Added CoreDNS plugin setup and replaced forward

upstream/setup.go

@@ -0,0 +1,83 @@
+package upstream
+
+import (
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+	"github.com/mholt/caddy"
+	"log"
+)
+
+func init() {
+	caddy.RegisterPlugin("upstream", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+// Read the configuration and initialize upstreams
+func setup(c *caddy.Controller) error {
+
+	p, err := setupPlugin(c)
+	if err != nil {
+		return err
+	}
+	config := dnsserver.GetConfig(c)
+	config.AddPlugin(func(next plugin.Handler) plugin.Handler {
+		p.Next = next
+		return p
+	})
+
+	c.OnShutdown(p.onShutdown)
+	return nil
+}
+
+// Read the configuration
+func setupPlugin(c *caddy.Controller) (*UpstreamPlugin, error) {
+
+	p := New()
+
+	log.Println("Initializing the Upstream plugin")
+
+	bootstrap := ""
+	upstreamUrls := []string{}
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) > 0 {
+			upstreamUrls = append(upstreamUrls, args...)
+		}
+		for c.NextBlock() {
+			switch c.Val() {
+			case "bootstrap":
+				if !c.NextArg() {
+					return nil, c.ArgErr()
+				}
+				bootstrap = c.Val()
+			}
+		}
+	}
+
+	for _, url := range upstreamUrls {
+		u, err := NewUpstream(url, bootstrap)
+		if err != nil {
+			log.Printf("Cannot initialize upstream %s", url)
+			return nil, err
+		}
+
+		p.Upstreams = append(p.Upstreams, u)
+	}
+
+	return p, nil
+}
+
+func (p *UpstreamPlugin) onShutdown() error {
+	for i := range p.Upstreams {
+
+		u := p.Upstreams[i]
+		err := u.Close()
+		if err != nil {
+			log.Printf("Error while closing the upstream: %s", err)
+		}
+	}
+
+	return nil
+}