EC2 t2.micro Instance Randomly Stops with Array-Index-Out-Of-Bounds Error

Question

Hello AWS Community,

I am experiencing an issue with my EC2 t2.micro instance, where it randomly stops, and I am forced to manually stop and restart it. This issue leads to downtime for my websites, which is quite problematic. I am currently on the EC2 free tier.

The logs show an "array-index-out-of-bounds" error related to the Xen virtualization environment. Here's the relevant part of the log:

```
UBSAN: array-index-out-of-bounds in /build/linux-aws-6.5-Sh4SK5/linux-aws-6.5-6.5.0/drivers/block/xen-blkfront.c:554:14
index 1 is out of range for type 'blkif_sring_entry [1]'
```

This seems to occur in the xen-blkfront.c driver, which I understand is related to the management of virtual block devices.

I am seeking advice on the following points:

Why might this "array-index-out-of-bounds" error be occurring, particularly in the context of a seemingly low-utilization instance?
Are there any steps I can take or configurations I can adjust to prevent this issue from recurring?
Is this indicative of a deeper problem with the instance type or the specific configuration I am using?
How can I prevent my instance from randomly stopping like this in the future?

Any insights or recommendations would be greatly appreciated as I look to resolve this issue and reduce the downtime experienced on my sites.

Thank you in advance for your help!

Ganesh Kudikala · Answer

Hi

First, sorry for the inconience caused for your applications, as Engineer i can understand your problem. This is the first time i saw the strage error reported by you, However lets try to debug and i will try to help you as my best.

Regarding Error:

I just tried searching for the Error seems like a Bug, This error indicates that your code is trying to access an element in an array that doesn't exist. In this case, the error is within the **xen-blkfront.c **driver, which handles virtual block devices (storage) on your EC2 instance. I assume because of this your machine is rebooting multiple times.

Best Practices and Recommendations:
* t2.micro instances are known for their "burstable" performance. Such a small instance never recommended for the Production workloads
* You can try to create New machine with larger size than t2.micro, Or try using Simple way with AWS lightsail
* AWS always recommends to use high availability to your applications. https://docs.aws.amazon.com/autoscaling/ec2/userguide/tutorial-ec2-auto-scaling-load-balancer.html

EC2 t2.micro Instance Randomly Stops with Array-Index-Out-Of-Bounds Error

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