Add the ability to create execute jobs on long running containers

docker-compose.yml

@@ -10,9 +10,17 @@ services:
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock:ro
 
-  echoer:
+  start_echoer:
     image: busybox:latest
     command: ["date"]
     labels:
       # Execute every minute
       - 'dockron.schedule=* * * * *'
+
+  exec_echoer:
+    image: busybox:latest
+    command: sh -c "date > /out && tail -f /out"
+    labels:
+      # Execute every minute
+      - 'dockron.date.schedule=* * * * *'
+      - 'dockron.date.command=date >> /out'

logging.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"log"
+	"os"
+)
+
+var (
+	// DebugLevel indicates if we should log at the debug level
+	DebugLevel = true
+
+	loggerDebug   = log.New(os.Stderr, "DEBUG", log.LstdFlags)
+	loggerWarning = log.New(os.Stderr, "WARNING", log.LstdFlags)
+	loggerError   = log.New(os.Stderr, "ERROR", log.LstdFlags)
+)
+
+// LogDebug will log with a DEBUG prefix if DebugLevel is set
+func LogDebug(format string, v ...interface{}) {
+	if !DebugLevel {
+		return
+	}
+	loggerDebug.Printf(format, v...)
+}
+
+// LogWarning will log with a WARNING prefix
+func LogWarning(format string, v ...interface{}) {
+	loggerWarning.Printf(format, v...)
+}
+
+// LogError will log with a ERROR prefix
+func LogError(format string, v ...interface{}) {
+	loggerError.Printf(format, v...)
+}
+
+// WarnErr will provide a warning if an error is provided
+func WarnErr(err error, format string, v ...interface{}) {
+	if err != nil {
+		loggerWarning.Printf(format, v...)
+		loggerError.Print(err)
+	}
+}
+
+// FatalErr will log out details of an error and exit
+func FatalErr(err error, format string, v ...interface{}) {
+	if err != nil {
+		loggerError.Printf(format, v...)
+		loggerError.Fatal(err)
+	}
+}
+
+// PanicErr will log out details of an error and exit
+func PanicErr(err error, format string, v ...interface{}) {
+	if err != nil {
+		loggerError.Printf(format, v...)
+		loggerError.Panic(err)
+	}
+}

main.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"regexp"
 	"strings"
 	"time"
 
@@ -20,75 +21,225 @@ var (
 
 	// schedLabel is the string label to search for cron expressions
 	schedLabel = "dockron.schedule"
+	// execLabelRegex is will capture labels for an exec job
+	execLabelRegexp = regexp.MustCompile(`dockron\.([a-zA-Z0-9_-]+)\.(schedule|command)`)
 
 	// version of dockron being run
 	version = "dev"
-
-	// Debug can be used to show or supress certain log messages
-	Debug = true
 )
 
 // ContainerClient provides an interface for interracting with Docker
 type ContainerClient interface {
-	ContainerStart(context context.Context, containerID string, options dockerTypes.ContainerStartOptions) error
+	ContainerExecCreate(ctx context.Context, container string, config dockerTypes.ExecConfig) (dockerTypes.IDResponse, error)
+	ContainerExecInspect(ctx context.Context, execID string) (dockerTypes.ContainerExecInspect, error)
+	ContainerExecStart(ctx context.Context, execID string, config dockerTypes.ExecStartCheck) error
+	ContainerInspect(ctx context.Context, containerID string) (dockerTypes.ContainerJSON, error)
 	ContainerList(context context.Context, options dockerTypes.ContainerListOptions) ([]dockerTypes.Container, error)
+	ContainerStart(context context.Context, containerID string, options dockerTypes.ContainerStartOptions) error
+}
+
+// ContainerCronJob is an interface of a job to run on containers
+type ContainerCronJob interface {
+	Run()
+	Name() string
+	UniqueName() string
+	Schedule() string
 }
 
