feat: Remove hard requirements for HTTP/2

cmd/agent/main.go

@@ -35,21 +35,22 @@ import (
 
 func NewAgentRunCommand() *cobra.Command {
 	var (
-		serverAddress string
-		serverPort    int
-		logLevel      string
-		logFormat     string
-		insecure      bool
-		rootCAPath    string
-		kubeConfig    string
-		kubeContext   string
-		namespace     string
-		agentMode     string
-		creds         string
-		showVersion   bool
-		versionFormat string
-		tlsClientCrt  string
-		tlsClientKey  string
+		serverAddress   string
+		serverPort      int
+		logLevel        string
+		logFormat       string
+		insecure        bool
+		rootCAPath      string
+		kubeConfig      string
+		kubeContext     string
+		namespace       string
+		agentMode       string
+		creds           string
+		showVersion     bool
+		versionFormat   string
+		tlsClientCrt    string
+		tlsClientKey    string
+		enableWebSocket bool
 	)
 	command := &cobra.Command{
 		Short: "Run the argocd-agent agent component",
@@ -96,6 +97,7 @@ func NewAgentRunCommand() *cobra.Command {
 			if tlsClientCrt != "" && tlsClientKey != "" {
 				remoteOpts = append(remoteOpts, client.WithTLSClientCertFromFile(tlsClientCrt, tlsClientKey))
 			}
+			remoteOpts = append(remoteOpts, client.WithWebSocket(enableWebSocket))
 			remoteOpts = append(remoteOpts, client.WithClientMode(types.AgentModeFromString(agentMode)))
 			if serverAddress != "" && serverPort > 0 && serverPort < 65536 {
 				remote, err = client.NewRemote(serverAddress, serverPort, remoteOpts...)
@@ -161,6 +163,9 @@ func NewAgentRunCommand() *cobra.Command {
 	command.Flags().StringVar(&tlsClientKey, "tls-client-key",
 		env.StringWithDefault("ARGOCD_AGENT_TLS_CLIENT_KEY_PATH", nil, ""),
 		"Path to TLS client key")
+	command.Flags().BoolVar(&enableWebSocket, "enable-websocket",
+		env.BoolWithDefault("ARGOCD_AGENT_ENABLE_WEBSOCKET", false),
+		"Agent will rely on gRPC over WebSocket to stream events to the Principal")
 
 	command.Flags().StringVar(&kubeConfig, "kubeconfig", "", "Path to a kubeconfig file to use")
 	command.Flags().StringVar(&kubeContext, "kubecontext", "", "Override the default kube context")

cmd/principal/main.go

@@ -55,6 +55,7 @@ func NewPrincipalRunCommand() *cobra.Command {
 		autoNamespaceAllow     bool
 		autoNamespacePattern   string
 		autoNamespaceLabels    []string
+		enableWebSocket        bool
 	)
 	var command = &cobra.Command{
 		Short: "Run the argocd-agent principal component",
@@ -146,6 +147,8 @@ func NewPrincipalRunCommand() *cobra.Command {
 				observer(10 * time.Second)
 			}
 
+			opts = append(opts, principal.WithWebSocket(enableWebSocket))
+
 			s, err := principal.NewServer(ctx, kubeConfig, namespace, opts...)
 			if err != nil {
 				cmd.Fatal("Could not create new server instance: %v", err)
@@ -225,6 +228,10 @@ func NewPrincipalRunCommand() *cobra.Command {
 		env.StringWithDefault("ARGOCD_PRINCIPAL_USER_DB_PATH", nil, ""),
 		"Path to userpass passwd file")
 
