feat(agent): add script data dir for binaries and files (#12205)

The agent is extended with a `--script-data-dir` flag, defaulting to the
OS temp dir. This dir is used for storing `coder-script-data/bin` and
`coder-script/[script uuid]`. The former is a place for all scripts to
place executable binaries that will be available by other scripts, SSH
sessions, etc. The latter is a place for the script to store files.

Since we default to OS temp dir, files are ephemeral by default. In the
future, we may consider adding new env vars or changing the default
storage location. Workspace startup speed could potentially benefit from
scripts being able to skip steps that require downloading software. We
may also extend this with more env variables (e.g. persistent storage in
HOME).

Fixes #11131

agent/agent.go

@@ -66,6 +66,7 @@ type Options struct {
 	Filesystem                   afero.Fs
 	LogDir                       string
 	TempDir                      string
+	ScriptDataDir                string
 	ExchangeToken                func(ctx context.Context) (string, error)
 	Client                       Client
 	ReconnectingPTYTimeout       time.Duration
@@ -112,9 +113,19 @@ func New(options Options) Agent {
 	if options.LogDir == "" {
 		if options.TempDir != os.TempDir() {
 			options.Logger.Debug(context.Background(), "log dir not set, using temp dir", slog.F("temp_dir", options.TempDir))
+		} else {
+			options.Logger.Debug(context.Background(), "using log dir", slog.F("log_dir", options.LogDir))
 		}
 		options.LogDir = options.TempDir
 	}
+	if options.ScriptDataDir == "" {
+		if options.TempDir != os.TempDir() {
+			options.Logger.Debug(context.Background(), "script data dir not set, using temp dir", slog.F("temp_dir", options.TempDir))
+		} else {
+			options.Logger.Debug(context.Background(), "using script data dir", slog.F("script_data_dir", options.ScriptDataDir))
+		}
+		options.ScriptDataDir = options.TempDir
+	}
 	if options.ExchangeToken == nil {
 		options.ExchangeToken = func(ctx context.Context) (string, error) {
 			return "", nil
@@ -152,6 +163,7 @@ func New(options Options) Agent {
 		filesystem:                   options.Filesystem,
 		logDir:                       options.LogDir,
 		tempDir:                      options.TempDir,
+		scriptDataDir:                options.ScriptDataDir,
 		lifecycleUpdate:              make(chan struct{}, 1),
 		lifecycleReported:            make(chan codersdk.WorkspaceAgentLifecycle, 1),
 		lifecycleStates:              []agentsdk.PostLifecycleRequest{{State: codersdk.WorkspaceAgentLifecycleCreated}},
@@ -183,6 +195,7 @@ type agent struct {
 	filesystem        afero.Fs
 	logDir            string
 	tempDir           string
+	scriptDataDir     string
 	// ignorePorts tells the api handler which ports to ignore when
 	// listing all listening ports. This is helpful to hide ports that
 	// are used by the agent, that the user does not care about.
@@ -249,11 +262,12 @@ func (a *agent) init(ctx context.Context) {
 	}
 	a.sshServer = sshSrv
 	a.scriptRunner = agentscripts.New(agentscripts.Options{
-		LogDir:     a.logDir,
-		Logger:     a.logger,
-		SSHServer:  sshSrv,
-		Filesystem: a.filesystem,
-		PatchLogs:  a.client.PatchLogs,
+		LogDir:      a.logDir,
+		DataDirBase: a.scriptDataDir,
+		Logger:      a.logger,
+		SSHServer:   sshSrv,
+		Filesystem:  a.filesystem,
+		PatchLogs:   a.client.PatchLogs,
 	})
 	// Register runner metrics. If the prom registry is nil, the metrics
 	// will not report anywhere.
@@ -954,6 +968,13 @@ func (a *agent) updateCommandEnv(current []string) (updated []string, err error)
 		envs[k] = v
 	}
 
+	// Prepend the agent script bin directory to the PATH
+	// (this is where Coder modules place their binaries).
+	if _, ok := envs["PATH"]; !ok {
+		envs["PATH"] = os.Getenv("PATH")
+	}
+	envs["PATH"] = fmt.Sprintf("%s%c%s", a.scriptRunner.ScriptBinDir(), filepath.ListSeparator, envs["PATH"])
+
 	for k, v := range envs {
 		updated = append(updated, fmt.Sprintf("%s=%s", k, v))
 	}