Detecting if a MySQL server supports partitioning

This morning, this Percona XtraBackup bug came to my attention: – basically, it’s now really quite tricky to determine if a MySQL server you’re connected to supports partitioning or not.

If you’re connected to anything less than MySQL 5.6, you can use have_partitioning variable. But since that’s gone in 5.6, you’re going to get a false negative if you’re connected to 5.6. You could use INFORMATION_SCHEMA.PLUGINS table, but that’s not there in 5.0, so you have some added workarounds to add there too.

A simple version check could be the solution… but what if you compiled the server without partitioning support?

Sessions at the Percona Live MySQL Conference that interest me

For the past many years, there’s been a conference in April, at the Santa Clara Convention Centre where the topic has been MySQL and the surrounding ecosystem. The first year I went, I gave a talk on the new features in MySQL Cluster 5.1 to a overflowing room of attendees. For me, it’s an event that’s mixed with speaking about something I’ve been working on and talking to other attendees about everything from how a particular part of the server works to where we can escape to for nearby good vegan food.

So, I thought I’d share some of the sessions that I’m really looking forward to. My selection is probably atypical, but may be interesting to others. I’m not going to list the keynotes, although they are often of a lot of value. I’m also going to attempt to avoid listing a few really awesome well known speakers simply because there are other really interesting sessions that also need exposure!

  • Starring Sakila: Building Data Warehouses and BI solutions using MySQL and Pentaho
    I need to base decisions off data, not simply a gut feeling (I’m not Stephen Colbert after all). I ran into a bunch of stumbling blocks when trying to work with Pentaho a couple of weeks ago, and I’m really hoping that this session shines some light on how to use it to better and more easily make arguments based on evidence to others in the company.
  • Testing MySQL Databases: The State Of The Art
    I’ve worked with Patrick for several years now, and he’s currently a valuable member of my team at Percona. For those who are interested in the state of the art of open source database testing, this is the session to be in.
  • Getting InnoDB Compression Ready for Facebook Scale
    This session is on at the same time as I’m speaking, so I probably won’t be able to attend (people keep coming to my sessions so I usually can’t sneak out). I’m really interested in how they’ve modified the compression code to help with their (large) workload.
  • Backing Up Facebook
    I hear that Facebook has a couple of database servers, a few dozen users and a few floppy disks full of data. This should be a fun story :)
  • Introducing XtraBackup Manager
    Being responsible for XtraBackup development at Percona, the XtraBackup topics really interest me. Lachlan has been working on a simple backup manager for XtraBackup to help create something that is a more complete backup solution than a tool which simply creates a backup.
  • Extending Xtrabackup – A Point-In-Time System
    Another good case of using XtraBackup as part of a comprehensive backup strategy. I have to be honest, I’m looking for ways in which we can improve XtraBackup to better fit the needs of people. It may be that there are a few small things we can do to make it easier for people do deploy and use.
  • Getting Started with Drizzle 7.1
    We’re about to do the 7.1 release of Drizzle! If you’re interested in having a SQL database that is designed to be used in large scale web applications and cloud environments, come along to this talk.
  • MySQL Idiosyncrasies That Bite
    I have to admit, I’m interested in Ronalds talk here to basically ensure we didn’t miss fixing anything in Drizzle. I do promise not to at any point yell out “Fixed in Drizzle” though.

Go here to register: (early bird pricing and discounted hotel rooms end March 12th, so you want to register sooner rather than later).

xtrabackup bazaar repositories upgraded to 2a format

I have just upgraded the xtrabackup bazaar code repositories to the 2a format. This means that bzr 1.16 is required to access the source code repositories now.

If you get an error like the one below when working with a local branch, you’ll need to run “bzr upgrade” in it (see below for example). For branches on launchpad, you can use the web UI and hit the “upgrade branch” button.

stewart@willster:~/src/percona-xtrabackup$ bzr pull
Using saved parent location: bzr+ssh://
Doing on-the-fly conversion from RemoteRepositoryFormat(_network_name='Bazaar repository format 2a (needs bzr 1.16 or later)\n') to RepositoryFormatKnitPack1().
This may take some time. Upgrade the repositories to the same format for better performance.
bzr: ERROR: KnitPackRepository('file:///home/stewart/src/percona-xtrabackup/.bzr/repository/')
is not compatible with
different rich-root support
stewart@willster:~/src/percona-xtrabackup$ bzr upgrade
Upgrading branch file:///home/stewart/src/percona-xtrabackup/ ...              
starting upgrade of file:///home/stewart/src/percona-xtrabackup/
making backup of file:///home/stewart/src/percona-xtrabackup/.bzr
  to file:///home/stewart/src/percona-xtrabackup/backup.bzr.~1~
starting repository conversion                                                 
repository converted                                                           

xtrabackup for Drizzle merge request

Follow it over on launchpad.

After having fixed an incredibly odd compiler warning (and with -Werror that we build with, error) on OSX (die die die) – xtrabackup for Drizzle is ready to be merged. This will bring it into our next milestone: freemont. Over the next few weeks you should see some good tests merged in for backup and restore too.

While not final final, I’m thinking that the installed binary name will be drizzlebackup.innobase. A simple naming scheme for various backup tools that are Drizzle specific. This casually pre-empts a drizzlebackup tool that can co-ordinate all of these (like the innobackupex script).

