logger_disk_log_h(3erl) Erlang Module Definition logger_disk_log_h(3erl)
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 us-
ing disk_log. Multiple instances of this handler can be added to Log-
ger, 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 de-
scribed in the User's Guide.
To add a new instance of the disk_log handler, use logger:add_han-
dler/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 cir-
cular 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 dis-
abled. 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)
Ericsson AB kernel 7.0 logger_disk_log_h(3erl)