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backoffs.js
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'use strict';
const _ = require('lodash');
const builtinStrategies = {
fixed(delay) {
return function() {
return delay;
};
},
exponential(delay) {
return function(attemptsMade) {
return Math.round((Math.pow(2, attemptsMade) - 1) * delay);
};
}
};
function lookupStrategy(backoff, customStrategies) {
if (backoff.type in customStrategies) {
return customStrategies[backoff.type];
} else if (backoff.type in builtinStrategies) {
return builtinStrategies[backoff.type](backoff.delay);
} else {
throw new Error(
'Unknown backoff strategy ' +
backoff.type +
'. If a custom backoff strategy is used, specify it when the queue is created.'
);
}
}
module.exports = {
normalize(backoff) {
if (_.isFinite(backoff)) {
return {
type: 'fixed',
delay: backoff
};
} else if (backoff) {
return backoff;
}
},
calculate(backoff, attemptsMade, customStrategies, err) {
if (backoff) {
const strategy = lookupStrategy(backoff, customStrategies);
return strategy(attemptsMade, err);
}
}
};