Re: [Tarantool-patches] [PATCH v1] test: fix flaky replication/wal_rw_stress.test.lua

[Alexander Turenko <alexander.turenko@tarantool.org>]

On Fri, Jun 19, 2020 at 04:38:00PM +0300, Alexander V. Tikhonov wrote:
> Hi Alexander, thanks for the review, please check my comments.
> Also found that the comment in the original test mistakenly has
> issue number 3893 instead of 3883 - I've fixed it.
> 
> On Thu, Jun 18, 2020 at 11:50:46PM +0300, Alexander Turenko wrote:
> > TL;DR: Can you verify that the problem we want to detect with the test
> > still may be detected after the fix?
> > 
> > (More details are below.)
> > 
> > WBR, Alexander Turenko.
> > 
> > > diff --git a/test/replication/wal_rw_stress.test.lua b/test/replication/wal_rw_stress.test.lua
> > > index 08570b285..48d68c5ac 100644
> > > --- a/test/replication/wal_rw_stress.test.lua
> > > +++ b/test/replication/wal_rw_stress.test.lua
> > > @@ -38,7 +38,7 @@ test_run:cmd("setopt delimiter ''");
> > >  -- are running in different threads, there shouldn't be any rw errors.
> > >  test_run:cmd("switch replica")
> > >  box.cfg{replication = replication}
> > > -box.info.replication[1].downstream.status ~= 'stopped' or box.info
> > > +test_run:wait_cond(function() return box.info.replication[1].downstream.status ~= 'stopped' end) or box.info
> > >  test_run:cmd("switch default")
> > 
> > The comment above says 'there shouldn't be any rw errors'. Your fix
> > hides a transient 'writev(1), <...>', which I guess is a temporary
> > connectivity problem. But I guess it also may hide an rw error for which
> > the test case was added (related to disc). Or such error should keep the
> > relay in the stopped state forever?
> 
> I've checked the error for which the test was added. I've reverted the
> b9db91e1cdcc97c269703420c7b292e0f125f0ec ('xlog: fix fallocate vs read
> race') patch and successfully got the needed error "tx checksum
> mismatch":

Thanks for the verification! Okay so. LGTM.

Nit: I would add a comment to the test that wait_cond() allows to
overcome a transient network connectivity errors, but 'tx checksum
mismatch' is persistent one and will be catched.

WBR, Alexander Turenko.