Minor refactor of proxy parsing to make upstreams re-usable in other plugins (#1426)

plugin/proxy/upstream.go

@@ -28,6 +28,18 @@ type staticUpstream struct {
 func NewStaticUpstreams(c *caddyfile.Dispenser) ([]Upstream, error) {
 	var upstreams []Upstream
 	for c.Next() {
+		u, err := NewStaticUpstream(c)
+		if err != nil {
+			return upstreams, err
+		}
+		upstreams = append(upstreams, u)
+	}
+	return upstreams, nil
+}
+
+// NewStaticUpstream parses the configuration of a single upstream
+// starting from the FROM
+func NewStaticUpstream(c *caddyfile.Dispenser) (Upstream, error) {
 	upstream := &staticUpstream{
 		from: ".",
 		HealthCheck: healthcheck.HealthCheck{
@@ -38,28 +50,28 @@ func NewStaticUpstreams(c *caddyfile.Dispenser) ([]Upstream, error) {
 	}
 
 	if !c.Args(&upstream.from) {
-			return upstreams, c.ArgErr()
+		return upstream, c.ArgErr()
 	}
 	upstream.from = plugin.Host(upstream.from).Normalize()
 
 	to := c.RemainingArgs()
 	if len(to) == 0 {
-			return upstreams, c.ArgErr()
+		return upstream, c.ArgErr()
 	}
 
 	// process the host list, substituting in any nameservers in files
 	toHosts, err := dnsutil.ParseHostPortOrFile(to...)
 	if err != nil {
-			return upstreams, err
+		return upstream, err
 	}
 
 	if len(toHosts) > max {
-			return upstreams, fmt.Errorf("more than %d TOs configured: %d", max, len(toHosts))
+		return upstream, fmt.Errorf("more than %d TOs configured: %d", max, len(toHosts))
 	}
 
 	for c.NextBlock() {
 		if err := parseBlock(c, upstream); err != nil {
-				return upstreams, err
+			return upstream, err
 		}
 	}
 
@@ -75,9 +87,7 @@ func NewStaticUpstreams(c *caddyfile.Dispenser) ([]Upstream, error) {
 	}
 	upstream.Start()
 
-		upstreams = append(upstreams, upstream)
-	}
-	return upstreams, nil
+	return upstream, nil
 }
 
 func parseBlock(c *caddyfile.Dispenser, u *staticUpstream) error {