client: alloc/task context

client/alloc_context.go

@@ -24,10 +24,11 @@ type AllocContext struct {
 // NewAllocContext is used to create a new allocation context
 func NewAllocContext(client *Client, alloc *structs.Allocation) *AllocContext {
 	ctx := &AllocContext{
-		client:   client,
-		logger:   client.logger,
-		alloc:    alloc,
-		updateCh: make(chan *structs.Allocation, 8),
+		client:    client,
+		logger:    client.logger,
+		alloc:     alloc,
+		updateCh:  make(chan *structs.Allocation, 8),
+		destroyCh: make(chan struct{}),
 	}
 	return ctx
 }

client/task_context.go

@@ -0,0 +1,72 @@
+package client
+
+import (
+	"log"
+	"sync"
+
+	"github.com/hashicorp/nomad/nomad/structs"
+)
+
+// TaskContext is used to wrap a task within an allocation and provide the execution context.
+type TaskContext struct {
+	ctx    *AllocContext
+	logger *log.Logger
+
+	task *structs.Task
+
+	updateCh chan *structs.Task
+
+	destroy     bool
+	destroyCh   chan struct{}
+	destroyLock sync.Mutex
+}
+
+// NewTaskContext is used to create a new task context
+func NewTaskContext(ctx *AllocContext, task *structs.Task) *TaskContext {
+	tc := &TaskContext{
+		ctx:       ctx,
+		logger:    ctx.logger,
+		task:      task,
+		updateCh:  make(chan *structs.Task, 8),
+		destroyCh: make(chan struct{}),
+	}
+	return tc
+}
+
+// Run is a long running routine used to manage the task
+func (t *TaskContext) Run() {
+	t.logger.Printf("[DEBUG] client: starting task context for '%s' (alloc '%s')", t.task.Name, t.ctx.Alloc().ID)
+
+	// TODO: Start
+	for {
+		select {
+		case update := <-t.updateCh:
+			// TODO: Update
+			t.task = update
+		case <-t.destroyCh:
+			// TODO: Destroy
+			return
+		}
+	}
+}
+
+// Update is used to update the task of the context
+func (t *TaskContext) Update(update *structs.Task) {
+	select {
+	case t.updateCh <- update:
+	default:
+		t.logger.Printf("[ERR] client: dropping task update '%s' (alloc '%s')", update.Name, t.ctx.Alloc().ID)
+	}
+}
+
+// Destroy is used to indicate that the task context should be destroyed
+func (t *TaskContext) Destroy() {
+	t.destroyLock.Lock()
+	defer t.destroyLock.Unlock()
+
+	if t.destroy {
+		return
+	}
+	t.destroy = true
+	close(t.destroyCh)
+}