feat: expose read-only cache to runner containers

internal/driver/driver.go

@@ -6,7 +6,7 @@ import (
 
 type ContainerDriver interface {
 	Pull(string) error
-	Start(string, string) error
+	Start(string, string, string) error
 	Stop(string) error
 	Exec(containerId string, command string, options CommandOptions) CommandResult
 }

internal/driver/mock_container_driver.go

@@ -32,7 +32,7 @@ func (d *MockDriver) Pull(uri string) error {
 	return nil
 }
 
-func (d *MockDriver) Start(uri string, containerName string) error {
+func (d *MockDriver) Start(uri string, containerName string, cacheRoot string) error {
 	if _, init := d.Calls["Start"]; !init {
 		d.Calls["Start"] = []MockCall{}
 	}

internal/driver/podman_driver.go

@@ -31,14 +31,14 @@ func (d PodmanDriver) Pull(uri string) error {
 //
 // The volume created is labeled with `owner=<containerName>` so it
 // can be easily collected and cleaned up on stop.
-func (d PodmanDriver) Start(uri string, containerName string) error {
+func (d PodmanDriver) Start(uri string, containerName string, cachePath string) error {
 	volumeName := fmt.Sprintf("%s-workspace", containerName)
 
 	if err := podmanCommand("volume", "create", volumeName, "--label", fmt.Sprintf("owner=%s", containerName)).Run(); err != nil {
 		return err
 	}
 
-	if err := podmanCommand("run", "-td", "--name", containerName, "-v", fmt.Sprintf("%s:/workspace", volumeName), uri).Run(); err != nil {
+	if err := podmanCommand("run", "-td", "--name", containerName, "-v", fmt.Sprintf("%s:/workspace", volumeName), "-v", fmt.Sprintf("%s:/cache:ro", cachePath), uri).Run(); err != nil {
 		return err
 	}
 

internal/driver/podman_driver_test.go

@@ -13,6 +13,8 @@ const TEST_IMAGE_NAME = "busybox:stable"
 
 type PodmanMountDetails struct {
 	Name        string `json:"Name"`
+	Source      string `json:"Source"`
+	ReadWrite   bool   `json:"RW"`
 	Destination string `json:"Destination"`
 }
 
@@ -91,7 +93,7 @@ func TestStartCreatesAContainerWithTheDesiredUriAndName(t *testing.T) {
 
 		defer CleanAll(containerName)
 
-		driver.Start(TEST_IMAGE_NAME, containerName)
+		driver.Start(TEST_IMAGE_NAME, containerName, t.TempDir())
 
 		inspectOut := InspectContainer(containerName)
 
@@ -112,11 +114,11 @@ func TestStartCreatesAContainerWithAnAttachedVolume(t *testing.T) {
 
 		defer CleanAll(containerName)
 
-		driver.Start(TEST_IMAGE_NAME, containerName)
+		driver.Start(TEST_IMAGE_NAME, containerName, t.TempDir())
 
 		inspectOut := InspectContainer(containerName)
 
-		if len(inspectOut.Mounts) != 1 {
+		if len(inspectOut.Mounts) == 0 {
 			t.Error("Expected a mount.")
 		}
 
@@ -135,6 +137,28 @@ func TestStartCreatesAContainerWithAnAttachedVolume(t *testing.T) {
 	})
 }
 
+func TestStartCreatesAContainerWithAReadonlyCacheVolume(t *testing.T) {
+	MustPodman(t, func() {
+		driver := PodmanDriver{}
+		containerName := "test-container"
+
+		defer CleanAll(containerName)
+		cacheRoot := t.TempDir()
+		driver.Start(TEST_IMAGE_NAME, containerName, cacheRoot)
+
+		inspectOut := InspectContainer(containerName)
+
+		cacheVolume := inspectOut.Mounts[1]
+
+		if cacheVolume.ReadWrite {
+			t.Error("Expected cache volume to be read-only.")
+		}
+
+		if cacheVolume.Destination != "/cache" || cacheVolume.Source != cacheRoot {
+			t.Error("Expected cache volume to map from provided cache root to /cache")
+		}
+	})
+}
 func TestStopStopsAContainerByName(t *testing.T) {
 	MustPodman(t, func() {
 		driver := PodmanDriver{}
@@ -142,7 +166,7 @@ func TestStopStopsAContainerByName(t *testing.T) {
 
 		defer CleanAll(containerName)
 
-		driver.Start(TEST_IMAGE_NAME, containerName)
+		driver.Start(TEST_IMAGE_NAME, containerName, t.TempDir())
 		driver.Stop(containerName)
 
 		if ContainerExists(containerName) {
@@ -158,7 +182,7 @@ func TestStopCleansUpWorkspaceVolume(t *testing.T) {
 
 		defer CleanAll(containerName)
 
-		driver.Start(TEST_IMAGE_NAME, containerName)
+		driver.Start(TEST_IMAGE_NAME, containerName, t.TempDir())
 		driver.Stop(containerName)
 
 		if VolumeExists(fmt.Sprintf("%s-workspace", containerName)) {

internal/runner/runner.go

@@ -137,7 +137,7 @@ func (r *Runner) RunCommandInContainer(containerId string, command string, optio
 //
 // The container is started before the job steps are run and cleaned up after.
 func (r *Runner) RunJobInContainer(imageUri string, containerId string, jobContext context.Context) error {
-	r.Driver.Start(imageUri, containerId)
+	r.Driver.Start(imageUri, containerId, r.Cache.Root)
 
 	r.deferred.Queue(fmt.Sprintf("job-%s", containerId), func() {
 		logger.Info("Started cleaning up %s", containerId)