how would you handle cleanup after timeouts in https://github.com/tc39/proposal-using-statement? <https://github.com/tc39/proposal-using-statement?>
when managing io-complexity at the integration-level, i feel the reliable/zero-magic/verifiable way to guarantee cleanup in all scenarios is still to use traditional-callbacks, with a timeout-closure. here are 2 examples using the recursive-callback approach, where cleanup is guaranteed-to-run in the “default” switch-statement; one is real-world [1], and the other is this working, standalone nodejs code: [1] real-world example of guaranteed cleanup https://github.com/kaizhu256/node-utility2/blob/2018.9.8/lib.utility2.js#L3320 <https://github.com/kaizhu256/node-utility2/blob/2018.9.8/lib.utility2.js#L3320> ```js // example.js // fully-working standalone code to fetch data from https://api.github.com <https://api.github.com/> // and cleanup afterwards /*jslint node: true*/ /*property GITHUB_TOKEN, authorization, concat, created_at, date, destroy, end, env, error, exit, headers, html_url, log, map, on, parse, push, request, responseHeaders, responseStatusCode, size, slice, stargazers_count, status, statusCode, stringify, updated_at */ (function () { "use strict"; var cleanup; var chunkList; var modeNext; var onNext; var request; var response; var timerTimeout; cleanup = function () { // cleanup timerTimeout clearTimeout(timerTimeout); // cleanup request-stream try { request.destroy(); } catch (ignore) { } // cleanup response-stream try { response.destroy(); } catch (ignore) { } console.error( "\u001b[31mcleaned up request and response streams\u001b[39m" ); }; onNext = function (error, data) { try { // guarantee cleanup on callback-error if (error) { console.error(error); modeNext = Infinity; } modeNext += 1; switch (modeNext) { case 1: // guarantee cleanup after 150000ms timeout timerTimeout = setTimeout(function () { onNext(new Error("timeout error")); }, 15000); // fetch json repository-data from // https://api.github.com/tc39/repos request = require("url").parse( "https://api.github.com/orgs/tc39/repos"; ); request.headers = {}; request.headers["user-agent"] = "undefined"; // add optional oauth-token to increase rate-limit quota if (process.env.GITHUB_TOKEN) { request.headers.authorization = ( "token " + process.env.GITHUB_TOKEN ); } request = require("https").request( request, // concatenate data-chunks from response-stream function (_response) { chunkList = []; response = _response; response .on("data", function (chunk) { chunkList.push(chunk); }) .on("end", function () { onNext(null, Buffer.concat(chunkList)); }) // guarantee cleanup on response-error .on("error", onNext); } ); // guarantee cleanup on request-error request.on("error", onNext) .end(); break; case 2: // print response data console.log(JSON.stringify( { responseStatusCode: response.statusCode, responseHeaders: { date: response.headers.date, status: response.headers.status, "content-type": response.headers["content-type"], "content-length": ( response.headers["content-length"] ) } }, null, 4 )); // print first 5 results of abridged, // JSON.parsed concatenated-data console.log(JSON.stringify( JSON.parse(String(data)) .slice(0, 5) .map(function (githubRepo) { return { html_url: githubRepo.html_url, created_at: githubRepo.created_at, updated_at: githubRepo.updated_at, size: githubRepo.size, stargazers_count: githubRepo.stargazers_count }; }), null, 4 )); // guarantee cleanup on successful-operation onNext(); break; // cleanup default: cleanup(); process.exit(Boolean(error)); } // guarantee cleanup on misc thrown-error } catch (errorCaught) { onNext(errorCaught); } }; modeNext = 0; onNext(); }()); ``` kai zhu [email protected] > On 20 Sep 2018, at 11:48 PM, Isiah Meadows <[email protected]> wrote: > > Could you chime in with this here as an alternative? > https://github.com/tc39/proposal-using-statement > > ----- > > Isiah Meadows > [email protected] > www.isiahmeadows.com > On Thu, Sep 20, 2018 at 7:36 AM kdex <[email protected]> wrote: >> >> So, when is a function supposed to be invoked when `defer`red in a generator? >> >> On Thursday, September 20, 2018 11:21:06 AM CEST Ayush Gupta wrote: >>> Hi, >>> >>> I would like to propose a `defer` keyword(or something else as the keyword >>> name) which would allow us to "defer" a function which will be executed >>> once the current function either returns or throws. >>> >>> The idea for this is taken from the Go programming language. >>> >>> It would allow us to perform cleanup activities in a function which has >>> multiple branches in a single place. >>> >>> For example, a sample server side code can look like: >>> >>> ``` js >>> function doSomeDbWork() { >>> const connection = databasepool.getConnection(); >>> defer function () { connection.release(); } // function would be called >>> no matter when/if the function returns or throws >>> // do your work >>> } >>> ``` >>> >>> Regards >>> Ayush Gupta_______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss
_______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
