Man Linux: Main Page and Category List


       logsys_overview - Logsys Library Overview


       The  logsys  library  provides a generically usable logging and tracing
       system for use by applications.  It supports many features including:

       Configurable subsystem logging or single system logging

       Threaded non-blocking logging  of  log  output  data  for  better  non-
       blocking performance

       Support  for  8  tracing levels and tracing the entering and leaving of

       Declaration  of  logging  system  or  subsystem  without  calling   any

       Dynamic reconfiguration of the logging system parameters

       Logging to syslog, file, stderr.

Declaration of the System logger

       The  logsys  library  is initially configured by including logsys.h and
       declaring a logger.  Once the logger is  declared,  optional  subsystem
       loggers can be declared in every file.

       The  definition  LOGSYS_DECLARE_SYSTEM  is  placed  after  the  include
       section of one C file in the application.  This declaration  creates  a
       constructor  function  which will be called automatically before main()
       is executed.  This technique avoids the  need  for  calling  any  setup
       functions  in short applications that don’t require it and enables full
       logging capabilities before any application code is executed.

       #define LOGSYS_DECLARE_SYSTEM (name, mode, debug, file,  file_priority,
       syslog_facility, syslog_priority, format, fltsize)

       The name parameter is the name of the application or system.

       The  mode  parameter  is the logging mode of the system.  The following
       modes can be configured by logically ORing these flags:

       LOGSYS_MODE_OUTPUT_FILE: Output all log data to the file  parameter  of
       this declaration

       LOGSYS_MODE_OUTPUT_STDERR: Output all log data to the stderr descriptor

       LOGSYS_MODE_OUTPUT_SYSLOG: Output all log data to syslog using  a  non-
       blocking thread

       LOGSYS_MODE_FORK:  This flags tells logsys to queue all data untill the
       application has forked. The application is  then  responsible  to  call
       logsys_fork_completed to flush the queue and start logging.

       LOGSYS_MODE_THREADED:  Starts  a separate thread to handle non-blocking
       logging operations.   If  this  flag  is  not  specified,  the  logging
       operations are blocking.

       The  debug  parameter,  if  enabled,  turns  off  all messages priority
       filtering, recording everything everywhere.

       The file parameter specifies the filename that should be  used  to  log
       messages.   This parameter may be NULL and no log file will be created.

       The file_priority parameter specifies the message priority that  should
       be logged to file.

       The  syslog_facility  parameter  is  the syslog facility that should be
       used when logging messages.

       The syslog_priority, similar to file_priority,  specifies  the  message
       priority that should be logged to syslog.

       The  format  parameter allows to set custom output format.  Set to NULL
       to use built-in default.

       The fltsize parameter specifies the  flight  recorder  buffer  size  in
       bytes.  The requested value is increased by the size of 2 unsigned ints
       and rounded to the next PAGE_SIZE.

       An example declaration would be:

       #include <corosync/logsys.h>

       LOGSYS_DECLARE_SYSTEM ("test",                            /* name */
               0,                                                /* debug */
               NULL,                                              /*   logfile
       path */
               LOGSYS_LEVEL_INFO,                                           /*
       logfile_priority */
               LOG_DAEMON,                                         /*   syslog
       facility */
               LOGSYS_LEVEL_INFO,                                  /*   syslog
       level */
               NULL,                                                /*     use
       default format */
               1000000);                                           /*   flight
       recorder size */

Declaration of subsystems

       The logsys library supports the logging  of  information  to  one  main
       system  or  subsystem.   This  is specified in each individual object C
       file in the system and it is entirely optional.

       An example:

       LOGSYS_DECLARE_SUBSYS ("subsystest");

       It is possible to use the same subsystem name in separate object files.
       In  this  case,  the  individual logging parameters for those subsystem
       identifier will be used.

       A newly created subsystem inherits the system configuration at the time
       of creation.

       It  is  possible  to override every configuration option on a subsystem
       base throught the configuration API.

Logging Messages

       The definition log_printf is used to log information to  the  log.   It
       works  in a similiar fashion to printf, except it has a first parameter
       of   level   which   may   be   the    following:    LOGSYS_LEVEL_EMERG

       An example of using log_printf would be

       log_printf  (LOGSYS_LEVEL_EMERG,  "This  is  an emergency %s value %d0,
       string, value);

       Tracing of functions can be done using ENTER(), LEAVE();

       An example of using ENTER is void  function  (char  *name)  {  ENTER();
       LEAVE(); }

       Individual   tracing   levels   are   supported   through   the  macros
       TRACE1(format, args) TRACE2(format, args) TRACE8(format, args)

       An example of using TRACE is

       char *name = "test"; TRACE7 ("This is a trace  7  log  with  name  %s0,

       Note  that  ENTER/LEAVE/TRACE*  calls  are  recorded only in the flight


       logsys_fork_completed(3),  logsys_atexit(3),   logsys_log_rec_store(3),
       logsys_format_set(3),  logsys_format_get(3), logsys_config_mode_set(3),
       logsys_config_file_set(3),        logsys_config_syslog_facility_set(3),
       logsys_config_syslog_facility_get(3),        logsys_config_mode_set(3),
       logsys_config_mode_get(3),                   logsys_config_file_set(3),
       logsys_config_logfile_priority_set(3),      logsys_config_debug_set(3),
       logsys_facility_id_get(3),                 logsys_facility_name_get(3),
       logsys_priority_id_get(3), logsys_priority_name_get(3),