Module sprotector_pie_meter

Description
Data Types

Registers the process with and updates the sprotector_server using the "basic" PIE active queue management using approximate queue sojourn times.

Behaviours: sbroker_meter.

References

Rong Pan, Prem Natarajan, Chiara Piglione, Mythili Suryanarayana Prabhu, Venkatachalam Subramanian, Fred Baker, and Bill Ver Steeg, PIE: A lightweight control scheme to address the bufferbloat problem, 2013.
Stuart Card, George Robertson and Jock Mackinlay, The Information Visualizer: An Information Workspace, ACM Conference on Human Factors in Computing Systems, 1991.

See also: sprotector, sprotector_server.

Description

Registers the process with and updates the sprotector_server using the "basic" PIE active queue management using approximate queue sojourn times.

sprotector_pie_meter can be used as a sbroker_meter in a sbroker or a sregulator. It will provide a short circuiter that will drop requests without messaging the broker or regulator with a probability using PIE for the ask and ask_r queue when the message queue length is approximately above a minimum and all requests when it is approximately above a maximum. Its argument, spec(), is of the form:

  #{ask    => #{target   => AskTarget :: non_neg_integer(), % default: 100
                interval => AskInterval :: pos_integer()}, % default: 1000
    ask_r  => #{target   => AskRTarget :: non_neg_integer(), % default: 100
                interval => AskRInterval :: pos_integer()}, % default: 1000
    update => Update :: pos_integer(), % default: 100
    min    => Min :: non_neg_integer(), % default: 0
    max    => Max :: non_neg_integer() | infinity}. % default: infinity

AskTarget is the target delay in milliseconds (defaults to 100) for the ask queue and AskInterval is the initial interval in milliseconds (defaults to 1000) before the first drop when the process's message queue is above the minimum size Min (defaults to 0) and below the maximum size Max (defaults to infinity). `AskRTarget and AskRInterval are equivalent for the ask_r queue. Update is the interval between updating the drop probability (defaults to 100).

A person perceives a response time of 100 milliseconds or less as instantaneous, and feels engaged with a system if response times are 1000 milliseconds or less. Therefore it is desirable for a system to respond within 1000 milliseconds as a worst case (upper percentile response time) and ideally to respond within 100 milliseconds (target response time). Thus the default target is 100 milliseconds and the default is interval 1000 milliseconds.

Data Types

spec()

spec() = #{ask => #{target => AskTarget::non_neg_integer(), interval => AskInterval::pos_integer()}, ask_r => #{target => AskRTarget::non_neg_integer(), interval => AskRInterval::pos_integer()}, update => Update::pos_integer(), min => Min::non_neg_integer(), max => Max::non_neg_integer() | infinity}

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