Since the debut of the test-driver, we didn't obtain
a race timer with the test execution to ensure that tests doesn't run beyond
a certain amount of time.
This is particularly important when you are running into hanging tests
which cannot be detected by current facilities (requires more pvpanic wiring up, QMP
API stuff, etc.).
Two easy examples:
- Some QEMU tests may get stuck in some situation and run for more than 24 hours → we default to 1 hour max.
- Some QEMU tests may panic in the wrong place, e.g. UEFI firmware or worse → end users can set a "reasonable" amount of time
And then, we should let the retry logic retest them until they succeed and adjust
their global timeouts.
Of course, this does not help with the fact that the timeout may need to be
a function of the actual busyness of the machine running the tests.
This is only one step towards increased reliability.
This warning was added a year and a half ago, but still no test in
NixOS directly instantiates the machine class, presumably because it's
not actually possible for a test to do so without losing
functionality. For example, there's no way for a NixOS test to access
the output directory that create_machine passes to the Machine
constructor.
This warning is therefore just contributing to alert fatigue for
users, who are unable to follow its advice. Once it's actually
possible to do what it suggests, the warning can be reintroduced.
Naively deduplicate VLANs in the python driver for NixOS tests. The
current implementation accidentally works, since the VLan class mutates
the environment. On construction it sets QEMU_VDE_SOCKET_${id} and this
environment variable gets overwritten once a second VLAN with the same
id is constructed. Because the NIC flags passed to qemu just use the
QEMU_VDE_SOCKET_${id} environment variable, this implicitly chooses a
single vde_switch process for each VLAN.
However, this leads to unusable vde_switch processes being spawned in
each test run and as a side effect makes it impossible to access the
correct VLan objects in the interactive test driver. It also makes it
remarkably hard to understand why the current implementation ever
worked.
