Fallacies of distributed computing

The fallacies are:^[1]

• The network is reliable
• Latency is zero
• Bandwidth is infinite
• The network is secure
• Topology doesn't change
• There is one administrator
• Transport cost is zero
• The network is homogeneous

Although, there are some writings about they are not fallacies anymore... 

iostat vmstat

- vmstat 30
  cpu intensive ?
  memory paging ?
  r, free, si, so

- iostat -x
  avgqr-z
  await
  %util (100%?!)

Run iostat with kilobytes unit, 2 seconds interval with 3 times reports
# iostat -k 2 3

1. https://devwebcl.blogspot.com/2014/05/distinctive-recipes-2nd-ed-1212-1211.html
2. https://www.geeksforgeeks.org/iostat-command-in-linux-with-examples/
3. https://www.techrepublic.com/article/how-to-use-the-linux-iostat-command-to-check-on-your-storage-subsystem/

HTTP 1.0 Performance

HTTP 1.0 had performance issues by slow-start of TCP. The 3-way handshaking was guilty.

https://devwebcl.blogspot.com/2018/09/tcpip-illustrated.html

This was fixed in HTTP 1.1 reusing the connections. Similar to a pool of TCP connections.

2.

• Under HTTP 1.0, connections are not considered persistent unless a keepalive header is included,^[1]
  
  
  ^{-Dhttp.keepAlive=false (it can be configured at java system property)}
  
  
•  In HTTP 1.1, all connections are considered persistent unless declared otherwise.^[2]

Resources:

- https://www.w3.org/Protocols/HTTP/1.0/HTTPPerformance.html
- https://hpbn.co/http1x/
- https://blog.insightdatascience.com/learning-about-the-http-connection-keep-alive-header-7ebe0efa209d
- https://en.wikipedia.org/wiki/HTTP_persistent_connection#HTTP_1.0
- https://en.wikipedia.org/wiki/TCP_congestion_control