Jauder Ho - links and things

Typically, when you upgrade, there is usually a short downtime while the application is restarted.

However, nginx has come up with an elegant way of upgrading without any downtime by using different signals to manage the master and worker processes. The process is outlined on the nginx wiki.

Essentially, the upgrade happens in the following steps:

1. Send USR2 signal to the existing master process
2. This starts up a new master process and renames the pid file for the old process to nginx.pid.oldbin
3. Send QUIT signal to old master process to shut down master & worker processes

Since the default nginx init script does not account for this, I have added an “upgrade” option to the init file.

Note: Recent versions of the development branch now have a -s switch that can be used to pass signals.

UPDATE: Switched the init file to using kill directly instead of start-stop-daemon as it was generating errors.

In light of the MySQL conference, I decided to get try to get drizzle up and running on Ubuntu 8.04. I typically try to avoid installing dependencies from source as much as possible and a little bit of Googling turned up some available libraries.

The Drizzle wiki was useful in getting started but did not include all of the available packages.

First, the basic dependencies:

sudo apt-get install libpcre3-dev libevent-dev autoconf \ 
automake bison libtool ncurses-dev libreadline-dev libz-dev g++ \
libssl-dev uuid-dev libpam0g libpam0g-dev gperf

Next, the libevent on 8.04 is too old so a newer version needs to be installed.

sudo apt-get install libevent-dev

Google’s Protocol Buffers as well as libdrizzle need to be installed and the packages are available on the drizzle-developers PPA on Launchpad.

sudo apt-get install libdrizzle-dev libprotobuf-dev \
protobuf-compiler

Finally, download the drizzle sources and compile:

bzr branch lp:drizzle
cd drizzle
./config/autorun.sh
./configure
make
make install

Install and have fun!

For some reason, Ubuntu 8.04 LTS uses ‘reno’ for TCP congestion control instead of ‘cubic’ even though upstream kernels have had cubic as the default for a while.

Until a new kernel package comes out to fix this, you need to load the module at boot time via /etc/modules or modprobe tcp_cubic for now.

Next, edit /etc/sysctl.conf and set net.ipv4.tcp_congestion_control to cubic. Reload the parameters via “sysctl -p”