[Bug 1657256] Re: Percona crashes when doing a a 'larger' update

Wed Oct 4 13:57:04 UTC 2017

There seems to be a ton of confusion here. I have commented to various
people on IRC as they have asked me. But the messages don't seem to have
been received. I'll try and summarize my opinion here.

0. I asked for a link to document upstream's rejection of this patch in
comment 33 and on IRC[1].

1. It seems inappropriate for an SRU affecting users to be blocked on an
unrelated FTBFS fix for the development release, such as in this case
where the build for the actual fix in the development release has got
caught up with the transition to gcc-7. I would not block the progress
of the SRU on this.

2. However, if the fixing of the development release is trivial, then
I'd expect it to be done to minimise risk to users in the future, in the
spirit of the SRU policy. In other words, if it takes just half an hour
of developer time, can we just do it? If what I think is the most
appropriate fix for the development release turns out to be non-trivial,
then sure, we can proceed with the SRU without it.

3. To fix this in the development release, I suggested a minimal distro
patch that stops warning->error for non-bugs is OK to fix this and
suggested that you could look at a recent and similar fix in squid3 for
an example[2].

4. In response to the debdiff in comment 38, I said that I didn't
understand why you didn't follow my previous suggestion, and that the
approach there is not suitable for the development release since it
would hold back the gcc-7 transition rather than progressing it[3].

[1] https://irclogs.ubuntu.com/2017/09/01/%23ubuntu-devel.html#t15:59
[2] https://irclogs.ubuntu.com/2017/09/01/%23ubuntu-devel.html#t16:20
[3] https://irclogs.ubuntu.com/2017/09/19/%23ubuntu-devel.html#t16:14

To make progress, in the first instance, please work on 3. If it turns
out to be non-trivial, please talk to me again. I'd also appreciate you
resolving 0 but I don't think that's a blocker right now.

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https://bugs.launchpad.net/bugs/1657256

Title:
  Percona crashes when doing a a 'larger' update

Status in OpenStack Charm Test Infra:
  Confirmed
Status in percona-xtradb-cluster-5.5 package in Ubuntu:
  Confirmed
Status in percona-xtradb-cluster-5.6 package in Ubuntu:
  In Progress
Status in percona-xtradb-cluster-5.5 source package in Trusty:
  Confirmed
Status in percona-xtradb-cluster-5.6 source package in Xenial:
  Confirmed
Status in percona-xtradb-cluster-5.6 source package in Zesty:
  Confirmed
Status in percona-xtradb-cluster-5.6 source package in Artful:
  In Progress

Bug description:
  [Impact]

   * Percona will segfault when exposed to medium load, almost imediately
   * This is because of a bug in upstream, which manifests only on PPC

  [Test Case]

   * Install and configure percona-xtradb-cluster-server
    * Run sysbench against configured node (only one node is needed, no need for proper cluster):
     # sysbench --test=oltp --oltp-test-mode=complex --max-time=60 --num-threads=110 run
   * mysqld will segfault seconds withing starting the test

  [Regression Potential]

   * This is a cherry-pick from an upstream fix (https://jira.mariadb.org/browse/MDEV-6450)
   * This is not fixed in upstream Percona becasue Percona does not officially support non-intel archs.
   * Because code adds additional memory barriers there was a chance of performance degradation on i386/amd64. However, intensive sysbench syntetic loads proved this is not the case - there are no performance penalties.

  [Other Info]

   *  percona-xtradb-cluster-5.5 is only available for Trusty.
  $ rmadison percona-xtradb-cluster-5.5
   percona-xtradb-cluster-5.5 | 5.5.34-25.9+dfsg-0ubuntu4          | trusty/universe          | source
   percona-xtradb-cluster-5.5 | 5.5.37-25.10+dfsg-0ubuntu0.14.04.1 | trusty-security/universe | source
   percona-xtradb-cluster-5.5 | 5.5.37-25.10+dfsg-0ubuntu0.14.04.2 | trusty-updates/universe  | source

  * See comment #22 for more context about other releases that offers percona-xtradb-cluster-5.6 : 
  https://bugs.launchpad.net/ubuntu/+source/percona-xtradb-cluster-5.5/+bug/1657256/comments/22

   * Upstream commit:
  https://github.com/MariaDB/server/commit/40497577ffd9f85557b15e08ad913f627b2e9530

  [Original Description]

  I'm trying to set up percona-xtradb-cluster-5.5 on PPC machine. While
  the package installs fine, as soon as I run sysbench oltp becnhmark
  against it, Percona dies (even when I start the benchmark with just
  one connection).

  I can also crash mysql manually, by updating the sbtest table (which
  is created by the sysbench utility):

  mysql> update sbtest set pad = 'mario1' limit 1000000;
  ERROR 2013 (HY000): Lost connection to MySQL server during query

  Sometimes I need to repeat this update (with different values for
  'pad' field) few times. This happens regardless of whether I run the
  UPDATE inside the transaction or not.

  This is the assertion found in the log file:

  170117 21:10:55 InnoDB: Assertion failure in thread 70366668321152 in file buf0buf.ic line 1277
  InnoDB: Failing assertion: block->page.buf_fix_count > 0

  This is a single-node percona-xtradb-cluster server, without
  wsrep_provied configured, run inside 14.04 lxc container on 16.04
  host.

  I'm attaching the full log file, mysql configuration file and the core
  dumped.

  The version of the package installed is this 5.5.37-25.10+dfsg-
  0ubuntu0.14.04.2.

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