memoise shared top-level renderers

and add a comment indicating non-memoisation of other, not shared
top-level renderers.

This memoisation is effective when the browser requests multiple
topologies for the same report.

render/container.go

@@ -182,11 +182,11 @@ func (r containerWithImageNameRenderer) Render(rpt report.Report, dct Decorator)
 
 // ContainerWithImageNameRenderer is a Renderer which produces a container
 // graph where the ranks are the image names, not their IDs
-var ContainerWithImageNameRenderer = containerWithImageNameRenderer{ContainerRenderer}
+var ContainerWithImageNameRenderer = Memoise(containerWithImageNameRenderer{ContainerRenderer})
 
 // ContainerImageRenderer is a Renderer which produces a renderable container
 // image graph by merging the container graph and the container image topology.
-var ContainerImageRenderer = FilterEmpty(report.Container,
+var ContainerImageRenderer = Memoise(FilterEmpty(report.Container,
 	MakeMap(
 		MapContainerImage2Name,
 		MakeReduce(
@@ -197,10 +197,12 @@ var ContainerImageRenderer = FilterEmpty(report.Container,
 			SelectContainerImage,
 		),
 	),
-)
+))
 
 // ContainerHostnameRenderer is a Renderer which produces a renderable container
 // by hostname graph..
+//
+// not memoised
 var ContainerHostnameRenderer = FilterEmpty(report.Container,
 	MakeReduce(
 		MakeMap(

render/ecs.go

@@ -5,7 +5,7 @@ import (
 )
 
 // ECSTaskRenderer is a Renderer for Amazon ECS tasks.
-var ECSTaskRenderer = ConditionalRenderer(renderECSTopologies,
+var ECSTaskRenderer = Memoise(ConditionalRenderer(renderECSTopologies,
 	renderParents(
 		report.Container, []string{report.ECSTask}, UnmanagedID,
 		MakeFilter(
@@ -13,9 +13,11 @@ var ECSTaskRenderer = ConditionalRenderer(renderECSTopologies,
 			ContainerWithImageNameRenderer,
 		),
 	),
-)
+))
 
 // ECSServiceRenderer is a Renderer for Amazon ECS services.
+//
+// not memoised
 var ECSServiceRenderer = ConditionalRenderer(renderECSTopologies,
 	renderParents(
 		report.ECSTask, []string{report.ECSService}, "",

render/host.go

@@ -6,6 +6,8 @@ import (
 
 // HostRenderer is a Renderer which produces a renderable host
 // graph from the host topology.
+//
+// not memoised
 var HostRenderer = MakeReduce(
 	MakeMap(
 		MapEndpoint2Host,

render/pod.go

@@ -42,7 +42,7 @@ func isPauseContainer(n report.Node) bool {
 
 // PodRenderer is a Renderer which produces a renderable kubernetes
 // graph by merging the container graph and the pods topology.
-var PodRenderer = ConditionalRenderer(renderKubernetesTopologies,
+var PodRenderer = Memoise(ConditionalRenderer(renderKubernetesTopologies,
 	MakeFilter(
 		func(n report.Node) bool {
 			state, ok := n.Latest.Lookup(kubernetes.State)
@@ -65,10 +65,12 @@ var PodRenderer = ConditionalRenderer(renderKubernetesTopologies,
 			ConnectionJoin(MapPod2IP, selectPodsWithDeployments{}),
 		),
 	),
-)
+))
 
 // PodServiceRenderer is a Renderer which produces a renderable kubernetes services
 // graph by merging the pods graph and the services topology.
+//
+// not memoised
 var PodServiceRenderer = ConditionalRenderer(renderKubernetesTopologies,
 	renderParents(
 		report.Pod, []string{report.Service}, "",
@@ -80,6 +82,8 @@ var PodServiceRenderer = ConditionalRenderer(renderKubernetesTopologies,
 // Pods with no controller are mapped to 'Unmanaged'
 // We can't simply combine the rendered graphs of the high level objects as they would never
 // have connections to each other.
+//
+// not memoised
 var KubeControllerRenderer = ConditionalRenderer(renderKubernetesTopologies,
 	renderParents(
 		report.Pod, []string{report.Deployment, report.DaemonSet, report.StatefulSet, report.CronJob}, UnmanagedID,

render/process.go

@@ -74,10 +74,14 @@ func (r processWithContainerNameRenderer) Render(rpt report.Report, dct Decorato
 
 // ProcessWithContainerNameRenderer is a Renderer which produces a process
 // graph enriched with container names where appropriate
+//
+// not memoised
 var ProcessWithContainerNameRenderer = processWithContainerNameRenderer{ProcessRenderer}
 
 // ProcessNameRenderer is a Renderer which produces a renderable process
 // name graph by munging the progess graph.
+//
+// not memoised
 var ProcessNameRenderer = ConditionalRenderer(renderProcesses,
 	MakeMap(
 		MapProcess2Name,

render/swarm.go

@@ -5,6 +5,8 @@ import (
 )
 
 // SwarmServiceRenderer is a Renderer for Docker Swarm services
+//
+// not memoised
 var SwarmServiceRenderer = ConditionalRenderer(renderSwarmTopologies,
 	renderParents(
 		report.Container, []string{report.SwarmService}, UnmanagedID,

render/weave.go

@@ -6,6 +6,8 @@ import (
 )
 
 // WeaveRenderer is a Renderer which produces a renderable weave topology.
+//
+// not memoised
 var WeaveRenderer = MakeMap(
 	MapWeaveIdentity,
 	SelectOverlay,