App "forgets" about checks if opened without Internet connection

[Ein-Tim]

Avoid duplicates

• Bug is not mentioned in the FAQ
• Bug is not already reported in another issue (see related Issues at the the bottom)

Describe the bug

The App "forgets" old checks (which are not yet 24h old) if you open it without a connection to the internet.

Expected behaviour

The App should not download new data more than once in 24h.

Steps to reproduce the issue

1. Make sure the last check was min. 10 minutes ago performed
2. Switch off Internet
3. Open the App, you will see this screen
4. Close the App (don't leave it in the background, swipe it up)
5. Open the App agian with Internet Connection, a check will be performed

Technical details

• iOS Version: 14.2
• Device: iPhone XR
• CWA Version: 1.6.1

Additional Inforamtion

How it looks

App without Internet Connection at 15:05, last check was done at 10:36	Open the App with Internet, Check is instantly done	Screenshot of the EN Log in Settings	App without Internet Connection at 15:19, last check was done at 15:06	Open the App with Internet, Check is instantly done	Screenshot of the EN Log in Settings

EN-Log:
ExposureChecks-2020-11-15.txt (There are 3 checks at 16:09, this was also the time I tested this again, so this behaviour is surely also linked to this Issue...)

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Related Issues

• Exposure check failed when opening the CWA Version 1.6.0 / 1.6.1 (ExposureDetectionIsAlreadyRunning)  #1497
• Duplicate risk check performed after recovering from #1497 #1505

[thomasaugsten]

This behavior is in 1.6.1 intended because we cannot load the configuration of the app. After a successful load of the configuration we do the exposure check again to ensure the result based on the latest config. But we will improve this in the future.

[ndegendogo]

Expected behaviour
The App should not download new data more than once in 24h.

@Ein-Tim actually, we are requesting more frequent checks since long - of course as long as this does not have negative side-effects

[Ein-Tim]

@thomasaugsten

But we will improve this in the future.

Do you refer to this PR: #1506?
One more question, when will we see more frequent checks? With 1.7.0 or 1.8.0?

@ndegendogo

actually, we are requesting more frequent checks since long - of course as long as this does not have negative side-effects

That's true, but, correct me if I'm wrong, the server still only publishes new data once a day, or? So these checks always download the same data -> fill up more space on the users device...

And what definetly should not happen is that sveral checks are done at the same time (this did not happen only once but now again, and also on another device)... (But this Issue is already tracked in #1505)

[AnOtherMuenchner]

This "feature" can be used to shift the time point of comparison the an earlier point of time.

Normally, the app updates after at least 24 hours. Means: today at 12:00pm, tomorrow: 12:03pm, next day: 12:10pm and so an.

But when I open the app in the morning without connection, I get an error that the comparison has failed. When I switch on the connection, the app does the update. Also if it is before the update time of the day before.

[Ein-Tim]

@AnOtherMuenchner Yes I understand, I will close this Issue after my questions here are answered 👍

[ndegendogo]

That's true, but, correct me if I'm wrong, the server still only publishes new data once a day,

as far as I know: yes. But if the client downloads more often, the strategy can change with a server update.
Of course the other order is possible as well: prepare 'hourly' endpoints at the server additionally to the 'daily' endpoints, then you can switch with a client update.

[ndegendogo]

@Ein-Tim by the way, your ENF log shows a corrupted list of files, with duplicate entries, similar to #1475 this comment

all checks on 15 Nov, and even the check on 14 Nov show this pattern
look at file with hash 54EB...

[thomasaugsten]

@Ein-Tim
Yes this PR will improve this. No new key files are downloaded they are cached based on the hash.
Every 4h exposure checks based on the hourly key files is planned for 1.7

[Ein-Tim]

Okay thanks, since now everything is clear I will close this Issue.