16504234e5
* 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
73 lines
2.1 KiB
Go
73 lines
2.1 KiB
Go
// Package forward implements a forwarding proxy. It caches an upstream net.Conn for some time, so if the same
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// client returns the upstream's Conn will be precached. Depending on how you benchmark this looks to be
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// 50% faster than just openening a new connection for every client. It works with UDP and TCP and uses
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// inband healthchecking.
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package forward
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import (
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"github.com/coredns/coredns/request"
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"github.com/miekg/dns"
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"golang.org/x/net/context"
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)
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// Forward forward the request in state as-is. Unlike Lookup that adds EDNS0 suffix to the message.
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// Forward may be called with a nil f, an error is returned in that case.
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func (f *Forward) Forward(state request.Request) (*dns.Msg, error) {
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if f == nil {
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return nil, errNoForward
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}
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fails := 0
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for _, proxy := range f.list() {
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if proxy.Down(f.maxfails) {
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fails++
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if fails < len(f.proxies) {
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continue
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}
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// All upstream proxies are dead, assume healtcheck is complete broken and randomly
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// select an upstream to connect to.
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proxy = f.list()[0]
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}
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ret, err := proxy.connect(context.Background(), state, f.forceTCP, true)
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if err != nil {
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if fails < len(f.proxies) {
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continue
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}
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break
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}
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return ret, nil
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}
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return nil, errNoHealthy
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}
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// Lookup will use name and type to forge a new message and will send that upstream. It will
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// set any EDNS0 options correctly so that downstream will be able to process the reply.
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// Lookup may be called with a nil f, an error is returned in that case.
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func (f *Forward) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
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if f == nil {
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return nil, errNoForward
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}
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req := new(dns.Msg)
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req.SetQuestion(name, typ)
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state.SizeAndDo(req)
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state2 := request.Request{W: state.W, Req: req}
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return f.Forward(state2)
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}
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// NewLookup returns a Forward that can be used for plugin that need an upstream to resolve external names.
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// Note that the caller must run Close on the forward to stop the health checking goroutines.
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func NewLookup(addr []string) *Forward {
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f := New()
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for i := range addr {
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p := NewProxy(addr[i], nil)
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f.SetProxy(p)
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}
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return f
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}
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