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  • Galera data on Percona Cloud Tools (and other MySQL monitoring tools)
    I was talking with a Percona Support customer earlier this week who was looking for Galera data on Percona Cloud Tools. (Percona Cloud Tools, now in free beta, is a hosted service providing access to query performance insights for all MySQL uses.)The customer mentioned they were already keeping track of some Galera stats on Cacti, and given they were inclined to use Percona Cloud Tools more and more, they wanted to know if it was already supporting Percona XtraDB Cluster. My answer was: “No, not yet: you can install agents in each node (the regular way in the first node, then manually on the other nodes… and when prompted say “No” to create MySQL user and provide the one you’re using already) and monitor them as autonomous MySQL servers – but the concept of cluster and specially the “Galera bits” has yet to be implemented there.”Except I was wrong.By “concept of cluster” I mean supporting the notion of group instances, which should allow a single cluster-wide view for metrics and query reports, such as the slow queries (which are recorded locally on the node where the query was run and thus observed in a detached way). This still needs to be implemented indeed, but it’s on the roadmap.The “Galera bits” I mentioned above are the various “wsrep_” status variables. In fact, those refer to the Write Set REPlication patches (based in the wsrep API), a set of hooks applied to the InnoDB/XtraDB storage engine and other components of MySQL that modifies the way replication works (to put it in a very simplified way), which in turn are used by the Galera library to provide a “generic Synchronous Multi-Master replication plugin for transactional applications.” A patched version of Percona Server together with the Galera libray compose the base of Percona XtraDB Cluster.As I found out only now, Percona Cloud Tools does collect data from the various wsrep_ variables and it is available for use – it’s just not shown by default. A user only needs to add a dashboard/chart manually on PCT to see these metrics:Click on the picture to enlarge itNow, I need to call that customer …Monitoring the clusterSince I’m touching this topic I thought it would be useful to include some additional information on monitoring a Galera (Percona XtraDB Cluster in particular) cluster, even though most of what I mention below has already been published in different posts here on the MySQL Performance Blog. There’s a succint documentation page bearing the same title of this section that indicates the main wsrep_ variables you should monitor to check the health status of the cluster and how well it’s coping with load along the time (performance). Remember you can get a grasp of the full set of variables at any time by issuing the following command from one (or each one) of the nodes:mysql> SHOW GLOBAL STATUS LIKE "wsrep_%";And for a broader and real time view of the wsrep_ status variables you can use Jay Janssen’s myq_gadgets toolkit, which he modified a couple of years ago to account for Galera.There’s also a specific Galera-template available in our Percona Monitoring Plugins (PMP) package that you can use in your Cacti server. That would cover the “how well the cluster copes with load along the time,” providing historical graphing. And while there isn’t a Galera specific plugin for Nagios in PMP, Jay explains in another post how you can customize pmp-check-mysql-status to “check any status variable you like,” describing his approach to keep a cluster’s “health status” in check by setting alerts on specific stats, on a per node basis.VividCortex recently added a set of templates for Galera in their product and you can also rely on Severalnines’ ClusterControl monitoring features to get that “global view” of your cluster that Percona Cloud Tools doesn’t yet provide. Even though ClusterControl is a complete solution for cluster deployment and management, focusing on the automation of the whole process, the monitoring part alone is particularly interesting as it encompasses cluster-wide information in a customized way, including the “Galera bits”. You may want to give it a try as the monitoring features are available in the Community version of the product (and if you’re a Percona customer with a Support contract covering Percona XtraDB Cluster, then you’re entitled to get support for it from us).One thing I should note that differentiate the monitoring solutions from above is that while you can install Cacti, Nagios and ClusterControl as servers in your own infrastructure both Percona Cloud Tools and VividCortex are hosted, cloud-based services. Having said that, neither one nor the other upload sensitive data to the cloud and both provide options for query obfuscation.SummaryContrary to what I believed, Percona Cloud Tools does provide support for “Galera bits” (the wsrep_ status variables), even though it has yet to implement support for the notion of group instances, which will allow for cluster-wide view for metrics and query reports. You can also rely on the Galera template for Cacti provided by Percona Monitoring Plugins for historical graphing and some clever use of Nagios’ pmp-check-mysql-status for customized cluster alerts. VividCortex and ClusterControl also provide monitoring for Galera.Percona Cloud Tools, now in free beta, is a hosted service providing access to query performance insights for all MySQL uses. After a brief setup, unlock new information about your database and how to improve your applications. Sign up to request access to the beta today.  The post Galera data on Percona Cloud Tools (and other MySQL monitoring tools) appeared first on MySQL Performance Blog.