+	command.Flags().BoolVar(&enableWebSocket, "enable-websocket",
+		env.BoolWithDefault("ARGOCD_PRINCIPAL_ENABLE_WEBSOCKET", false),
+		"Principal will rely on gRPC over WebSocket to stream events to the Agent")
+
 	command.Flags().StringVar(&kubeConfig, "kubeconfig", "", "Path to a kubeconfig file to use")
 	command.Flags().StringVar(&kubeContext, "kubecontext", "", "Override the default kube context")
 

go.mod

@@ -17,7 +17,9 @@ require (
 	github.com/stretchr/testify v1.9.0
 	github.com/wI2L/jsondiff v0.6.0
 	golang.org/x/crypto v0.27.0
+	golang.org/x/net v0.29.0
 	golang.org/x/sync v0.8.0
+	golang.stackrox.io/grpc-http1 v0.3.13
 	google.golang.org/genproto/googleapis/api v0.0.0-20240814211410-ddb44dafa142
 	google.golang.org/grpc v1.67.0
 	google.golang.org/protobuf v1.34.2
@@ -45,6 +47,7 @@ require (
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/chai2010/gettext-go v1.0.2 // indirect
 	github.com/cloudflare/circl v1.3.7 // indirect
+	github.com/coder/websocket v1.8.12 // indirect
 	github.com/cyphar/filepath-securejoin v0.2.4 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
@@ -68,6 +71,7 @@ require (
 	github.com/gobwas/glob v0.2.3 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang-jwt/jwt/v4 v4.5.0 // indirect
+	github.com/golang/glog v1.2.2 // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.4 // indirect
 	github.com/google/btree v1.1.2 // indirect
@@ -128,7 +132,6 @@ require (
 	go.uber.org/multierr v1.11.0 // indirect
 	go.uber.org/zap v1.26.0 // indirect
 	golang.org/x/mod v0.17.0 // indirect
-	golang.org/x/net v0.28.0 // indirect
 	golang.org/x/oauth2 v0.22.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/term v0.24.0 // indirect

go.sum

@@ -696,6 +696,8 @@ github.com/cncf/xds/go v0.0.0-20211011173535-cb28da3451f1/go.mod h1:eXthEFrGJvWH
 github.com/cncf/xds/go v0.0.0-20220314180256-7f1daf1720fc/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
 github.com/cncf/xds/go v0.0.0-20230105202645-06c439db220b/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
 github.com/cncf/xds/go v0.0.0-20230310173818-32f1caf87195/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
+github.com/coder/websocket v1.8.12 h1:5bUXkEPPIbewrnkU8LTCLVaxi4N4J8ahufH2vlo4NAo=
+github.com/coder/websocket v1.8.12/go.mod h1:LNVeNrXQZfe5qhS9ALED3uA+l5pPqvwXg3CKoDBB2gs=
 github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
@@ -815,6 +817,8 @@ github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGw
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/glog v1.0.0/go.mod h1:EWib/APOK0SL3dFbYqvxE3UYd8E6s1ouQ7iEp/0LWV4=
 github.com/golang/glog v1.1.0/go.mod h1:pfYeQZ3JWZoXTV5sFc986z3HTpwQs9At6P4ImfuP3NQ=
+github.com/golang/glog v1.2.2 h1:1+mZ9upx1Dh6FmUTFR1naJ77miKiXgALjWOZ3NVFPmY=
+github.com/golang/glog v1.2.2/go.mod h1:6AhwSGph0fcJtXVM/PEHPqZlFeoLxhs7/t5UDAwmO+w=
 github.com/golang/groupcache v0.0.0-20190129154638-5b532d6fd5ef/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/groupcache v0.0.0-20190702054246-869f871628b6/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/groupcache v0.0.0-20191227052852-215e87163ea7/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
@@ -1386,8 +1390,8 @@ golang.org/x/net v0.17.0/go.mod h1:NxSsAGuq816PNPmqtQdLE42eU2Fs7NoRIZrHJAlaCOE=
 golang.org/x/net v0.19.0/go.mod h1:CfAk/cbD4CthTvqiEl8NpboMuiuOYsAr/7NOjZJtv1U=
 golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
 golang.org/x/net v0.23.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
-golang.org/x/net v0.28.0 h1:a9JDOJc5GMUJ0+UDqmLT86WiEy7iWyIhz8gz8E4e5hE=
-golang.org/x/net v0.28.0/go.mod h1:yqtgsTWOOnlGLG9GFRrK3++bGOUEkNBoHZc8MEDWPNg=
+golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
+golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
@@ -1678,6 +1682,8 @@ golang.org/x/xerrors v0.0.0-20220411194840-2f41105eb62f/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20220517211312-f3a8303e98df/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
 golang.org/x/xerrors v0.0.0-20220609144429-65e65417b02f/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
 golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
+golang.stackrox.io/grpc-http1 v0.3.13 h1:Fu54UK9A2Q4IcAzAGR2jLOn5/rwZzu5DizP/2SCj4Tk=
+golang.stackrox.io/grpc-http1 v0.3.13/go.mod h1:3WeU1sdO5IjWYgr0pYEPLIU6GULfYADtIq7Zseyy30Q=
 gonum.org/v1/gonum v0.0.0-20180816165407-929014505bf4/go.mod h1:Y+Yx5eoAFn32cQvJDxZx5Dpnq+c3wtXuadVZAcxbbBo=
 gonum.org/v1/gonum v0.8.2/go.mod h1:oe/vMfY3deqTw+1EZJhuvEW2iwGF1bW9wwu7XCu0+v0=
 gonum.org/v1/gonum v0.9.3/go.mod h1:TZumC3NeyVQskjXqmyWt4S3bINhy7B4eYwW69EbyX+0=

