UPDATE: Canvas Service is coming back. Canvas DevOps team is continuing to monitor the situation.
Canvas is currently experiencing service interruption for many users due to a related AWS outage. Please visit the following link for detailed status information: http://status.instructure.com/
"AWS Outage Making Canvas Inaccessible for Many Users
Investigating - Canvas is currently experiencing an outage that we are investigating. Our DevOps team has determined that this is an AWS (Amazon Web Services) Outage. We will post updates as they become available."