64 lines
2.2 KiB
Go
64 lines
2.2 KiB
Go
// Package split is a CoreDNS plugin that prints "example" to stdout on every packet received.
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//
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// It serves as an example CoreDNS plugin with numerous code comments.
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package split
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import (
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"context"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/metrics"
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clog "github.com/coredns/coredns/plugin/pkg/log"
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"github.com/miekg/dns"
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)
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// Define log to be a logger with the plugin name in it. This way we can just use log.Info and
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// friends to log.
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var log = clog.NewWithPlugin("split")
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// Split is an example plugin to show how to write a plugin.
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type Split struct {
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Next plugin.Handler
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}
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// ServeDNS implements the plugin.Handler interface. This method gets called when example is used
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// in a Server.
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func (e Split) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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// This function could be simpler. I.e. just fmt.Println("example") here, but we want to show
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// a slightly more complex example as to make this more interesting.
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// Here we wrap the dns.ResponseWriter in a new ResponseWriter and call the next plugin, when the
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// answer comes back, it will print "example".
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// Debug log that we've have seen the query. This will only be shown when the debug plugin is loaded.
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log.Debug("Received response")
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// Wrap.
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pw := NewResponsePrinter(w)
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// Export metric with the server label set to the current server handling the request.
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requestCount.WithLabelValues(metrics.WithServer(ctx)).Inc()
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// Call next plugin (if any).
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return plugin.NextOrFailure(e.Name(), e.Next, ctx, pw, r)
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}
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// Name implements the Handler interface.
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func (e Split) Name() string { return "split" }
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// ResponsePrinter wrap a dns.ResponseWriter and will write example to standard output when WriteMsg is called.
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type ResponsePrinter struct {
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dns.ResponseWriter
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}
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// NewResponsePrinter returns ResponseWriter.
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func NewResponsePrinter(w dns.ResponseWriter) *ResponsePrinter {
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return &ResponsePrinter{ResponseWriter: w}
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}
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// WriteMsg calls the underlying ResponseWriter's WriteMsg method and prints "example" to standard output.
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func (r *ResponsePrinter) WriteMsg(res *dns.Msg) error {
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log.Info("example")
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return r.ResponseWriter.WriteMsg(res)
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}
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