Add support for subPath in configMaps volumes (#116)

charts/k8s-service/templates/_deployment_spec.tpl

@@ -294,6 +294,9 @@ spec:
             {{- if eq $value.as "volume" }}
             - name: {{ $name }}-volume
               mountPath: {{ quote $value.mountPath }}
+              {{- if $value.subPath }}
+              subPath: {{ quote $value.subPath }}
+              {{- end }}
             {{- end }}
           {{- end }}
           {{- range $name, $value := .Values.secrets }}

charts/k8s-service/values.yaml

@@ -398,6 +398,10 @@ additionalContainerEnv: {}
 #     : For ConfigMaps mounted as a volume, specify the mount path on the container file system where the config values
 #       will be available.  Required when the ConfigMap is exposed as a volume. Ignored when the ConfigMap is exposed as
 #       environment variables.
+#   - subPath (string)
+#     : For ConfigMaps mounted as a volume, specify the sub path on the volume system where the config values will be
+#       available.  Optional when the ConfigMap is exposed as a volume. Ignored when the ConfigMap is exposed as
+#       environment variables.
 #   - items (map[ConfigMapItem])
 #     : Specify how each ConfigMap value should be made available. The keys are the key of the ConfigMap that you wish
 #       to configure, while the value is another map that controls how that key should be exposed. Required when the

test/k8s_service_config_injection_template_test.go

@@ -162,7 +162,7 @@ func TestK8SServiceEnvironmentConfigMapAddsEnvVarsToPod(t *testing.T) {
 //   dbsettings:
 //     as: volume
 //     mountPath: /etc/db
-func TestK8SServiceVolumeConfigMapAddsVolumeAndVolumeMountToPod(t *testing.T) {
+func TestK8SServiceVolumeConfigMapAddsVolumeAndVolumeMountWithoutSubPathToPod(t *testing.T) {
 	t.Parallel()
 
 	deployment := renderK8SServiceDeploymentWithSetValues(
@@ -191,6 +191,47 @@ func TestK8SServiceVolumeConfigMapAddsVolumeAndVolumeMountToPod(t *testing.T) {
 	volumeMount := appContainer.VolumeMounts[0]
 	assert.Equal(t, volumeMount.Name, "dbsettings-volume")
 	assert.Equal(t, volumeMount.MountPath, "/etc/db")
+	assert.Empty(t, volumeMount.SubPath)
+}
+
+// Test that setting the `configMaps` input value with volume include the volume mount and subpath for the config map
+// We test by injecting to configMaps:
+// configMaps:
+//   dbsettings:
+//     as: volume
+//     mountPath: /etc/db/host.txt
+//     subPath: host.xt
+func TestK8SServiceVolumeConfigMapAddsVolumeAndVolumeMountWithSubPathToPod(t *testing.T) {
+	t.Parallel()
+
+	deployment := renderK8SServiceDeploymentWithSetValues(
+		t,
+		map[string]string{
+			"configMaps.dbsettings.as":        "volume",
+			"configMaps.dbsettings.mountPath": "/etc/db/host.txt",
+			"configMaps.dbsettings.subPath":   "host.txt",
+		},
+	)
+
+	// Verify that there is only one container and only one volume
+	renderedPodContainers := deployment.Spec.Template.Spec.Containers
+	require.Equal(t, len(renderedPodContainers), 1)
+	appContainer := renderedPodContainers[0]
+	renderedPodVolumes := deployment.Spec.Template.Spec.Volumes
+	require.Equal(t, len(renderedPodVolumes), 1)
+	podVolume := renderedPodVolumes[0]
+
+	// Check that the pod volume is a configmap volume
+	assert.Equal(t, podVolume.Name, "dbsettings-volume")
+	require.NotNil(t, podVolume.ConfigMap)
+	assert.Equal(t, podVolume.ConfigMap.Name, "dbsettings")
+
+	// Check that the pod volume will be mounted
+	require.Equal(t, len(appContainer.VolumeMounts), 1)
+	volumeMount := appContainer.VolumeMounts[0]
+	assert.Equal(t, volumeMount.Name, "dbsettings-volume")
+	assert.Equal(t, volumeMount.MountPath, "/etc/db/host.txt")
+	assert.Equal(t, volumeMount.SubPath, "host.txt")
 }
 
 // Test that setting the `configMaps` input value with volume and individual file mount paths will set the appropriate