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package com.box.sdk;
class BackoffCounter {
private static final BoxLogger LOGGER = BoxLogger.defaultLogger();
private static final int BASE_TIMEOUT = 1000;
private static final double RANDOM_FACTOR = 0.5;
private final Time time;
private int maxAttempts;
private int attemptsRemaining;
BackoffCounter() {
this(Time.getInstance());
}
BackoffCounter(Time time) {
this.time = time;
}
public int getAttemptsRemaining() {
return this.attemptsRemaining;
}
/**
* Waits for some random amount of time {@link BackoffCounter#calculateDelay()}
* @throws InterruptedException
*/
public void waitBackoff() throws InterruptedException {
int delay = this.calculateDelay();
this.waitBackoff(delay);
}
/**
* Waits for specified amount of miliseconds.
* @param delay Time to wait for in miliseconds.
* @throws InterruptedException
*/
public void waitBackoff(int delay) throws InterruptedException {
if (LOGGER.isWarnEnabled()) {
LOGGER.warn(String.format(
"Backing off for %d seconds before retrying %d more time%s.",
(delay / 1000),
this.attemptsRemaining,
this.attemptsRemaining > 1 ? "s" : ""
));
}
this.time.waitDuration(delay);
}
public boolean decrement() {
this.attemptsRemaining--;
return (this.attemptsRemaining > 0);
}
public void reset(int maxAttempts) {
this.maxAttempts = maxAttempts;
this.attemptsRemaining = maxAttempts;
}
/**
* Generates some random amount of time to backoff.
* Time is within <16000, 48000) ms
* @return Time in miliseconds.
*/
private int calculateDelay() {
int exponent = this.maxAttempts - this.attemptsRemaining;
double minWindow = 1 - RANDOM_FACTOR;
double maxWindow = 1 + RANDOM_FACTOR;
double jitter = (Math.random() * (maxWindow - minWindow)) + minWindow;
return (int) (Math.pow(2, exponent) * BASE_TIMEOUT * jitter);
}
}