Copyright 1996-2003 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
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* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgment:
* This product includes software developed by John D. Polstra.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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INTERFACE BackoffTimer;
IMPORT Thread, Time;
TYPE
T <: ROOT;
A BackoffTimer.T, or backoff timer, supports timed retries through
exponential backoff with random jitter.
PROCEDURE New(min, max: Time.T;
backoff: REAL;
jitter: REAL): T;
Creates a new backoff timer with the given parameters.
Disregarding jitter for a moment, the first retry interval will be
min. Subsequent retry intervals will increase by the factor
backoff each time, until max is reached.
jitter is applied after the above calculation. It specifies the
magnitude of the random component relative to the number calculated
above. For example, a jitter of 0.1 will cause the interval to be
perturbed randomly each time by plus or minus 10 percent.
PROCEDURE Pause(bt: T);
Pause until it is time for the next retry.
PROCEDURE AlertPause(bt: T) RAISES {Thread.Alerted};
Like Pause, but alertable.
PROCEDURE Get(bt: T): Time.T;
Returns the retry interval that will be used the next time Pause or
AlertPause is called.
END BackoffTimer.