Cwa-app-ios: Duplicate risk check performed after recovering from #1497

[ndegendogo]

Avoid duplicates

• [ ] Bug is not mentioned in the FAQ
• [ ] Bug is not already reported in another issue

Describe the bug

A friend installed cwa 1.5.3 two days ago for his first time; next day updated to 1.6.0. Before his very first risk check he opened the app, but was affected by issue #1497. He pressed home button while error message was still visible, and waited for several hours.
Several hours later he followed the recommendations in the FAQ, stopped cwa (swipe), and started cwa again - this time successfull - and got the check.
But ENF exposure log shows two attempts: first with 13 files (the newest missing), immediately followed by another loop (now all 14 files).

cwa 1.6.0 / iOS 14.2 / iPhone 12

Expected behaviour

A single loop of all 14 files.

Steps to reproduce the issue

Guessing a bit:

• have 14 files downloaded, but then a serious issue like #1497 blocks the check
• check is blocked for several hours
• oldest file expires
• cwa is started again, unblocks the pending check, and triggers another checking task (file download and check).

So the unblocked check presents only 13 files, and the new check presents all 14 files.

Does this make sense? 🤪

See screenshot with timestamps and ENF log file.
Note : the check on 12 Nov was already with cwa 1.6.1

Technical details

• cwa 1.6.0
• iOS Version: 14.2
• Device: iPhone 12

Possible Fix

Additional context

ExposureChecks-2020-11-12.json.txt

---

Internal Tracking ID: EXPOSUREAPP-3711

[dsarkar]

Hi @ndegendogo,

Thanks for posting this issue. It seems similar if not the same issue https://github.com/corona-warn-app/cwa-app-ios/issues/1475#issuecomment-724365359.

Best wishes,
DS

Corona-Warn-App Open Source Team

[ndegendogo]

@dsarkar well - I was aware of #1475, but decided for a new ticket because the error pattern is different. And only the devs can analyse if it has maybe a single root cause or not.

• #1475: a single error check with corrupted list of files (containing duplicate entries)
• this ticket: two error checks in close sequence

[dsarkar]

@ndegendogo, thanks for pointing out the difference. There is an internal JIRA ticket (Internal Tracking ID: EXPOSUREAPP-3711), regarding risk calculation being triggered too often, sometimes within seconds. We will let know the developers also about this specific issue you published here.

[Ein-Tim]

Related PR: https://github.com/corona-warn-app/cwa-app-ios/pull/1506 (planed for 1.7.0)

[ndegendogo]

... and today I could watch it live.

As always, I firstly checked the ENF log. It showed two checks today, at 13:49 with 14 files (too early; yesterday was at 17:45). Second check at 17:49 (in time, but 0 files!)

Then I opened cwa - it showed some error screen, I don't remember the exact message.
Edit: iirc the error screen showed some contradictional messages like "exposure logging active / exposure logging stopped", similar to here

After ~2 seconds it started to download data for some time, then performed the check for some time. After this another download and another check.

ENF log file shows now 5 checks in total. 17:49 now has 13 files (oldest missing). All other have full 14 files.

cwa 1.6.1(0) / iOS 14.2 / iPhone 8

ExposureChecks-2020-11-13.json.txt

[Ein-Tim]

Sometimes there are not only 2 checks performed at the same time but more, e.g. 3

I think this is also the root cause for the "ExposureDetectionIsAlreadyRunning"-Error. (#1497)

[mss1010]

Sometimes there are not only 2 checks performed at the same time but more, e.g. 3

I think this is also the root cause for the "ExposureDetectionIsAlreadyRunning"-Error. (#1497)

I also had the same behavior. Three checks when I opened the app manually before the 24-hour period finished.

[Ein-Tim]

@mss1010

before the 24-hour period finished.

This is at the moment (with 1.6.1) intended behavior (see https://github.com/corona-warn-app/cwa-app-ios/issues/1514#issuecomment-727602796)

[Ein-Tim]

I think this is solved with 1.7.1, or @ndegendogo

[ndegendogo]

I think this is solved with 1.7.1

Yes, this one and a lot more.
1.7.1 is the best release since long. 🚀

Closing the ticket