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/**
*
* \section COPYRIGHT
*
* Copyright 2013-2020 Software Radio Systems Limited
*
* By using this file, you agree to the terms and conditions set
* forth in the LICENSE file which can be found at the top level of
* the distribution.
*
*/
#ifndef SRSLOG_BACKEND_WORKER_H
#define SRSLOG_BACKEND_WORKER_H
#include "srslte/srslog/detail/log_entry.h"
#include "srslte/srslog/detail/support/work_queue.h"
#include "srslte/srslog/shared_types.h"
#include <mutex>
#include <thread>
namespace srslog {
/// The backend worker runs in a secondary thread a routine that endlessly pops
/// log entries from a work queue and dispatches them to the selected sinks.
class backend_worker
{
/// This period defines the maximum time the worker will sleep while waiting
/// for new entries. This is required to check the termination variable
/// periodically.
static constexpr unsigned sleep_period_ms = 500;
public:
explicit backend_worker(detail::work_queue<detail::log_entry>& queue) :
queue(queue), running_flag(false)
{}
backend_worker(const backend_worker&) = delete;
backend_worker& operator=(const backend_worker&) = delete;
~backend_worker() { stop(); }
/// Starts the backend worker thread. After returning from this function the
/// secondary thread is ensured to be running. Calling this function more than
/// once has no effect.
void start();
/// Stops the backend worker thread if it is running, otherwise the call has
/// no effect. After returning from this function the secondary thread is
/// ensured to have terminated. Calling this function more than once has no
/// effect.
void stop();
/// Returns true if the worker thread is currently running, otherwise
/// returns false.
bool is_running() const { return running_flag; }
/// Uses the specified error handler to receive error notifications. Calls to
/// this method when the worker is running will get ignored.
void set_error_handler(error_handler new_err_handler)
{
// Ignore new handlers when the worker is running.
if (is_running()) {
return;
}
// Install a dummy callback if the input one is empty. This avoids having to
// check for null at each call site.
if (!new_err_handler) {
err_handler = [](const std::string&) {};
return;
}
err_handler = std::move(new_err_handler);
}
private:
/// Creates the worker thread.
/// NOTE: This function should be only called once.
void create_worker();
/// Entry function used by the secondary thread.
void do_work();
/// Processes the log entry.
void process_log_entry(detail::log_entry&& entry);
/// Processes outstanding entries in the queue until it gets empty.
void process_outstanding_entries();
/// Checks the current size of the queue reporting an error message if it is
/// about to reach its maximum capacity.
/// Error message is only reported once to avoid spamming.
void report_queue_on_full_once()
{
if (queue.is_almost_full()) {
err_handler(
fmt::format("The backend queue size is about to reach its maximum "
"capacity of {} elements, new log entries will get "
"discarded.\nConsider increasing the queue capacity.",
queue.get_capacity()));
err_handler = [](const std::string&) {};
}
}
private:
detail::work_queue<detail::log_entry>& queue;
detail::shared_variable<bool> running_flag;
error_handler err_handler = [](const std::string& error) {
fmt::print(stderr, "srsLog error - {}\n", error);
};
std::once_flag start_once_flag;
std::thread worker_thread;
};
} // namespace srslog
#endif // SRSLOG_BACKEND_WORKER_H