alarm_handler(3erl) [linux man page]
alarm_handler(3erl) Erlang Module Definition alarm_handler(3erl) NAME
alarm_handler - An Alarm Handling Process DESCRIPTION
The alarm handler process is a gen_event event manager process which receives alarms in the system. This process is not intended to be a complete alarm handler. It defines a place to which alarms can be sent. One simple event handler is installed in the alarm handler at start-up, but users are encouraged to write and install their own handlers. The simple event handler sends all alarms as info reports to the error logger, and saves all of them in a list which can be passed to a user defined event handler, which may be installed at a later stage. The list can grow large if many alarms are generated. So it is a good reason to install a better user defined handler. There are functions to set and clear alarms. The format of alarms are defined by the user. For example, an event handler for SNMP could be defined, together with an alarm MIB. The alarm handler is part of the SASL application. When writing new event handlers for the alarm handler, the following events must be handled: {set_alarm, {AlarmId, AlarmDescr}} : This event is generated by alarm_handler:set_alarm({AlarmId, AlarmDecsr}) . {clear_alarm, AlarmId} : This event is generated by alarm_handler:clear_alarm(AlarmId) . The default simple handler is called alarm_handler and it may be exchanged by calling gen_event:swap_handler/3 as gen_event:swap_han- dler(alarm_handler, {alarm_handler, swap}, {NewHandler, Args}) . NewHandler:init({Args, {alarm_handler, Alarms}}) is called. Refer to gen_event(3erl) for further details. EXPORTS
clear_alarm(AlarmId) -> void() Types AlarmId = term() Clears all alarms with id AlarmId . get_alarms() -> [alarm()] Returns a list of all active alarms. This function can only be used when the simple handler is installed. set_alarm(alarm()) Types alarm() = {AlarmId, AlarmDescription} AlarmId = term() AlarmDescription = term() Sets an alarm with id AlarmId . This id is used at a later stage when the alarm is cleared. SEE ALSO
error_logger(3erl), gen_event(3erl) Ericsson AB sasl 2.1.9.3 alarm_handler(3erl)
Check Out this Related Man Page
memsup(3erl) Erlang Module Definition memsup(3erl) NAME
memsup - A Memory Supervisor Process DESCRIPTION
memsup is a process which supervises the memory usage for the system and for individual processes. It is part of the OS_Mon application, see os_mon(7) . Available for Unix, Windows and VxWorks. Periodically performs a memory check: * If more than a certain amount of available system memory is allocated, as reported by the underlying operating system, the alarm {sys- tem_memory_high_watermark, []} is set. * If any Erlang process Pid in the system has allocated more than a certain amount of total system memory, the alarm {process_mem- ory_high_watermark, Pid} is set. Alarms are reported to the SASL alarm handler, see alarm_handler(3erl) . To set an alarm, alarm_handler:set_alarm(Alarm) is called where Alarm is either of the alarms specified above. The alarms are cleared automatically when the alarm cause is no longer valid. The function get_memory_data() can be used to retrieve the result of the latest periodic memory check. There is also a interface to system dependent memory data, get_system_memory_data() . The result is highly dependent on the underlying operating system and the interface is targeted primarily for systems without virtual memory (e.g. VxWorks). The output on other systems is however still valid, although sparse. A call to get_system_memory_data/0 is more costly than a call to get_memory_data/0 as data is collected synchronously when this function is called. The total system memory reported under UNIX is the number of physical pages of memory times the page size, and the available memory is the number of available physical pages times the page size. This is a reasonable measure as swapping should be avoided anyway, but the task of defining total memory and available memory is difficult because of virtual memory and swapping. CONFIGURATION
The following configuration parameters can be used to change the default values for time intervals and thresholds: memory_check_interval = int()>0 : The time interval, in minutes, for the periodic memory check. The default is one minute. system_memory_high_watermark = float() : The threshold, as percentage of system memory, for how much system memory can be allocated before the corresponding alarm is set. The default is 0.80 (80%). process_memory_high_watermark = float() : The threshold, as percentage of system memory, for how much system memory can be allocated by one Erlang process before the correspond- ing alarm is set. The default is 0.05 (5%). memsup_helper_timeout = int()>0 : A timeout, in seconds, for how long the memsup process should wait for a result from a memory check. If the timeout expires, a warning message "OS_MON (memsup) timeout" is issued via error_logger and any pending, synchronous client calls will return a dummy value. Nor- mally, this situation should not occur. There have been cases on Linux, however, where the pseudo file from which system data is read is temporarily unavailable when the system is heavily loaded. The default is 30 seconds. memsup_system_only = bool() : Specifies whether the memsup process should only check system memory usage ( true ) or not. The default is false , meaning that infor- mation regarding both system memory usage and Erlang process memory usage is collected. It is recommended to set this parameter to false on systems with many concurrent processes, as each process memory check makes a tra- versal of the entire list of processes. See config(5) for information about how to change the value of configuration parameters. EXPORTS
