Merge pull request #94 from acmacalister/feature/custom-policies

added custom policy support

middleware/proxy/policy.go

@@ -13,6 +13,12 @@ type Policy interface {
 	Select(pool HostPool) *UpstreamHost
 }
 
+func init() {
+	RegisterPolicy("random", func() Policy { return &Random{} })
+	RegisterPolicy("least_conn", func() Policy { return &LeastConn{} })
+	RegisterPolicy("round_robin", func() Policy { return &RoundRobin{} })
+}
+
 // Random is a policy that selects up hosts from a pool at random.
 type Random struct{}
 

middleware/proxy/policy_test.go

@@ -4,6 +4,12 @@ import (
 	"testing"
 )
 
+type customPolicy struct{}
+
+func (r *customPolicy) Select(pool HostPool) *UpstreamHost {
+	return pool[0]
+}
+
 func testPool() HostPool {
 	pool := []*UpstreamHost{
 		&UpstreamHost{
@@ -55,3 +61,12 @@ func TestLeastConnPolicy(t *testing.T) {
 		t.Error("Expected least connection host to be first or second host.")
 	}
 }
+
+func TestCustomPolicy(t *testing.T) {
+	pool := testPool()
+	customPolicy := &customPolicy{}
+	h := customPolicy.Select(pool)
+	if h != pool[0] {
+		t.Error("Expected custom policy host to be the first host.")
+	}
+}

middleware/proxy/upstream.go

@@ -12,6 +12,8 @@ import (
 	"github.com/mholt/caddy/config/parse"
 )
 
+var supportedPolicies map[string]func() Policy = make(map[string]func() Policy)
+
 type staticUpstream struct {
 	from   string
 	Hosts  HostPool
@@ -53,14 +55,10 @@ func NewStaticUpstreams(c parse.Dispenser) ([]Upstream, error) {
 				if !c.NextArg() {
 					return upstreams, c.ArgErr()
 				}
-				switch c.Val() {
-				case "random":
-					upstream.Policy = &Random{}
-				case "round_robin":
-					upstream.Policy = &RoundRobin{}
-				case "least_conn":
-					upstream.Policy = &LeastConn{}
-				default:
+
+				if policyCreateFunc, ok := supportedPolicies[c.Val()]; ok {
+					upstream.Policy = policyCreateFunc()
+				} else {
 					return upstreams, c.ArgErr()
 				}
 			case "fail_timeout":
@@ -147,6 +145,11 @@ func NewStaticUpstreams(c parse.Dispenser) ([]Upstream, error) {
 	return upstreams, nil
 }
 
+// RegisterPolicy adds a custom policy to the proxy.
+func RegisterPolicy(name string, policy func() Policy) {
+	supportedPolicies[name] = policy
+}
+
 func (u *staticUpstream) From() string {
 	return u.from
 }

middleware/proxy/upstream_test.go

@@ -41,3 +41,13 @@ func TestSelect(t *testing.T) {
 		t.Error("Expected select to not return nil")
 	}
 }
+
+func TestRegisterPolicy(t *testing.T) {
+	name := "custom"
+	customPolicy := &customPolicy{}
+	RegisterPolicy(name, func() Policy { return customPolicy })
+	if _, ok := supportedPolicies[name]; !ok {
+		t.Error("Expected supportedPolicies to have a custom policy.")
+	}
+
+}