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After 30m, no graphing is observed in the configured Poll Interval, but the rrd update at 16:22 is observed.
We wait another 30m and the service continues without graphing, but we do see a new update in the rrd.
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The charts are recovering, but there is already a 1-hour gap.
New tests with a monitor with 30m from the beginning:
Poll Interval is changed to 1h and continues to work fine:
Conclusion
If a Poll Interval of a service that is 1m, 2m, 10m, 15m to 30m or more, is modified, the service graphs are stopped.
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