Monday, July 17, 2017

Fun with Bugs #53 - On Some Percona Software Bugs I've Reported

So far in this series I had written only/mostly about MySQL server bugs. Does it mean that there are no unique or interesting bugs in other MySQL-related software or MySQL forks and projects that use MySQL code?

Surely no, it doesn't. So, today I'd like to present a short list of currently active (that is, new or probably not yet resolved) bugs that I had reported for Percona's software at Launchpad over the years I use it. The list is based on this link, but I excluded minor reports and those that probably are just forgotten, while the problem is fixed long time ago.

Let me start with bugs in XtraBackup, the tool that plays a key role in most MySQL environments that are not using Oracle's Enterprise subscriptions:
  • lp:1704636 - "xtrabackup 2.4.7 crashes while backing up MariaDB 10.2.x with ftwrl-* options". I've reported it yesterday. Probably some unique background thread of MariaDB 10.2.x is not taken into account and some calculations are performed for it that lead to crash. Sorry, but there is no way to use --ftwrl-* options of XtraBackup with MariaDB 10.2.x.
  • lp:1418150 - "Provide a way for xtrabackup to communicate with storage managers via XBSA API". This is a feature request created based on customer's request to store backups in Tivoli Storage Manager. Similar request was recently noted from MariaDB customer as well. MySQL's Enterprise Backup allows to work with storage managers, even if not in the most direct way. I've used TSM a lot in the past in production as Informix DBA, so I care about this feature more than about many others...
Let's continue with another unique software package from Percona, Percona Toolkit. I still use some of the tools every day (and do not hesitate to write about this), and would like to see more attention to the toolkit in areas other than MongoDB. I've reported the following two bugs in the past that are still active:
  • lp:1566939 - "pt-stalk should not call mysqladmin debug by default". Having in mind documentation Bug #71346 that Oracle just refuses to fix, I'd say there may be a dozen of people in the world who can make a good use of the output even when it's correct, useful and really needed. For the rest of us it just pollutes error logs and pt-stalk data collections.
  • lp:1533271 - "pt-online-schema-change does not report anything when it waits for slave to replicate new table creation". The problem is clear enough from description. There is nothing useful to find out the reason for the hang in this case without PTDEBUG=1.
Finally, let's check several Percona Server bugs. Note that in many cases i had to file bug for Percona Server even if upstream MySQL was also affected, in a hope that Percona may fix the problem faster (and this happened sometimes). The following bugs were not inherited from MySQL directly:
  • lp:1455432 - "Audit log plugin should allow to include or exclude logging for specific users". This was request for the same functionality that was originally provided in MariaDB's implementation. Actually the bug was fixed in Percona Server 5.6.32-78.0 and 5.7.14-7, but remains in the list as it is still just "Triaged" for 5.5.x branch. Time to close it completely, I'd say.
  • lp:1408971 - "Manual does not describe Innodb_current_row_locks in any useful way". Nothing changed, check the manual.
  • lp:1401528 - "Add option to switch to "old" get_lock() behavior". It's hard to introduce new features in minor release during GA period, and do it right. Somebody had to think about backward compatibility, upgrades and downgrades, and about the completeness of implementation (see lp:1396336 about that). In this specific case Percona failed to do it right.
  • lp:1396035 - "Percona-Server-test-56 RPM package does NOT check /usr/share/percona-server directory and thus is unusable "as is". Packaging is another thing that is hard to do right. I was not lazy today, so I re-check this on CentOS 6.x. with 5.7.18, and ./mtr is somewhat useful there:

    [root@centos mysql-test]# ls -l ./mtr
    lrwxrwxrwx. 1 root root 19 Jun  7 18:20 ./mtr -> ./
    [root@centos mysql-test]# perl ./mtr analyze
    Logging: ./mtr  analyze
    MySQL Version 5.7.18
    Checking supported features...
     - SSL connections supported
    Collecting tests...
    Checking leftover processes...
    Removing old var directory...
    Creating var directory '/usr/share/mysql-test/var'...
    Installing system database...
    Using parallel: 1


    TEST                                      RESULT   TIME (ms) or COMMENT

    worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 13000..13009
    worker[1] mysql-test-run: WARNING: running this script as _root_ will cause some tests to be skipped
    main.analyze                             [ pass ]  10920
    The servers were restarted 0 times
    Spent 10.920 of 58 seconds executing testcases

    Completed: All 1 tests were successful.
  • lp:1263968 - "DOCS: does not provide enough details on further steps after installing .deb". I'd still say that some details requested are missing. Writing proper manuals is hard.
I had surely reported a lot more bugs, but many of them have related upstream MySQL ones, so there are no reasons to discuss them separately now. Also, note that in Percona I was involved in setting priorities for the bugs and mostly reported them based on customer issues or complains. So, no wonder that my bug reports were fixed fast, and not so many active ones left by now.

There was yet another Percona tool that I spent as lot of time on, both on building it from current sources, using it and  reporting problems with it. It's Percona Playback, Based on this, they seem to work on other but similar tool now. Still, I consider this request useful for any tool that allows to replay specific load: lp:1365538.

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