Add Connect function

Author: jsafrane

connection/connection.go

@@ -0,0 +1,35 @@
+package connection
+
+import (
+	"context"
+	"net"
+	"strings"
+	"time"
+
+	"google.golang.org/grpc"
+)
+
+const (
+	// Default timeout when connecting to CSI driver. I.e. if used in a CSI sidecar container, corresponding CSI driver
+	// must be up and running within this time.
+	DefaultDriverConnectionTimeout = time.Minute
+)
+
+// Connect opens insecure gRPC connection to a CSI driver. Address must have either '<protocol>://' prefix, or be
+// a path to a socket file. The function tries to connect every second until timeout expires.
+func Connect(address string, timeout time.Duration, dialOptions ...grpc.DialOption) (*grpc.ClientConn, error) {
+	dialOptions = append(dialOptions,
+		grpc.WithInsecure(),                   // Don't use TLS, it's usually local Unix domain socket in a container.
+		grpc.WithBlock(),                      // Block until it succeeds (or times out).
+		grpc.WithBackoffMaxDelay(time.Second), // Retry every second after failure.
+	)
+	if strings.HasPrefix(address, "/") {
+		// It looks like filesystem path.
+		dialOptions = append(dialOptions, grpc.WithDialer(func(addr string, timeout time.Duration) (net.Conn, error) {
+			return net.DialTimeout("unix", addr, timeout)
+		}))
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+	return grpc.DialContext(ctx, address, dialOptions...)
+}