* Rename middleware to plugin
first pass; mostly used 'sed', few spots where I manually changed
text.
This still builds a coredns binary.
* fmt error
* Rename AddMiddleware to AddPlugin
* Readd AddMiddleware to remain backwards compat
* Switches out Unhealthy bool for OkUntil timestamp
* Make sure servers are healthy forever if there are no health checks
* Moves health check off into a go routine to avoid blocking conditions
* Improved logging info
* Fixes initial date
* Fixes health checking; alters tests to adapt to async health checking
* Moves future variable into static upstream and populates it in more places
* Restores silencing of stdout during testing
* Restores silencing of stdout during testing
* keeps check url string once built
* Removes debug message
* uses zero value to signal no checking; reduces in-mutex code to a fetch
Add deadline to break the connection. We use the default of 5 seconds.
After this the backend is marked unhealthy and not used for some time.
Fixes#467
* middleware/proxy
Use connection pooling for communicating with an upstream, instead of
opening a new socket every time.
This makes the proxy more efficient and allowed for some cleanups.
* Some cleanups
* Some fixes
* more
* Kill pool
* Add nil check
* remove pool