  • Does MySQL need a mentoring program?
    Does MySQL need a mentoring program? I get calls, emails, and other requests for trained MySQL DBAs and Developers. Human Resources, managers, team leads, and entrepreneurs have the need but can not find the bodies. It is easy enough to download MySQL, get it running, and use it. But the next steps seem problematic for many. There are programs like MySQL Marinate and Girl Develop It to provide some hands on help for beginners. Autodidacts can find tons of MySQL Books and on line information. But how do we take the beginners and get them to intermediate or beyond? How do we support these new comers, give them a hand if needed, a shoulder to cry on, or just provide someone who has been there before to bounce ideas around when needed? How do we pull them into social networks to warn them of pitfalls, pass on information about new technologies, or just be there as a friendly voice when the air movement device is being impacted by non optimal material? How do we pass on best practices, professional guidance, and the norms of our community? There is only so much forums, IRC, and Stack Overflow can handle. Local users groups are good if you have a local user group. A good place to start is to see what other Open Source projects are doing. PHP Mentorting is a formal, personal, long term, peer to peer mentorship organization focused on creating networks of skilled developers from all walks of life. Read their info and let me know if you think the MySQL Community needs something similar. Being a mentor has benefits too. There is an old saying that you really do not know a subject until you can pass on your knowledge to someone else. It also helps bring along someone who could replace you if you decided to climb the corporate ladder. Plus you never know what you fledgling might teach you. So do we need a MySQL mentoring program?

  • Percona Server 5.6.20-68.0 is now available
    Percona is glad to announce the release of Percona Server 5.6.20-68.0 on August 29, 2014. Download the latest version from the Percona web site or from the Percona Software Repositories.Based on MySQL 5.6.20, including all the bug fixes in it, Percona Server 5.6.20-68.0 is the current GA release in the Percona Server 5.6 series. All of Percona’s software is open-source and free. Complete details of this release can be found in the 5.6.20-68.0 milestone on Launchpad.New Features:Percona Server has implemented the MySQL 5.7 SHOW SLAVE STATUS NONBLOCKING syntax for Lock-Free SHOW SLAVE STATUS feature. The existing SHOW SLAVE STATUS NOLOCK is kept as a deprecated alias and will be removed in Percona Server 5.7. There were no functional changes for the feature.Percona Server Audit Log Plugin now supports JSON and CSV formats. The format choice is controlled by audit_log_format variable.Percona Server Audit Log Plugin now supports streaming the audit log to syslog.TokuDB storage engine package has been updated to version 7.1.8.Bugs Fixed:Querying INNODB_CHANGED_PAGES table with a range condition START_LSN > x AND END_LSN < y would lead to a server crash if the range was empty with x greater than y. Bug fixed #1202252 (Jan Lindström and Sergei Petrunia).SQL statements of other connections were missing in the output of SHOW ENGINE INNODB STATUS, in LATEST DETECTED DEADLOCK and TRANSACTIONS sections. This bug was introduced by Statement Timeout patch in Percona Server 5.6.13-61.0. Bug fixed #1328824.Some of TokuDB distribution files were missing in the TokuDB binary tarball. Bug fixed #1338945.With XtraDB changed page tracking feature enabled, queries from the INNODB_CHANGED_PAGES could read the bitmap data whose write was in still progress. This would cause the query to fail with an ER_CANT_FIND_SYSTEM_REC and a warning printed to the server error log. The workaround has been to add an appropriate END_LSN-limiting condition to the query. Bug fixed #1193332.mysqld-debug was missing from Debian packages. This regression was introduced in Percona Server 5.6.16-64.0. Bug fixed #1290087.Fixed a memory leak in Slow Query Log Rotation and Expiration. Bug fixed #1314138.The audit log plugin would write log with XML syntax errors when OLD and NEW formats were used. Bug fixed #1320879.Combination of Log Archiving for XtraDB, XtraDB changed page tracking, and small InnoDB logs could hang the server on the bootstrap shutdown. Bug fixed #1326379.--tc-heuristic-recover option values were broken. Bug fixed #1334330 (upstream #70860).If the bitmap directory has a bitmap file sequence with a start LSN of one file less than a start LSN of the previous file, a debug build would assert when queries were run on INNODB_CHANGED_PAGES table. Bug fixed #1342494.Other bugs fixed: #1337247, #1350386, #1208371, #1261341, #1151723, #1182050, #1182068, #1182072, #1184287, #1280875, #1338937, #1334743, #1349394, #1182046, #1182049, and #1328482 (upstream #73418).Release notes for Percona Server 5.6.20-68.0 are available in the online documentation. Please report any bugs on the launchpad bug tracker.The post Percona Server 5.6.20-68.0 is now available appeared first on MySQL Performance Blog.

