One of the many cool new features in Java EE 6, is support for the DataSourceDefinition annotation.

The DataSourceDefinition annotation provides a way to define a DataSource and register it with JNDI. The annotation provided annotation elements for the commonly used DataSource properties. Additional standard and vendor specific properties may also be specified.

So let us look at an example:

@DataSourceDefinition(name = "java:global/MyApp/myDS",
className = "org.apache.derby.jdbc.ClientDataSource",
portNumber = 1527,
serverName = "localhost",
databaseName = "testDB",
user = "lance",
password = "secret",
properties = {"createDatabase=create"}) )

The data source will be registered using the value specified in the name element and can be defined in any valid Java EE name space and that will determine the accessibility of the data source from other …

One of the many cool new features in Java EE 6, is support for the DataSourceDefinition annotation.

The DataSourceDefinition annotation provides a way to define a DataSource and register it with JNDI. The annotation provided annotation elements for the commonly used DataSource properties. Additional standard and vendor specific properties may also be specified.

So let us look at an example:

@DataSourceDefinition(name = "java:global/MyApp/myDS",

className = "org.apache.derby.jdbc.ClientDataSource",

portNumber = 1527,

serverName = "localhost",

databaseName = "testDB",

user = "lance",

password = "secret",

properties = {"createDatabase=create"}) )

The data source will be registered using the value specified in the name element and can be defined in any valid Java EE name space and that will determine the accessibility of the data …

A MySQL is running happily on a machine situated in a land far far away. I grant access to a user@machine_aaaaaa (grant select on db.* to ‘user’@'machine_aaaaa’ identified by ‘password’; flush privileges;), send an email to the user saying it should run fine and happily go off my way. Mistake!

It seems this user can’t connect to the mysql gets access denied:
Access denied for user ‘user’@'machine_bbbbb’ (using password: YES)

Note that the machine the user is being seen from is totally different from the one I set up in the grant!! WHY?

run a reverse lookup on the ip of machine_aaaaa, turns out it shows machine_bbbbb. So I figure a big bad guy messed up /etc/hosts, I was right! `cat /etc/hosts` just to find an entry for machine_aaaaa blehh

Ok, solution is to remove the entry from /etc/hosts (after finding out it wasn’t even necessary and wasn’t even supposed to be there in the first …

WIKIPEDIA -

Irony (from the Ancient Greek εἰρωνεία eirōneía, meaning hypocrisy, deception, or feigned ignorance) is a situation, literary technique or rhetorical device, in which there is an incongruity, discordance or unintended connection that goes beyond the most evident meaning. It is the expression of one’s meaning by using language that normally signifies the opposite.

Types of irony
Modern theories of rhetoric distinguish among verbal, dramatic and situational irony.
▪ Verbal irony is a disparity of expression and intention: when a speaker says one thing but means another, or when a literal meaning is contrary to its intended effect. An example of this is sarcasm.
▪ Dramatic irony is a disparity of expression and awareness: when words and actions possess a significance that the listener or audience understands, but the speaker or character does not.
▪ Situational irony …

MySQL instance running an Infobright engine


mysql> explain SELECT COUNT(ac.UID) FROM ACTIVE ac JOIN ALL a;
+----+-------------+-------+------+---------------+------+---------+------+---------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+------+---------+------+---------+-------+
| 1 | SIMPLE | ac | ALL | NULL | NULL | NULL | NULL | 124426 | |
| 1 | SIMPLE | a | ALL | NULL | NULL | NULL | NULL | 7594256 | |
+----+-------------+-------+------+---------------+------+---------+------+---------+-------+
2 rows in set (0.01 sec)

mysql> SELECT COUNT(ac.UID) FROM ACTIVE ac JOIN ALL a ON ac.UID=a.UID;
+---------------+
| COUNT(ac.UID) |
+---------------+
| 17466 |
+---------------+
1 row in set (0.23 sec)

…

If you have more then a single MySQL database for your production environment, e.g. a development and test environment, or a MySQL replication topology, ensuring your schema’s are in sync can be task that requires some time if not managed correctly.

There is a tool I do use for MySQL environments called Schema Sync – a MySQL Schema Versioning and Migration Utility. There are many reasons why schema’s get out of sync. Developers may not ensure their changes are reflected in any software to be deployed, and when not tested you could end up with broken functionality. A DBA might try some different index strategies on a slave, but not the master, and never implement or revert.

While some people want the quick and hidden just sync version akin to Rails, I really like this product as it produces proper patch and revert SQL scripts. As a DBA I really want to know what’s going to …

It just works. In absence of any MySQL monitoring for your site, I have found no solution that gets you operational as quickly and easily. MONyog can be deployed in 60 seconds, and configured in another 60 seconds. Within 5 minutes you can have visual monitoring of your MySQL environment.

MONyog is an agentless process, which is an advantage for easy install, but does not provide for monitoring redundancy in the capture of information due to agentless nature. It’s a static standalone executable which is great if you need something to work out of the box. You can easily configure multiple servers in a replication topology, or different servers in your environment. You get the ability to monitor all the usual information, with a dashboard and detailed graphs. While MONyog does provide customizations of rules for the graphs and presentation order, that’s about it. You can’t at this time …

I am working with a client that is using managed hosting on dedicated servers. This has presented new challenges in obtaining the right permissions to undertake MySQL tasks but not have either ‘root’ or ‘mysql’ access and not have to involve a third party everytime.

Adding the following to the /etc/sudoers file enabled the ability to restart MySQL.

User_Alias      DBA = rbradfor, user2, etc
Host_Alias      DB_SERVERS = server1.example.com, server2.example.com, etc
Cmnd_Alias      MYSQL = /etc/init.d/mysqld, /usr/sbin/tcpdump

DBA DB_SERVERS = MYSQL

As you can see I also got tcpdump, which I find valuable to monitor via mk-query-digest.

Next, permissions for log files.

It’s been a while since I’ve posted anything new. In the meantime I’ve been pretty busy. Working on production systems often means that you are not running bleading edge. That’s fine but sometimes you need to look at doing the upgrade and to do that you have to do quite a few checks to see how well newer versions of the software you use will work.

I’ve been in that situation with MySQL. I have quite a few boxes most of which are 5.0 and have been working fine. MySQL-5.1 has been GA now for some time, and I have started to look at it as support for 5.0 is about to end.  I’ve already found quite a few 5.1 bugs, good enough to crash the server, but again that’s to be expected. Heavy loads and odd usage of the server means that MySQL can never be able to test all things.  Replication problems caused a few issues with the first versions of 5.1 but they all seem to have been ironed out now.  The other …

1. ChipHacker -- collaborative FAQ site for electronics hacking. Based on the same StackExchange software as RedMonk's FOSS FAQ for open source software.
2. Democracy Live -- BBC launch searchable coverage of parliamentary discussion, using speech-to-text. One aspect we're particularly proud of is that we've managed to deliver good results for speech-to-text in Welsh, which, we're told, is unique. I think of this as the start of a They Work For You for video coverage. I'd love to be able to scale this to local government coverage, which is disappearing as local newspapers turn into …