 // ContainerStartJob represents a scheduled container task
 // It contains a reference to a client, the schedule to run on, and the
 // ID of that container that should be started
 type ContainerStartJob struct {
-	Client      ContainerClient
+	client      ContainerClient
-	ContainerID string
+	context     context.Context
-	Context     context.Context
+	name        string
-	Name        string
+	containerID string
-	Schedule    string
+	schedule    string
 }
 
 // Run is executed based on the ContainerStartJob Schedule and starts the
 // container
 func (job ContainerStartJob) Run() {
-	log.Println("Starting:", job.Name)
+	log.Println("Starting:", job.name)
-	err := job.Client.ContainerStart(
+
-		job.Context,
+	// Check if container is already running
-		job.ContainerID,
+	containerJSON, err := job.client.ContainerInspect(
+		job.context,
+		job.containerID,
+	)
+	PanicErr(err, "Could not get container details for job %s", job.name)
+
+	if containerJSON.State.Running {
+		LogWarning("Container is already running. Skipping %s", job.name)
+		return
+	}
+
+	// Start job
+	err = job.client.ContainerStart(
+		job.context,
+		job.containerID,
 		dockerTypes.ContainerStartOptions{},
 	)
-	if err != nil {
+	PanicErr(err, "Could not start container for jobb %s", job.name)
-		panic(err)
+
+	// Check results of job
+	for check := true; check; check = containerJSON.State.Running {
+		LogDebug("Still running %s", job.name)
+
+		containerJSON, err = job.client.ContainerInspect(
+			job.context,
+			job.containerID,
+		)
+		PanicErr(err, "Could not get container details for job %s", job.name)
+
+		time.Sleep(1 * time.Second)
 	}
+	LogDebug("Done execing %s. %+v", job.name, containerJSON.State)
+	// Log exit code if failed
+	if containerJSON.State.ExitCode != 0 {
+		LogError(
+			"Exec job %s existed with code %d",
+			job.name,
+			containerJSON.State.ExitCode,
+		)
+	}
+
+}
+
+// Name returns the name of the job
+func (job ContainerStartJob) Name() string {
+	return job.name
+}
+
+// Schedule returns the schedule of the job
+func (job ContainerStartJob) Schedule() string {
+	return job.schedule
 }
 
 // UniqueName returns a unique identifier for a container start job
 func (job ContainerStartJob) UniqueName() string {
 	// ContainerID should be unique as a change in label will result in
 	// a new container as they are immutable
-	return job.ContainerID
+	return job.name + "/" + job.containerID
 }
 
-// QueryScheduledJobs queries Docker for all containers with a schedule and
+// ContainerExecJob is a scheduled job to be executed in a running container
-// returns a list of ContainerStartJob records to be scheduled
+type ContainerExecJob struct {
-func QueryScheduledJobs(client ContainerClient) (jobs []ContainerStartJob) {
+	ContainerStartJob
-	if Debug {
+	shellCommand string
-		log.Println("Scanning containers for new schedules...")
 }
-	containers, err := client.ContainerList(
+
-		context.Background(),
+// Run is executed based on the ContainerStartJob Schedule and starts the
-		dockerTypes.ContainerListOptions{All: true},
+// container
+func (job ContainerExecJob) Run() {
+	log.Println("Execing:", job.name)
+	containerJSON, err := job.client.ContainerInspect(
+		job.context,
+		job.containerID,
+	)
+	PanicErr(err, "Could not get container details for job %s", job.name)
+
+	if !containerJSON.State.Running {
+		LogWarning("Container not running. Skipping %s", job.name)
+		return
+	}
+
+	execID, err := job.client.ContainerExecCreate(
+		job.context,
+		job.containerID,
+		dockerTypes.ExecConfig{
+			Cmd: []string{"sh", "-c", strings.TrimSpace(job.shellCommand)},
+		},
+	)
+	PanicErr(err, "Could not create container exec job for %s", job.name)
+
+	err = job.client.ContainerExecStart(
+		job.context,
+		execID.ID,
+		dockerTypes.ExecStartCheck{},
+	)
+	PanicErr(err, "Could not start container exec job for %s", job.name)
+
+	// Wait for job results
+	execInfo := dockerTypes.ContainerExecInspect{Running: true}
+	for execInfo.Running {
+		LogDebug("Still execing %s", job.name)
+		execInfo, err = job.client.ContainerExecInspect(
+			job.context,
+			execID.ID,
 		)
 		if err != nil {
 			panic(err)
 		}
+		time.Sleep(1 * time.Second)
+	}
+	LogDebug("Done execing %s. %+v", job.name, execInfo)
+	// Log exit code if failed
+	if execInfo.ExitCode != 0 {
+		LogError("Exec job %s existed with code %d", job.name, execInfo.ExitCode)
+	}
+}
+
+// QueryScheduledJobs queries Docker for all containers with a schedule and
+// returns a list of ContainerCronJob records to be scheduled
+func QueryScheduledJobs(client ContainerClient) (jobs []ContainerCronJob) {
+	LogDebug("Scanning containers for new schedules...")
+
+	containers, err := client.ContainerList(
+		context.Background(),
+		dockerTypes.ContainerListOptions{All: true},
+	)
+	PanicErr(err, "Failure querying docker containers")
 
