log_sink_buffer.h

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/**
  @file log_sink_buffer.h
 
  This file contains
 
  a) the API for the log-sink that buffers errors logged during start-up
  so they can be flushed once all configured log-components have become
  available;
 
  b) the API for querying and setting the phase the server is in
  with regard to logging (buffering, normal operation, and so forth);
 
  c) the API for flushing the buffered information (to force writing
  out this information in cases of early shutdowns and so on).
*/
 
#ifndef LOG_SINK_BUFFER_H
#define LOG_SINK_BUFFER_H
 
#include "log_builtins_internal.h"
#include "my_sys.h"
 
extern mysql_mutex_t THR_LOCK_log_buffered;  // let log_builtins init/destroy
 
enum log_sink_buffer_flush_mode {
  LOG_BUFFER_DISCARD_ONLY,        ///< discard all buffered log-events
  LOG_BUFFER_PROCESS_AND_DISCARD  ///< process+discard buffered log-events
};
 
enum log_error_stage {
  LOG_ERROR_STAGE_BUFFERING,           ///< no log-destination yet
  LOG_ERROR_STAGE_COMPONENTS,          ///< external services available
  LOG_ERROR_STAGE_COMPONENTS_AND_PFS,  ///< full logging incl. to pfs
  LOG_ERROR_STAGE_SHUTTING_DOWN        ///< no external components
};
 
struct log_line_buffer {
  log_line ll;            ///< log-event we're buffering
  log_line_buffer *next;  ///< chronologically next log-event
};
 
/// Set error-logging stage hint (e.g. are loadable services available yet?).
void log_error_stage_set(enum log_error_stage les);
 
/// What mode is error-logging in (e.g. are loadable services available yet)?
enum log_error_stage log_error_stage_get(void);
 
/// Write a log-event to the buffer sink.
int log_sink_buffer(void *instance [[maybe_unused]], log_line *ll);
 
/**
  Release all buffered log-events (discard_error_log_messages()),
  optionally after running them through the error log stack first
  (flush_error_log_messages()). Safe to call repeatedly (though
  subsequent calls will only output anything if further events
  occurred after the previous flush).
 
  @param  mode  LOG_BUFFER_DISCARD_ONLY (to just
                throw away the buffered events), or
                LOG_BUFFER_PROCESS_AND_DISCARD to
                filter/print them first
*/
void log_sink_buffer_flush(enum log_sink_buffer_flush_mode mode);
 
/**
  Prepend a list of log-events to the already buffered events.
 
  @param[in]  head  Head of the list to prepend to the main list
  @param[out] tail  Pointer to the `next` pointer in last element to prepend
*/
void log_sink_buffer_prepend_list(log_line_buffer *head,
                                  log_line_buffer **tail);
 
#endif /* LOG_SINK_BUFFER_H */