get_memory_data() -> {Total,Allocated,Worst} Types Total = Allocated = int() Worst = {Pid, PidAllocated} | undefined Pid = pid() PidAllocated = int() Returns the result of the latest memory check, where Total is the total memory size and Allocated the allocated memory size, in bytes. Worst is the pid and number of allocated bytes of the largest Erlang process on the node. If memsup should not collect process data, that is if the configuration parameter memsup_system_only was set to true , Worst is undefined . The function is normally asynchronous in the sense that it does not invoke a memory check, but returns the latest available value. The one exception if is the function is called before a first memory check is finished, in which case it does not return a value until the memory check is finished. Returns {0,0,{pid(),0}} or {0,0,undefined} if memsup is not available, or if all memory checks so far have timed out. get_system_memory_data() -> MemDataList Types MemDataList = [{Tag, Size}] Tag = atom() Size = int() Invokes a memory check and returns the resulting, system dependent, data as a list of tagged tuples, where Tag can be one of the following: total_memory : The total amount of memory available to the Erlang emulator, allocated and free. May or may not be equal to the amount of memory configured in the system. free_memory : The amount of free memory available to the Erlang emulator for allocation. system_total_memory : The amount of memory available to the whole operating system. This may well be equal to total_memory but not necessarily. largest_free : The size of the largest contiguous free memory block available to the Erlang emulator. number_of_free : The number of free blocks available to the Erlang runtime system. This gives a fair indication of how fragmented the memory is. buffered_memory : The amount of memory the system uses for temporary storing raw disk blocks. cached_memory : The amount of memory the system uses for cached files read from disk. total_swap : The amount of total amount of memory the system has available for disk swap. free_swap : The amount of memory the system has available for disk swap. All memory sizes are presented as number of bytes . The largest_free and number_of_free tags are currently only returned on a VxWorks system. Returns the empty list [] if memsup is not available, or if the memory check times out. Note: On linux the memory available to the emulator is cached_memory and buffered_memory in addition to free_memory . get_os_wordsize() -> Wordsize Types Wordsize = 32 | 64 | unsupported_os Returns the wordsize of the current running operating system. get_check_interval() -> MS Types MS = int() Returns the time interval, in milliseconds, for the periodic memory check. set_check_interval(Minutes) -> ok Types Minutes = int()>0 Changes the time interval, given in minutes, for the periodic memory check. The change will take effect after the next memory check and is non-persistent. That is, in case of a process restart, this value is forgotten and the default value will be used. See Configuration above. get_procmem_high_watermark() -> int() Returns the threshold, in percent, for process memory allocation. set_procmem_high_watermark(Float) -> ok Changes the threshold, given as a float, for process memory allocation. The change will take effect during the next periodic memory check and is non-persistent. That is, in case of a process restart, this value is forgotten and the default value will be used. See Configuration above. get_sysmem_high_watermark() -> int() Returns the threshold, in percent, for system memory allocation. set_sysmem_high_watermark(Float) -> ok Changes the threshold, given as a float, for system memory allocation. The change will take effect during the next periodic memory check and is non-persistent. That is, in case of a process restart, this value is forgotten and the default value will be used. See Configuration above. get_helper_timeout() -> Seconds Types Seconds = int() Returns the timeout value, in seconds, for memory checks. set_helper_timeout(Seconds) -> ok Types Seconds = int() (>= 1) Changes the timeout value, given in seconds, for memory checks. The change will take effect for the next memory check and is non-persistent. That is, in the case of a process restart, this value is forgotten and the default value will be used. See Configuration above. SEE ALSO
alarm_handler(3erl) , os_mon(3erl) Ericsson AB os_mon 2.2.5 memsup(3erl)