook() {
        if (verdict_ == Verdict::kSkip) {
            // fast path
            return;
        }
 
        const engine::Deadline deadline = CalcPostHookDeadline();
        if (deadline.IsReached()) {
            return;
        }
 
        LOG_ERROR() << "Error injection hook triggered verdict: max-delay / random-delay";
        auto scope_time = tracing::Span::CurrentSpan().CreateScopeTime("error_injection_delay");
        engine::InterruptibleSleepUntil(deadline);
    }
 
private:
    engine::Deadline CalcPostHookDeadline();
 
    static Verdict ReturnVerdict(const Settings& settings);
 
    const Verdict verdict_;
    const engine::Deadline deadline_;
};
 
}  // namespace error_injection
 
USERVER_NAMESPACE_END