MySQL Bugs: #43570: MTR2 hangs when test fails and named pipe created

Bug #43570	MTR2 hangs when test fails and named pipe created
Submitted:	11 Mar 2009 17:39	Modified:	29 May 2009 1:12
Reporter:	Ingo Strüwing	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Tools: MTR / mysql-test-run	Severity:	S7 (Test Cases)
Version:	5.1+	OS:	Any
Assigned to:	Bjørn Munch	CPU Architecture:	Any

Description:
When setting the server variable 'backupdir', creating a named pipe, and not removing the pipe before test end, MTR2 hangs indefinitely (suite-timeout works though). There must not be a writer on the pipe. When writing to the pipe, MTR2 awakes and finishes.

I report this against MTR2 because mysqld, mysqltest, and all other clients exit normally. Only two perl processes remain.

The problem with this bug is that mysqltest exits if any unexpected error happens. This does not leave a chance for removing the pipe.

Using --no-check-testcase does not avoid the hang.

How to repeat:
Take an arbitrary test case, e.g. backup_default.
Insert these lines somewhere, e.g. at the end:

SET @old_backupdir = @@backupdir;
SET @@global.backupdir = @old_backupdir;
--exec mkfifo $MYSQLTEST_VARDIR/tmp/backup_fifo

As you can see, it is not required to actually change 'backupdir' to some specific value. It is sufficient to set it to same value it has already.

It is not necessary to do anything with the named pipe. Just create it.

Run the test like:

(cd mysql-test && ./mysql-test-run.pl --parallel=1 backup_default)

When the test hangs, look at the system's process list, e.g. ps -fe. You will notice that no mysqld, mysqltest, mysqladmin, or whatever exist, unless from independent usage (other tests or other applications).

You can release MTR from the hang by:

echo > mysql-test/var/tmp/backup_fifo

Note that the path of the named pipe may vary if not --parallel=1 is given.

Suggested triage values:
Defect: medium. Not critical, but destroys a test run when it happens.
Workaround: none. Test case cleanup doesn't help if an unexpected error happens.
Impact: substantial. All pushbuild tests are in danger as we need to test pipes.

This has notning to do with setting backup dir; any test that fails and has created pipes will hang while MTR tries to copy the tmp directory.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/71097

2780 Bjorn Munch	2009-04-01
      Bug #43570 MTR2 hangs when test fails and named pipe created
      Hangs when trying to copy the pipe
      Amend copytree() to only copy regular files
      modified:
        mysql-test/lib/My/File/Path.pm

Pushed to 6.0-mtr and 5.1-mtr

Pushed into 6.0.12-alpha (revid:alik@sun.com-20090514161729-xiup7q8jlu1zfy7s) (version source revid:bjorn.munch@sun.com-20090401202316-ft6r1mluuyuq0knq) (merge vers: 6.0.11-alpha) (pib:6)

Test suite changes. No changelog entry needed.

Setting report to NDI pending push into 5.1.x.

Pushed into 5.1.36 (revid:joro@sun.com-20090528073639-yohsb4q1jzg7ycws) (version source revid:bjorn.munch@sun.com-20090525205831-zitq9aysxy5zgf5r) (merge vers: 5.1.36) (pib:6)

Test suite change. No changelog entry needed.

Pushed into 5.1.37-ndb-7.0.8 (revid:jonas@mysql.com-20090826132541-yablppc59e3yb54l) (version source revid:jonas@mysql.com-20090826132541-yablppc59e3yb54l) (merge vers: 5.1.37-ndb-7.0.8) (pib:11)

Pushed into 5.1.37-ndb-6.3.27 (revid:jonas@mysql.com-20090826105955-bkj027t47gfbamnc) (version source revid:jonas@mysql.com-20090826105955-bkj027t47gfbamnc) (merge vers: 5.1.37-ndb-6.3.27) (pib:11)

Pushed into 5.1.37-ndb-6.2.19 (revid:jonas@mysql.com-20090825194404-37rtosk049t9koc4) (version source revid:jonas@mysql.com-20090825194404-37rtosk049t9koc4) (merge vers: 5.1.37-ndb-6.2.19) (pib:11)

Pushed into 5.1.35-ndb-7.1.0 (revid:magnus.blaudd@sun.com-20090827163030-6o3kk6r2oua159hr) (version source revid:jonas@mysql.com-20090826132541-yablppc59e3yb54l) (merge vers: 5.1.37-ndb-7.0.8) (pib:11)