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cups vm tests: fix race condition, add more tests #338193

Merged
merged 4 commits into from
Oct 29, 2024
Merged

cups vm tests: fix race condition, add more tests #338193

merged 4 commits into from
Oct 29, 2024

Commits on Oct 27, 2024

  1. cups: add 'cups-pdf' vm test to passthru.tests 

    While aimed at the cups-pdf printing package,
this vm tests also serves as a test for
the cups printing module in general.
    @Yarny0
    Yarny0 committed Oct 27, 2024
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  2. nixos/tests/printing: fix race of lpstat and ensure-printers 

    There is a nasty race condition in the cups tests.
To understand what is going on, one must first note that
printers are installed in the vms with ensure-printers.service,
which is started as part of multi-user.target.
ensure-printers.service in turn triggers a start of
cups.service as it needs to connect to the local cups daemon.

This is what happens when the test runs:
1  the test waits for cups.socket or cups.service to start up
   (subtest "Make sure that cups is up on both sides...")
2  after cups.service started
   (it starts even in the "socket" case,
   triggered by ensure-printers.service),
   ensure-printers.service is started
3  the test tries to connect to the cups daemons via curl
   (subtest "HTTP server is available too")
4  the test verifies the required printers are installed
   ("lpstat -a" called by subtest "LP status checks")

Usually, 3 needs some time, so ensure-printers.service
already installed all printers that are required by 4.
But if 3 is too fast, or if ensure-printers.service is too slow,
4 fails to find the printers it is looking for.

One can provoke the problem by adding

> systemd.services.ensure-printers.serviceConfig.ExecStartPre = "/run/current-system/sw/bin/sleep 10";

to the `nodes.client` configuration.

The commit at hand fixes the problem by changing 1:
Instead of waiting for cups,
it now waits for ensure-printers.service
(which in turn waits for cups.service and cups.socket).
This is also in accordance with the
subtest description in the code that promises to
"Make sure that cups is up [...] and printers are set up".
    @Yarny0
    Yarny0 committed Oct 27, 2024
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  3. nixos/tests/printing: inherit lib

    @Yarny0
    Yarny0 committed Oct 27, 2024
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  4. nixos/tests/printing: test cases for domain socket only config 

    Add two new vm tests for the printing configuration that
test `listenAddresses = []`, i.e., the situation where cups
only listens on the unix domain socket `/run/cups/cups.sock`.

This helps catching bugs like this:

OpenPrinting/cups#985
NixOS#337748
    @Yarny0
    Yarny0 committed Oct 27, 2024
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