disksup(3erl) [linux man page]
disksup(3erl) Erlang Module Definition disksup(3erl) NAME
disksup - A Disk Supervisor Process DESCRIPTION
disksup is a process which supervises the available disk space in the system. It is part of the OS_Mon application, see os_mon(7) . Avail- able for Unix and Windows. Periodically checks the disks. For each disk or partition which uses more than a certain amount of the available space, the alarm {{disk_almost_full, MountedOn}, []} is set. On Unix : All (locally) mounted disks are checked, including the swap disk if it is present. On WIN32 : All logical drives of type "FIXED_DISK" are checked. 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 the alarm specified above. The alarms are cleared automatically when the alarm cause is no longer valid. CONFIGURATION
The following configuration parameters can be used to change the default values for time interval and threshold: disk_space_check_interval = int()>0 : The time interval, in minutes, for the periodic disk space check. The default is 30 minutes. disk_almost_full_threshold = float() : The threshold, as percentage of total disk space, for how much disk can be utilized before the disk_almost_full alarm is set. The default is 0.80 (80%). See config(5) for information about how to change the value of configuration parameters. EXPORTS
get_disk_data() -> [DiskData] Types DiskData = {Id, KByte, Capacity} Id = string() KByte = int() Capacity = int() Returns the result of the latest disk check. Id is a string that identifies the disk or partition. KByte is the total size of the disk or partition in kbytes. Capacity is the percentage of disk space used. The function is asynchronous in the sense that it does not invoke a disk check, but returns the latest available value. Returns [{"none",0,0}] if disksup is not available. get_check_interval() -> MS Types MS = int() Returns the time interval, in milliseconds, for the periodic disk space check. set_check_interval(Minutes) -> ok Types Minutes = int()>=1 Changes the time interval, given in minutes, for the periodic disk space check. The change will take effect after the next disk space check and is non-persist. That is, in case of a process restart, this value is forgotten and the default value will be used. See Configuration above. get_almost_full_threshold() -> Percent Types Percent = int() Returns the threshold, in percent, for disk space utilization. set_almost_full_threshold(Float) -> ok Types Float = float(), 0=<Float=<1 Changes the threshold, given as a float, for disk space utilization. The change will take effect during the next disk space check and is non-persist. That is, in 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 disksup(3erl)
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overload(3erl) Erlang Module Definition overload(3erl) NAME
overload - An Overload Regulation Process DESCRIPTION
overload is a process which indirectly regulates CPU usage in the system. The idea is that a main application calls the request/0 function before starting a major job, and proceeds with the job if the return value is positive; otherwise the job must not be started. overload is part of the sasl application, and all configuration parameters are defined there. A set of two intensities are maintained, the total intensity and the accept intensity . For that purpose there are two configuration param- eters, the MaxIntensity and the Weight value (both are measured in 1/second). Then total and accept intensities are calculated as follows. Assume that the time of the current call to request/0 is T(n) , and that the time of the previous call was T(n-1) . * The current total intensity , denoted TI(n) , is calculated according to the formula, TI(n) = exp(-Weight*(T(n) - T(n-1)) * TI(n-1) + Weight , where TI(n-1) is the previous total intensity. * The current accept intensity , denoted AI(n) , is determined by the formula, AI(n) = exp(-Weight*(T(n) - T(n-1)) * AI(n-1) + Weight , where AI(n-1) is the previous accept intensity, provided that the value of exp(-Weight*(T(n) - T(n-1)) * AI(n-1) is less than MaxInten- sity ; otherwise the value is AI(n) = exp(-Weight*(T(n) - T(n-1)) * AI(n-1) . The value of configuration parameter Weight controls the speed with which the calculations of intensities will react to changes in the underlying input intensity. The inverted value of Weight , T = 1/Weight can be thought of as the "time constant" of the intensity calculation formulas. For example, if Weight = 0.1 , then a change in the under- lying input intensity will be reflected in the total and accept intensities within approximately 10 seconds. The overload process defines one alarm, which it sets using alarm_handler:set_alarm(Alarm) . Alarm is defined as: {overload, []} : This alarm is set when the current accept intensity exceeds MaxIntensity . A new overload alarm is not set until the current accept intensity has fallen below MaxIntensity . To prevent the overload process from generating a lot of set/reset alarms, the alarm is not reset until the current accept intensity has fallen below 75% of MaxIntensity , and it is not until then that the alarm can be set again. EXPORTS
request() -> accept | reject Returns accept or reject depending on the current value of the accept intensity. The application calling this function should be processed with the job in question if the return value is accept ; otherwise it should not continue with that job. get_overload_info() -> OverloadInfo Types OverloadInfo = [{total_intensity, TotalIntensity}, {accept_intensity, AcceptIntensity}, {max_intensity, MaxIntensity}, {weight, Weight}, {total_requests, TotalRequests}, {accepted_requests, AcceptedRequests}]. TotalIntensity = float() > 0 AcceptIntensity = float() > 0 MaxIntensity = float() > 0 Weight = float() > 0 TotalRequests = integer() AcceptedRequests = integer() Returns the current total and accept intensities, the configuration parameters, and absolute counts of the total number of requests, and accepted number of requests (since the overload process was started). SEE ALSO
alarm_handler(3erl), sasl(3erl) Ericsson AB sasl 2.1.9.3 overload(3erl)