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Web service

Next step will be to run dotnet application in service that starts with your virtual PC and system will restart it if application crashes. We will create specific user (www.example.com) that will run dotnet application. Why do we need specific user? Answer is quite simple – security.

Let me elaborate on that. Nginx is running from specific user (www-data). Service will run from another user that we will create (www.example.com). Surely you can run everything from root account, but if nginx or dotnet has some vulnerability then hacker will get access to whole system. If each service has own quite limited account that not even able to login. Moreover,

Previous part is here.

Configuring Web Server

I chose nginx as web server because after research it looks like it is gaining a lot of popularity while second contender Apache2 is losing popularity.

First step is to ensure that your web server is working correctly. Because http port is opened in Amazon router and in your virtual PC you should be able to access it from outside from your browser. Just type https://<you static IP address> in your browser and press Enter. You should see standard nginx web page.

Next step is to make sure that nginx will not serve anything that is not specifically added. Edit file /etc/nginx/sites-available/default and replace it content with following:

server {
	listen 80 default_server;
	listen [::]:80 default_server;
	return   444;
}

Some time ago I needed simple tutorial site. Initially I was thinking about static page hosting and I started research. But during research I found AWS Lightsail service. It cost $3.5 per month and offers 1 vCPU, 512 MB of RAM, 20 GB of SSD space and 1 TB of data transfer. It is about that the same as my current hosting offers but in case of Amazon it is your own virtual PC, and you can do whatever you like there. It looks attractive, but there is one catch. It is Linux. I had some experience with Linux, but it was far from extensive. On another side I really like challenges, so I decided to try it.

But before

  •   Posted in:
  • .NET

Recently I got relatively simple deadlock case, but I found quite interesting things during investigation. Our application hangs when user tries to quit it. I got dump file for this case and started investigation.

Call stack for main thread looks like this:

...
clr!JITutil_MonContention+0x115
System_ni!System.ComponentModel.Component.Dispose(Boolean)$##60031F8+0x40
System_ni!System.IO.FileSystemWatcher.Dispose(Boolean)$##600266D+0xd7
System_ni!System.IO.FileSystemWatcher.Dispose(Boolean)$##600266D+0xa6
System_ni!System.ComponentModel.Component.Dispose()$##60031F7+0x1a
...

As you clearly see, application waiting in FileSystemWatcher’s  System.ComponentModel.Component.Dispose. If you go to https://sourceof.net and paste name of the method there to see source code, you will see that there is lock(this) and it looks like some other thread obtained lock before us. Obviously, I went over other 168 threads and found 2 similar call stacks. First thread was executing event from first

Case of frozen File Explorer

Some time ago I started to get strange freezes when I try to open File Explorer. New File Explorer appears on screen, renders left and top part and then displays “Working on it…” where files supposed to be and then nothing. And today I would like to share my discoveries.

Obviously, first thing I tried to kill File Explorer and start over. Exactly the same behavior. I rarely use File Explorer because I prefer FAR file manager. But sometimes I do use File Explorer, mostly to copy files via Remote Desktop. In this particular case I decided to start FAR file manager to check something. And to my surprise, exactly the same happens to FAR.