cache : add cache service (#457)

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/grpc/server.go

@@ -0,0 +1,94 @@
+package grpc // import "github.com/pomerium/pomerium/internal/grpc"
+
+import (
+	"crypto/tls"
+	"net"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+
+	"github.com/pomerium/pomerium/internal/log"
+	"github.com/pomerium/pomerium/internal/telemetry/metrics"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+)
+
+// NewServer creates a new gRPC serve.
+// It is the callers responsibility to close the resturned server.
+func NewServer(opt *ServerOptions, registrationFn func(s *grpc.Server), wg *sync.WaitGroup) (*grpc.Server, error) {
+	if opt == nil {
+		opt = defaultServerOptions
+	} else {
+		opt.applyServerDefaults()
+	}
+	ln, err := net.Listen("tcp", opt.Addr)
+	if err != nil {
+		return nil, err
+	}
+	grpcOpts := []grpc.ServerOption{grpc.StatsHandler(metrics.NewGRPCServerStatsHandler(opt.Addr))}
+
+	if opt.TLSCertificate != nil {
+		log.Debug().Str("addr", opt.Addr).Msg("internal/grpc: serving over TLS")
+		cert := credentials.NewServerTLSFromCert(opt.TLSCertificate)
+		grpcOpts = append(grpcOpts, grpc.Creds(cert))
+	} else {
+		log.Warn().Str("addr", opt.Addr).Msg("internal/grpc: serving without TLS")
+	}
+
+	srv := grpc.NewServer(grpcOpts...)
+	registrationFn(srv)
+	log.Info().Interface("grpc-service-info", srv.GetServiceInfo()).Msg("internal/grpc: registered")
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		if err := srv.Serve(ln); err != grpc.ErrServerStopped {
+			log.Error().Str("addr", opt.Addr).Err(err).Msg("internal/grpc: unexpected shutdown")
+		}
+	}()
+
+	return srv, nil
+}
+
+// ServerOptions contains the configurations settings for a gRPC server.
+type ServerOptions struct {
+	// Addr specifies the host and port on which the server should serve
+	// gRPC requests. If empty, ":443" is used.
+	Addr string
+
+	// TLS certificates to use, if any.
+	TLSCertificate *tls.Certificate
+
+	// InsecureServer when enabled disables all transport security.
+	// In this mode, Pomerium is susceptible to man-in-the-middle attacks.
+	// This should be used only for testing.
+	InsecureServer bool
+}
+
+var defaultServerOptions = &ServerOptions{
+	Addr: ":443",
+}
+
+func (o *ServerOptions) applyServerDefaults() {
+	if o.Addr == "" {
+		o.Addr = defaultServerOptions.Addr
+	}
+
+}
+
+// Shutdown attempts to shut down the server when a os interrupt or sigterm
+// signal are received without interrupting any
+// active connections. Shutdown stops the server from
+// accepting new connections and RPCs and blocks until all the pending RPCs are
+// finished.
+func Shutdown(srv *grpc.Server) {
+	sigint := make(chan os.Signal, 1)
+	signal.Notify(sigint, os.Interrupt)
+	signal.Notify(sigint, syscall.SIGTERM)
+	rec := <-sigint
+	log.Info().Str("signal", rec.String()).Msg("internal/grpc: shutting down servers")
+	srv.GracefulStop()
+	log.Info().Str("signal", rec.String()).Msg("internal/grpc: shut down servers")
+}