I am linking this issue to MDEV-28856 because the CI failures in the
description appear in bb-11.2-ycp-mdev-28856, development branch
with spider commits that are under review or have been reviewed,
with the changes for MDEV-28856 on top.

Actually, this issue is probably not related to MDEV-28856, as the
failures don't appear in bb-11.3-mdev-28856, and given it is failing
in multiple builds in bb-11.3-ycp-mdev-28856, it is probably some
other commits in the latter branch.

Lowering the prio since it is not appearing in main branches.

Hi julien.fritsch, I do not see it happening in 11.2, so I'm not
sure if it makes sense to add 11.2 as a fixversion.

The bug appeared in some of my custom branches, which contain unpushed
commits (probably the cause), or pushed but not merged commits
(probably not the cause).

I think it is ok for it to not appear in my queue atm, as it will
re-emerge if it still exists.

Some observations:

Today I applied commits for MDEV-32157 to a custom branch
(bb-11.0-ycp-mdev-26247):

2f2fbabe24c MDEV-32157 MDEV-28856 Spider: Tests, documentation, small fixes and cleanups
13ca614e1b3 MDEV-32157 MDEV-28856 Spider: drop server in tests

Before the application, the branch seems to consistently fail
mdev_27240 when running mtr on spider suites:

./mysql-test/mtr --suite spider,spider/,spider//* --skip-test="spider/oracle.|./t\..*" --parallel=auto --big-test --force --max-test-fail=0

But after the application of these commits, the failure disappeared.

I could not reproduce the failure in a debuggable way, and
ER_NET_READ_ERROR is a very rare and strange error. Given that the
failure is pretty consistent, unlike MDEV-31586 which displays
multiple errors, and the alternative error code is more a nuisance
than a problem, and is irrelevant to the actual bug in MDEV-27240, I
am going to add the alternative error code as an option in the test
file, like so:

976ab215416 upstream/bb-10.10-mdev-22979 MDEV-32046 Fix flaky error codes in spider/bugfix.mdev_27240

Another one, even rarer failure, this time on spider/bugfix.mdev_27239.

https://buildbot.mariadb.org/#/builders/160/builds/23176

spider/bugfix.mdev_27239                 w12 [ fail ]

        Test ended at 2023-10-05 20:53:32

CURRENT_TEST: spider/bugfix.mdev_27239

--- /home/buildbot/ppc64le-ubuntu-2004/build/storage/spider/mysql-test/spider/bugfix/r/mdev_27239.result	2023-10-05 08:00:34.000000000 +0000

+++ /home/buildbot/ppc64le-ubuntu-2004/build/storage/spider/mysql-test/spider/bugfix/r/mdev_27239.reject	2023-10-05 20:53:31.877054131 +0000

@@ -9,10 +9,11 @@

 CREATE TABLE tbl_a (a INT) ENGINE=SPIDER;

 FLUSH TABLE tbl_a WITH READ LOCK;

 Warnings:

+Error	1158	Got an error reading communication packets

 Error	1429	Unable to connect to foreign data source: localhost

-Error	1429	Unable to connect to foreign data source: localhost

-Error	1429	Unable to connect to foreign data source: localhost

-Error	1429	Unable to connect to foreign data source: localhost

+Error	1429	Got an error reading communication packets

+Error	1429	Got an error reading communication packets

+Error	1429	Got an error reading communication packets

 BEGIN;

 DROP DATABASE auto_test_local;

 for master_1

It is worth further investigation, but not important enough to block
MDEV-22979, so I'm gonna lower the prio back to major and push the
workaround in the previous comment and leave this ticket open.

Updated on [2023-10-17 Tue]: this happened again, in the recent
10.6->10.10 push: https://buildbot.mariadb.org/#/builders/181/builds/23899