rudimentary implementation of 'zrok share reserved' using dual-pathed approach (#751)

agent/agentClient/agentClient.go

@@ -3,18 +3,20 @@ package agentClient
 import (
 	"context"
 	"github.com/openziti/zrok/agent/agentGrpc"
+	"github.com/openziti/zrok/build"
 	"github.com/openziti/zrok/environment/env_core"
-	"github.com/openziti/zrok/tui"
+	"github.com/pkg/errors"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/resolver"
 	"net"
+	"strings"
 )
 
 func NewClient(root env_core.Root) (client agentGrpc.AgentClient, conn *grpc.ClientConn, err error) {
 	agentSocket, err := root.AgentSocket()
 	if err != nil {
-		tui.Error("error getting agent socket", err)
+		return nil, nil, err
 	}
 
 	opts := []grpc.DialOption{
@@ -26,8 +28,24 @@ func NewClient(root env_core.Root) (client agentGrpc.AgentClient, conn *grpc.Cli
 	resolver.SetDefaultScheme("passthrough")
 	conn, err = grpc.NewClient(agentSocket, opts...)
 	if err != nil {
-		tui.Error("error connecting to agent socket", err)
+		return nil, nil, err
 	}
 
 	return agentGrpc.NewAgentClient(conn), conn, nil
 }
+
+func IsAgentRunning(root env_core.Root) (bool, error) {
+	client, conn, err := NewClient(root)
+	if err != nil {
+		return false, err
+	}
+	defer func() { _ = conn.Close() }()
+	resp, err := client.Version(context.Background(), &agentGrpc.VersionRequest{})
+	if err != nil {
+		return false, nil
+	}
+	if !strings.HasPrefix(resp.GetV(), build.Series) {
+		return false, errors.Errorf("agent reported version '%v'; we expected version '%v'", resp.GetV(), build.Series)
+	}
+	return true, nil
+}