pkg/client/remote.go

@@ -31,6 +31,7 @@ import (
 	"github.com/argoproj-labs/argocd-agent/pkg/types"
 	"github.com/golang-jwt/jwt/v5"
 	"github.com/sirupsen/logrus"
+	grpchttp1client "golang.stackrox.io/grpc-http1/client"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
@@ -64,18 +65,19 @@ func NewToken(tok string) (*token, error) {
 
 // Remote represents a remote argocd-agent server component. Remote is used only by the agent component, and not by principal.
 type Remote struct {
-	hostname     string
-	port         int
-	tlsConfig    *tls.Config
-	accessToken  *token
-	refreshToken *token
-	authMethod   string
-	creds        auth.Credentials
-	backoff      wait.Backoff
-	conn         *grpc.ClientConn
-	clientID     string
-	clientMode   types.AgentMode
-	timeouts     timeouts
+	hostname        string
+	port            int
+	tlsConfig       *tls.Config
+	accessToken     *token
+	refreshToken    *token
+	authMethod      string
+	creds           auth.Credentials
+	backoff         wait.Backoff
+	conn            *grpc.ClientConn
+	clientID        string
+	clientMode      types.AgentMode
+	timeouts        timeouts
+	enableWebSocket bool
 }
 
 type RemoteOption func(r *Remote) error
@@ -181,6 +183,15 @@ func WithInsecureSkipTLSVerify() RemoteOption {
 	}
 }
 
+// The agent will rely on gRPC over WebSocket for bi-directional streaming. This option could be enabled
+// when there is an intermediate component that is HTTP/2 incompatible and downgrades the incoming request to HTTP/1.1
+func WithWebSocket(enableWebSocket bool) RemoteOption {
+	return func(r *Remote) error {
+		r.enableWebSocket = enableWebSocket
+		return nil
+	}
+}
+
 func WithAuth(method string, creds auth.Credentials) RemoteOption {
 	return func(r *Remote) error {
 		r.authMethod = method
@@ -286,16 +297,32 @@ func (r *Remote) Connect(ctx context.Context, forceReauth bool) error {
 
 	// Some default options
 	opts := []grpc.DialOption{
-		grpc.WithTransportCredentials(creds),
 		grpc.WithConnectParams(cparams),
 		grpc.WithUserAgent("argocd-agent/v0.0.1"),
 		grpc.WithUnaryInterceptor(r.unaryAuthInterceptor),
 		grpc.WithStreamInterceptor(r.streamAuthInterceptor),
 	}
 
