Feeds

How a tiny leap-day miscalculation trashed Microsoft Azure

Redmond drills into cause of eight-hour outage

Beginner's guide to SSL certificates

As soon as Microsoft's cloudy platform Azure crashed to Earth, and stayed there for eight hours, on 29 February, every developer who has ever had to handle dates immediately figured it was a leap-day bug.

Now the software biz behemoth has put its hands up and admitted in a detailed dissection of the blunder how a calendar glitch trashed its server farm. It's also a handy guide to setting up your own wholesale-sized cloud platform.

The mega-crash stemmed from the handling of messages passed between a virtual machine running a client's application and the underlying host operating system running on each of the Azure servers.

These messages are encrypted using a public-private key pair taken from a "transfer certificate" generated within the VM. This security measure allows the host OS and the VM to trust their communications channel, through which stuff such as SSL certificates and diagnostic health checks are sent.

A transfer certificate is valid for a year from its creation date. A certificate created by an agent in a VM on 29 February 2012 will expire on 29 February 2013, a date that simply doesn't exist. This crashed the certificate validation process, bringing the start up of the VM to a halt.

The host OS tries to restart a crashed app VM every 25 minutes, which would have been fruitless in this case. After a series of failures, the host OS declares the hardware to be at fault and reports the server as knackered. Automatic systems that manage the clusters of servers try to self-heal the cloud by restarting the VMs on other boxes - in this scenario it caused them to also fall over, cascading the gaffe into a full-blown outage.

It didn't help that, at the time, new versions of the cloud's platform software were being rolled out, which required the generation of new albeit broken transfer certificates. Once enough servers are reported faulty in a cluster, the whole set is put on red alert - halting self-healing and software updates to minimise the damage.

Microsoft engineers confessed that in a rush to roll out the fix to the servers, they hit incompatibility problems within their own code, which knocked out services again.

You can read the full cock-up, blow by blow, here. Microsoft has said it will cough up service credits for customers walloped by the Azure outage. ®

Security for virtualized datacentres

More from The Register

next story
It's Big, it's Blue... it's simply FABLESS! IBM's chip-free future
Or why the reversal of globalisation ain't gonna 'appen
'Hmm, why CAN'T I run a water pipe through that rack of media servers?'
Leaving Las Vegas for Armenia kludging and Dubai dune bashing
Facebook slurps 'paste sites' for STOLEN passwords, sprinkles on hash and salt
Zuck's ad empire DOESN'T see details in plain text. Phew!
CAGE MATCH: Microsoft, Dell open co-located bit barns in Oz
Whole new species of XaaS spawning in the antipodes
Microsoft and Dell’s cloud in a box: Instant Azure for the data centre
A less painful way to run Microsoft’s private cloud
AWS pulls desktop-as-a-service from the PC
Support for PCoIP protocol means zero clients can run cloudy desktops
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Storage capacity and performance optimization at Mizuno USA
Mizuno USA turn to Tegile storage technology to solve both their SAN and backup issues.