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by Martin Fowler.
Original Post: Bliki: PhoenixServer
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Feed Description: A cross between a blog and wiki of my partly-formed ideas on software development
One day I had this fantasy of starting a certification service
for operations. The certification assessment would consist of a
colleague and I turning up at the corporate data center and setting
about critical production servers with a baseball bat, a chainsaw,
and a water pistol. The assessment would be based on how long it
would take for the operations team to get all the applications up
and running again.
This may be a daft fantasy, but the there's a nugget of wisdom
here. While you should forego the baseball bats, it is a good idea
to virtually burn down you servers at regular intervals. A server
should be like a phoenix, regurlarly rising from the ashes.[1]
The primary advantage of using phoenix servers is to avoid configuration
drift: ad hoc changes to a systems configuration that go
unrecorded. Drift is the name of a street that leads to
SnowflakeServers, and you don't want to go there without
a big plough.
One way to combat drift is to use software that automatically
re-syncs servers with a known baseline. Tools like Puppet and Chef
have facilities to do this, automatically re-applying their defined
configuration. [2] The limitiation is that
re-applying configuration like this can only spot
drift in areas that you've defined that the tools control.
Configuration drift that occurs outside those areas doesn't get
fixed. Since phoenixes start from scratch, however,
they will pick up any drift from the source configuration.
This doesn't mean that re-applying configuration isn't useful
since it's usually faster and less disruptive than burning down a
server. But it's valuable to use both strategies to fight away the
snowflakes.
1:
My colleague Kornelis
Sietsma came up with the term "Phoenix Server" on an internal
discussion list.
2:
These tools are also excellent for building phoenixes.
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