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!

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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