 	for _, container := range containers {
+		// Add start job
 		if val, ok := container.Labels[schedLabel]; ok {
 			jobName := strings.Join(container.Names, "/")
 			jobs = append(jobs, ContainerStartJob{
-				Schedule:    val,
+				client:      client,
-				Client:      client,
+				containerID: container.ID,
-				ContainerID: container.ID,
+				context:     context.Background(),
-				Context:     context.Background(),
+				schedule:    val,
-				Name:        jobName,
+				name:        jobName,
+			})
+		}
+
+		// Add exec jobs
+		execJobs := map[string]map[string]string{}
+		for label, value := range container.Labels {
+			results := execLabelRegexp.FindStringSubmatch(label)
+			if len(results) == 3 {
+				// We've got part of a new job
+				jobName, jobField := results[1], results[2]
+				if partJob, ok := execJobs[jobName]; ok {
+					// Partial exists, add the other value
+					partJob[jobField] = value
+				} else {
+					// No partial exists, add this part
+					execJobs[jobName] = map[string]string{
+						jobField: value,
+					}
+				}
+			}
+		}
+		for jobName, jobConfig := range execJobs {
+			schedule, ok := jobConfig["schedule"]
+			if !ok {
+				continue
+			}
+			shellCommand, ok := jobConfig["command"]
+			if !ok {
+				continue
+			}
+			jobs = append(jobs, ContainerExecJob{
+				ContainerStartJob: ContainerStartJob{
+					client:      client,
+					containerID: container.ID,
+					context:     context.Background(),
+					schedule:    schedule,
+					name:        strings.Join(append(container.Names, jobName), "/"),
+				},
+				shellCommand: shellCommand,
 			})
 		}
 	}
@@ -98,40 +249,39 @@ func QueryScheduledJobs(client ContainerClient) (jobs []ContainerStartJob) {
 
 // ScheduleJobs accepts a Cron instance and a list of jobs to schedule.
 // It then schedules the provided jobs
-func ScheduleJobs(c *cron.Cron, jobs []ContainerStartJob) {
+func ScheduleJobs(c *cron.Cron, jobs []ContainerCronJob) {
 	// Fetch existing jobs from the cron
 	existingJobs := map[string]cron.EntryID{}
 	for _, entry := range c.Entries() {
-		existingJobs[entry.Job.(ContainerStartJob).UniqueName()] = entry.ID
+		// This should be safe since ContainerCronJob is the only type of job we use
+		existingJobs[entry.Job.(ContainerCronJob).UniqueName()] = entry.ID
 	}
 
 	for _, job := range jobs {
 		if _, ok := existingJobs[job.UniqueName()]; ok {
 			// Job already exists, remove it from existing jobs so we don't
 			// unschedule it later
-			if Debug {
+			LogDebug("Job %s is already scheduled. Skipping", job.Name())
-				log.Printf("Job %s is already scheduled. Skipping", job.Name)
-			}
 			delete(existingJobs, job.UniqueName())
 			continue
 		}
 
