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plugin/forward using pkg/up (#1493)

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* 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
This commit is contained in:
Miek Gieben
2018-02-15 10:21:57 +01:00
committed by GitHub
parent 8b035fa938
commit 16504234e5
15 changed files with 306 additions and 221 deletions
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36
plugin/forward/forward.go
View File

@@ -20,8 +20,9 @@ import (
// Forward represents a plugin instance that can proxy requests to another (DNS) server. It has a list
// of proxies each representing one upstream proxy.
type Forward struct {
proxies []*Proxy
p Policy
proxies []*Proxy
p Policy
hcInterval time.Duration
from string
ignored []string
@@ -31,22 +32,21 @@ type Forward struct {
maxfails uint32
expire time.Duration
forceTCP bool // also here for testing
hcInterval time.Duration // also here for testing
forceTCP bool // also here for testing
Next plugin.Handler
}
// New returns a new Forward.
func New() *Forward {
f := &Forward{maxfails: 2, tlsConfig: new(tls.Config), expire: defaultExpire, hcInterval: hcDuration, p: new(random)}
f := &Forward{maxfails: 2, tlsConfig: new(tls.Config), expire: defaultExpire, p: new(random), from: ".", hcInterval: hcDuration}
return f
}
// SetProxy appends p to the proxy list and starts healthchecking.
func (f *Forward) SetProxy(p *Proxy) {
f.proxies = append(f.proxies, p)
go p.healthCheck()
p.start(f.hcInterval)
}
// Len returns the number of configured proxies.
@@ -92,7 +92,27 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
child.Finish()
}
// If you query for instance ANY isc.org; you get a truncated query back which miekg/dns fails to unpack
// because the RRs are not finished. The returned message can be useful or useless. Return the original
// query with some header bits set that they should retry with TCP.
if err == dns.ErrTruncated {
// We may or may not have something sensible... if not reassemble something to send to the client.
if ret == nil {
ret = new(dns.Msg)
ret.SetReply(r)
ret.Truncated = true
ret.Authoritative = true
ret.Rcode = dns.RcodeSuccess
}
err = nil // and reset err to pass this back to the client.
}
if err != nil {
// Kick off health check to see if *our* upstream is broken.
if f.maxfails != 0 {
proxy.Healthcheck()
}
if fails < len(f.proxies) {
continue
}
@@ -140,8 +160,8 @@ func (f *Forward) isAllowedDomain(name string) bool {
func (f *Forward) list() []*Proxy { return f.p.List(f.proxies) }
var (
errInvalidDomain = errors.New("invalid domain for proxy")
errNoHealthy = errors.New("no healthy proxies")
errInvalidDomain = errors.New("invalid domain for forward")
errNoHealthy = errors.New("no healthy proxies or upstream error")
errNoForward = errors.New("no forwarder defined")
)