MySQL Bugs: #40150: Please make mtr print result diff on all failures

Bug #40150	Please make mtr print result diff on all failures
Submitted:	19 Oct 2008 18:03	Modified:	21 Jan 2009 12:41
Reporter:	Sven Sandberg	Email Updates:
Status:	Won't fix	Impact on me:	None
Category:	Tests	Severity:	S7 (Test Cases)
Version:	5.1	OS:	Any
Assigned to:	Bjørn Munch	CPU Architecture:	Any
Tags:	mtr, result diff, timeout

Description:
When a test fails with timeout, there is almost no debug info (except SHOW PROCESSLIST in the last version of mtr, but it's usually not enough).

mtr should print a result diff when timeouts happen. That would make it possible to derive which command was last issued, and if anything unusual happened prior to the timeout.

This was requested in BUG#38181 and BUG#38817, both of which have been partially implemented. I'm opening this bug since it's one of the most important features missing from those requests. (Another outstanding feature request is printing stack trace under Windows, but see BUG#38817 for details.)

How to repeat:
-

triage: setting tag to checked as this is a feature request

Additional request: timeouts sometimes happen because the server has hanged. Therefore, we should also get a stack trace from the running process. With gdb, this can be done by "gdb /path/to/mysqld PID --eval-command='thread apply all bt'"

In fact, we should *always* have a result diff, no matter what type of failure it was. I think we currently don't get this if mysqltest crashes, for instance. There may be other cases too.

Please go through all mtr's execution paths and check that a result diff is always created if the test was at all started.

Please ignore my additional request for stack traces: that should be fixed in BUG#40399. The present bug is only to get a result diff after every failure.

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/58701

2692 Serge Kozlov	2008-11-13
      Bug#39861:
      1. mysqltest.cc - added flush to log file after each executed command in a testcase. 
      2. mtr shows 20 last lines from test case log file if timeout reached.
      3. Optimizing the code by Magnus review.
      4. It is partially fix bug#40150

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/58844

2698 Serge Kozlov	2008-11-14
      Bug#39861:
      1. mysqltest.cc - added flush to log file after each executed command in a testcase.
      2. mtr shows 20 last lines from test case log file if timeout reached.
      3. Optimizing the code by Magnus review.
      4. It is partially fix bug#40150

With the fix for bug #39861 which prints the last 20 lines of test case log, the "show processlist" output and the recent fix #40399 adding stack trace from servers, I think there would be very little extra to gain from printing the result diff. This diff would most likely just show what's missing after the test hanged or timed out (which could be quite much), and that can already be deduced from the last 20 lines which should show where it stopped.

Pushed into 6.0.10-alpha (revid:luis.soares@sun.com-20090129165607-wiskabxm948yx463) (version source revid:luis.soares@sun.com-20090129163120-e2ntks4wgpqde6zt) (merge vers: 6.0.10-alpha) (pib:6)

Pushed into 5.1.32 (revid:luis.soares@sun.com-20090129165946-d6jnnfqfokuzr09y) (version source revid:skozlov@mysql.com-20081114203532-hc6b88uie725xjkh) (merge vers: 5.1.31) (pib:6)

Pushed into 5.1.32-ndb-6.3.23 (revid:tomas.ulin@sun.com-20090217131017-6u8qz1edkjfiobef) (version source revid:tomas.ulin@sun.com-20090203133556-9rclp06ol19bmzs4) (merge vers: 5.1.32-ndb-6.3.22) (pib:6)

Pushed into 5.1.32-ndb-6.4.3 (revid:tomas.ulin@sun.com-20090217134419-5ha6xg4dpedrbmau) (version source revid:tomas.ulin@sun.com-20090203133556-9rclp06ol19bmzs4) (merge vers: 5.1.32-ndb-6.3.22) (pib:6)

Pushed into 5.1.32-ndb-6.2.17 (revid:tomas.ulin@sun.com-20090217134216-5699eq74ws4oxa0j) (version source revid:tomas.ulin@sun.com-20090201210519-vehobc4sy3g9s38e) (merge vers: 5.1.32-ndb-6.2.17) (pib:6)