 		// Job doesn't exist yet, schedule it
-		_, err := c.AddJob(job.Schedule, job)
+		_, err := c.AddJob(job.Schedule(), job)
 		if err == nil {
 			log.Printf(
 				"Scheduled %s (%s) with schedule '%s'\n",
-				job.Name,
+				job.Name(),
-				job.ContainerID[:10],
+				job.UniqueName(),
-				job.Schedule,
+				job.Schedule(),
 			)
 		} else {
 			// TODO: Track something for a healthcheck here
-			log.Printf(
+			LogError(
-				"Error scheduling %s (%s) with schedule '%s'. %v\n",
+				"Could not schedule %s (%s) with schedule '%s'. %v\n",
-				job.Name,
+				job.Name(),
-				job.ContainerID[:10],
+				job.UniqueName(),
-				job.Schedule,
+				job.Schedule(),
 				err,
 			)
 		}
@@ -154,7 +304,7 @@ func main() {
 	var watchInterval time.Duration
 	flag.DurationVar(&watchInterval, "watch", defaultWatchInterval, "Interval used to poll Docker for changes")
 	var showVersion = flag.Bool("version", false, "Display the version of dockron and exit")
-	flag.BoolVar(&Debug, "debug", false, "Show debug logs")
+	flag.BoolVar(&DebugLevel, "debug", false, "Show debug logs")
 	flag.Parse()
 
 	// Print version if asked

main_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"log"
+	"sort"
 	"testing"
 
 	dockerTypes "github.com/docker/docker/api/types"
@@ -13,6 +14,9 @@ import (
 // FakeDockerClient is used to test without interracting with Docker
 type FakeDockerClient struct {
 	FakeContainers           []dockerTypes.Container
+	FakeExecIDResponse       string
+	FakeContainerExecInspect dockerTypes.ContainerExecInspect
+	FakeContainerInspect     dockerTypes.ContainerJSON
 }
 
 // ContainerStart pretends to start a container
@@ -24,18 +28,29 @@ func (fakeClient *FakeDockerClient) ContainerList(context context.Context, optio
 	return fakeClient.FakeContainers, nil
 }
 
-// NewFakeDockerClient creates an empty client
+func (fakeClient *FakeDockerClient) ContainerExecCreate(ctx context.Context, container string, config dockerTypes.ExecConfig) (dockerTypes.IDResponse, error) {
-func NewFakeDockerClient() *FakeDockerClient {
+	return dockerTypes.IDResponse{ID: fakeClient.FakeExecIDResponse}, nil
+}
+
+func (fakeClient *FakeDockerClient) ContainerExecStart(ctx context.Context, execID string, config dockerTypes.ExecStartCheck) error {
+	return nil
+}
+
+func (fakeClient *FakeDockerClient) ContainerExecInspect(ctx context.Context, execID string) (dockerTypes.ContainerExecInspect, error) {
+	return fakeClient.FakeContainerExecInspect, nil
+}
+
+func (fakeClient *FakeDockerClient) ContainerInspect(ctx context.Context, containerID string) (dockerTypes.ContainerJSON, error) {
+	return fakeClient.FakeContainerInspect, nil
+}
+
+// newFakeDockerClient creates an empty client
+func newFakeDockerClient() *FakeDockerClient {
 	return &FakeDockerClient{}
 }
 
-// NewFakeDockerClientWithContainers creates a client with the provided containers
+// errorUnequal checks that two values are equal and fails the test if not
-func NewFakeDockerClientWithContainers(containers []dockerTypes.Container) *FakeDockerClient {
+func errorUnequal(t *testing.T, expected interface{}, actual interface{}, message string) {
-	return &FakeDockerClient{FakeContainers: containers}
-}
-
-// ErrorUnequal checks that two values are equal and fails the test if not
-func ErrorUnequal(t *testing.T, expected interface{}, actual interface{}, message string) {
 	if expected != actual {
 		t.Errorf("%s Expected: %+v Actual: %+v", message, expected, actual)
 	}
@@ -44,17 +59,17 @@ func ErrorUnequal(t *testing.T, expected interface{}, actual interface{}, messag
 // TestQueryScheduledJobs checks that when querying the Docker client that we
 // create jobs for any containers with a dockron.schedule
 func TestQueryScheduledJobs(t *testing.T) {
-	client := NewFakeDockerClient()
+	client := newFakeDockerClient()
 
