Are session apps automatically created in background when regular apps opened?

[mountaindude]

I am pulling data from the healthcheck API, works great.

I am however seeing something that I don't quite understand: 

• I start with a freshly restarted QSEoW, April 2020 (the same thing happens on earlier versions too). No apps loaded in the engine thus.
• From the hub I open one app.
• Sure enough, after a second or so that app shows up in the healthcheck API's list of loaded apps. But there is also a new session app, coming from somewhere.
• I open a second app from the hub. It shows up in the healthcheck API's list of apps loaded in memory, together with another new session app.

I have a vague feeling that I long ago heard about these session apps being used for behind-the-scenes data profiling... or something. Can't remember. 

Anyone knows under what circumstances these session apps are created, what they do, how big they will be (I am thinking performance impact etc)?

More visual example below:

[RadovanOresky]

Hi,

Also noticed this. Since I upgraded from Feb 2020 to June 2020 the number of Total Sessions basically doubled, because there is the regular + session app returned in the healthcheck for each app opened in the client.

Maybe @Levi_Turner could know what is the purpose of these apps and how they influence performance / resource utilization?

[juraj_misina]

Hi Göran,

at least once I was able to track a session app to Data manager being opened. This spawned a session app and started reload, effectively overwriting a QVD or two in production. It was fun to track and trace, I tell you 😕

Juraj

[gandalfgray]

Hi Göran!

Did you find out anything about these SessionApp apps?

As far as I can see they are related to the editing of apps, I have only checked once (right now) and of the 8 nodes we have the only node having SessionApp apps is the one where Development is allowed.

They seem to be temporary apps, if you try to find the app using the ID (with or without removing the "SessionApp_" part of it) you don't find anything.

Would be nice if someone from Qlik could explain this a bit!

[Øystein_Kolsrud · Accepted solution]

If you look at the websockets that are opened when you open an app in a browser, then you'll see that there are two of them. One of them has the path /app/{appid}, and this is the one communicating directly to the engine where all the user interaction occurs. Then there is another one with the path /dataprepservice/app/{appid}. This is, as the path shows, used for communicating with the dataprep service which is used by the product for some background operations especially when you use the data manager. This service creates a session app behind the scenes to do it's analysis, so that is probably where the session app you are observing is coming from.

[mountaindude]

I came to more or less the conclusion that @Øystein_Kolsrud describes, but coming from the source I suggest we take that explanation as the truth :).

Accepted as solution. 

[PabloLabbeImaps]

Now I'm struggling with same issue on a saturated server .

How we can know how much memory this apps can take when on memory ? 

Do the dynamic view also create this session apps ?