hphp/util/health-monitor-types.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com)  |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #ifndef incl_HPHP_HOST_HEALTH_MONITOR_TYPES_H_
  18 #define incl_HPHP_HOST_HEALTH_MONITOR_TYPES_H_
  19
  20 #include <string>
  21
  22 #include <folly/Likely.h>
  23
  24 namespace HPHP {
  25 ////////////////////////////////////////////////////////////////////////////////
  26
  27 /*
  28  * The enum type for describing various system health level.  The
  29  * system health monitor will expose one of the listed health level.
  30  *
  31  * Beware if you change the order or the numerical values, as we
  32  * assume smaller numbers indicating better health condition here.
  33  */
  34 enum class HealthLevel {
  35   Bold = 0,
  36   Moderate = 1,
  37   Cautious = 2,
  38   NoMore = 3,
  39   BackOff = 4,
  40   NumLevels = 5                  // insert new values before NumLevels
  41 };
  42
  43 /*
  44  * The interface of specific system metrics used by the system health
  45  * monitor.
  46  */
  47 struct IHealthMonitorMetric {
  48   virtual ~IHealthMonitorMetric() {}
  49   virtual HealthLevel evaluate() = 0;
  50   virtual bool enabled() = 0;
  51   void registerSelf();           // register the metric in the monitor
  52 };
  53
  54 /*
  55  * The interface for observers which subscribe the output of the
  56  * system health monitor.
  57  */
  58 struct IHostHealthObserver {
  59   virtual ~IHostHealthObserver() {}
  60   virtual void notifyNewStatus(HealthLevel newStatus) = 0;
  61   virtual HealthLevel getHealthLevel() = 0;
  62 };
  63
  64 /*
  65  * Helper function to convert HealthLevel enum value to integer number that is
  66  * bigger for better health condition.
  67  */
  68 inline int64_t healthLevelToInt(HealthLevel level) {
  69   constexpr int32_t kMaxHealth = 100;
  70   // Smaller HealthLevel indicates better health condition, under
  71   // which this function returns a bigger number.
  72   static_assert(static_cast<int>(HealthLevel::Bold) == 0, "");
  73   constexpr int32_t kMaxLevel =
  74     static_cast<int32_t>(HealthLevel::NumLevels) - 1;
  75   if (LIKELY(level == HealthLevel::Bold)) {
  76     return kMaxHealth;
  77   }
  78   auto const result = kMaxHealth *
  79     (kMaxLevel - static_cast<int32_t>(level)) / kMaxLevel;
  80   return result;
  81 }
  82
  83 ////////////////////////////////////////////////////////////////////////////////
  84 }
  85
  86 #endif