 	cases := []struct {
 		name           string
 		fakeContainers []dockerTypes.Container
-		expectedJobs   []ContainerStartJob
+		expectedJobs   []ContainerCronJob
 	}{
 		{
 			name:           "No containers",
 			fakeContainers: []dockerTypes.Container{},
-			expectedJobs:   []ContainerStartJob{},
+			expectedJobs:   []ContainerCronJob{},
 		},
 		{
 			name: "One container without schedule",
@@ -64,7 +79,7 @@ func TestQueryScheduledJobs(t *testing.T) {
 					ID:    "no_schedule_1",
 				},
 			},
-			expectedJobs: []ContainerStartJob{},
+			expectedJobs: []ContainerCronJob{},
 		},
 		{
 			name: "One container with schedule",
@@ -77,13 +92,13 @@ func TestQueryScheduledJobs(t *testing.T) {
 					},
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
 				},
 			},
 		},
@@ -102,13 +117,101 @@ func TestQueryScheduledJobs(t *testing.T) {
 					},
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
+				},
+			},
+		},
+		{
+			name: "Incomplete exec job, schedule only",
+			fakeContainers: []dockerTypes.Container{
+				dockerTypes.Container{
+					Names: []string{"exec_job_1"},
+					ID:    "exec_job_1",
+					Labels: map[string]string{
+						"dockron.test.schedule": "* * * * *",
+					},
+				},
+			},
+			expectedJobs: []ContainerCronJob{},
+		},
+		{
+			name: "Incomplete exec job, command only",
+			fakeContainers: []dockerTypes.Container{
+				dockerTypes.Container{
+					Names: []string{"exec_job_1"},
+					ID:    "exec_job_1",
+					Labels: map[string]string{
+						"dockron.test.command": "date",
+					},
+				},
+			},
+			expectedJobs: []ContainerCronJob{},
+		},
+		{
+			name: "Complete exec job",
+			fakeContainers: []dockerTypes.Container{
+				dockerTypes.Container{
+					Names: []string{"exec_job_1"},
+					ID:    "exec_job_1",
+					Labels: map[string]string{
+						"dockron.test.schedule": "* * * * *",
+						"dockron.test.command":  "date",
+					},
+				},
+			},
+			expectedJobs: []ContainerCronJob{
+				ContainerExecJob{
+					ContainerStartJob: ContainerStartJob{
+						name:        "exec_job_1/test",
+						containerID: "exec_job_1",
+						schedule:    "* * * * *",
+						context:     context.Background(),
+						client:      client,
+					},
+					shellCommand: "date",
+				},
+			},
+		},
+		{
+			name: "Dual exec jobs on single container",
+			fakeContainers: []dockerTypes.Container{
+				dockerTypes.Container{
+					Names: []string{"exec_job_1"},
+					ID:    "exec_job_1",
+					Labels: map[string]string{
+						"dockron.test1.schedule": "* * * * *",
+						"dockron.test1.command":  "date",
+						"dockron.test2.schedule": "* * * * *",
+						"dockron.test2.command":  "date",
+					},
+				},
+			},
+			expectedJobs: []ContainerCronJob{
+				ContainerExecJob{
+					ContainerStartJob: ContainerStartJob{
+						name:        "exec_job_1/test1",
+						containerID: "exec_job_1",
+						schedule:    "* * * * *",
+						context:     context.Background(),
+						client:      client,
+					},
+					shellCommand: "date",
+				},
+				ContainerExecJob{
+					ContainerStartJob: ContainerStartJob{
+						name:        "exec_job_1/test2",
+						containerID: "exec_job_1",
+						schedule:    "* * * * *",
+						context:     context.Background(),
+						client:      client,
+					},
+					shellCommand: "date",
 				},
 			},
 		},
@@ -123,12 +226,15 @@ func TestQueryScheduledJobs(t *testing.T) {
 			client.FakeContainers = c.fakeContainers
 
