* plugin/forward: erase expired connection by timer
- in previous implementation, the expired connections resided in
cache until new request to the same upstream/protocol came. In
case if the upstream was unhealthy new request may come long time
later or may not come at all. All this time expired connections
held system resources (file descriptors, ephemeral ports). In my
fix the expired connections and related resources are released
by timer
- decreased the complexity of taking connection from cache. The list
of connections is treated as stack (LIFO queue), i.e. the connection
is taken from the end of queue (the most fresh connection) and
returned to the end (as it was implemented before). The remarkable
thing is that all connections in the stack appear to be ordered by
'used' field
- the cleanup() method finds the first good (not expired) connection
in stack with binary search, since all connections are ordered by
'used' field
* fix race conditions
* minor enhancement
* add comments
* plugin/forward: on demand healtchecking
Only start doing health checks when we encouner an error (any error).
This uses the new pluing/pkg/up package to abstract away the actual
checking. This reduces the LOC quite a bit; does need more testing, unit
testing and tcpdumping a bit.
* fix tests
* Fix readme
* Use pkg/up for healthchecks
* remove unused channel
* more cleanups
* update readme
* * Again do go generate and go build; still referencing the wrong forward
repo? Anyway fixed.
* Use pkg/up for doing the healtchecks to cut back on unwanted queries
* Change up.Func to return an error instead of a boolean.
* Drop the string target argument as it doesn't make sense.
* Add healthcheck test on failing to get an upstream answer.
TODO(miek): double check Forward and Lookup and how they interact with
HC, and if we correctly call close() on those
* actual test
* Tests here
* more tests
* try getting rid of host
* Get rid of the host indirection
* Finish removing hosts
* moar testing
* import fmt
* field is not used
* docs
* move some stuff
* bring back health_check
* maxfails=0 test
* git and merging, bah
* review
* plugin/forward: add it
This moves coredns/forward into CoreDNS. Fixes as a few bugs, adds a
policy option and more tests to the plugin.
Update the documentation, test IPv6 address and add persistent tests.
* Always use random policy when spraying
* include scrub fix here as well
* use correct var name
* Code review
* go vet
* Move logging to metrcs
* Small readme updates
* Fix readme
