Zabbix 3.2.1 Changing trends value of an item affecting graphs

[IT-Yannick]

Hello,

I recently found out that I had items with the value 0d (trends) and 90d (History). This makes me only see data up to 90 days on graphs.
These items were added +5 months ago.

Therefore, I changed the trends from 0 to 365 days and now I only get data of the last 1 hour.
So I changed back to 0 days and I can see the last 3 months(90d) again.

Is there a way I can see my last 90 days and new data using 365d on trends?

Thanks.


Attached 2 screenshots (trends 0 days and trends 365 days)

[nick0909]

Trend data values should be larger than history. History keeps all records as collected. Trends are a less-detailed view of averaged history data. The process of creating trends from history is done by the housekeeper.

For example, in general I use 7 day history and 365 day trends. After a history item is older than 7 days it gets merged in to history data and the trend data is purged. If you changed your history and trend values and the housekeeper ran, you could have lost data, so be sure you know what you are changing before you make adjustments. After you adjust these items sometimes you have to wait for the housekeeper to run before the graphs will show up without gaps or dotted lines it seems. Mine runs every hour.

Zabbix documentation on history and trends

[IT-Yannick]

Thank you very much for the reply and example

The strange part is that I can still see older data, but for that I have to change the item trends back to 0d (original config). So it didn't delete the history (90d)

Yes yes I know that the trends should be longer than the history but at the time I created it wrong.

I'll keep the new item configuration (365d) as it's more future proof.

------------------------------------------------------------------------
before:
trends:0d - history:90d - I see a maximum of 90d of data

Now:
trends:365d - history:90d - I only see new data (that will grow with time)

[glebs.ivanovskis]

That's how frontend graphing logic works...

[IT-Yannick]

That's how frontend graphing logic works...

So it's normal that changing trends deletes all data from that item?

[glebs.ivanovskis]

I didn't say it's normal You are free to go to support.zabbix.com and create a ZBX

And it does not delete data, it simply does not see data. It thinks like so: "I was requested a graph for a month, I'd better use trends for performance, keep trends is not zero, so there must be some, right? Oh, there is nothing in trends, so I will draw nothing." Actually, this works fine most of the time. If you simply wait a bit (or configure everything "correctly" from the beginning) you should see expected graphs.

[IT-Yannick]

Thanks it makes sense the way you put it.
I was expecting to use the existent history instead of the "nonexistent" trends.

[kloczek]

TThe process of creating trends from history is done by the housekeeper.

Just small correction: calculating trends ponts have nothing to do with housekeeper. It is seperated part of zabbix server code.
Trend point is calculated every full hour and consist from 4 values: max, min, avg value of all history points within last hour + timestamp.
Housekeeper is only responsible for delete oldest trends data out of HK time window.

Another qute frequent misconception is how zabbix calculates trends points. They are not calculated by query each full hour each item last hour data from DB backend and calculate last hour trend point. They are calculated on receive every new point in each item. These temporary values are kept in cache. Each full hour those cached values are only read, stored in trends tables and zeroed. It is very effective technique allowing minimize interraction with DB backend.