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81 lines
3.0 KiB
TypeScript
81 lines
3.0 KiB
TypeScript
import Logger from '@joplin/lib/Logger';
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import time from '@joplin/lib/time';
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const logger = Logger.create('BackOffHandler');
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// This handler performs two checks:
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//
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// 1. If the plugin makes many API calls one after the other, a delay is going
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// to be applied before responding. The delay is set using backOffIntervals_.
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// When a plugin needs to be throttled that way a warning is displayed so
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// that the author gets an opportunity to fix it.
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//
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// 2. If the plugin makes many simultaneous calls, the handler throws an
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// exception to stop the plugin. In that case the plugin will be broken, but
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// most plugins will not get this error anyway because call are usually made
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// in sequence. It might reveal a bug though - for example if the plugin
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// makes a call every 1 second, but does not wait for the response (or assume
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// the response will come in less than one second). In that case, the back
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// off intervals combined with the incorrect code will make the plugin fail.
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export default class BackOffHandler {
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// The current logic is:
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//
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// - Up to 1000 calls per 10 seconds without restrictions
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// - For calls 1000 to 2000, a 100 ms wait time is applied
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// - Over 2000 calls, a 200 ms wait time is applied
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// - After 10 seconds without making any call, the limits are reset (back to
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// 0 second between calls).
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//
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// If more than 5000 simultaneous calls are being throttled, it's a bug in
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// the plugin (not waiting for API responses), so we stop responding and
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// throw an error.
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private backOffIntervals_ =
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Array(1000).fill(0).concat(
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Array(1000).fill(100)).concat(
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[200]);
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private lastRequestTime_ = 0;
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private pluginId_: string;
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private resetBackOffInterval_ = 10 * 1000;
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private backOffIndex_ = 0;
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private waitCount_ = 0;
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private maxWaitCount_ = 5000;
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public constructor(pluginId: string) {
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this.pluginId_ = pluginId;
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}
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private backOffInterval() {
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const now = Date.now();
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if (now - this.lastRequestTime_ > this.resetBackOffInterval_) {
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this.backOffIndex_ = 0;
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} else {
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this.backOffIndex_++;
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}
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this.lastRequestTime_ = now;
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const effectiveIndex = this.backOffIndex_ >= this.backOffIntervals_.length ? this.backOffIntervals_.length - 1 : this.backOffIndex_;
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return this.backOffIntervals_[effectiveIndex];
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}
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public async wait(path: string, args: any) {
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const interval = this.backOffInterval();
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if (!interval) return;
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this.waitCount_++;
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logger.warn(`Plugin ${this.pluginId_}: Applying a backoff of ${interval} milliseconds due to frequent plugin API calls. Consider reducing the number of calls, caching the data, or requesting more data per call. API call was: `, path, args, `[Wait count: ${this.waitCount_}]`);
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if (this.waitCount_ > this.maxWaitCount_) throw new Error(`Plugin ${this.pluginId_}: More than ${this.maxWaitCount_} API calls are waiting - aborting. Please consider queuing the API calls in your plugins to reduce the load on the application.`);
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await time.msleep(interval);
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this.waitCount_--;
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}
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}
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