add restic integration for doing pod volume backups/restores

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

pkg/util/sync/error_group.go

@@ -0,0 +1,71 @@
+/*
+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 sync
+
+import "sync"
+
+// An ErrorGroup waits for a collection of goroutines that return errors to finish.
+// The main goroutine calls Go one or more times to execute a function that returns
+// an error in a goroutine. Then it calls Wait to wait for all goroutines to finish
+// and collect the results of each.
+type ErrorGroup struct {
+	wg      sync.WaitGroup
+	errChan chan error
+}
+
+// Go runs the specified function in a goroutine.
+func (eg *ErrorGroup) Go(action func() error) {
+	if eg.errChan == nil {
+		eg.errChan = make(chan error)
+	}
+
+	eg.wg.Add(1)
+	go func() {
+		eg.errChan <- action()
+		eg.wg.Done()
+	}()
+}
+
+// GoErrorSlice runs a function that returns a slice of errors
+// in a goroutine.
+func (eg *ErrorGroup) GoErrorSlice(action func() []error) {
+	if eg.errChan == nil {
+		eg.errChan = make(chan error)
+	}
+
+	eg.wg.Add(1)
+	go func() {
+		for _, err := range action() {
+			eg.errChan <- err
+		}
+		eg.wg.Done()
+	}()
+}
+
+// Wait waits for all functions run via Go to finish,
+// and returns all of their errors.
+func (eg *ErrorGroup) Wait() []error {
+	var errs []error
+	go func() {
+		for {
+			errs = append(errs, <-eg.errChan)
+		}
+	}()
+
+	eg.wg.Wait()
+	return errs
+}