Failure rate = number of users who failed to use the service/total user who used the service.
How to collect the data for failure rate? User send a log to server when it visited our website
What happened wen you enter http://www.google.com in your browser and hit enter.
first go to DNS and get the IP address of http://www.google.com
DNS lookup and prepare reply
DNS send reply back.
send request to the webserver.
prepare webpage reply.
send web page reply.
DNS failure :
WebServer failure: Reverse Proxy (add more servers). Reduce the size of webpage (Simplify content, Rewrite JS code). Compress/merge images. Lazy Load, batch connection
More Cacheable pages. Change dynamic webpage into static webpage.
Process File download
1. send request to the file server
2. Network error (file server failure?),
3. fail to establish connect,
4. fail to find file,
5. Network error when responding.
Distributed File server.address is provided by the web server, no need to go to the DNS.