[#MDEV-7643] MTR creates nested links when tests are run with --mem

Compare behavior in MySQL 5.5, MariaDB 5.5.41 and MariaDB 5.5.42:

MySQL 5.5
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l \| grep var
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l /dev/shm/ \| grep var
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ perl ./mtr main.1st --mem
Logging: ./mtr main.1st --mem
MySQL Version 5.5.42
...
Creating var directory '/data/repo/git/mysql-5.5/mysql-test/var'...
- symlinking 'var' to '/dev/shm/var_auto_UXHl'
...
Completed: All 1 tests were successful.

elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l \| grep var
lrwxrwxrwx 1 elenst disk 22 Feb 27 02:52 var -> /dev/shm/var_auto_UXHl
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l /dev/shm/ \| grep var
drwxr-xr-x 8 elenst disk 180 Feb 27 02:52 var_auto_UXHl

elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ perl ./mtr main.1st --mem
Logging: ./mtr main.1st --mem
MySQL Version 5.5.42
...
Creating var directory '/data/repo/git/mysql-5.5/mysql-test/var'...
- symlinking 'var' to '/dev/shm/var_auto_uUQE'
...
Completed: All 1 tests were successful.

elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l \| grep var
lrwxrwxrwx 1 elenst disk 22 Feb 27 02:52 var -> /dev/shm/var_auto_uUQE
elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l /dev/shm/ \| grep var
drwxr-xr-x 8 elenst disk 180 Feb 27 02:52 var_auto_uUQE

This is good behavior: a new folder in /dev/shm gets created, the old one gets removed, var points at the new one.

MariaDB 5.5.41
elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l \| grep var
elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l /dev/shm/ \| grep var
elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ perl ./mtr main.1st --mem
Logging: ./mtr main.1st --mem
vardir: /data/releases/mariadb-5.5.41-linux-x86_64/mysql-test/var
Removing old var directory...
Creating var directory '/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test/var'...
- symlinking 'var' to '/dev/shm/var_auto_frKD'
Checking supported features...
...
Completed: All 1 tests were successful.

elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l \| grep var
lrwxrwxrwx 1 elenst disk 22 Feb 27 02:56 var -> /dev/shm/var_auto_frKD
elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l /dev/shm/ \| grep var
drwxr-xr-x 8 elenst disk 180 Feb 27 02:56 var_auto_frKD

elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ perl ./mtr main.1st --mem
Logging: ./mtr main.1st --mem
vardir: /run/shm/var_auto_frKD
Checking leftover processes...
Removing old var directory...
Creating var directory '/run/shm/var_auto_frKD'...
Checking supported features...
MariaDB Version 5.5.41-MariaDB
...
Completed: All 1 tests were successful.

elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l \| grep var
lrwxrwxrwx 1 elenst disk 22 Feb 27 02:56 var -> /dev/shm/var_auto_frKD
elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l /dev/shm/ \| grep var
drwxr-xr-x 8 elenst disk 180 Feb 27 02:56 var_auto_frKD
drwx------ 2 elenst disk 40 Feb 27 02:56 var_auto_nlxl

It's bad behavior: a new folder gets created, the old one is kept, var points at the old one. Eventually there will be lots of folders in /dev/shm, but it's only marginally dangerous since they all will be empty.

elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l /dev/shm/ | grep var

elenst@wheezy-64:~/git/5.5/mysql-test$ perl ./mtr 1st --mem

Logging: ./mtr  1st --mem

vardir: /data/repo/git/5.5/mysql-test/var

Removing old var directory...

Creating var directory '/data/repo/git/5.5/mysql-test/var'...

 - symlinking 'var' to '/dev/shm/var_auto_aE7b'

Checking supported features...

MariaDB Version 5.5.42-MariaDB-debug

...

Completed: All 1 tests were successful.

elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l | grep var

lrwxrwxrwx  1 elenst disk     22 Feb 27 02:59 var -> /dev/shm/var_auto_aE7b

elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l /dev/shm/ | grep var

drwxr-xr-x 9 elenst   disk          200 Feb 27 02:59 var_auto_aE7b

elenst@wheezy-64:~/git/5.5/mysql-test$ perl ./mtr 1st --mem

Logging: ./mtr  1st --mem

vardir: /run/shm/var_auto_aE7b

Checking leftover processes...

Removing old var directory...

Creating var directory '/run/shm/var_auto_aE7b'...

 - symlinking 'var' to '/dev/shm/var_auto_Ex34'

Checking supported features...

MariaDB Version 5.5.42-MariaDB-debug

...

Completed: All 1 tests were successful.

elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l | grep var

lrwxrwxrwx  1 elenst disk     22 Feb 27 02:59 var -> /dev/shm/var_auto_aE7b

elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l /dev/shm/ | grep var

lrwxrwxrwx 1 elenst   disk           22 Feb 27 02:59 var_auto_aE7b -> /dev/shm/var_auto_Ex34

drwxr-xr-x 9 elenst   disk          200 Feb 27 02:59 var_auto_Ex34

This is awful behavior: a new folder gets created, instead of the old folder a link with the same name points at the new folder, var points at the old folder (now a link). Soon enough the chain becomes too long and further tests refuse to run.

At least the old behavior should be restored. Better still, it should work the way MySQL does.

[MDEV-7643] MTR creates nested links when tests are run with --mem Created: 2015-02-27 Updated: 2015-03-09 Resolved: 2015-03-09
Status:	Closed
Project:	MariaDB Server
Component/s:	Tests
Affects Version/s:	5.5.42, 10.0.16
Fix Version/s:	5.5.43, 10.0.18

[MDEV-7643] MTR creates nested links when tests are run with --mem Created: 2015-02-27 Updated: 2015-03-09 Resolved: 2015-03-09