CAT-RD9: nfs-server asks the assigner's seat-holders once and follows its events, no reads

modules/nfs-server/cmd/nfs-server/main.go

@@ -23,6 +23,8 @@ import (
 	stdio "git.novox.be/novox/mesh-sdk/go"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/health"
+
+	"git.novox.be/novox/mesh-delivery/sdk/views"
 )
 
 // ExportsState is the state the exports are kept in on the bus; MountsState the `mounts` modules' state,
@@ -47,8 +49,10 @@ func main() {
 		return
 	}
 	m := Here()
+	seats.Follow(delivery.AssignerModule, delivery.SeatHoldersState, SeatHoldersTool)
+	seats.Start(context.Background())
 	go ShareExports(m)
-	if err := stdio.Serve("", Tools(m)); err != nil {
+	if err := stdio.Serve("", append(Tools(m), seats.Tools("nfs_server")...)); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
@@ -117,25 +121,15 @@ func readingsOf(node string) ([]health.Reading, error) {
 	return out, nil
 }
 
-// seatHolderKeys reads the placement seat's state of who holds which seat, every key.
-func seatHolderKeys() (map[string][]byte, error) {
-	state := stdio.State(delivery.SeatHoldersRead)
-	names, err := state.Keys()
-	if err != nil {
-		return nil, err
-	}
-	keys := map[string][]byte{}
-	for _, k := range names {
-		e, err := state.Get(k)
-		if err != nil {
-			return nil, err
-		}
-		if e != nil {
-			keys[k] = e.Value
-		}
-	}
-	return keys, nil
-}
+// SeatHoldersTool is the assigner's read tool of who holds which seat, which the manifest invokes (ADR 0615).
+const SeatHoldersTool = delivery.AssignerModule + ".assigner_read_seat_holders"
+
+// seats is the picture of the placement seat's state of who holds which seat: asked of the assigner once and followed by
+// its events, never read from its state (ADR 0615).
+var seats = &views.Reader{Module: "nfs-server", Logf: func(f string, a ...any) { fmt.Fprintf(os.Stderr, "nfs-server: "+f+"\n", a...) }}
+
+// seatHolderKeys is the placement seat's state of who holds which seat, every key.
+func seatHolderKeys() (map[string][]byte, error) { return seats.Values(delivery.SeatHoldersRead) }
 
 // TakeWants reads every node's `mounts` state from the bus and writes what is asked of this machine to
 // the wants file, for the root process. When the bus does not answer, the last wants stay.

modules/nfs-server/cmd/nfs-server/manifest_test.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"encoding/json"
-	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/health"
 	"os"
 	"regexp"
@@ -132,16 +131,22 @@ func TestTheDefinitionNamesNoFolderNoMachineAndGivesTheSharesNoDefault(t *testin
 func TestTheManifestCarriesGrantsTheRosterTheWantsAndTheRemovalOrder(t *testing.T) {
 	m, raw := readManifest(t)
 	var full struct {
-		Reads  []string                     `json:"reads"`
-		Facts  map[string]map[string]string `json:"facts"`
-		Config map[string]map[string]any    `json:"config"`
+		Reads    []string                     `json:"reads"`
+		Invokes  []string                     `json:"invokes"`
+		Consumes []string                     `json:"consumes"`
+		Facts    map[string]map[string]string `json:"facts"`
+		Config   map[string]map[string]any    `json:"config"`
 	}
 	if err := json.Unmarshal([]byte(raw), &full); err != nil {
 		t.Fatal(err)
 	}
-	if len(full.Reads) != 3 || full.Reads[0] != health.ReadingsRead || full.Reads[1] != delivery.SeatHoldersRead || full.Reads[2] != MountsState {
+	// The assigner's seat-holders is asked once and followed by its events (ADR 0615), no longer read.
+	if len(full.Reads) != 2 || full.Reads[0] != health.ReadingsRead || full.Reads[1] != MountsState {
 		t.Errorf("reads: %v", full.Reads)
 	}
+	if len(full.Invokes) != 1 || full.Invokes[0] != SeatHoldersTool || len(full.Consumes) != 1 || full.Consumes[0] != "mesh-delivery-assigner.views.seat-holders" {
+		t.Errorf("invokes %v, consumes %v", full.Invokes, full.Consumes)
+	}
 	roster := full.Facts["machines"]
 	if roster["path"] != RosterFile || !strings.Contains(roster["template"], "{{range .Machines}}{{.Name}} {{.Address}}") {
 		t.Errorf("the roster fact: %v", roster)

modules/nfs-server/module.json

@@ -49,7 +49,6 @@
   ],
   "reads": [
     "disk-load.readings",
-    "mesh-delivery-assigner.seat-holders",
     "mounts.shares"
   ],
   "config": {
@@ -188,5 +187,11 @@
         "from": "files"
       }
     ]
-  }
+  },
+  "invokes": [
+    "mesh-delivery-assigner.assigner_read_seat_holders"
+  ],
+  "consumes": [
+    "mesh-delivery-assigner.views.seat-holders"
+  ]
 }