NAME

       logger_disk_log_h - A disk_log based handler for Logger

DESCRIPTION

       This  is  a  handler  for  Logger  that  offers circular (wrapped) logs by using disk_log.
       Multiple instances of this handler can be added to Logger, and each instance prints to its
       own  disk  log  file,  created  with  the  name  and  settings  specified  in  the handler
       configuration.

       The default standard handler, logger_std_h, can be  replaced  by  a  disk_log  handler  at
       startup of the Kernel application. See an example of this below.

       The  handler  has  an overload protection mechanism that keeps the handler process and the
       Kernel application alive during high loads of log events. How overload  protection  works,
       and how to configure it, is described in the User's Guide.

       To  add  a  new  instance  of  the disk_log handler, use logger:add_handler/3. The handler
       configuration argument is a map which can contain  general  configuration  parameters,  as
       documented  in  the  User's  Guide,  and handler specific parameters. The specific data is
       stored in a sub map with the key config, and can contain the following parameters:

         file:
           This is the full name of the disk  log  file.  The  option  corresponds  to  the  name
           property in the dlog_option() datatype.

           The value is set when the handler is added, and it cannot be changed in runtime.

           Defaults to the same name as the handler identity, in the current directory.

         type:
           This  is  the disk log type, wrap or halt. The option corresponds to the type property
           in the dlog_option() datatype.

           The value is set when the handler is added, and it cannot be changed in runtime.

           Defaults to wrap.

         max_no_files:
           This is the maximum number of files that disk_log uses for its circular  logging.  The
           option corresponds to the MaxNoFiles element in the size property in the dlog_option()
           datatype.

           The value is set when the handler is added, and it cannot be changed in runtime.

           Defaults to 10.

           The setting has no effect on a halt log.

         max_no_bytes:
           This is the maximum number of bytes that is written to  a  log  file  before  disk_log
           proceeds  with  the  next  file in order, or generates an error in case of a full halt
           log. The option corresponds to the MaxNoBytes element in  the  size  property  in  the
           dlog_option() datatype.

           The value is set when the handler is added, and it cannot be changed in runtime.

           Defaults to 1048576 bytes for a wrap log, and infinity for a halt log.

         filesync_repeat_interval:
           This  value,  in  milliseconds,  specifies  how often the handler does a disk_log sync
           operation to  write  buffered  data  to  disk.  The  handler  attempts  the  operation
           repeatedly, but only performs a new sync if something has actually been logged.

           Defaults to 5000 milliseconds.

           If  no_repeat  is  set as value, the repeated sync operation is disabled. The user can
           also call the filesync/1 function to perform a disk_log sync.

       Other configuration parameters exist, to be used for customizing the  overload  protection
       behaviour.  The  same  parameters  are  used both in the standard handler and the disk_log
       handler, and are documented in the User's Guide.

       Notice that when changing the configuration  of  the  handler  in  runtime,  the  disk_log
       options (file, type, max_no_files, max_no_bytes) must not be modified.

       Example of adding a disk_log handler:

       logger:add_handler(my_disk_log_h, logger_disk_log_h,
                          #{config => #{file => "./my_disk_log",
                                        type => wrap,
                                        max_no_files => 4,
                                        max_no_bytes => 10000,
                                        filesync_repeat_interval => 1000}}).

       To  use  the  disk_log  handler  instead  of the default standard handler when starting an
       Erlang node, change the Kernel default logger to use logger_disk_log_h. Example:

       erl -kernel logger '[{handler,default,logger_disk_log_h,
                             #{config => #{file => "./system_disk_log"}}}]'

EXPORTS

       filesync(Name) -> ok | {error, Reason}

              Types:

                 Name = atom()
                 Reason = handler_busy | {badarg, term()}

              Write buffered data to disk.

SEE ALSO

       logger(3erl), logger_std_h(3erl), disk_log(3erl)