#pragma once

#include <memory>

#include "envoy/common/pure.h"

namespace Envoy {

namespace Upstream {

/**

 * A monitor for "passive" health check events that might happen on every thread. For example, if a

 * special HTTP header is received, the data plane may decide to fast fail a host to avoid waiting

 * for the full Health Check interval to elapse before determining the host is active health check

 * failed.

 */

class HealthCheckHostMonitor {

public:

  /**

   * The reason the host is being set unhealthy via the monitor.

   */

  enum class UnhealthyType {

    // Protocol indication (e.g., x-envoy-immediate-health-check-fail) that the host should be

    // immediately taken out of rotation.

    ImmediateHealthCheckFail

  };

  /**

   * Mark the host as unhealthy. Note that this may not be immediate as events may need to be

   * propagated between multiple threads.

   * @param type specifies the reason the host is being marked unhealthy.

   */

  virtual void setUnhealthy(UnhealthyType type) PURE;

};

using HealthCheckHostMonitorPtr = std::unique_ptr<HealthCheckHostMonitor>;

} // namespace Upstream

} // namespace Envoy