oracular (3) logger_disk_log_h.3erl.gz

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)