Gmail Outage Was Caused by Heavy Load on the Contacts Service

Gmail was hit by yet another problem last week, rather soon after a major issue affected the service, causing massive disruptions and outages a month ago. The problem affected quite a few users, preventing them from accessing their contacts or event the entire service at one point. Now Google has come out with an explanation for the issues and it's a good one. Apparently Google's massive infrastructure couldn't handle the load put on Google Contacts and the engineers decided to cut off access to the feature entirely as a temporary solution.

Last week a number of users reported problems with the webmail service with timeout errors and general slowness. They were then unable to access their contacts in Gmail, Talk or Apps. The problem was caused by an overload on the servers running the feature, which was brought in by several converging factors as is usually the case.

The engineers traced the issue to three main causes. The trigger for the event was a network problem at one of Google's many data centers which put additional strain on the Contacts service. As it happens, the problem came up on a day when Contacts had already much bigger traffic than usual. Finally a Gmail update caused even more additional load leading to a very unresponsive service.

“The Google Engineering team investigated the issue, and at 7:57 AM PDT | 14:57 GMT, they temporarily stopped all requests to use the Contacts feature from the Gmail interface to alleviate the Gmail issue. By 8:30 AM PDT | 15:30 GMT, Gmail access returned to normal for all users,” Google explained in a report [PDF] after the incident. “During this period, affected users also could not access Google Talk or add new user accounts to their Google Apps accounts. To restore these features, the Engineering team deployed additional capacity to the Contacts service through Google's flexible capacity server systems.”

Interestingly, a Gmail update was also the cause for the bigger outage in August. While the problem wasn't a major one and Google managed to resolve it relatively quickly the irony is that it makes a very bad case for cloud computing, of which Google is a great supporter, and it gives the naysayers plenty of fodder to feed their arguments.