Currently, there are some useless includes in the codebase. We can use a tool named include-what-you-use to optimize these includes. By using a strict include-what-you-use policy, we can get lots of benefits from it.
After tablet level metrics is supported, the http metrics API may response
a very large body when a BE holds a large number of tablets, and cause heavy
network traffic.
This patch introduce http content compression to reduce network traffic.
