src/base/RunnersRegistry.h

   1 /*
   2  * Copyright (C) 1996-2021 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_BASE_RUNNERSREGISTRY_H
  10 #define SQUID_BASE_RUNNERSREGISTRY_H
  11
  12 /**
  13  * This API allows virtually any module to register its interest in receiving
  14  * notification about initial configuration availability, configuration changes
  15  * and other critical events in Squid lifetime without exposing the notifier
  16  * to the details of the module.
  17  *
  18  * For example, main.cc may activate registered I/O modules after parsing
  19  * squid.conf and deactivate them before exiting, all without knowing what
  20  * those I/O modules really are.
  21  *
  22  * A module in this context is code providing a functionality or service to the
  23  * rest of Squid, such as src/DiskIO/Blocking, src/fs/ufs, or Cache Manager. To
  24  * receive notifications, a module must declare a RegisteredRunner child class
  25  * and implement the methods corresponding to the events the module is
  26  * interested in.
  27  *
  28  * The order of events is documented in this header (where applicable), but
  29  * the order in which runners are notified about a given event is undefined.
  30  * If a specific notification order is required, split the event into two or
  31  * more related event(s), documenting their relative order here.
  32  *
  33  */
  34
  35 /// a runnable registrant API
  36 /// kids must override [only] the methods they are interested in
  37 class RegisteredRunner
  38 {
  39 public:
  40     /* Related methods below are declared in their calling order */
  41
  42     /* Configuration events */
  43
  44     /// Called after parsing squid.conf.
  45     /// Meant for setting configuration options that depend on other
  46     /// configuration options and were not explicitly configured.
  47     virtual void finalizeConfig() {}
  48
  49     /// Called after finalizeConfig().
  50     /// Meant for announcing memory reservations before memory is allocated.
  51     virtual void claimMemoryNeeds() {}
  52
  53     /// Called after claimMemoryNeeds().
  54     /// Meant for activating modules and features using a finalized
  55     /// configuration with known memory requirements.
  56     virtual void useConfig() {}
  57
  58     /* Reconfiguration events */
  59
  60     /// Called after receiving a reconfigure request and before parsing squid.conf.
  61     /// Meant for modules that need to prepare for their configuration being changed
  62     /// [outside their control]. The changes end with the syncConfig() event.
  63     virtual void startReconfigure() {}
  64
  65     /// Called after parsing squid.conf during reconfiguration.
  66     /// Meant for adjusting the module state based on configuration changes.
  67     virtual void syncConfig() {}
  68
  69     /* Shutdown events */
  70
  71     /// Called after receiving a shutdown request and before stopping the main
  72     /// loop. At least one main loop iteration is guaranteed after this call.
  73     /// Meant for cleanup and state saving that may require other modules.
  74     virtual void startShutdown() {}
  75
  76     /// Called after shutdown_lifetime grace period ends and before stopping
  77     /// the main loop. At least one main loop iteration is guaranteed after
  78     /// this call.
  79     /// Meant for cleanup and state saving that may require other modules.
  80     virtual void endingShutdown() {}
  81
  82     /// Called after stopping the main loop and before releasing memory.
  83     /// Meant for quick/basic cleanup that does not require any other modules.
  84     virtual ~RegisteredRunner() {}
  85
  86     /// Meant for cleanup of services needed by the already destroyed objects.
  87     virtual void finishShutdown() {}
  88
  89     /// a pointer to one of the above notification methods
  90     typedef void (RegisteredRunner::*Method)();
  91
  92 };
  93
  94 /// registers a given runner with the given registry and returns true on success
  95 bool RegisterRunner(RegisteredRunner *rr);
  96
  97 /// Calls a given method of all runners.
  98 /// All runners are destroyed after the finishShutdown() call.
  99 void RunRegistered(const RegisteredRunner::Method &m);
 100
 101 /// A RegisteredRunner with lifetime determined by forces outside the Registry.
 102 class IndependentRunner: public RegisteredRunner
 103 {
 104 public:
 105     virtual ~IndependentRunner() { unregisterRunner(); }
 106
 107 protected:
 108     void registerRunner();
 109     void unregisterRunner(); ///< unregisters self; safe to call multiple times
 110 };
 111
 112 /// convenience macro to describe/debug the caller and the method being called
 113 #define RunRegisteredHere(m) \
 114     debugs(1, 2, "running " # m); \
 115     RunRegistered(&m)
 116
 117 /// convenience function to "use" an otherwise unreferenced static variable
 118 bool UseThisStatic(const void *);
 119
 120 /// convenience macro: register one RegisteredRunner kid as early as possible
 121 #define RunnerRegistrationEntry(Who) \
 122     static const bool Who ## _Registered_ = \
 123         RegisterRunner(new Who) > 0 && \
 124         UseThisStatic(& Who ## _Registered_);
 125
 126 #endif /* SQUID_BASE_RUNNERSREGISTRY_H */
 127