feat: adds support for starting in debug mode.

cmd/up.go

@@ -17,6 +17,7 @@ limitations under the License.
 package cmd
 
 import (
+	"fmt"
 	"gatehill.io/imposter/config"
 	"gatehill.io/imposter/engine"
 	"gatehill.io/imposter/fileutil"
@@ -46,6 +47,7 @@ var upFlags = struct {
 	environment         []string
 	dirMounts           []string
 	recursiveConfigScan bool
+	debugMode           bool
 }{}
 
 // upCmd represents the up command
@@ -107,6 +109,7 @@ If CONFIG_DIR is not specified, the current working directory is used.`,
 			EnableFileCache: upFlags.enableFileCache,
 			Environment:     buildStartEnvironment(upFlags.environment),
 			DirMounts:       upFlags.dirMounts,
+			DebugMode:       upFlags.debugMode,
 		}
 		start(&lib, startOptions, configDir, upFlags.restartOnChange)
 	},
@@ -126,6 +129,7 @@ func init() {
 	upCmd.Flags().StringArrayVarP(&upFlags.environment, "env", "e", []string{}, "Explicit environment variables to set")
 	upCmd.Flags().StringArrayVar(&upFlags.dirMounts, "mount-dir", []string{}, "(Docker engine type only) Extra directory bind-mounts in the form HOST_PATH:CONTAINER_PATH (e.g. $HOME/somedir:/opt/imposter/somedir) or simply HOST_PATH, which will mount the directory at /opt/imposter/<dir>")
 	upCmd.Flags().BoolVarP(&upFlags.recursiveConfigScan, "recursive-config-scan", "r", false, "Scan for config files in subdirectories")
+	upCmd.Flags().BoolVar(&upFlags.debugMode, "debug-mode", false, fmt.Sprintf("Enable JVM debug mode and listen on port %v", engine.DefaultDebugPort))
 	registerEngineTypeCompletions(upCmd)
 	rootCmd.AddCommand(upCmd)
 }

engine/api.go

@@ -29,6 +29,7 @@ type StartOptions struct {
 	EnableFileCache bool
 	Environment     []string
 	DirMounts       []string
+	DebugMode       bool
 }
 
 type PullPolicy int
@@ -95,3 +96,5 @@ type ManagedMock struct {
 	Port   int
 	Health MockHealth
 }
+
+const DefaultDebugPort = 8000

engine/builder.go

@@ -150,7 +150,11 @@ func SanitiseVersionOutput(s string) string {
 }
 
 func BuildEnv(options StartOptions, includeHome bool) []string {
-	return buildEnvFromParent(os.Environ(), options, includeHome)
+	env := buildEnvFromParent(os.Environ(), options, includeHome)
+	if options.DebugMode {
+		env = append(env, fmt.Sprintf("JAVA_TOOL_OPTIONS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=0.0.0.0:%v", DefaultDebugPort))
+	}
+	return env
 }
 
 func buildEnvFromParent(parentEnv []string, options StartOptions, includeHome bool) []string {

engine/docker/engine.go

@@ -70,35 +70,24 @@ func (d *DockerMockEngine) startWithOptions(wg *sync.WaitGroup, options engine.S
 		stopDuplicateContainers(d, cli, ctx, mockHash)
 	}
 
-	containerPort := nat.Port(fmt.Sprintf("%d/tcp", options.Port))
-	hostPort := fmt.Sprintf("%d", options.Port)
-
 	// if not specified, falls back to default in container image
 	containerUser := viper.GetString("docker.containerUser")
 	logger.Tracef("container user: %s", containerUser)
 
+	exposedPorts, portBindings := buildPorts(options)
 	resp, err := cli.ContainerCreate(ctx, &container.Config{
 		Image: d.provider.imageAndTag,
 		Cmd: []string{
 			"--configDir=" + containerConfigDir,
 			fmt.Sprintf("--listenPort=%d", options.Port),
 		},
-		Env: buildEnv(options),
-		ExposedPorts: nat.PortSet{
-			containerPort: {},
-		},
-		Labels: containerLabels,
-		User:   containerUser,
+		Env:          buildEnv(options),
+		ExposedPorts: exposedPorts,
+		Labels:       containerLabels,
+		User:         containerUser,
 	}, &container.HostConfig{
-		Binds: buildBinds(d, options),
-		PortBindings: nat.PortMap{
-			containerPort: []nat.PortBinding{
-				{
-					HostIP:   "0.0.0.0",
-					HostPort: hostPort,
-				},
-			},
-		},
+		Binds:        buildBinds(d, options),
+		PortBindings: portBindings,
 	}, nil, nil, "")
 	if err != nil {
 		logger.Fatal(err)
@@ -125,6 +114,31 @@ func (d *DockerMockEngine) startWithOptions(wg *sync.WaitGroup, options engine.S
 	return up
 }
 
+func buildPorts(options engine.StartOptions) (nat.PortSet, nat.PortMap) {
+	ports := map[int]int{
+		options.Port: options.Port,
+	}
+	if options.DebugMode {
+		ports[engine.DefaultDebugPort] = engine.DefaultDebugPort
+	}
+
+	exposedPorts := nat.PortSet{}
+	portBindings := nat.PortMap{}
+	for hp, cp := range ports {
+		containerPort := nat.Port(fmt.Sprintf("%d/tcp", cp))
+		hostPort := fmt.Sprintf("%d", hp)
+
+		exposedPorts[containerPort] = struct{}{}
+		portBindings[containerPort] = []nat.PortBinding{
+			{
+				HostIP:   "0.0.0.0",
+				HostPort: hostPort,
+			},
+		}
+	}
+	return exposedPorts, portBindings
+}
+
 func buildEnv(options engine.StartOptions) []string {
 	env := engine.BuildEnv(options, false)
 	if options.EnableFileCache {