Fri, 2015-07-31 12:14guillaumelefranc

Mandatory disclaimer: the techniques described in this blog post are experimental, so use at your own risk. Neither me nor MariaDB Corporation will be held responsible if anything bad happens to your servers.

Context

MaxScale 1.2.0 and above can call external scripts on monitor events. In the case of a classic Master-Slave setup, this can be used for automatic failover and promotion using MariaDB Replication Manager. The following use case is exposed using three MariaDB servers (one master, two slaves) and a MaxScale server. Please refer to my Vagrant files if you want to jumpstart such a testing platform.

Requirements

• A mariadb-repmgr binary, version 0.4.0 or above. Grab it from the github Releases page, and extract in /usr/local/bin/ on your MaxScale server. …

 Article on Information Age:

From obscurity to the mainstream, the journey of MySQL shows the power of the open source community to drive innovation. Read the full article here: http://goo.gl/bqFZPb

Welcome to the 10th episode in the MySQL QA series! Today we’ll talk about reproducing and simplifying: How to get it Right.

Note that unless you are a QA engineer stuck on a remote, and additionally difficult-to-reproduce or difficult-to-reduce bug, this episode will largely be non-interesting for you.

However, what you may like to see – especially if you watched episodes 7 (and possibly 8 and 9) – is how reducer automatically generates handy start/stop/client (cl) etc. scripts, all packed into a handy bug tarball, in combination with the reduced SQL testcase.

This somewhat separate part is covered directly after the introduction (ends at 11:17), as well as with an example towards the end of the video (starts at time index 30:35).

The “in between part” (11:17 to 30:35) is all about reproducing and simplifying, which – unless you are working on a remote case – can likely be skipped by …

Taxonomy upgrade extras:  max_used_connections user account connection configuration

How many connections can be opened concurrently against my MySQL or MariaDB database can be configured and checked with the following command:

SHOW GLOBAL VARIABLES LIKE 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 505   |
+-----------------+-------+

If this limit was ever reached in the past can be checked with:

SHOW GLOBAL STATUS LIKE 'max_use%';
+----------------------+-------+
| Variable_name        | …

Generally in MySQL we send queries massaged to a point where optimizer doesn’t have to think about anything. In our major user database environment 99.9% of queries don’t have alternative query plans available (either because of forced indexes or just straightforward Primary Key read). We have various other systems and from time to time we have to do SQL work there and chase optimizer errors.

There’re multiple places where optimizer can make a choice in very basic queries, for example:

• Which index returns less rows
• Which index can be used for ORDER BY

A query that I was looking asked a very basic question, on a job instances table, show state and status for latest-by-ID entry for job name=’Ship Christmas Presents’ (real name was a bit different ;-). So, it was SELECT c,d FROM t WHERE b=X ORDER BY a DESC LIMIT 1, where PK is (a) and a possible index is on …

Learn how VMware Continuent adds HA, DR and real-time data warehouse loading to off-the-shelf MySQL operating on-prem and in VMware vCloud Air public cloud. 

We introduce vCloud Air basics, then do a deep dive into the VMware Continuent system architecture covering important issues like fail-over, zero-downtime maintenance, and load scaling. We will conclude with a demonstration of using

Replication is the process that transfers data from an active master to a slave server, which reproduces the data stream to achieve, as best as possible, a faithful copy of the data in the master.

To check replication health, you may start with sampling the service, i.e. committing some Sentinel value in the master and retrieving it from the slave.

Sentinel data: Tap tap… Is this thing on?
If you want to make sure that replication is working, the easiest test is using replication itself to see if data is being copied across from the master to the slaves. The method is easy:

1. Make sure that the data you want to see is NOT in the master or in the slave. If you skip this step, you may think that replication is working, while in fact it may not.
2. Either create a table …

There is an error which is definitely new to people which have encountered such situation at first time.
It was reported a long time before:
#1689 -> 28 Oct 2003 4:46
#1478 -> 4 Oct 2003 10:58
#7501 -> 23 Dec 2004 5:35

Error is -> ERROR 1054 (42S22): Unknown column ‘c2’ in ‘field list’
The Place where you can encounter this error is something similar below:

mysql> show create table t1;
| t1    | CREATE TABLE `t1` (
  `id` int(11) DEFAULT NULL,
  `c1` varchar(85) DEFAULT NULL
) /*!50100 TABLESPACE innodb_file_per_table */ ENGINE=InnoDB DEFAULT CHARSET=utf8 |

If you try to insert …

Hi Julien
Thanks. As Enterprise Monitor is one of the commercial tools, previous versions can be downloaded from support.oracle.com under the Patches tab. Remember, as part of the Enterprise Edition, you’ll need a valid Support contract.
Hope this helps.
rgds
K.

Thanks a lot for this post.

Unfortunately, i can’t find mysqlmonitoragent v2.3 anymore.

Do you know where i can find it?