Ask over mesh-sdk's composition: a question makes no pair credential and reads the mesh once (issue 1387)

The callers that only ask (status, the doctor's probes, facts, bindings, data, acts, nodes show, images, release, recorded push, consumers) resolve through resolveNode and compose through composeQuestion, over one Input read per operation (withInputCache). A question composes with Reading or Foreseeing and never calls PairCredential's maker: the credential a send would make is named, and perform makes it on a send.

cmd/mesh-controller/data.go

@@ -152,6 +152,8 @@ type consumerCopy struct {
 
 // probeData is D13.
 func probeData(ctx context.Context, d *doctor) ([]conditions.Observation, error) {
+	// One reading of the mesh for every machine this looks at.
+	ctx = withInputCache(ctx)
 	if d.js == nil {
 		return nil, errors.New("no bus to ask the machines over")
 	}
@@ -180,7 +182,7 @@ func probeData(ctx context.Context, d *doctor) ([]conditions.Observation, error)
 	}
 	var machines []*machine
 	for _, n := range nodes {
-		plan, _, err := planFor(ctx, open, n.Name)
+		plan, _, err := resolveNode(ctx, open, n.Name)
 		if err != nil {
 			if ctx.Err() != nil {
 				return nil, ctx.Err()
@@ -849,7 +851,7 @@ func deleteRetiredData(ctx context.Context, conn *nats.Conn, open *stores, r inv
 		return fmt.Errorf("%s of %s on %s was never measured, so where it is was never said; nothing was deleted",
 			r.Item, r.Module, r.Machine)
 	}
-	if plan, _, err := planFor(ctx, open, r.Machine); err == nil {
+	if plan, _, err := resolveNode(ctx, open, r.Machine); err == nil {
 		for _, m := range plan.Modules {
 			if _, still := m.DataItem(r.Item); still && m.Module == r.Module {
 				return fmt.Errorf("%s runs on %s again and declares %s: it is not retired any more. Nothing was done",