Drizzle online backup with xtrabackup

For backups, historically in the MySQL world you’ve had mysqldump (a SQL dump, means on restore you have to rebuild indexes), InnoDB Hot Backup (proprietary, but takes a copy of the InnoDB data files, so restore is much quicker), LVM snapshots (various scripts exist, does have larger IO impact, requires LVM) and more recently xtrabackup. Xtrabackup essentially does the same thing as InnoDB hot backup except that it’s free and open source software.

Many people have been using xtrabackup successfully for quite a while now.

In Drizzle7, our default storage engine is InnoDB. There have been a few changes, but it is totally InnoDB. This leaves us with the question of backup solutions. We have drizzledump (the Drizzle equivalent to MySQL dump – although with fewer gotchas), you could always use LVM snapshots and the probability of Oracle releasing InnoDB Hot Backup for Drizzle is rather minimal.

So enter xtrabackup as a possible solution… I had though of porting xtrabackup across for a while. Last weekend, while waiting for one of my iterations of catalog support to compile, I decided to give it a go. I wanted to see how far I could get with it also in that weekend.

I was successful – there’s a tree up at lp:~stewart/drizzle/xtrabackup thatproduces an xtrabackup binary that’s built for Drizzle (it’s not quite ready for merging yet, there are some obivous bugs around command line option parsing… but a backup and restore did work).

I wanted the following:

  • build to be integrated with Drizzle, using the same innobase build that we use to build the server
  • build with strict compiler warnings and -Werror (which we do forDrizzle)
  • build with a C++ compiler (as we do with innobase in Drizzle)
  • not re-add parts of mysys into the Drizzle build just for xtrabackup

I’ve already submitted merge requests to upstream xtrabackup containing the compiler fixes and added compiler warnings (they’ve also by now been merged into xtrabackup). Already my work has improved the quality of xtrabackup for everyone. Some of the warnings were fixed slightly differently in xtrabackup than in my Drizzle tree, but I plan to merge.

One issue was that the command line parsing library that xtrabackup uses – my_getopt which is part of mysys (the portability library inside MySQL) is long since gone from Drizzle. We currently use Boost::program_options. Thanks to the heroic efforts of Andrew Hutchings, xtrabackp in Drizzle is also using boost::program_options. This was a brilliant “hey, can you have a look at this conversion” followed by handing him a tree that did not even remotely compile, followed by a “I have to take the kids somewhere, here’s a tree – it may compile”. Amazingly enough, it pretty much did compile once I fixed the other issues.

An unresolved issue is how to deal with this going forward – my guess is that upstream xtrabackup doesn’t want to require Boost.

One solution could be just to factor out command line options into a sepfile that we can ignore for Drizzle and replace with our own. The other option could be to use a differnt command line option parsing library (perhaps from CCAN, as it’s then maintained by somebody else and doesn’t require heaps and heaps of other stuff).

Another issue I had to tackle is the patch to innobase that’s required to build xtrabackup.

I took a very minimal approach for the Drizzle patch. We are currently based on innobase 1.1.4 from MySQL 5.5 – so I mostly looked at the xtradb55 patch. I think it would be great if these were instead of one giant patch a series of patches to apply (a-la quilt) to a) make iteasier maintain and b) easier for myself to work out the exact reasoning of each bit (also, generating the patches with -p would help a fair bit too).

So how did I do it?

Step 0
was removing support for old innobase – we totally don’t need it for Drizzle.

Step 1
was creating a srv_read_only option for Drizzle’s innobase. This was fairly easy. The one thing I did have to change was adding a checkin os_file_lock() so that we don’t attempt to write lock the ibdatafiles when in read only (otherwise backups can’t be taken while drizzledis running). I’m a little surprised that this wasn’t hit in 5.5 at all.

Step 2
was implementing srv_fake_write. I’m pretty sure I’ve gotten this right in the Drizzle implementation, but the patch wasn’t as easy toread as I’d really like. I probably need to do a bit more of a code audit that this is actually correct (I may try and come up with anLD_PRELOAD library that will scream loudly if writes are made to files matching a pattern).

Step 3
was implemnting srv_apply_log_only. Pretty sure I have this right, again, more testing will be required. Why? Because I’m that paranoid about getting things very, very right.

Step 4
was to go through all the functions that xtrabackup needed to not be static. Instead of having prototypes for them, I instead added a xtrabackup_api.h header to Innobase and included it where needed (including in xtrabackup). I’d recommend this way going forward for xtrabackup too as it could be a lot less problematic to maintain (and makes xtrabackup source a bit easier to read)

Step 5
was fixing up a few skeleton functions that were needed to make our innobase happy. It may not be a bad idea to split out the skeleton functions into a sep source file so it’s a bit easier to track (and some #ifdefs around those not needed for certain releases).

I’m hoping to work with the upstream xtrabackup devs on the various points I’ve made above.
Another thought of mine is to port xtrabackup into HailDB where we can use much more neat API functions to create good tests for xtrabackup.

Thanks go out to all who’ve worked on xtrabackup. It honestly wasn’t too hardgetting it ported across to Drizzle – and with a bit of collaboration I think we can make it easy to keep up to date.

What’s the future for Xtrabackup in Drizzle? It’ll likely end up being a binary named drizzlebackup-innobase or similar (this means that there is a clear difference between xtrabackup for MySQL and what we have in Drizzle – which is more accurately defined as based on xtrabackup). We’ll also probably want a nice wrapper or integration with a backup tool to deal with everything Drizzle related. We shall also introduce a lot of testing; backups are important.

Xtrabackup is topical, check out the latest OurSQL podcast and the the Percona Xtrabackup website for more info!