Forum Discussion
Resolver IWhy is there CU usage while no activity running?
Community ChampionPlease watch this YouTube video about the Fabric Capacity Metrics App. Hopefully you will be able to find the answer to the issue after watching it:
Tips on Using the Fabric Capacity Metrics App
https://youtu.be/EuBA5iK1BiA?si=8hm207pOqcrn6pt7
I think what confuses many users, is the fact that some visuals in the Metrics app show the smoothed consumption (while other visuals show the raw consumption). Please watch the video, it explains it quite well.
Also, please note that when you pause a capacity, the remaining cumulative overages and smoothed operations on your capacity are summed, and added to your Azure bill. https://learn.microsoft.com/en-us/fabric/enterprise/pause-resume
Jerome22yes, I know the remaining CUs are billed.
but for now there is a bug, the system still counting terminated activities and background activities still appeared without any reason.
so my background CU is going higher and higher and never down like we can see anywhere else.
the extra CU I pay are just few minutes of CUs, so normally these CU should be recovered during IDLE time without any issue, but it's not the case.
for example, during 1am and 5am there is no activity in fabric, this mean that any terminated background activity can use this available capacity to "reimburse" Microsoft. but I'm seeing an increase in usage...
in the video you sent, we can clearly see that the blue chart (background) is going up than down and than back to 0 most of the time, even after there was big front activities.
also in the video the number of background activities is pretty low, few hundreds.
in my case this value jump to hundred of thousands !!! yes more than 200 000 background activities, during IDLE time. really crazy.
and I'm not doing something complicated or resource intensive. (compared to the video)
well... there are issues and MS has to solve this. or improve the way background activities are "billed"
- frithjof_v
When we use the Multi Metric Ribbon Chart to drill down to a specific day and a specific hour (for example 1 am), and then click on the specific hour on the x-axis of the Multi Metric Ribbon Chart, this crossfilters the Items (14 days) visual so that it changes name to Items (1 day).
However, when we select a specific day and hour combination in the Multi Metric Ribbon Chart, we are actually able to see the list of which artifacts are consuming CU (s) in that specific hour, by looking at the Items (1 day) visual.
Which artifacts in your capacity are using CU (s) at that time? What type of items do you have in the Items (1 day) visual when you use the Multi Metrics Ribbon Chart to cross-filter down to a specific day and hour? For example, 1 am on Oct 13. This is very useful to understand what is going on.
The two visuals mentioned above show the actual, raw consumption. So these are the visuals which are easiest to interpret.
The CU (%) Over Time visual shows the smoothed consumption, so it is a bit more difficult to interpret. However, if the CU (%) Over Time visual is rising in the specified hour, there must be some artifacts in the Item (1 day) visual that tells which artifacts are the cause of the rise.
The drill-through page (Timepoint) also shows smoothed consumption mainly, so that page is also more difficult to interpret. Also note that a single refresh of a semantic model will trigger several background operations. So it's better to use the main page's Multi Metric Ribbon Chart to cross-filter the Items (14 days) visual in order to identify which artifacts are the cause of the CU (s) consumption. And use the tooltip in the Items (14 days) visual to see which kind of operations are consuming CU (s) for your items.
- Jerome22
I did extensive analysis of these background operations.
they starts as soon as I pause and resume my instance, before conducting any type of activity.
and like I said, I can go up to 200 000 background operations!!!!
and the system is counting terminated activities in the background % usage for days.
I was able to track a background activity related to a simple SQL query consuming my CU for more than 24h!!!
like currently I have 0.625CU consumed by a process terminated yesterday (a pipeline), the dataflow consumed 1800CU, paid yesterday.
so this background activity will cost me 53 568CU per 24h for something which cost only 1800CU during its execution and was burndown in seconds.
and when I'll pause my instance, MS will charge me for these CUs!!!!
I'm curious to know if you see the same behaviors. a standard process staying in background operation for 1 day or more. and a consumption during this time greater than the activity itself.