Since Windows 8.1 doesn't allow system-wide "Windows XP style" high DPI support, how can I make the Microsoft Management Console apps (mmc.exe) high-DPI aware? There is no "Troubleshoot compatibility" context menu item for it.
I want to temporarily block port 80 for the outside world, but want the load balancer to pass through the firewall (via security group) so it won't see the instance as unhealthy. How can I do that?
Update: I also want to know how can I allow only myself accessing to the elastic load balancer via port 80 (but prevent others access). I know that the load balancer doesn't have specific security groups that I can setup and tell it to only accept my IP address, but is there any other way to do it?
What kernel parameter or other settings control the maximum number of TCP sockets that can be open on a Linux server? What are the tradeoffs of allowing more connections?
I noticed while load testing an Apache server with ab that it's pretty easy to max out the open connections on the server. If you leave off ab's -k option, which allows connection reuse, and have it send more than about 10,000 requests then Apache serves the first 11,000 or so requests and then halts for 60 seconds. A look at netstat output shows 11,000 connections in the TIME_WAIT state. Apparently, this is normal. Connections are kept open a default of 60 seconds even after the client is done with them for TCP reliability reasons.
It seems like this would be an easy way to DoS a server and I'm wondering what the usual tunings and precautions for it are.
Here's my test output:
# ab -c 5 -n 50000 http://localhost/
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking localhost (be patient)
Completed 5000 requests
Completed 10000 requests
apr_poll: The timeout specified has expired (70007)
Total of 11655 requests completed
Here's the netstat command I run during the test:
# netstat --inet -p | grep "localhost:www" | sed -e 's/ \+/ /g' | cut -d' ' -f 1-4,6-7 | sort | uniq -c
11651 tcp 0 0 localhost:www TIME_WAIT -
1 tcp 0 1 localhost:44423 SYN_SENT 7831/ab
1 tcp 0 1 localhost:44424 SYN_SENT 7831/ab
1 tcp 0 1 localhost:44425 SYN_SENT 7831/ab
1 tcp 0 1 localhost:44426 SYN_SENT 7831/ab
1 tcp 0 1 localhost:44428 SYN_SENT 7831/ab
Not going into specifics on the specs since I know there is no real answer for this. But I've been doing load testing today with the ab command in apache.
And got to the number of 70 requests per second (1000 requests with 100 concurrent users), on a page that is loading from 4 different DB tables, and doing some manipulation with the data. So it's a fairly heavy page.
The server isn't used for anything else for now and the load on it is just me, since it's in development. But the application will be used daily by many users.
But is this enough? Or should I even worry (just as long as it's over X requests a second)
I'm thinking that I shouldn't worry but I'd like some tips on this.
I'm working on a website that could eventually have a very large database. The website will be an art community not until deviantART. I'll be running a lot of queries for analyzing how the site is used. I expect some of the queries to kill the database because I don't know how to optimize SQL queries (yet). I'm starting out with a small linux VPS and would move to physical servers in the future.
Which database would scale the best given this situation?