Automatically submitted.

TestLookupAutoPathErratic sometimes fail on TravisCI saying below

```
=== RUN   TestLookupAutoPathErratic
--- FAIL: TestLookupAutoPathErratic (8.30s)
    erratic_autopath_test.go:39: Test 0, failed to sent query: "read udp [::1]:39758->[::1]:56643: i/o timeout"
FAIL
```

The failure happens when Google replies slowly.
This PR changes to not use Google but run CoreDNS locally and proxy to the server.

---

Because the failure depends on Google, sometimes it happens frequently but sometimes it doesn't happen.
I hope following test help you reproduce it.

```
func TestLookupAutoPathErratic2(t *testing.T) {
	for i := 0; i < 200; i++ {
		TestLookupAutoPathErratic(t)
	}
}
```

or I can reproduce it by changing proxy to other DNS like 1.1.1.1 instead of 8.8.8.8 too

Imports should be sorted by Go coding convention

* Fix some typos

Corect some words for reading more easily

* Update NOERROR response code

NOERROR is a response code so I revert the typo checking for it

Signed-off-by: Nguyen Van Trung <trungnv@vn.fujitsu.com>

The [ADDRESS] field in the metrics plugin is not explained in a manner
that makes it immediately obvious, that what we are talking about here
is a listening address.

* plugin/hosts provide more configuration flexibility

This patch adds few features to the host plugin
 * no-reverse (both as first argument on the plugin line and inline)
   disable the automatic generation of reserve entries for hosts
 * ttl <duration> (inline only atm)
   allows to change the default ttl (default 5 minutes)
 * reload <duration> (inline only atm)
   allows to change the reloading interval (default 5s)

* plugin/hosts remove superfluous parameters to parse

* pkg/replace: make it more efficient.

Remove the map that is allocated on every write and make it more static,
but just defining a function that gets called for a label and returns
its value.

Remove the interface definition and just implement what is needed in our
case. Add benchmark test for replace as well.

Extend metadata test to test multiple values (pretty sure this didn't
work, but there wasn't a test for it, so can't be sure).

Update all callers to use it - concurrent use should be fine as we pass
everything by value.

Benchmarks in replacer:

new: BenchmarkReplacer-4   300000      4717 ns/op     240 B/op       8 allocs/op
old: BenchmarkReplacer-4   300000      4368 ns/op     384 B/op      11 allocs/op

Added benchmark function to the old code to test it.

~~~
func BenchmarkReplacer(b *testing.B) {
	w := dnstest.NewRecorder(&test.ResponseWriter{})
	r := new(dns.Msg)
	r.SetQuestion("example.org.", dns.TypeHINFO)
	r.MsgHdr.AuthenticatedData = true
	b.ResetTimer()
	b.ReportAllocs()
	repl := New(context.TODO(), r, w, "")
	for i := 0; i < b.N; i++ {
		repl.Replace("{type} {name} {size}")
	}
}
~~~

New code contains (of course a different one). The amount of ops is
more, which might be good to look at some more. For all the allocations
is seems it was quite performant.

This looks to be 50% faster, and there is less allocations in log
plugin:

old: BenchmarkLogged-4   	   20000	     70526 ns/op
new: BenchmarkLogged-4   	   30000	     57558 ns/op
Signed-off-by: Miek Gieben <miek@miek.nl>

* Stickler bot
Signed-off-by: Miek Gieben <miek@miek.nl>

* Improve test coverage
Signed-off-by: Miek Gieben <miek@miek.nl>

* typo
Signed-off-by: Miek Gieben <miek@miek.nl>

* Add test for malformed log lines
Signed-off-by: Miek Gieben <miek@miek.nl>

This was added, but didn't see any use. For a large, complex chunk of
code we should have some users of it.

Remove all watch functionally from plugins, servers and packages.

Fixes: #2548
Signed-off-by: Miek Gieben <miek@miek.nl>

Signed-off-by: zhoulin xie <zhoulin.xie@daocloud.io>

Currently, when you run `TestEtcdCredentials` at etcd_credentials_test.go multiple times without clearing data of etcd, you will get following errors.

```
etcd_credentials_test.go:38: Failed to create root role: etcdserver: role name already exists
etcd_credentials_test.go:41: Failed to create user: etcdserver: user name already exists
```

symlink from within .github

This should be enough to show it in pull request; unless github has
something against symlinks.
Signed-off-by: Miek Gieben <miek@miek.nl>

* doc: update CONTRIBUTING.md

Remove bunch of old/stale text, but add a section (and clarify) using
issues to describe a future PR and that those need to be small (if you
want it merged faster)
Signed-off-by: Miek Gieben <miek@miek.nl>

* Update CONTRIBUTING.md
Co-Authored-By: miekg <miek@miek.nl>

Signed-off-by: zhoulin xie <zhoulin.xie@daocloud.io>

* Parse as well as  setlogtostderr flag

* Enforce setting of logtostderr for klog

* Clearup comment on klog

This patch fixes broken link in README.md

Signed-off-by: Miek Gieben <miek@miek.nl>

* support etcd credentials in etcd plugin

fixes #2441

* try to fix cleanup of authentication

Signed-off-by: zhoulin xie <zhoulin.xie@daocloud.io>

Signed-off-by: yeya24 <ben.ye@daocloud.io>

When a query, different from a TXT lookup is performed, all services
with a missing `Host` field should be filtered out, as these otherwize
cause a line in the answer section with a single dot (`.`) as the
result. This behavior manifests for example when a TXT record is present
on a domain, eg. an A or SRV lookup is performed on said domain.

If there are no services containing a `Host` field, a `NODATA` response
should be given. If there are other Services, these alone should be
returned for the query.

Filter any service that has an empty Host field from all lookup types
other than TXT to solve this issue. At the same time the check for empty
`Text` fields in TXT queries are also moved to the same check in the
etcd ServiceBackend.

* fix for ipv4-in-ipv6

* update comment as requested

* readme: add text on backward incompat changes

Document the process of releasing backwards incompatible changes.
Signed-off-by: Miek Gieben <miek@miek.nl>

* slightly better
Signed-off-by: Miek Gieben <miek@miek.nl>

* Add an example
Signed-off-by: Miek Gieben <miek@miek.nl>

* Be more explicit in naming the segments increased
Signed-off-by: Miek Gieben <miek@miek.nl>

This PR is a small golint fix:
```
coredns/plugin/test/helpers.go
Line 283: warning: redundant if ...; err != nil check, just return error instead. (golint)
```
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

There are string ttls at commands at README.md.
But because `TTL` of `Service` is uint32, commands at README is wrong.

e.g.) `etcdctl put /skydns/local/skydns/x1 '{"host":"1.1.1.1","ttl":"60"}'`.

The `b` struct is just copying all the fields into a new one, to
check if it already existed in a set. This isn't needed as all the
fields are identical, and a small rearrangement of the code solves the
same problem without the copy.

Fix a small error

* inform users of the reload feature

* modified as requested

The check is done through
```
if [[ $(go list -f '{{ join .Deps " "}}') == *" testing "* ]]; then
   error..
fi
```
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>