add restic integration for doing pod volume backups/restores

Signed-off-by: Steve Kriss <steve@heptio.com>

cmd/restic-init-container/main.go

@@ -0,0 +1,77 @@
+/*
+Copyright 2018 the Heptio Ark contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintln(os.Stderr, "ERROR: exactly one argument must be provided, the restore's UID")
+		os.Exit(1)
+	}
+
+	ticker := time.NewTicker(time.Second)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			if done() {
+				fmt.Println("All restic restores are done")
+				return
+			}
+		}
+	}
+}
+
+// done returns true if for each directory under /restores, a file exists
+// within the .ark/ subdirectory whose name is equal to os.Args[1], or
+// false otherwise
+func done() bool {
+	children, err := ioutil.ReadDir("/restores")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "ERROR reading /restores directory: %s\n", err)
+		return false
+	}
+
+	for _, child := range children {
+		if !child.IsDir() {
+			fmt.Printf("%s is not a directory, skipping.\n", child.Name())
+			continue
+		}
+
+		doneFile := filepath.Join("/restores", child.Name(), ".ark", os.Args[1])
+
+		if _, err := os.Stat(doneFile); os.IsNotExist(err) {
+			fmt.Printf("Not found: %s\n", doneFile)
+			return false
+		} else if err != nil {
+			fmt.Fprintf(os.Stderr, "ERROR looking for %s: %s\n", doneFile, err)
+			return false
+		}
+
+		fmt.Printf("Found %s", doneFile)
+	}
+
+	return true
+}