 			jobs := QueryScheduledJobs(client)
+			// Sort so we can compare each list of jobs
+			sort.Slice(jobs, func(i, j int) bool {
+				return jobs[i].UniqueName() < jobs[j].UniqueName()
+			})
 
 			t.Logf("Expected jobs: %+v, Actual jobs: %+v", c.expectedJobs, jobs)
-
+			errorUnequal(t, len(c.expectedJobs), len(jobs), "Job lengths don't match")
-			ErrorUnequal(t, len(c.expectedJobs), len(jobs), "Job lengths don't match")
 			for i, job := range jobs {
-				ErrorUnequal(t, c.expectedJobs[i], job, "Job value does not match")
+				errorUnequal(t, c.expectedJobs[i], job, "Job value does not match")
 			}
 		})
 	}
@@ -142,82 +248,82 @@ func TestScheduleJobs(t *testing.T) {
 	// Tests must be executed sequentially!
 	cases := []struct {
 		name         string
-		queriedJobs  []ContainerStartJob
+		queriedJobs  []ContainerCronJob
-		expectedJobs []ContainerStartJob
+		expectedJobs []ContainerCronJob
 	}{
 		{
 			name:         "No containers",
-			queriedJobs:  []ContainerStartJob{},
+			queriedJobs:  []ContainerCronJob{},
-			expectedJobs: []ContainerStartJob{},
+			expectedJobs: []ContainerCronJob{},
 		},
 		{
 			name: "One container with schedule",
-			queriedJobs: []ContainerStartJob{
+			queriedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 			},
 		},
 		{
 			name: "Add a second job",
-			queriedJobs: []ContainerStartJob{
+			queriedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 				ContainerStartJob{
-					Name:        "has_schedule_2",
+					name:        "has_schedule_2",
-					ContainerID: "has_schedule_2",
+					containerID: "has_schedule_2",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 				ContainerStartJob{
-					Name:        "has_schedule_2",
+					name:        "has_schedule_2",
-					ContainerID: "has_schedule_2",
+					containerID: "has_schedule_2",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 			},
 		},
 		{
 			name: "Replace job 1",
-			queriedJobs: []ContainerStartJob{
+			queriedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1_prime",
+					containerID: "has_schedule_1_prime",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 				ContainerStartJob{
-					Name:        "has_schedule_2",
+					name:        "has_schedule_2",
-					ContainerID: "has_schedule_2",
+					containerID: "has_schedule_2",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_2",
+					name:        "has_schedule_2",
-					ContainerID: "has_schedule_2",
+					containerID: "has_schedule_2",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1_prime",
+					containerID: "has_schedule_1_prime",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
 				},
 			},
 		},
@@ -234,9 +340,9 @@ func TestScheduleJobs(t *testing.T) {
 			scheduledEntries := croner.Entries()
 			t.Logf("Cron entries: %+v", scheduledEntries)
 
-			ErrorUnequal(t, len(c.expectedJobs), len(scheduledEntries), "Job and entry lengths don't match")
+			errorUnequal(t, len(c.expectedJobs), len(scheduledEntries), "Job and entry lengths don't match")
 			for i, entry := range scheduledEntries {
-				ErrorUnequal(t, c.expectedJobs[i], entry.Job, "Job value does not match entry")
+				errorUnequal(t, c.expectedJobs[i], entry.Job, "Job value does not match entry")
 			}
 		})
 	}
@@ -248,17 +354,17 @@ func TestScheduleJobs(t *testing.T) {
 // TestDoLoop is close to an integration test that checks the main loop logic
 func TestDoLoop(t *testing.T) {
 	croner := cron.New()
-	client := NewFakeDockerClient()
+	client := newFakeDockerClient()
 
