persist config digest on caddy instance

caddy.go

@@ -16,22 +16,24 @@
 //
 // To use this package:
 //
-//   1. Set the AppName and AppVersion variables.
-//   2. Call LoadCaddyfile() to get the Caddyfile.
-//      Pass in the name of the server type (like "http").
-//      Make sure the server type's package is imported
-//      (import _ "github.com/coredns/caddy/caddyhttp").
-//   3. Call caddy.Start() to start Caddy. You get back
-//      an Instance, on which you can call Restart() to
-//      restart it or Stop() to stop it.
+//  1. Set the AppName and AppVersion variables.
+//  2. Call LoadCaddyfile() to get the Caddyfile.
+//     Pass in the name of the server type (like "http").
+//     Make sure the server type's package is imported
+//     (import _ "github.com/coredns/caddy/caddyhttp").
+//  3. Call caddy.Start() to start Caddy. You get back
+//     an Instance, on which you can call Restart() to
+//     restart it or Stop() to stop it.
 //
 // You should call Wait() on your instance to wait for
 // all servers to quit before your process exits.
 package caddy
 
 import (
 	"bytes"
+	"crypto/sha512"
 	"encoding/gob"
+	"encoding/json"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -121,6 +123,9 @@ type Instance struct {
 	// to access this value safely
 	Storage   map[interface{}]interface{}
 	StorageMu sync.RWMutex
+
+	// store a digest of the used configuration
+	ConfigDigest [64]byte
 }
 
 // Instances returns the list of instances.
@@ -599,6 +604,12 @@ func ValidateAndExecuteDirectives(cdyfile Input, inst *Instance, justValidate bo
 		return err
 	}
 
+	sblocksJson, err := json.Marshal(sblocks)
+	if err != nil {
+		return err
+	}
+	inst.ConfigDigest = sha512.Sum512(sblocksJson)
+
 	inst.context = stype.NewContext(inst)
 	if inst.context == nil {
 		return fmt.Errorf("server type %s produced a nil Context", stypeName)
@@ -1030,3 +1041,16 @@ var (
 
 // CtxKey is a value type for use with context.WithValue.
 type CtxKey string
+
+// ConfigDigest returns a digest value of the provided caddy.Input
+func ConfigDigest(cdyfile Input) ([64]byte, error) {
+	sblocks, err := loadServerBlocks(cdyfile.ServerType(), cdyfile.Path(), bytes.NewReader(cdyfile.Body()))
+	if err != nil {
+		return [64]byte{}, err
+	}
+	sblocksJson, err := json.Marshal(sblocks)
+	if err != nil {
+		return [64]byte{}, err
+	}
+	return sha512.Sum512(sblocksJson), nil
+}

plugins.go

@@ -271,6 +271,15 @@ func RegisterEventHook(name string, hook EventHook) {
 	}
 }
 
+// RegisterOrUpdateEventHook plugs in hook. All the hooks should register themselves
+// and they must have a name.
+func RegisterOrUpdateEventHook(name string, hook EventHook) {
+	if name == "" {
+		panic("event hook must have a name")
+	}
+	eventHooks.Store(name, hook)
+}
+
 // EmitEvent executes the different hooks passing the EventType as an
 // argument. This is a blocking function. Hook developers should
 // use 'go' keyword if they don't want to block Caddy.