/usr/lib/cnf-update-db:sqlite3.OperationalError:/usr/lib/cnf-update-db@26:create

imho we should be resilient.

Catch errors, ignore them, report success / skip, and ensure that ux is fine.

As a reproducer, one should be able to lock the db externally, run apt-update and see how it looks like.

This is a working reproducer:

sudo cp /var/lib/command-not-found/commands.db /var/lib/command-not-found/commands.db.tmp
sudo sqlite3 /var/lib/command-not-found/commands.db.tmp
SQLite version 3.31.1 2020-01-27 19:55:54
Enter ".help" for usage hints.
sqlite> PRAGMA locking_mode = EXCLUSIVE;
exclusive
sqlite> BEGIN EXCLUSIVE;
sqlite>

sudo rm /var/lib/command-not-found/commands.db.metadata
sudo PYTHONPATH=. ./cnf-update-db --verbose
Traceback (most recent call last):
  File "./cnf-update-db", line 26, in <module>
    col.create(db)
  File "/home/lukas/canonical/01-Distro/command-not-found/CommandNotFound/db/creator.py", line 92, in create
    con.executescript(create_db_sql)
sqlite3.OperationalError: database is locked

I've attached two debdiff patches to fix the problem for focal (command-not-found 20.04.2) and groovy (command-not-found 20.10.0). I'm looking for a sponsor/review.

This bug was fixed in the package command-not-found - 20.10.1

---------------
command-not-found (20.10.1) groovy; urgency=medium

  * Avoid crash if tmpdb is locked. Skip execution and let the other process
    do its job. (LP: #1875760)

 -- Lukas Märdian <email address hidden> Mon, 03 Aug 2020 13:06:59 +0200

Apparently version 20.04.3 has already be used/burned in focal.
Attaching another debdiff `cnf-focal2.debdiff`, to bump the version to 20.04.4 ...

Hello errors.ubuntu.com, or anyone else affected,

Accepted command-not-found into focal-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/command-not-found/20.04.4 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-focal to verification-done-focal. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-focal. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Hello Lukasz,

I could successfully verify this SRU inside a Focal LXD container for command-not-found 20.04.4:
root@f:~# dpkg -l | grep command-not-found
ii command-not-found 20.04.4 all Suggest installation of packages in interactive bash sessions
ii python3-commandnotfound 20.04.4 all Python 3 bindings for command-not-found.

root@f:~# apt update
...
root@f:~# cp /var/lib/command-not-found/commands.db /var/lib/command-not-found/commands.db.tmp
root@f:~# ll /var/lib/command-not-found/
total 6064
drwxr-xr-x 2 root root 4096 Aug 27 07:11 ./
drwxr-xr-x 24 root root 4096 Aug 27 07:08 ../
-rw-r--r-- 1 root root 3096576 Aug 27 07:11 commands.db
-rw-r--r-- 1 root root 3634 Aug 27 07:11 commands.db.metadata
-rw-r--r-- 1 root root 3096576 Aug 27 07:11 commands.db.tmp
root@f:~# sqlite3 /var/lib/command-not-found/commands.db.tmp
SQLite version 3.31.1 2020-01-27 19:55:54
Enter ".help" for usage hints.
sqlite> PRAGMA locking_mode = EXCLUSIVE;
exclusive
sqlite> BEGIN EXCLUSIVE;
sqlite>

root@f:~# rm /var/lib/command-not-found/commands.db.metadata
root@f:~# /usr/lib/cnf-update-db --verbose
WARNING:root:/var/lib/command-not-found/commands.db.tmp is locked by another process. Ignoring.
root@f:~# echo $?
0

After the database is unlocked, the application runs as expected:
root@f:~# /usr/lib/cnf-update-db --verbose
INFO:root:processed 14855 packages in 1.45s

This bug was fixed in the package command-not-found - 20.04.4

---------------
command-not-found (20.04.4) focal; urgency=medium

  * Avoid crash if tmpdb is locked. Skip execution and let the other process
    do its job. (LP: #1875760)

 -- Lukas Märdian <email address hidden> Mon, 03 Aug 2020 13:10:24 +0200

The verification of the Stable Release Update for command-not-found has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.