AllocDirBuilder that creates the alloc directory structure

client/allocdir/alloc_dir.go

@@ -0,0 +1,65 @@
+package allocdir
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/hashicorp/nomad/nomad/structs"
+)
+
+var (
+	// The name of the directory that is shared across tasks in a task group.
+	SharedAllocName = "alloc"
+
+	// The set of directories that exist inside eache shared alloc directory.
+	SharedAllocDirs = []string{"logs", "tmp", "data"}
+
+	// The name of the directory that exists inside each task directory
+	// regardless of driver.
+	TaskLocal = "local"
+)
+
+// Builds the necessary directory structure for running an alloc.
+type AllocDirBuilder interface {
+	// Given a list of a task build the correct alloc structure.
+	Build([]*structs.Task) error
+
+	// Tears down previously build directory structure.
+	Destroy() error
+
+	// Returns the directory of a task if it was created, otherwise an error is
+	// returned.
+	TaskDir(task string) (string, error)
+}
+
+type AllocDir struct {
+	// AllocDir is the directory used for storing any state
+	// of this allocation. It will be purged on alloc destroy.
+	AllocDir string
+
+	// The shared directory is available to all tasks within the same task
+	// group.
+	SharedDir string
+
+	// TaskDirs is a mapping of task names to their non-shared directory.
+	TaskDirs map[string]string
+}
+
+func NewAllocDir(allocDir string) *AllocDir {
+	d := &AllocDir{AllocDir: allocDir, TaskDirs: make(map[string]string)}
+	d.SharedDir = filepath.Join(d.AllocDir, SharedAllocName)
+	return d
+}
+
+func (d *AllocDir) Destroy() error {
+	return os.RemoveAll(d.AllocDir)
+}
+
+func (d *AllocDir) TaskDir(task string) (string, error) {
+	if dir, ok := d.TaskDirs[task]; ok {
+		return dir, nil
+	}
+
+	return "", fmt.Errorf("Task directory doesn't exist for task %v", task)
+}