[Libguestfs] [nbdkit PATCH] RFC: blocksize: Add test for sharding behavior

[Nikolaus Rath]

On May 26 2022, "Richard W.M. Jones" <rjones at redhat.com> wrote:
> Is there any way to do this without the literal sleeps?  Gitlab CI in
> particular appears to be very contended (I guess it runs in parallel
> on huge systems with vast numbers of unrelated containers).  I've seen
> threads being created that are so starved they never run at all even
> in tests running for many tens of seconds.
>
> I'm thinking some kind of custom plugin which orders operations using
> its own clock that it is incremented as certain requests arrive, but I
> don't have a fully-formed idea of how it would work.

I think this should be possible. I've written similar tests for
S3QL. However, it is much more complex and prone to result in deadlocks
in cases where the tests should fail. Is there a timeout mechanism that
is applied to individual tests?

One way to do it is to have the test code and NBD server in the same
process, so we can use mutexes etc to ensure that we are testing the
intended sequence of events.

Another way would be to have the test communicate with the NBD server
through a side-channel (say a pipe), so that the test knows when to send
the second request.


Best,
-Nikolaus

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