-	conn, err := grpc.NewClient(r.Addr(), opts...)
-	if err != nil {
-		return err
+	var (
+		conn *grpc.ClientConn
+		err  error
+	)
+	if r.enableWebSocket {
+		grpcHTTP1Opts := []grpchttp1client.ConnectOption{
+			grpchttp1client.UseWebSocket(true),
+			grpchttp1client.DialOpts(opts...),
+		}
+
+		conn, err = grpchttp1client.ConnectViaProxy(ctx, r.Addr(), r.tlsConfig, grpcHTTP1Opts...)
+		if err != nil {
+			return err
+		}
+	} else {
+		opts = append(opts, grpc.WithTransportCredentials(creds))
+		conn, err = grpc.NewClient(r.Addr(), opts...)
+		if err != nil {
+			return err
+		}
 	}
 
 	authC := authapi.NewAuthenticationClient(conn)

principal/listen.go

@@ -18,10 +18,13 @@ import (
 	"context"
 	"fmt"
 	"net"
+	"net/http"
 	"strconv"
 	"strings"
 	"time"
 
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/h2c"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
 	"k8s.io/apimachinery/pkg/util/wait"
@@ -32,6 +35,7 @@ import (
 	"github.com/argoproj-labs/argocd-agent/principal/apis/auth"
 	"github.com/argoproj-labs/argocd-agent/principal/apis/eventstream"
 	"github.com/argoproj-labs/argocd-agent/principal/apis/version"
+	grpchttp1server "golang.stackrox.io/grpc-http1/server"
 )
 
 const listenerRetries = 5
@@ -160,11 +164,26 @@ func (s *Server) serveGRPC(ctx context.Context, errch chan error) error {
 	versionapi.RegisterVersionServer(s.grpcServer, version.NewServer(s.authenticate))
 	eventstreamapi.RegisterEventStreamServer(s.grpcServer, eventstream.NewServer(s.queues))
 
-	// The gRPC server lives in its own go routine
-	go func() {
-		err = s.grpcServer.Serve(s.listener.l)
-		errch <- err
-	}()
+	if s.enableWebSocket {
+		opts := []grpchttp1server.Option{grpchttp1server.PreferGRPCWeb(true)}
+
+		downgradingHandler := grpchttp1server.CreateDowngradingHandler(s.grpcServer, http.NotFoundHandler(), opts...)
+		downgradingServer := &http.Server{
+			TLSConfig: s.tlsConfig,
+			Handler:   h2c.NewHandler(downgradingHandler, &http2.Server{}),
+		}
+
+		go func() {
+			err = downgradingServer.ServeTLS(s.listener.l, s.options.tlsCertPath, s.options.tlsKeyPath)
+			errch <- err
+		}()
+	} else {
+		// The gRPC server lives in its own go routine
+		go func() {
+			err = s.grpcServer.Serve(s.listener.l)
+			errch <- err
+		}()
+	}
 
 	return nil
 }

principal/options.go

@@ -356,3 +356,10 @@ func WithAutoNamespaceCreate(enabled bool, pattern string, labels map[string]str
 		return nil
 	}
 }
+
+func WithWebSocket(enableWebSocket bool) ServerOption {
+	return func(o *Server) error {
+		o.enableWebSocket = enableWebSocket
+		return nil
+	}
+}

principal/server.go

@@ -82,6 +82,10 @@ type Server struct {
 	autoNamespaceAllow   bool
 	autoNamespacePattern *regexp.Regexp
 	autoNamespaceLabels  map[string]string
+
+	// The Principal will rely on gRPC over WebSocket for bi-directional streaming. This option could be enabled
+	// when there is an intermediate component that is HTTP/2 incompatible and downgrades the incoming request to HTTP/1.1
+	enableWebSocket bool
 }
 
 // noAuthEndpoints is a list of endpoints that are available without the need