tencentcloud-edgeone-migration-nodejs-v2
Version:
tencentcloud cdn config copy to edgeone
77 lines • 3.32 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.EDFLoadBalancer = void 0;
const utils_1 = require("../../utils");
const base_1 = require("./base");
/**
* Earliest Deadline First (EDF) Load Balancer
* (https://en.wikipedia.org/wiki/Earliest_deadline_first_scheduling)
*
* @description
* Algorithm:
* 1. `S` = {S0, S1, S2, ..., Sn}, `W(Si)` = Si.weight, `D(Si)` = Si.deadline
* 2. Sx = Pick(Min(D(Si)))
* 3. D(Sx) = D(Sx) + 1 / W(Sx)
* 4. return Sx
*/
class EDFLoadBalancer extends base_1.StatelessLoadBalancer {
constructor() {
super(...arguments);
this.name = "EDFLoadBalancer";
this.callStat = Object.create(null);
}
/**
* 1. 选取拥有最小 `deadline` 的实例
* 2. 将当前时间 `currentTime` 置为选取实例的 `deadline`
* 3. 将选取实例的 `deadline` 增加一个 `step`
*/
choose(namespace, service, instances) {
let callStat = this.callStat[`${namespace}.${service}`];
if (!callStat) {
callStat = {
currentTime: 0,
instanceDeadline: new WeakMap()
};
this.callStat[`${namespace}.${service}`] = callStat;
this.randomChoose(namespace, service, instances);
}
let earliestDeadline = Infinity;
let selectedInstance;
for (let i = 0; i < instances.length; i += 1) { // eslint-disable-line @typescript-eslint/prefer-for-of
const instance = instances[i];
let deadline = callStat.instanceDeadline.get(instance);
// 正常情况下 `deadline` 应大于当前时间; 但是由于某些前置的条件，导致某 `instance` 不在 `instances` 中
// 则此 `instance` 的 `deadline` 有可能滞后于 `currentTime`，需要为其重置 `deadline`
if (typeof deadline === "undefined" || deadline < callStat.currentTime) {
deadline = callStat.currentTime + (1 / this.instanceWeight(instance));
callStat.instanceDeadline.set(instance, deadline);
}
if (deadline < earliestDeadline) {
earliestDeadline = deadline;
selectedInstance = instance;
}
}
if (selectedInstance) {
callStat.instanceDeadline.set(selectedInstance, earliestDeadline + (1 / this.instanceWeight(selectedInstance)));
callStat.currentTime = earliestDeadline;
return selectedInstance;
}
(0, utils_1.UNREACHABLE)();
}
onStatusChange(namespace, service, instance, prevStatus) {
// 发生以下两种状态转移时，不希望实例被太早选出，因此重置其 deadline
if (
/* eslint-disable max-len */
(instance.status === 2 /* HalfClose */ && prevStatus === 1 /* HalfOpen */) /** `HalfOpen` ---> `HalfClose` */
|| (instance.status === 0 /* Normal */ && prevStatus === 3 /* Fused */) /** `Fused` ---> `Normal` */
/* eslint-enable max-len */
) {
const callStat = this.callStat[`${namespace}.${service}`];
if (callStat) {
callStat.instanceDeadline.delete(instance);
}
}
}
}
exports.EDFLoadBalancer = EDFLoadBalancer;
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