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[Michael Leinartas <question193066@xxxxxxxxxxxxxxxxxxxxx>]

Question #193066 on Graphite changed:
https://answers.launchpad.net/graphite/+question/193066

    Status: Open => Answered

Michael Leinartas proposed the following answer:
Sorry - I only *just* now understood what was going on. Re-reading the
description it sounds like you had a good idea of what was happening
already

I'll summarize:

Your daily summary graphs are generated from a process that fires
metrics off once per day. Because of the way Whisper rounds times into
buckets (as quoted in the description), the timestamp stored is at 00:00
UTC.  The expected behavior is that the metric will be stored at the
beginning of the day - this is true if you're in UTC, but when the
timezone adjustment goes into effect, it's displaying at 4am which is
*not* the beginning of your day.

This rounding happens for any retention, but once the retention value
goes above 1 hour the timezone conversion starts to shift the time
buckets away from the correct local time.


Unfortunately, I don't see a clear route to fix this behavior in the webapp at the moment. There are a few ways you can mitigate the effect though:

1. Use timeShift as above. This is certainly a pain as it involves  modifying each target individually
2. Set the timezone to UTC for the affected graphs - this can be done by appending &tz=UTC to the graph URL.
3. Use a retention of 1hour instead of 1day for these graphs and use the 'connected' line mode (&lineMode=connected)

None of these are great, but I think 2 is most reasonable as it's merely
appending to the existing URLs and doesn't involve any data migration.

I'll file a bug to track this as well

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