Lightsail Instance Unreachable, Snapshots also does not work.

Question

Today, my wordpress website installed on Centos became unreachable.

When connected with SSH, there is only a black screen.

Server is not overloaded. Checked from metrics.

Rebooted server. Nothing changed.

Stopped and Started. Nothing changed.

There are 7 snapshots taken last 7 days automatically. All of them should be working. Reinstated the server from last 3 snapshots and none of them worked. All same.

Reinstated last snapshot to a bigger instance. Still everything same.

I have another website, exactly same setup and site, just name is different and it works without a problem.

Also, last week, sometimes web site was unreachable for short period of times. I checked metrics history and no overload exists.

Also, there is no failure record on server status checks.

What should I do?

Snapshots are not working and that confuses me. Because, website has been working last 7 days. So, snapshots should be ok.

UPDATE AFTER 6 HOURS:

I got asleep. I woke up and web site works now. So, I logined the system and tried to connect with SSH and still black screen. CPU usage %9.

After I wait, it says;

"An error occurred and we were unable to connect or stay connected to your instance. If this instance has just started up, try again in a minute or two.

UPSTREAM_NOT_FOUND [519]"

UPDATE 2:

Ram usage ise %88-89. May be, it is time to upgrade the server may be... I will check everything in couple of days.

Accepted Answer

It sounds like you're encountering some complex and persistent issues with your Amazon Lightsail instance. Even though it's challenging to diagnose the exact problem without accessing your AWS Account, I can suggest a few more avenues to explore.

1. **Disk Space**: Make sure you're not running out of disk space. Although you've mentioned that there are no server overloads, sometimes, running out of disk space might not be reflected in CPU usage or server load metrics.

2. **Server Logs**: Check the server logs for any abnormal behavior or error messages. If you can SSH into your server, you can check logs such as `/var/log/syslog` (system logs) or `/var/log/auth.log` (authentication logs). The error messages in these logs might give you a clue as to what is going wrong.

3. **AWS Service Health Dashboard**: Visit the AWS Service Health Dashboard to check if there are any ongoing issues in the AWS region where your Lightsail instance is hosted.

4. **Network Issues**: Check for network connectivity issues, specifically if your instance is unreachable, but its CPU usage is normal. These issues might arise from either AWS side or your own network. AWS provides tools like VPC Flow Logs to monitor network traffic.

5. **Reach out to AWS Support**: If your instance and all snapshots are showing the same symptoms and you've verified that there is no issue with your server setup or AWS services, it would be advisable to reach out to AWS Support. They have deeper visibility into the infrastructure and may be able to diagnose what's happening.

6. **Other Wordpress and CentOS Checks**: Ensure the WordPress and CentOS software are up-to-date and have the necessary permissions and configurations. Also, check the status of the Apache or Nginx and MySQL services. Make sure your firewall settings are correct and are not blocking necessary ports (like 22 for SSH).

The message "UPSTREAM_NOT_FOUND [519]" usually indicates a problem with the upstream server, which could mean a network issue, server issue, or even a problem with the service provider. All these checks should ideally help you pinpoint where the problem lies.

**If the answer is helpful, please click "Accept Answer" and upvote it.**

Answer

Finally Figured out the issue, by creating another instance & was trying to replicate my issue that is: **"ssh: connect to host x.x.x.x port 22: Operation timed out"**. on my lightsail instance.

Why I am unable to connect to the instance via SSH is that I did turn on the UFW in my ubuntu instance by typing `sudo ufw enable`, that is the main mistake I made, after doing this when I tried to connect my instance again via same steps, I was unable to connect.

**The solution is, whenever we turn on the ufw, we must allow ufw with port 22, by running the command `sudo ufw allow 22`**

Lightsail Instance Unreachable, Snapshots also does not work.

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