Only ever run one scan at the same time

Also use a logging library

worker.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"github.com/docker/docker/client"
+)
+
+var (
+	triggerCh = make(chan struct{})
+)
+
+func TriggerScan() {
+	triggerCh <- struct{}{}
+}
+
+func Worker() {
+	Logger.Debugf("background worker starting")
+
+	responseCh := make(chan struct{})
+
+	workerRunning := false
+	triggerWaiting := false
+
+	for true {
+		select {
+		case _ = <-triggerCh:
+			if workerRunning {
+				triggerWaiting = true
+			} else {
+				workerRunning = true
+				go func() {
+					checkAndDoUpdate()
+					responseCh <- struct{}{}
+				}()
+			}
+		case _ = <-responseCh:
+			if triggerWaiting {
+				triggerWaiting = false
+				go func() {
+					checkAndDoUpdate()
+					responseCh <- struct{}{}
+				}()
+			} else {
+				workerRunning = false
+			}
+		}
+	}
+}
+
+func checkAndDoUpdate() {
+	Logger.Infof("starting scan")
+
+	cli, err := client.NewEnvClient()
+	if err != nil {
+		panic(err)
+	}
+
+	hub, err := anonymousClient()
+	if err != nil {
+		panic(err)
+	}
+
+	labeledContainers := getLabeledContainers(cli)
+
+	Logger.Infof("found %d valid containers", len(labeledContainers))
+
+	for _, lc := range labeledContainers {
+		owner, repository, tag := lc.SplitImageParts()
+		name := lc.GetName()
+		imageName := combineImageParts(owner, repository, nil)
+
+		if tag == nil {
+			Logger.Errorf(`no tag specified for container "%s", ignoring`, name)
+			continue
+		}
+
+		Logger.Infof(`container "%s" image="%s" mode=%s tag="%s"`, name, imageName, lc.Mode.Label(), *tag)
+
+		repoTags, err := getDockerRepoTags(hub, owner, repository)
+		if err != nil {
+			panic(err)
+		}
+
+		Logger.Infof(`tags in registry for "%s": %d`, name, len(repoTags))
+		for _, tag := range repoTags {
+			svt := parseTagAsSemVer(tag.Name)
+			Logger.Infof(`tag_name="%s" semver=%t digest=%s`, tag.Name, svt != nil, tag.Digest)
+		}
+
+		shouldUpdateTo := lc.Mode.ShouldUpdate(*tag, repoTags)
+		if shouldUpdateTo != nil {
+			Logger.Infof(`updating %s from %s to: %s`, name, *tag, shouldUpdateTo.Name)
+			err = lc.UpdateTo(cli, *shouldUpdateTo)
+			if err != nil {
+				panic(err)
+			}
+		} else {
+			Logger.Infof("no update available for container %s", name)
+		}
+	}
+	Logger.Infof("all done")
+}