[Profiling] Add support for variable sampling frequency #128086
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rockdaboot
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:UniversalProfiling/Application
elasticsearchmachine
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rockdaboot
commented
May 15, 2025
| @@ -76,6 +76,10 @@ | |||
| "type": "short", | |||
| "index": false | |||
| }, | |||
| "Stacktrace.sampling_frequency": { | |||
| "type": "long", | |||
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Using long here to
a) avoid hardly compressible FP type (no use case in sight for non-integer frequencies in sight)
b) long compresses as well as any other integer type (variable length encoding)
rockdaboot
commented
May 15, 2025
| .missing("") | ||
| .field("Stacktrace.sampling_frequency") | ||
| // missing(DEFAULT_SAMPLING_RATE) is used to include documents where the field is missing. | ||
| .missing((long) DEFAULT_SAMPLING_FREQUENCY) |
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This allows compatibility with old data that doesn't have the sampling_frequency field.
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Pinging @elastic/obs-ux-infra_services-team (Team:obs-ux-infra_services) |
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This PR adds support for a variable sampling frequency.
So far, all trace events are assumed to be sampled at exactly 19 Hz (19 samples per second).
The profiling agent allows to configure this frequency as positive integer values - as allowed by the eBPF API. But due to limitations in our backend processing, which only support 19 Hz, we could not expose this option to customers. Once we support variable sampling frequencies in our backend and UI, we can open this configuration option to customers. A second use case could, in theory, be that we implement changing sampling frequency on-demand during runtime. "On-demand" could be increase accuracy during selected APM traces and spans.
In short, a sampling variable frequency allows reducing the storage costs significantly and/or allows increasing accuracy of profiling data.
TODO: