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Displaying posts with tag: Tech (reset)

Introduction to memcached
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These are the slides to a talk I did earlier this week for students of the professional bachelor in ICT course at KaHo St. Lieven. I wanted to give a clear and simple introduction to the memcached service, as I think it’s an invaluable tool in today’s web development.

MongoDB Early Impressions
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I’ve been doing some prototyping work to see how suitable MongoDB is for replacing a small (in number, not size) cluster of MySQL servers. The motivation for looking at MongoDB in this role is that we need a flexible and reliable document store that can handle sharding, a small but predictable write volume (1.5 – 2.0 million new documents daily), light indexing, and map/reduce operations for heavier batch queries. Queries to fetch individual documents aren’t that common–let’s say 100/sec in aggregate at peak times.

What I’ve done so far is to …

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My MySQL wishlist (revised)
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I wrote about my MySQL wishlist on November 14th 2007 and now it's time for an update. I will copy-paste the old entry. The original text will be in italics.

1. Per user and/or per database quota
Would very useful in setups for shared hosting. This would also prevent one database from bringing down the whole server. Separate tablespaces on different mountpoint can ease the pain, but I consider that a nasty hack.

No update. Still problematic

2. External authentication
I've seen numerous scripts which fetch the authentication info from ldap, a file, another …






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Using the MySQL Test Suite
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Earlier I reported about two crashes related to MySQL 5.0.22 on Ubuntu 6.06 LTS.

I think those bugs show a lack of testing on the side of Cannonical/Ubuntu. And for MySQL there is a quite good test suite available, so it's not rocketsience.

There are multiple reasons why you could use the MySQL Test Framework:
1. Test if bug you previously experienced exists in the version you are using or planning to use.
2. Test if configuration changes have a good or bad result on the stability of mysqld.
3. Test if important functions still return the correct results …






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Another Crash in MySQL 5.0.22 on Ubuntu 6.06 LTS
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1. Set this variable
thread_stack = 265K

2. Execute this query
mysql> SELECT 0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0
+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+
0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0
+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+
0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0
+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+










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Crash in MySQL 5.0.22 on Ubuntu 6.06 LTS
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I found a new crasher in the MySQL 5.0 version which ships with Ubuntu 6.06 LTS.

> SELECT * FROM (SELECT mu.User FROM mysql.user mu UNION SELECT mu.user FROM mysql.user mu ORDER BY mu.user) a;
ERROR 2013 (HY000): Lost connection to MySQL server during query

The bug report: LP392236

On MySQL 5.0.51 on Debian stable it returns this error (like it should):
ERROR 1054 (42S22): Unknown column 'mu.user' in 'order clause'

The correct query should be like this (Using culumn a number):
> SELECT * FROM (SELECT …










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MySQL scanning module for Metasploit
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I've created a very simple MySQL scanning module for the metasploit framework.

1. Download the mysql_version file and rename it to mysql_version.rb and put it in the framework-3.2/modules/auxiliary/scanner/mysql directory of your metasploit installation.
http://compukid.no-ip.org/dev/scripts/mysql_version

2. Use using msfcli
./msfcli auxiliary/scanner/mysql/mysql_version RHOSTS=192.168.0.1 E
[*] 192.168.0.1:3306, MySQL server version: 5.0.81-1-log (Protocol 10)

3. More options:
set THREADS to 10 and RHOSTS to 192.168.0.0/24 to scan a whole network.

Hibernate Wars: The Query Cache Strikes Back
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Not so long ago, in a galaxy not very far away... a middle-aged programmer battled to free memory from the dark side of the hibernate query cache.  He was successful, or so it seemed. For the query cache memory problems had risen from the ashes -- stronger and more bloated than ever...


What's With All This Garbage?
We hit a case at work (again), where the java server process came to a grinding halt.  It wasn't dead, it just wasn't making much forward progress either.  A quick look at the heap stats showed we were …



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Arbitrary Replication/Proxy Topologies with MySQL Sandbox
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How would you like to use MySQL Sandbox to deploy and test any replication topology imaginable? Do you want to describe load balancer and proxy configurations, too? If you already love sandbox (or even if you don't), and you want to play with arbitrarily complex replication/proxy topologies... read on.

Sandbox Is Your Friend

MySQL Sandbox is a great tool. As of this writing, version 3 is feature complete -- and the new features are greatly desired. Replication support has been there a while for …



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Database Sharding at Netlog, with MySQL and PHP
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This article accompanies the slides from a presentation on database sharding. Sharding is a technique used for horizontal scaling of databases we are using at Netlog. If you’re interested in high performance, scalability, MySQL, php, caching, partitioning, Sphinx, federation or Netlog, read on …

This presentation was given at the second day of FOSDEM 2009 in Brussels. FOSDEM is an annual conference on open source software with …

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10 Newer Entries Showing entries 31 to 40 of 66 10 Older Entries

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