CSI: set plugin socket path on restore (#12149)

The Prestart hook for task runner hooks doesn't get called when we
restore a task, because the task is already running. The Postrun hook
for CSI plugin supervisors needs the socket path to have been
populated so that the client has a valid path.

client/allocrunner/taskrunner/plugin_supervisor_hook.go

@@ -129,12 +129,13 @@ func (*csiPluginSupervisorHook) Name() string {
 }
 
 // Prestart is called before the task is started including after every
-// restart. This requires that the mount paths for a plugin be idempotent,
-// despite us not knowing the name of the plugin ahead of time.
-// Because of this, we use the allocid_taskname as the unique identifier for a
-// plugin on the filesystem.
+// restart (but not after restore). This requires that the mount paths
+// for a plugin be idempotent, despite us not knowing the name of the
+// plugin ahead of time.  Because of this, we use the allocid_taskname
+// as the unique identifier for a plugin on the filesystem.
 func (h *csiPluginSupervisorHook) Prestart(ctx context.Context,
 	req *interfaces.TaskPrestartRequest, resp *interfaces.TaskPrestartResponse) error {
+
 	// Create the mount directory that the container will access if it doesn't
 	// already exist. Default to only nomad user access.
 	if err := os.MkdirAll(h.mountPoint, 0700); err != nil && !os.IsExist(err) {
@@ -167,19 +168,7 @@ func (h *csiPluginSupervisorHook) Prestart(ctx context.Context,
 		Readonly: false,
 	}
 
-	// TODO(tgross): https://github.com/hashicorp/nomad/issues/11786
-	// If we're already registered, we should be able to update the
-	// definition in the update hook
-
-	// For backwards compatibility, ensure that we don't overwrite the
-	// socketPath on client restart with existing plugin allocations.
-	pluginInfo, _ := h.runner.dynamicRegistry.PluginForAlloc(
-		string(h.task.CSIPluginConfig.Type), h.task.CSIPluginConfig.ID, h.alloc.ID)
-	if pluginInfo != nil {
-		h.socketPath = pluginInfo.ConnectionInfo.SocketPath
-	} else {
-		h.socketPath = filepath.Join(h.socketMountPoint, structs.CSISocketName)
-	}
+	h.setSocketHook()
 
 	switch h.caps.FSIsolation {
 	case drivers.FSIsolationNone:
@@ -206,11 +195,29 @@ func (h *csiPluginSupervisorHook) Prestart(ctx context.Context,
 	return nil
 }
 
+func (h *csiPluginSupervisorHook) setSocketHook() {
+
+	// TODO(tgross): https://github.com/hashicorp/nomad/issues/11786
+	// If we're already registered, we should be able to update the
+	// definition in the update hook
+
+	// For backwards compatibility, ensure that we don't overwrite the
+	// socketPath on client restart with existing plugin allocations.
+	pluginInfo, _ := h.runner.dynamicRegistry.PluginForAlloc(
+		string(h.task.CSIPluginConfig.Type), h.task.CSIPluginConfig.ID, h.alloc.ID)
+	if pluginInfo != nil && pluginInfo.ConnectionInfo.SocketPath != "" {
+		h.socketPath = pluginInfo.ConnectionInfo.SocketPath
+		return
+	}
+	h.socketPath = filepath.Join(h.socketMountPoint, structs.CSISocketName)
+}
+
 // Poststart is called after the task has started. Poststart is not
 // called if the allocation is terminal.
 //
 // The context is cancelled if the task is killed.
 func (h *csiPluginSupervisorHook) Poststart(_ context.Context, _ *interfaces.TaskPoststartRequest, _ *interfaces.TaskPoststartResponse) error {
+
 	// If we're already running the supervisor routine, then we don't need to try
 	// and restart it here as it only terminates on `Stop` hooks.
 	h.runningLock.Lock()
@@ -220,6 +227,8 @@ func (h *csiPluginSupervisorHook) Poststart(_ context.Context, _ *interfaces.Tas
 	}
 	h.runningLock.Unlock()
 
+	h.setSocketHook()
+
 	go h.ensureSupervisorLoop(h.shutdownCtx)
 	return nil
 }