Pythian Group

Pythian is very excited to return to the much-awaited RMOUG 12 held in Denver, Colorado from February 14-16, 2012. Keep your eyes open for Alex Gorbachev, Marc Fielding, Don Seiler and Gwen Shapira in attendance. We have a fantastic line-up of speakers this year featuring a total of seven papers presented by Alex, Marc, Don and Gwen. If you have any feedback on our sessions, please send your comments directly to the speaker or to Vanessa Simmons, Pythian Director of Marketing. Please also follow this link to sign up to receive notice of future speaking engagements, webinars or Pythian news.

Be sure to stop by our booth (#3,6,7,10) to say hello to our friends from the OakTable Network, and enter our draw to win the new Amazon Kindle with software provided by Cary Millsap (MR-Trace, MR-Tools & Method-R Profiler) and a pack of digital e-book downloads courtesy of Apress. Also slated is the RAC Attack workshop, which was first offered at Oracle Open World and UKOUG, and is now in its second year at RMOUG. Pythian is co-sponsoring this event with Apress and it’s a fun and informative way to learn from our experts how and when to properly build a RAC environment.

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A few days ago, we faced a Duplicate entry problem in the mysqld server on one of our customer’s slave after cold backup. We do regular data sync checks for all of our customer’s as daily reports and check for data discrepancies between master and slave server’s, if any got picked up by our checks to investigate, and there was no issues for the particular server and with the report. When checked the entry details, there is a row with the same data in the table that was mentioned by Slave status Last_error entity.

Quick check on the error log showed that the slave was started after cold back’s and immediately stopped with a duplicate entry error and the mysqld server version is 5.0.77-log Source distribution. From the analysis of the below statements, we found that the slave SQL thread was stopped with the error at a position backwards than the SQL thread initialized after cold backup’s. Read the rest of this entry . . .

The MySQL errorlog is an important point of reference when administering a MySQL Server. We can grasp much about the state of our MySQL instance by the informational and error messages written out to it by our MySQL daemon. Our monitoring suite is set up to check the mysqld  error log file periodically for any new nasties logged and then it alerts  us if there’s anything to know about. Recently I was asked to investigate some replication outage alerts a colleague had received overnight. One  of the primary directions I took was the error log file. This is where I would expect find any evidence of replication being stopped or crashes etc – I was looking for anything that could fill me  in on the causes of replication alerts. When I ran the command to tail the log I was shocked to see the log was totally empty. Read the rest of this entry . . .

This post was thought of as an attempt to make some performance test with new multi-threaded replication in 5.6, at least that was my initial intention. Based on Luis Soarez – Replication Team Leader in Oracle – post. I wanted to play with new set of variables and features in order to understand how new multi-threaded replication works and make some performance tests. Read the rest of this entry . . .

It seems to be assumed that fixed-point values, DECIMAL and NUMERIC, in MySQL are not susceptible to rounding errors because they are exact numeric data types. It must be kept it mind, that there are limits in precision, and the maximum number of digits for DECIMAL is 65. Additionally, a DECIMAL column can be assigned a precision or scale that could have the potential affect of truncation to the allowed number of digits. What I am discussing here is rounding error. Read the rest of this entry . . .

I’ve been following the development of Tungsten Replicator for quiet some time now, and recently was fortunate enough to find the time to take a look at the product in more detail.

If you haven’t heard of Tungsten Replicator yet, it’s an open source database replication engine that can be used to complement or completely replace native MySQL Replication.  In addition to providing standard replication functionality, Tungsten Replicator introduces exciting new features such as global transaction IDs, heterogeneous replication from MySQL to Oracle and Postgres, parallel replication, and the ability to replicate from multiple masters to a single slave.
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MySQL Replication is a powerful tool and it’s hard to find a production system not using it. On the other hand debugging replication issues can be very hard and time consuming. Especially if your replication setup is not straightforward and you are using filtering of some kind.
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Pythian is pleased to announce our speaking schedule at this year’s Oracle OpenWorld 2011, October 2-6, 2011 in San Francisco, CA.

We’re excited to be joined by our customers Western Union, and Worldwide Technologies (WWT) as we present real-world experiences and project success. If you’re attending, don’t miss the chance to hear our team of experts. Bring your toughest questions to be answered as they relate to any of the subjects below.

• Follow Pythian on LinkedIn for up to date OOW info
• Schedule a meeting with Pythian at OOW to discuss your database needs
• Planning to attend but not yet registered? August 12, 2011 is the deadline for early bird registration. Do it now.

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On many of our clients, we have a need to run XtraBackup as a regular OS user. Aside from running into the issue where tar4ibd was not provided with Percona’s xtrabackup-1.6.2.tar.gz package, our main issues have been with permissions when attempting a streaming backup.

I have found the following:

1. The user needs permissions for a temp directory to stream to/from. The my.cnf of the target database cannot be used because the user does not have permission to write to /tmp/mysql-stdout, so we set a tmpdir in a separate defaults-file.
2. A backup target directory must be used that the user has read/write permissions to. It seems to me a target directory should not be needed for a streaming backup, but it is.
3. A user who has SUPER privileges must be used to connect to the target database.
4. Group and datadir permissions:

• The primary group for the user should be the same as the mysql user running the target database, i.e. pythian:mysql.
• The user must have 770 access to the database schema directories.
• The user must have 740 access to the all files under the mysql datadir.

Here is the innobackupex command that works for us.

$ innobackupex --defaults-file=/home/pythian/my.cnf --user=root --stream=tar ./ | gzip - > /home/pythian/backups/2011-08-02_backup.tar.gz

So if you are seeing errors such as,

tar: -: Cannot write: Broken pipe
sh: /tmp/mysql-stout: Permission denied

do yourself a favor and run through this permission checklist. I hope it saves a lot of headaches.

PYTHIAN NEWS UPDATE

Pythian & Schooner today announced a partnership to delivery advanced support and high availability for MySQL. Customers who are deploying Schooner MySQL into their infrastructure and require additional MySQL technical resources to do so successfully now have a professional services option to consider through Pythian.

Pythian formally partnering with Schooner increases the awareness in the market that Schooner MySQL with Active Cluster is ready for the demands of enterprise deployments and workloads. Customers will benefit because Schooner solves the MySQL replication challenges which many organizations face.

• Read the press release.
• Visit Schooner Information Technology.
• Ask about Pythian services for MySQL.