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July 30, 2020 15:11
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TypeScript/JavaScript timeout handler - withTimeout
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| /* | |
| This is a simple function I wrote to make awaiting promises with timeouts easier. | |
| Pass it in a timeout length and a promise, and you can attach handlers for when | |
| the promise resolves on time, when it resolves late, and when the timeout expires. | |
| Here's a snippet from one of my projects as an example: | |
| withTimeout(request_timeout, this.kernel.handle(req)) | |
| .on_time(output_req => { // called if it resolves on time | |
| output_req.response.send() | |
| }) | |
| .late(output_req => { // called if it resolves late | |
| this.logger.error(`Request timed out. Response was already sent on path: ${req.path}. Consider increasing server.request_timeout.`) | |
| }) | |
| .timeout(async () => { // called when the timeout expires | |
| const factory = http(HTTPStatus.REQUEST_TIMEOUT) | |
| const output_req = await factory.write(req) | |
| output_req.response.send() | |
| }) | |
| .run() | |
| Copyright (C) 2020 Garrett Mills <garrett@garrettmills.dev>. | |
| Licensed under the terms of the MIT license. | |
| */ | |
| export interface TimeoutSubscriber<T> { | |
| on_time: (handler: (arg: T) => any) => TimeoutSubscriber<T>, | |
| late: (handler: (arg: T) => any) => TimeoutSubscriber<T>, | |
| timeout: (handler: () => any) => TimeoutSubscriber<T>, | |
| run: () => Promise<T>, | |
| } | |
| export function withTimeout<T>(timeout: number, promise: Promise<T>) { | |
| let on_time_handler: (arg: T) => any = (arg) => {} | |
| let late_handler: (arg: T) => any = (arg) => {} | |
| let timeout_handler: () => any = () => {} | |
| const sub = { | |
| on_time: handler => { | |
| on_time_handler = handler | |
| return sub | |
| }, | |
| late: handler => { | |
| late_handler = handler | |
| return sub | |
| }, | |
| timeout: handler => { | |
| timeout_handler = handler | |
| return sub | |
| }, | |
| run: async () => { | |
| let expired = false | |
| let resolved = false | |
| setTimeout(() => { | |
| expired = true | |
| if ( !resolved ) timeout_handler() | |
| }, timeout) | |
| const result: T = await promise | |
| resolved = true | |
| if ( !expired ) { | |
| await on_time_handler(result) | |
| } else { | |
| await late_handler(result) | |
| } | |
| return result | |
| } | |
| } as TimeoutSubscriber<T> | |
| return sub | |
| } |
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