Author Archive

Recently I started migrating an old server, which had skip-networking within my.cnf, which is not a dynamic option and requires you to restart the mysql server. I typically rsync the source code and static data to a new machine. Configure the webserver with the relevant vhosts and change the database connection details to point to […]

A while back a colleague and myself had a two week sprint to ensure that we could deliver 20k emails with up to 5mb attachments each. We experimented with 4k emails at 5mb each sending straight through the MTA, which we found to cause excessive load on the servers. Using exim filters we could add […]

After attaching an EBS volume and rsyncing files to the EBS device the server had a load average of 6 before the server became unresponsive to ssh connections and complained of a broken pipe for ssh. The server was still responding to http requests and ping, however trying to establish a ssh connection, it connected […]



26 May 2010

If you use LAST_INSERT_ID() and insert on the primary key value it will only return the last “insert id” which has not included the primary key DROP TABLE IF EXISTS `example`; CREATE TABLE IF NOT EXISTS `example` ( id INT(11) NOT NULL AUTO_INCREMENT, b CHAR(3), PRIMARY KEY(id)) ENGINE=InnoDB; INSERT INTO example SET id=1; INSERT INTO […]

I wrote a few munin plugins to monitor memory, CPU and IO usage per process. After collecting the stats for a few days I noticed that MySQL CPU usage had a constant value of 9.1, however all other processes collected CPU usage correctly.. CPU usage proc=mysqld value=$(ps u -C $proc | awk ‘BEGIN { sum […]

We have re-written parts of the default configuration for ucarp & haproxy to run several VIPs on the same interface. This works on debian, however some minor modifications maybe needed for other distributions. Ucarp implementation /etc/network/if-up.d/ucarp #!/bin/sh UCARP=/usr/sbin/ucarp EXTRA_PARAMS=”” if [ ! -x $UCARP ]; then exit 0 fi if [ -z “$IF_UCARP_UPSCRIPT” ]; then […]

We hold much of our server configuration within the office, which is restricted down by iptables. As such when spawning new instances on EC2 we need to allow access to our internal network via iptables, to allow nodes to connect to the office and configure themselves. The following script can be run within a crontab […]

I previously described how to configure HA Proxy and ucarp to load balance traffic between servers and share common IP addresses in the event of failure, however this still leaves holes in the availability of the application. The scenario only accounts for availability within a single data center and does not address how traffic and […]

Updated bash script 23/01/2010: The script was assumed to run from EC2 itself, however I have since modified this so its applicable to local environments and made a little more robust. There are quite a number of new tools from EC2, each requiring some form of setup on the server. As a result I have […]

I just read “How to use locks in PHP cron jobs to avoid cron overlaps” and I thought I would elaborate on this and provide some more examples. In order for a lock to work correctly it must handle, Atomicity / Race Conditions, and Signaling. I use the following bash script to create locks for […]

About this blog

I have been a developer for roughly 10 years and have worked with an extensive range of technologies. Whilst working for relatively small companies, I have worked with all aspects of the development life cycle, which has given me a broad and in-depth experience.