From 0abe44c0018b2a577e0cd43d25622b7a15a809ce Mon Sep 17 00:00:00 2001
From: Ramkumar Chinchani <rchincha@cisco.com>
Date: Mon, 13 Nov 2023 19:19:46 +0000
Subject: [PATCH] feat(cluster): initial commit for scale-out cluster

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>
---
 go.mod                   |  1 +
 go.sum                   |  2 +
 pkg/api/config/config.go |  8 ++++
 pkg/api/controller.go    |  7 ++++
 pkg/cluster/proxy.go     | 88 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 106 insertions(+)
 create mode 100644 pkg/cluster/proxy.go

diff --git a/go.mod b/go.mod
index 31441332e..73f9ef078 100644
--- a/go.mod
+++ b/go.mod
@@ -50,6 +50,7 @@ require (
 	github.com/aws/aws-sdk-go-v2/service/secretsmanager v1.28.6
 	github.com/aws/aws-secretsmanager-caching-go v1.1.3
 	github.com/containers/image/v5 v5.30.0
+	github.com/dchest/siphash v1.2.3
 	github.com/google/go-github/v52 v52.0.0
 	github.com/gorilla/securecookie v1.1.2
 	github.com/gorilla/sessions v1.2.2
diff --git a/go.sum b/go.sum
index d24ccf77e..666d7269f 100644
--- a/go.sum
+++ b/go.sum
@@ -591,6 +591,8 @@ github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dchest/siphash v1.2.3 h1:QXwFc8cFOR2dSa/gE6o/HokBMWtLUaNDVd+22aKHeEA=
+github.com/dchest/siphash v1.2.3/go.mod h1:0NvQU092bT0ipiFN++/rXm69QG9tVxLAlQHIXMPAkHc=
 github.com/depcheck-test/depcheck-test v0.0.0-20220607135614-199033aaa936 h1:foGzavPWwtoyBvjWyKJYDYsyzy+23iBV7NKTwdk+LRY=
 github.com/depcheck-test/depcheck-test v0.0.0-20220607135614-199033aaa936/go.mod h1:ttKPnOepYt4LLzD+loXQ1rT6EmpyIYHro7TAJuIIlHo=
 github.com/dgraph-io/badger/v3 v3.2103.5 h1:ylPa6qzbjYRQMU6jokoj4wzcaweHylt//CH0AKt0akg=
diff --git a/pkg/api/config/config.go b/pkg/api/config/config.go
index f474843ff..279764be5 100644
--- a/pkg/api/config/config.go
+++ b/pkg/api/config/config.go
@@ -121,6 +121,13 @@ type SchedulerConfig struct {
 	NumWorkers int
 }
 
+// ClusterConfig is the scale-out configuration which is identical for all
+// replicas
+type ClusterConfig struct {
+	Members []string
+	HashKey string
+}
+
 type LDAPCredentials struct {
 	BindDN       string
 	BindPassword string
@@ -230,6 +237,7 @@ type Config struct {
 	Log             *LogConfig
 	Extensions      *extconf.ExtensionConfig
 	Scheduler       *SchedulerConfig `json:"scheduler" mapstructure:",omitempty"`
+	Cluster         *ClusterConfig   `json:"cluster" mapstructure:",omitempty"`
 }
 
 func New() *Config {
diff --git a/pkg/api/controller.go b/pkg/api/controller.go
index e8c167c38..3f0852856 100644
--- a/pkg/api/controller.go
+++ b/pkg/api/controller.go
@@ -124,6 +124,13 @@ func (c *Controller) Run() error {
 		engine.Use(SessionAuditLogger(c.Audit))
 	}
 
+	/*
+		if c.Cluster != nil {
+			engine.Use(ProxyCluster)
+		}
+
+	*/
+
 	c.Router = engine
 	c.Router.UseEncodedPath()
 
diff --git a/pkg/cluster/proxy.go b/pkg/cluster/proxy.go
new file mode 100644
index 000000000..1a3c4e45a
--- /dev/null
+++ b/pkg/cluster/proxy.go
@@ -0,0 +1,88 @@
+package cluster
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/dchest/siphash"
+
+	"zotregistry.dev/zot/pkg/api"
+	"zotregistry.dev/zot/pkg/api/constants"
+	zreg "zotregistry.dev/zot/pkg/regexp"
+)
+
+type ProxyRouteHandler struct {
+	c *api.Controller
+}
+
+func NewRouteHandler(c *api.Controller) *RouteHandler {
+	rh := &ProxyRouteHandler{c: c}
+	rh.SetupRoutes()
+
+	// FIXME: this is a scale-out load balancer cluster so doesn't do replicas
+
+	return rh
+}
+
+func (rh *ProxyRouteHandler) SetupRoutes() {
+	prefixedRouter := rh.c.Router.PathPrefix(constants.RoutePrefix).Subrouter()
+	prefixedDistSpecRouter := prefixedRouter.NewRoute().Subrouter()
+
+	prefixedDistSpecRouter.HandleFunc(fmt.Sprintf("/{name:%s}/", zreg.NameRegexp.String()), proxyRequestResponse(rh.c.Config)())
+}
+
+func proxyRequestResponse(config rh.c.Config) func(http.HandlerFunc) http.HandlerFunc {
+	return func(next http.HandlerFunc) http.HandlerFunc {
+		return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
+			// if no cluster or single-node cluster, handle locally
+			if config.Cluster == nil || len(config.Cluster.Members) {
+				next.ServeHTTP(response, request)
+			}
+
+			vars := mux.Vars(request)
+
+			name, ok := vars["name"]
+
+			if !ok || name == "" {
+				response.WriteHeader(http.StatusNotFound)
+
+				return
+			}
+
+			h := siphash.New(key)
+			h.Write([]byte(name)
+			sum64 := h.Sum64(nil)
+
+			member := config.Cluster.Members[sum64%len(config.Cluster.Members)]
+			/*
+
+			// from the member list and our DNS/IP address, figure out if this request should be handled locally
+			if member == localMember {
+				next.ServeHTTP(response, request)
+			}
+
+			*/
+			handleHTTP(response, request)
+		})
+	}
+}
+
+func handleHTTP(w http.ResponseWriter, req *http.Request) {
+    resp, err := http.DefaultTransport.RoundTrip(req)
+    if err != nil {
+        http.Error(w, err.Error(), http.StatusServiceUnavailable)
+        return
+    }
+    defer resp.Body.Close()
+    copyHeader(w.Header(), resp.Header)
+    w.WriteHeader(resp.StatusCode)
+    io.Copy(w, resp.Body)
+}
+
+func copyHeader(dst, src http.Header) {
+    for k, vv := range src {
+        for _, v := range vv {
+            dst.Add(k, v)
+        }
+	}
+}