Fastly says just one customer caused huge internet outage by accident

‘This outage was broad and severe, and we’re truly sorry for the impact to our customers’

Fastly said the bug was in a software update shipped to customers on 12 May but was not triggered until one customer carried out settings changes (Getty)

The global internet outage that took down much of the internet for more than an hour was caused by a software bug, the company behind it said.

Fastly said that an issue in its software had been triggered when one of its customers changed their settings.

When that happened, it began a series of issues that knocked many of the world’s biggest websites offline. Reddit, Amazon, the UK government and many of the world’s biggest news organisations were unavailable, with users instead seeing an array of error messages.

“This outage was broad and severe, and we’re truly sorry for the impact to our customers and everyone who relies on them,” the company said in a blog post authored by Nick Rockwell, its senior engineering and infrastructure executive.

He said the problem should have been anticipated.

Fastly operates a group of servers strategically placed around the world to help customers move and store content close to their end users quickly and safely.

The company post gave a timeline of events and promised to examine and explain why Fastly had failed to detect the software bug during its own testing process.

Fastly said the bug was in a software update shipped to customers on 12 May but was not triggered until one unidentified customer carried out settings changes that triggered the problem “which caused 85 per cent of our network to return errors.”

Fastly noticed the outage within a minute it occurring at 9.47am, and engineers worked out the cause at 10.27am. Once they disabled the settings that triggered the problem, most of the company’s network quickly recovered.

“Within 49 minutes, 95 per cent of our network was operating as normal,” the company said.

Its networks were fully recovered at 12.35pm and it began rolling out a permanent software fix at 5.25pm, Fastly said.

Additional reporting by Reuters