add experimental priority sampling config as sampling rules #732
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rochdev
changed the title
rochdev
changed the title
brettlangdon
reviewed
Nov 5, 2019
| peers: ['foo'], | ||
| sampler: { | ||
| sampleRate: 1, | ||
| rateLimit: 1000, |
| @@ -87,6 +98,48 @@ class PrioritySampler { | |||
| } | |||
| } | |||
| } | |||
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| _isSampledByRule (context, rule) { | |||
| const sampled = this._limiter.isAllowed() && rule.sampler.isSampled(context) | |||
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this is backwards, we want to only apply the limit on p1 traces
| const sampled = this._limiter.isAllowed() && rule.sampler.isSampled(context) | ||
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||
| context._metrics[SAMPLING_LIMIT_DECISION] = this._limiter.effectiveRate() | ||
| context._metrics[SAMPLING_RULE_DECISION] = rule.sampleRate |
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we only want to set these if we used that method for sampling.
e.g.
context._metrics[SAMPLING_RULE_DECISION] = rule.sampleRate
if (!rule.sampler.isSampled(context)) return false
const sampled = this._limiter.isAllowed()
context._metrics[SAMPLING_LIMIT_DECISION] = this._limiter.effectiveRate()
return sampled(ish)
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The reason for that is so we can debug why a span was sampled or not. e.g. if we see SAMPLING_RULE_DECISION only, then we can assume it was a p0 because of the rule, not because of rate limiter.
brettlangdon
approved these changes
Nov 6, 2019
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What does this PR do?
Add priority sampling configuration as sampling rules.
Motivation
Right now the sample rates are provided by the agent and cannot be configured, which is incompatible with Tracing Without Limits. By adding a configuration, it becomes possible to override the agent and take the sample rate decision in the tracer.