fix(tracing): Don't send negative ttfb #10286
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AbhiPrasad
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mydea
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anonrig
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| DEBUG_BUILD && logger.log('[Measurements] Adding TTFB'); | ||
| _measurements['ttfb'] = { | ||
| value: (responseStartTimestamp - transactionStartTime) * 1000, | ||
| value: Math.max(responseStartTimestamp - transactionStartTime, 0) * 1000, |
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Can we add a comment to here? As well as a test?
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size-limit report 📦
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edwardgou-sentry
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anonrig
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mydea
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Jan 23, 2024
| ): void { | ||
| // Generate TTFB (Time to First Byte), which measured as the time between the beginning of the transaction and the | ||
| // start of the response in milliseconds | ||
| if (typeof responseStartTimestamp === 'number' && transactionStartTime) { |
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l: We can maybe save a few bytes by checking typeof responseStartTime !== 'number' above and returning early, as we now repeat this below as well. but maybe also doesn't make any difference 😅
mydea
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As per https://developer.mozilla.org/en-US/docs/Web/API/PerformanceResourceTiming/responseStart,
responseStartcan be 0 if the request is coming straight from the cache. This might lead us to calculate a negative ttfb.To account for these scenarios, use
Math.maxto make sure we always set to 0 in the case of a negative value.