 	cases := []struct {
 		name           string
 		fakeContainers []dockerTypes.Container
-		expectedJobs   []ContainerStartJob
+		expectedJobs   []ContainerCronJob
 	}{
 		{
 			name:           "No containers",
 			fakeContainers: []dockerTypes.Container{},
-			expectedJobs:   []ContainerStartJob{},
+			expectedJobs:   []ContainerCronJob{},
 		},
 		{
 			name: "One container without schedule",
@@ -268,7 +374,7 @@ func TestDoLoop(t *testing.T) {
 					ID:    "no_schedule_1",
 				},
 			},
-			expectedJobs: []ContainerStartJob{},
+			expectedJobs: []ContainerCronJob{},
 		},
 		{
 			name: "One container with schedule",
@@ -281,13 +387,13 @@ func TestDoLoop(t *testing.T) {
 					},
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
 				},
 			},
 		},
@@ -306,13 +412,13 @@ func TestDoLoop(t *testing.T) {
 					},
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
 				},
 			},
 		},
@@ -334,20 +440,20 @@ func TestDoLoop(t *testing.T) {
 					},
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1",
+					containerID: "has_schedule_1",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
 				},
 				ContainerStartJob{
-					Name:        "has_schedule_2",
+					name:        "has_schedule_2",
-					ContainerID: "has_schedule_2",
+					containerID: "has_schedule_2",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
 				},
 			},
 		},
@@ -369,20 +475,53 @@ func TestDoLoop(t *testing.T) {
 					},
 				},
 			},
-			expectedJobs: []ContainerStartJob{
+			expectedJobs: []ContainerCronJob{
 				ContainerStartJob{
-					Name:        "has_schedule_2",
+					name:        "has_schedule_2",
-					ContainerID: "has_schedule_2",
+					containerID: "has_schedule_2",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
 				},
 				ContainerStartJob{
-					Name:        "has_schedule_1",
+					name:        "has_schedule_1",
-					ContainerID: "has_schedule_1_prime",
+					containerID: "has_schedule_1_prime",
-					Schedule:    "* * * * *",
+					schedule:    "* * * * *",
-					Context:     context.Background(),
+					context:     context.Background(),
-					Client:      client,
+					client:      client,
+				},
+			},
+		},
+		{
+			name: "Remove second container and add exec to first",
+			fakeContainers: []dockerTypes.Container{
+				dockerTypes.Container{
+					Names: []string{"has_schedule_1"},
+					ID:    "has_schedule_1_prime",
+					Labels: map[string]string{
+						"dockron.schedule":      "* * * * *",
+						"dockron.test.schedule": "* * * * *",
+						"dockron.test.command":  "date",
+					},
+				},
+			},
+			expectedJobs: []ContainerCronJob{
+				ContainerStartJob{
+					name:        "has_schedule_1",
+					containerID: "has_schedule_1_prime",
+					schedule:    "* * * * *",
+					context:     context.Background(),
+					client:      client,
+				},
+				ContainerExecJob{
+					ContainerStartJob: ContainerStartJob{
+						name:        "has_schedule_1/test",
+						containerID: "has_schedule_1_prime",
+						schedule:    "* * * * *",
+						context:     context.Background(),
+						client:      client,
+					},
+					shellCommand: "date",
 				},
 			},
 		},
@@ -405,9 +544,9 @@ func TestDoLoop(t *testing.T) {
 			scheduledEntries := croner.Entries()
 			t.Logf("Cron entries: %+v", scheduledEntries)
 
-			ErrorUnequal(t, len(c.expectedJobs), len(scheduledEntries), "Job and entry lengths don't match")
+			errorUnequal(t, len(c.expectedJobs), len(scheduledEntries), "Job and entry lengths don't match")
 			for i, entry := range scheduledEntries {
-				ErrorUnequal(t, c.expectedJobs[i], entry.Job, "Job value does not match entry")
+				errorUnequal(t, c.expectedJobs[i], entry.Job, "Job value does not match entry")
 			}
 		})
 	}