chore: adds data structures for container dependency (#2393)

Incorporates data structures for container dependencies to address #2175.

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Author: xar-tol

internal/pkg/manifest/workload.go

@@ -60,9 +60,10 @@ type Workload struct {
 
 // Image represents the workload's container image.
 type Image struct {
-	Build        BuildArgsOrString `yaml:"build"`       // Build an image from a Dockerfile.
-	Location     *string           `yaml:"location"`    // Use an existing image instead.
-	DockerLabels map[string]string `yaml:"labels,flow"` // Apply Docker labels to the container at runtime.
+	Build        BuildArgsOrString `yaml:"build"`           // Build an image from a Dockerfile.
+	Location     *string           `yaml:"location"`        // Use an existing image instead.
+	DockerLabels map[string]string `yaml:"labels,flow"`     // Apply Docker labels to the container at runtime.
+	DependsOn    map[string]string `yaml:"depends_on,flow"` // Add any sidecar dependencies.
 }
 
 // ImageWithPort represents a container image with an exposed port.
@@ -375,6 +376,7 @@ type SidecarConfig struct {
 	Secrets      map[string]string   `yaml:"secrets"`
 	MountPoints  []SidecarMountPoint `yaml:"mount_points"`
 	DockerLabels map[string]string   `yaml:"labels"`
+	DependsOn    map[string]string   `yaml:"depends_on"`
 }
 
 // TaskConfig represents the resource boundaries and environment variables for the containers in the task.

internal/pkg/manifest/workload_test.go

@@ -579,3 +579,59 @@ network:
 		})
 	}
 }
+
+func TestDependency_UnmarshalYAML(t *testing.T) {
+	testCases := map[string]struct {
+		inContent []byte
+
+		wantedStruct Image
+		wantedError  error
+	}{
+		"Unspecified optional dependencies don't appear in image": {
+			inContent:    []byte(``),
+			wantedStruct: Image{},
+		},
+		"Empty dependencies don't appear in image": {
+			inContent:    []byte(`depends_on:`),
+			wantedStruct: Image{},
+		},
+		"Error when unmarshallable": {
+			inContent: []byte(`depends_on:
+    frontend: coolwebsite
+  sidecar2: wheels`),
+			wantedStruct: Image{
+				DependsOn: map[string]string{
+					"frontend": "coolwebsite",
+					"sidecar2": "wheels",
+				},
+			},
+			wantedError: errors.New("yaml: line 2: did not find expected key"),
+		},
+		"Valid yaml specified": {
+			inContent: []byte(`depends_on:
+  frontend: coolwebsite
+  sidecar2: wheels`),
+			wantedStruct: Image{
+				DependsOn: map[string]string{
+					"frontend": "coolwebsite",
+					"sidecar2": "wheels",
+				},
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			i := Image{}
+
+			err := yaml.Unmarshal(tc.inContent, &i)
+
+			if tc.wantedError != nil {
+				require.EqualError(t, err, tc.wantedError.Error())
+			} else {
+				require.NoError(t, err)
+				require.Equal(t, tc.wantedStruct.DependsOn, i.DependsOn)
+			}
+		})
+	}
+}

internal/pkg/template/workload.go

@@ -90,6 +90,7 @@ type SidecarOpts struct {
 	Secrets      map[string]string
 	MountPoints  []*MountPoint
 	DockerLabels map[string]string
+	DependsOn    map[string]string
 }
 
 // StorageOpts holds data structures for rendering Volumes and Mount Points
@@ -235,6 +236,7 @@ type WorkloadOpts struct {
 	Command            []string
 	DomainAlias        string
 	DockerLabels       map[string]string
+	DependsOn          map[string]string
 
 	// Additional options for service templates.
 	WorkloadType        string

templates/workloads/partials/cf/sidecars.yml

@@ -49,6 +49,13 @@
   DockerLabels:{{range $name, $value := $sidecar.DockerLabels}}
     {{$name | printf "%q"}}: {{$value | printf "%q"}}{{end}}
 {{- end -}}
+{{- if $sidecar.DependsOn}}
+  DependsOn:
+  {{- range $name, $conditionFrom := $sidecar.DependsOn}}
+    - Condition: {{$conditionFrom}}
+      ContainerName: {{$name}}
+  {{- end}}
+{{- end}}
 {{- if $sidecar.CredsParam}}
   RepositoryCredentials:
     CredentialsParameter: {{$sidecar.CredsParam}}

templates/workloads/partials/cf/workload-container.yml

@@ -11,6 +11,13 @@
   DockerLabels:{{range $name, $value := .DockerLabels}}
     {{$name | printf "%q"}}: {{$value | printf "%q"}}{{end}}
 {{- end}}
+{{- if .DependsOn}}
+  DependsOn:
+  {{- range $name, $conditionFrom := .DependsOn}}
+    - Condition: {{$conditionFrom}}
+      ContainerName: {{$name}}
+  {{- end}}
+{{- end}}
 {{- if eq .WorkloadType "Load Balanced Web Service"}}
   PortMappings:
     - ContainerPort: !Ref ContainerPort