From a0ff83f44caf0567506542d28b8a393f5fac67f4 Mon Sep 17 00:00:00 2001
From: Diptanu Choudhury <diptanuc@gmail.com>
Date: Thu, 4 Feb 2016 16:18:10 -0800
Subject: [PATCH] Added some docs

---
 client/driver/executor/executor.go       | 17 +++++++++++++++++
 client/driver/executor/executor_linux.go |  3 +++
 2 files changed, 20 insertions(+)

diff --git a/client/driver/executor/executor.go b/client/driver/executor/executor.go
index 60c18e17e..d4bc088e7 100644
--- a/client/driver/executor/executor.go
+++ b/client/driver/executor/executor.go
@@ -18,6 +18,8 @@ import (
 	"github.com/hashicorp/nomad/nomad/structs"
 )
 
+// ExecutorContext is a wrapper to hold context to configure the command user
+// wants to run
 type ExecutorContext struct {
 	TaskEnv          *env.TaskEnvironment
 	AllocDir         *allocdir.AllocDir
@@ -28,17 +30,22 @@ type ExecutorContext struct {
 	UnprivilegedUser bool
 }
 
+// ExecCommand is a wrapper to hold the user command
 type ExecCommand struct {
 	Cmd  string
 	Args []string
 }
 
+// ProcessState holds information about the state of
+// a user process
 type ProcessState struct {
 	Pid      int
 	ExitCode int
 	Time     time.Time
 }
 
+// Executor is the interface which allows a driver to launch and supervise
+// a process user wants to run
 type Executor interface {
 	LaunchCmd(command *ExecCommand, ctx *ExecutorContext) (*ProcessState, error)
 	Wait() (*ProcessState, error)
@@ -46,6 +53,9 @@ type Executor interface {
 	Exit() error
 }
 
+// UniversalExecutor is an implementation of the Executor which launches and
+// supervises processes. In addition to process supervision it provides resource
+// and file system isolation
 type UniversalExecutor struct {
 	cmd exec.Cmd
 	ctx *ExecutorContext
@@ -59,10 +69,13 @@ type UniversalExecutor struct {
 	lock   sync.Mutex
 }
 
+// NewExecutor returns an Executor
 func NewExecutor(logger *log.Logger) Executor {
 	return &UniversalExecutor{logger: logger, processExited: make(chan interface{})}
 }
 
+// LaunchCmd launches a process and returns it's state. It also configures an
+// applies isolation on certain platforms.
 func (e *UniversalExecutor) LaunchCmd(command *ExecCommand, ctx *ExecutorContext) (*ProcessState, error) {
 	e.ctx = ctx
 
@@ -113,6 +126,7 @@ func (e *UniversalExecutor) LaunchCmd(command *ExecCommand, ctx *ExecutorContext
 	return &ProcessState{Pid: e.cmd.Process.Pid, ExitCode: -1, Time: time.Now()}, nil
 }
 
+// Wait waits until a process has exited and returns it's exitcode and errors
 func (e *UniversalExecutor) Wait() (*ProcessState, error) {
 	<-e.processExited
 	return e.exitState, nil
@@ -140,6 +154,8 @@ func (e *UniversalExecutor) wait() {
 	e.exitState = &ProcessState{Pid: 0, ExitCode: exitCode, Time: time.Now()}
 }
 
+// Exit cleans up the alloc directory, destroys cgroups and kills the user
+// process
 func (e *UniversalExecutor) Exit() error {
 	e.logger.Printf("[INFO] Exiting plugin for task %q", e.ctx.TaskName)
 	if e.cmd.Process == nil {
@@ -161,6 +177,7 @@ func (e *UniversalExecutor) Exit() error {
 	return nil
 }
 
+// Shutdown sends an interrupt signal to the user process
 func (e *UniversalExecutor) ShutDown() error {
 	if e.cmd.Process == nil {
 		return fmt.Errorf("executor.shutdown error: no process found")
diff --git a/client/driver/executor/executor_linux.go b/client/driver/executor/executor_linux.go
index 4c946d429..0b3406e47 100644
--- a/client/driver/executor/executor_linux.go
+++ b/client/driver/executor/executor_linux.go
@@ -33,6 +33,7 @@ var (
 	}
 )
 
+// configureIsolation configures chroot and creates cgroups
 func (e *UniversalExecutor) configureIsolation() error {
 	if e.ctx.FSIsolation {
 		if err := e.configureChroot(); err != nil {
@@ -48,6 +49,7 @@ func (e *UniversalExecutor) configureIsolation() error {
 	return nil
 }
 
+// applyLimits puts a process in a pre-configured cgroup
 func (e *UniversalExecutor) applyLimits() error {
 	if !e.ctx.ResourceLimits {
 		return nil
@@ -140,6 +142,7 @@ func (e *UniversalExecutor) pathExists(path string) bool {
 	return true
 }
 
+// configureChroot configures a chroot
 func (e *UniversalExecutor) configureChroot() error {
 	allocDir := e.ctx.AllocDir
 	if err := allocDir.MountSharedDir(e.ctx.TaskName); err != nil {