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#ifndef _LIBEXPERIMENTS_EXPERIMENTS_H
#define _LIBEXPERIMENTS_EXPERIMENTS_H
#include <inttypes.h>
// Implements a library that supports the Gfiber Experiments framework, as
// explained in the following doc: go/gfiber-experiments-framework.
//
// Both C and C++ (class) implementations are available.
//
// C++ example:
// ====================================
// const char* kConfigFolderPath[] = "/fiber/config/experiments";
// int64_t kMinTimeBetweenRefreshUs = 60 * 1000 * 1000; // 60 secs
// e = new Experiments();
// if (!e->Initialize(kConfigFolderPath, kMinTimeBetweenRefreshUs,
// {"exp1", "exp2"})) {
// // handle error case
// }
//
// // later in the code
// if (e->IsEnabled("exp1")) {
// // exp1 is enabled
// [..]
// }
//
// C example:
// ===================================
// const char* kConfigFolderPath[] = "/fiber/config/experiments";
// int64_t kMinTimeBetweenRefreshUs = 60 * 1000 * 1000; // 60 secs
// if (!experiments_initialize(kConfigFolderPath, kMinTimeBetweenRefreshUs,
// NULL); // use default register function
// // handle error case
// }
//
// experiments_register("exp1");
// experiments_register("exp2");
//
// // later in the code
// if (experiments_is_enabled("exp1")) {
// // exp1 is enabled
// [..]
// }
#ifdef __cplusplus
extern "C" {
#endif
// Function called when registering a new experiment.
// Returns non-zero (boolean true) for success, else 0 (boolean false).
typedef int (*experiments_register_func_t) (const char *name);
// Default experiment register function. Calls the shell script
// "register_experiment <name>".
int DefaultExperimentsRegisterFunc(const char *name);
// Dummy experiment register function. Just returns true.
int DummyExperimentsRegisterFunc(const char *name);
#ifdef __cplusplus
}
#endif
//
// C++ implementation
//
#ifdef __cplusplus
#include <atomic>
#include <mutex> // NOLINT
#include <set>
#include <string>
#include <vector>
class Experiments {
public:
Experiments()
: initialized_(false),
min_time_between_refresh_usec_(0),
last_time_refreshed_usec_(0) {}
virtual ~Experiments() {}
// Initializes the instance and registers any provided experiments. In detail:
// * Sets the provided experiments config directory and register function and
// makes sure they are valid. If successful the instance is marked as
// initialized.
// * Calls the register function for the provided experiment names.
// * Scans the config folder to determine initial state of all registered
// experiments.
// The min_time_between_refresh_usec values sets a lower boundary on how
// often the config folder is scanned for updated experiment states.
// Returns true if successful.
bool Initialize(const std::string &config_dir,
int64_t min_time_between_refresh_usec,
experiments_register_func_t register_func,
const std::vector<std::string> &names_to_register);
// Convenience version, using default experiments register function.
bool Initialize(const std::string &config_dir,
int64_t min_time_between_refresh_usec,
const std::vector<std::string> &names_to_register) {
return Initialize(config_dir, min_time_between_refresh_usec,
&DefaultExperimentsRegisterFunc, names_to_register);
}
bool IsInitialized() const { return initialized_; }
// Registers the provided experiment(s).
bool Register(const std::vector<std::string> &names);
bool Register(const std::string &name) {
std::vector<std::string> names{name};
return Register(names);
}
int GetNumOfRegisteredExperiments() const {
return registered_experiments_.size();
}
// Returns true if the given experiment is registered.
bool IsRegistered(const std::string &name);
// Returns true if the given experiment is active, else false. If the minimum
// time between refreshes has passed, re-scans the config folder for updates
// first.
bool IsEnabled(const std::string &name);
private:
// Registers the given experiments. Unlocked version takes lock_ first.
// Returns true if successful, else false.
bool Register_Unlocked(const std::vector<std::string> &names);
bool Register_Locked(const std::vector<std::string> &names);
// Returns true if the given experiment is in the list of registered
// experiments.
bool IsInRegisteredList(const std::string &name) const {
return registered_experiments_.find(name) != registered_experiments_.end();
}
// Refreshes all registered experiment states by scanning the config folder.
void Refresh();
// Updates the state of the given experiment by checking its file in the
// config folder.
void UpdateState(const std::string &name);
// Returns true if the given experiment is in the list of enabled
// experiments.
bool IsInEnabledList(const std::string &name) {
return enabled_experiments_.find(name) != enabled_experiments_.end();
}
std::atomic<bool> initialized_;
std::mutex lock_;
// Experiments config folder, containing the system-wide list of experiments.
// An experiment is marked active if the folder contains the file named
// "<experiment_name>.active".
std::string config_dir_;
// External function called to register an experiment.
experiments_register_func_t register_func_;
std::set<std::string> registered_experiments_;
std::set<std::string> enabled_experiments_;
// Minimum time between accessing the config folder to refresh the experiment
// states. When set to 0 it refreshes on every call to IsEnabled().
uint64_t min_time_between_refresh_usec_;
uint64_t last_time_refreshed_usec_;
};
extern Experiments *experiments;
#endif // __cplusplus
//
// C-based API
//
#ifdef __cplusplus
extern "C" {
#endif
// Creates and initializes the experiments object:
// * Sets the provided experiments config directory and register function.
// * Calls the register function for the provided experiment names.
// * Scans the config folder to determine initial state of all registered
// experiments.
// The min_time_between_refresh_usec values sets a lower boundary on how often
// the config folder is scanned for updated experiment states. Set
// register_func to NULL to use the default register function
// (DefaultExperimentsRegisterFunc()).
// Returns non-zero (boolean true) if successful, 0 (boolean false) for error.
int experiments_initialize(const char *config_dir,
int64_t min_time_between_refresh_usec,
experiments_register_func_t register_func);
// Returns non-zero (boolean true) if the experiments object is initialized,
// else 0 (boolean false).
int experiments_is_initialized();
// Registers the provided experiment.
// Returns non-zero (boolean true) if successful, 0 (boolean false) for error.
int experiments_register(const char *name);
// Returns non-zero (boolean true) if the given experiment name is registered,
// else 0 (boolean false).
int experiments_is_registered(const char *name);
// Returns the number of experiments registered.
int experiments_get_num_of_registered_experiments();
// Returns non-zero (boolean true) if the given experiment is active, else 0
// (boolean false). If the minimum time between refreshes has passed, re-scans
// the config folder for updates first.
int experiments_is_enabled(const char *name);
#ifdef __cplusplus
}
#endif
#endif // _LIBEXPERIMENTS_EXPERIMENTS_H