feat: add polling jitter to target manager intervals#433
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niklastreml
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Apply configurable jitter to check, registration, and update timer resets to prevent thundering-herd when many sparrow instances poll the same backend simultaneously. - Add helper.ApplyJitter with bounded minimum [d*(1-f), d] - Add Jitter float64 field to General config with [0.0, 1.0] validation - Wire jitter into manager.Reconcile timer resets - Add jitter tests (helper bounds + validation cases) - Document jitter in chart/values.yaml
Replace the hand-rolled 1000-iteration bounds check with a proper Go fuzz test (FuzzApplyJitter) that generates random duration/factor pairs and asserts invariant properties. Add NaN/Inf guards to ApplyJitter to handle degenerate float inputs defensively. - Add math.IsNaN/IsInf guard in ApplyJitter (treat as identity) - Add FuzzApplyJitter with 8 seed corpus entries - Keep deterministic TestApplyJitter_EdgeCases for NaN/Inf/zero
Signed-off-by: lvlcn-t <75443136+lvlcn-t@users.noreply.github.com>
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Motivation
When many sparrow instances share the same polling intervals, they
synchronize into a thundering herd — all hitting the backend at the same
instant. Adding jitter spreads requests over time, reducing peak load on
the S3/GitLab backend and improving resilience.
Stack: PR 4/4 — builds on #432 (OIDC auth).
Changes
helper.ApplyJitter(d, factor)ininternal/helper/jitter.gowithbounded minimum
[d*(1-factor), d]NaNandInffactor inputs (treat as identity)Jitter float64field toGeneralconfig struct with[0.0, 1.0]validation and
ErrInvalidJittersentinelmanager.Reconcile()on all three timer resets(check, registration, update)
FuzzApplyJitterfuzz test (~3.7M executions, no failures) withproperty-based assertions (bounded minimum, never exceeds original,
non-negative result)
TestApplyJitter_EdgeCasesfor NaN/Inf/zerochart/values.yamlFor additional information look at the commits.
Tests done
TODO