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3fb881af26
I found it hard to understand how EvalTimestamp works, so I wanted to simplify the math there. This PR should be a noop.
Current formula is:
```
offset = g.hash % g.interval
adjNow = startTime - offset
base = adjNow - (adjNow % g.interval)
EvalTimestamp = base + offset
```
I simplify `EvalTimestamp`
```
EvalTimestamp = base + offset
# expand base
= adjNow - (adjNow % g.interval) + offset
# expand adjNow
= startTime - offset - ((startTime - offset) % g.interval) + offset
# cancel out offset
= startTime - ((startTime - offset) % g.interval)
# expand A+B (mod M) = (A (mod M) + B (mod M)) (mod M)
= startTime - (startTime % g.interval - offset % g.interval) % g.interval
# expand offset
= startTime - (startTime % g.interval - ((g.hash % g.interval) % g.interval)) % g.interval
# remove redundant mod g.interval
= startTime - (startTime % g.interval - g.hash % g.interval) % g.interval
# simplify (A (mod M) + B (mod M)) (mod M) = A+B (mod M)
= startTime - (startTime - g.hash) % g.interval
offset = (startTime - g.hash) % g.interval
EvalTimestamp = startTime - offset
```
Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
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| .. | ||
| fixtures | ||
| alerting.go | ||
| alerting_test.go | ||
| manager.go | ||
| manager_test.go | ||
| recording.go | ||
| recording_test.go | ||