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I am currently running wordpress on an Amazon ec2 instance, which runs fine with no problems most of the time, but occasionally outside connection to the instance shuts down. I can't access it over either http or ssh, and the server seems completely unresponsive (but the status checks pass). However, everything is fine if I simply stop and start the instance (not restart though). Although this problem is manageable, it is obviously extremely inconvenient and a problem for production. Does anyone know why this might happen? Thanks so much in advance!

  • How do CPU utilization and memory look, in the instance metrics in the console? Is this a micro instance? – Michael - sqlbot Sep 15 '14 at 3:27
  • The metrics all look like I'd expect -- nothing extraordinary when I can connect to the instance, and obviously everything's dead when the connections fail. It's a t2.micro instance. – cderwin Sep 15 '14 at 4:44
  • Well, not quite "obviously" if the status checks are still passing. You're saying all of the Cloudwatch metrics (in the AWS web console) stop updating? – Michael - sqlbot Sep 15 '14 at 11:08
  • No they update, but given that nothing can connect to the server and I had very little running, network in/out, memory write/read, and cpu utilization were all either near 0 or 0. – cderwin Sep 15 '14 at 17:03
  • I experience the same thing and yes it's a t2.micro instance. CPU utilization percent scale is 0 to 1...I assume that's 0% to 100% and if so, I am seeing a sustained +85% CPU before the instance tanks. Then I can no longer SSH to the instance. Have to launch a new one from AMI. – SomethingOn Mar 9 '15 at 19:38
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Usually this is something you would want to contact AWS support about. Your instance's virtual network adapter could be messed up causing the disconnections, and that's something that only AWS support can handle.

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It seems that you're running out of CPU credits and your instance freezes:

When an instance starts to run low on CPU Credits, its performance will gradually return to the baseline level (10% to 40% of a single core, as listed in the table above). This deceleration process takes place over the course of a 15 minute interval in order to provide a smooth and pleasant experience for your users.

https://aws.amazon.com/blogs/aws/low-cost-burstable-ec2-instances/

  • Can you please quote the relevant information from the link? – Ramhound Aug 16 '16 at 17:22
  • Is there any way to see my CPU credits on the AWS portal? – Mustafa Hussain Jan 12 '18 at 7:12

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