Node.js Practical — node-cron — Performance Bug

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Node.js Practical Debugging — node-cron (Performance Bug). The endpoint becomes slow with many records/requests. Identify the blocking or inefficient part and provide a scalable Node.js solution. The specific area is job runs twice or not at all. Assume a real Express/Node.js project where the developer needs a reliable, maintainable fix. Explain why the buggy version can fail, then provide corrected code and the expected behavior. Do not hide the root cause behind a generic 'restart the server' answer. BUGGY/PROBLEM CODE: cron.schedule('* * * * *', async () => { await syncData(); }); cron.schedule('* * * * *', async () => { await syncData(); }); TASK: Find the exact problem and write the production-safe correction.
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Answer & Explanation

4 Answers
Verified Correct Answer

Correct Code / Solution

let running = false; cron.schedule('* * * * *', async () => { if (running) return; running = true; try { await syncData(); } catch (error) { console.error('syncData failed:', error); } finally { running = false; } });
Additional Explanation
Root cause: job runs twice or not at all. The important debugging step is to verify the exact runtime value, module path, middleware order, environment variable, database/model export, or asynchronous result before changing unrelated code. The corrected version adds explicit validation/error handling where appropriate. Expected behavior: the code should either complete the requested operation or return/log a controlled error instead of failing silently, returning undefined unexpectedly, or crashing the process.
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Editorial Answer 1
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Possible but Incorrect Code

let running = false; cron.schedule('* * * * *', async () => { if (running) return; running = true; try { /* missing error handling */ await syncData(); } catch (error) { console.error('syncData failed:', error); } finally { running = false; } });
Additional Explanation
यह option जानबूझकर एक common bug/unsafe approach दिखाता है। इसे production solution के रूप में इस्तेमाल करने से पहले variable scope, async flow, module path, validation, error handling और security checks verify करें। ऊपर दिए गए correct option से exact difference compare करें.
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Editorial Answer 2
Verified

Possible but Incorrect Code

cron.schedule('* * * * *', async () => { await syncData(); }); cron.schedule('* * * * *', async () => { await syncData(); });
Additional Explanation
यह option जानबूझकर एक common bug/unsafe approach दिखाता है। इसे production solution के रूप में इस्तेमाल करने से पहले variable scope, async flow, module path, validation, error handling और security checks verify करें। ऊपर दिए गए correct option से exact difference compare करें.
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Editorial Answer 3
Verified

Possible but Incorrect Code

let running = false; cron.schedule('* * * * *', async () => { if (running) return; running = true; try { syncData(); } catch (error) { console.error('syncData failed:', error); } finally { running = false; } });
Additional Explanation
यह option जानबूझकर एक common bug/unsafe approach दिखाता है। इसे production solution के रूप में इस्तेमाल करने से पहले variable scope, async flow, module path, validation, error handling और security checks verify करें। ऊपर दिए गए correct option से exact difference compare करें.
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Editorial Answer 4