  • Percona Server 5.5.39-36.0 is now available
    Percona is glad to announce the release of Percona Server 5.5.39-36.0 on August 29, 2014 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.39, including all the bug fixes in it, Percona Server 5.5.39-36.0 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of the release can be found in the 5.5.39-36.0 milestone at Launchpad.New Features:Percona Server Audit Log Plugin now supports JSON and CSV formats. The format choice is controlled by audit_log_format variable.Percona Server Audit Log Plugin now supports streaming the audit log to syslog.Bugs Fixed:Querying INNODB_CHANGED_PAGES with a range condition START_LSN > x AND END_LSN < y would lead to a server crash if the range was empty with x greater than y. Bug fixed #1202252 (Jan Lindström and Sergei Petrunia).With XtraDB changed page tracking feature enabled, queries from the INNODB_CHANGED_PAGES could read the bitmap data whose write was in still progress. This would cause the query to fail with an ER_CANT_FIND_SYSTEM_REC and a warning printed to the server error log. The workaround has been to add an appropriate END_LSN-limiting condition to the query. Bug fixed #1346122.mysqld-debug was missing from Debian packages. This regression was introduced in Percona Server 5.5.36-34.0. Bug fixed #1290087.Fixed a memory leak in Slow Query Log Rotation and Expiration. Bug fixed #1314138.The audit log plugin would write log with XML syntax errors when OLD and NEW formats were used. Bug fixed #1320879.A server built with system OpenSSL support, such as the distributed Percona Server binaries, had SSL-related memory leaks. Bug fixed #1334743 (upstream #73126).If the bitmap directory has a bitmap file sequence with a start LSN of one file less than a start LSN of the previous file, a debug build would assert when queries were run on INNODB_CHANGED_PAGES table. Bug fixed #1342494.Other bugs fixed: #1337324, #1151723, #1182050, #1182072, #1280875, #1182046, #1328482 (upstream #73418), and #1334317 (upstream #73111).Release notes for Percona Server 5.5.39-36.0 are available in our online documentation. Bugs can be reported on the launchpad bug tracker.The post Percona Server 5.5.39-36.0 is now available appeared first on MySQL Performance Blog.

  • The InnoDB Mutex, part 3
    I repeated tests from part 1 and part 2 using a system that has an older/smaller CPU but more recent versions of glibc & Linux. In this case the CPU has dual sockets with 6 cores per socket and 24 vCPUs with HT enabled. The host uses Fedora, glibc 2.17 and Linux kernel 3.11.9-200. Tests were run up to 512 threads. There was an odd segfault at 1024 threads with the TTASFutexMutex that I chose not to debug. And tests were run for 1, 4 and 12 mutexes rather than 1, 4 and 16 because of the reduced vCPU count. The lock hold duration was ~6000 nsecs rather than ~4000 because of the different CPU.My conclusions from this platform were less strong than from the previous tests.The InnoDB syncarray mutex still has lousy behavior at high concurrency but it is less obvious here because I did not run a test for 1024 threads.pthread default is usually better than pthread adaptive, but in at least one case pthread adaptive was much betterThe new custom InnoDB mutex, TTASFutexMutex, was occasionally much worse than the alternatives. From looking at code in 5.7, it looks like the choice to use it is a compile time decision. If only to figure out the performance problems this choice should be a my.cnf option and it isn't clear to me that TTASFutexMutex is ready for prime time.Graphs for 0 nsec lock holdGraphs for 1000 nsec lock holdGraphs for 6000 nsec lock hold