Handle errors without halting

If we receive an error while trying to shutdown/startup a particular
container we don't want to immediately terminate the current update
cycle. Instead we should continue processing the remaining containers
and simply log the error.

actions/update.go

@@ -2,13 +2,15 @@ package actions
 
 import (
 	"math/rand"
+	"time"
 
 	"github.com/CenturyLinkLabs/watchtower/container"
 	log "github.com/Sirupsen/logrus"
 )
 
 var (
-	letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	letters  = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	waitTime = 10 * time.Second
 )
 
 func allContainersFilter(container.Container) bool { return true }
@@ -45,8 +47,8 @@ func Update(client container.Client) error {
 		}
 
 		if container.Stale {
-			if err := client.StopContainer(container, 10); err != nil {
+			if err := client.StopContainer(container, waitTime); err != nil {
-				return err
+				log.Error(err)
 			}
 		}
 	}
@@ -60,12 +62,13 @@ func Update(client container.Client) error {
 			// instance so that the new one can adopt the old name.
 			if container.IsWatchtower() {
 				if err := client.RenameContainer(container, randName()); err != nil {
-					return err
+					log.Error(err)
+					continue
 				}
 			}
 
 			if err := client.StartContainer(container); err != nil {
-				return err
+				log.Error(err)
 			}
 		}
 	}

container/client.go

@@ -160,8 +160,8 @@ func (client DockerClient) waitForStop(c Container, waitTime time.Duration) erro
 			} else if !ci.State.Running {
 				return nil
 			}
-
-			time.Sleep(1 * time.Second)
 		}
+
+		time.Sleep(1 * time.Second)
 	}
 }