nfs-server: learn the backup holder's data paths from disk-load's readings, not the controller's data (issue 1955, ADR 0571 clause 3)

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

@@ -14,13 +14,12 @@ package main
 // been read, what is exported stays exported and the status says the list is not known: the bus being
 // slow is no reason to take the library away, and the look below still guards against a repository.
 //
-// The parsing of mesh-controller.data's answer is a small copy of the mounts module's (DataFrom). Shared
-// code belongs in mesh-sdk: moving both there is mesh-sdk issue 13.
 
 import (
 	"encoding/json"
 	"fmt"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
 	"os"
 	"path"
 	"sort"
@@ -48,10 +47,10 @@ type BackupFromBus struct {
 }
 
 // BackupFrom reads the holder of node-backup on one machine from the placement seat's state of who holds which seat
-// (novox/hq ADR 0571 clause 4), and the paths that module keeps data in on that machine from mesh-controller.data's
-// answer. A machine whose backup seat nobody holds, and an answer with no data list, are errors: never an empty list
-// read as "nothing to fear".
-func BackupFrom(machine string, keys map[string][]byte, data json.RawMessage) (string, []string, error) {
+// (novox/hq ADR 0571 clause 4), and the paths that module keeps data in on that machine from disk-load's readings
+// (clause 3). A machine whose backup seat nobody holds, and no readings at all, are errors: never an empty list read as
+// "nothing to fear".
+func BackupFrom(machine string, keys map[string][]byte, readings []health.Reading) (string, []string, error) {
 	holders, err := delivery.HoldersOf(keys, BackupSeat, machine)
 	if err != nil {
 		return "", nil, err
@@ -65,36 +64,27 @@ func BackupFrom(machine string, keys map[string][]byte, data json.RawMessage) (s
 	if holder == "" {
 		return "", nil, fmt.Errorf("no module holds %s on %s", BackupSeat, machine)
 	}
-	var d struct {
-		Answer *struct {
-			Data *[]struct {
-				Machine string `json:"machine"`
-				Module  string `json:"module"`
-				Path    string `json:"path"`
-			} `json:"data"`
-		} `json:"answer"`
-	}
-	if err := json.Unmarshal(data, &d); err != nil || d.Answer == nil || d.Answer.Data == nil {
-		return "", nil, fmt.Errorf("the controller's data answer holds no data list (%v)", err)
+	if len(readings) == 0 {
+		return "", nil, fmt.Errorf("disk-load keeps no reading of this machine's data yet")
 	}
 	var paths []string
-	for _, item := range *d.Answer.Data {
-		if item.Module == holder && (item.Machine == "" || item.Machine == machine) && path.IsAbs(item.Path) {
-			paths = append(paths, path.Clean(item.Path))
+	for _, r := range readings {
+		if r.Module == holder && (r.Node == "" || r.Node == machine) && path.IsAbs(r.Path) {
+			paths = append(paths, path.Clean(r.Path))
 		}
 	}
 	sort.Strings(paths)
 	return holder, paths, nil
 }
 
-// TakeBackup asks the controller over the bus, as the module, through the runtime.
+// TakeBackup reads the bus, as the module, through the runtime.
 func (m *Machine) TakeBackup(machine string) {
-	m.TakeBackupWith(machine, askBus, seatHolderKeys)
+	m.TakeBackupWith(machine, readingsOf, seatHolderKeys)
 }
 
 // TakeBackupWith is TakeBackup with the ask and the reading of the seat-holders state given, for tests. A failed ask keeps the last holder and
 // paths and adds why.
-func (m *Machine) TakeBackupWith(machine string, ask func(key string, body any) (json.RawMessage, error),
+func (m *Machine) TakeBackupWith(machine string, readings func(node string) ([]health.Reading, error),
 	holderKeys func() (map[string][]byte, error)) {
 	var last BackupFromBus
 	if text, err := m.Read(BackupFile); err == nil {
@@ -104,9 +94,9 @@ func (m *Machine) TakeBackupWith(machine string, ask func(key string, body any)
 	next.Looked = m.Now().UTC().Format(time.RFC3339)
 	next.Error = ""
 	seats, err := holderKeys()
-	var data json.RawMessage
+	var data []health.Reading
 	if err == nil {
-		data, err = ask("seat:mesh-controller.data", map[string]any{"machine": machine})
+		data, err = readings(machine)
 	}
 	if err == nil {
 		var holder string

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

@@ -4,6 +4,8 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/health"
 	"strings"
 	"testing"
 	"time"
@@ -82,7 +84,7 @@ func TestWithoutTheBackupListTheExportsStayAndItIsSaid(t *testing.T) {
 
 func TestBackupFromTheSeatsAndTheData(t *testing.T) {
 	seats := backupHolders("ace", "restic")
-	data := json.RawMessage(`{"answer":{"data":[{"machine":"ace","module":"restic","item":"repository","path":"/storage/restic"},{"machine":"ace","module":"restic","item":"state","path":"/var/lib/restic"},{"machine":"ace","module":"plex","item":"data","path":"/mnt/plex/data"}]},"ok":true}`)
+	data := readingsOfPaths("ace", map[string]string{"restic/repository": "/storage/restic", "restic/state": "/var/lib/restic", "plex/data": "/mnt/plex/data"})
 	holder, paths, err := BackupFrom("ace", seats, data)
 	if err != nil || holder != "restic" || strings.Join(paths, " ") != "/storage/restic /var/lib/restic" {
 		t.Errorf("got %q %v %v", holder, paths, err)
@@ -90,8 +92,8 @@ func TestBackupFromTheSeatsAndTheData(t *testing.T) {
 	if _, _, err := BackupFrom("g14", seats, data); err == nil {
 		t.Errorf("a machine whose backup seat nobody holds is not said")
 	}
-	if _, _, err := BackupFrom("ace", seats, json.RawMessage(`{"ok":true}`)); err == nil {
-		t.Errorf("an answer with no data list reads as an empty list")
+	if _, _, err := BackupFrom("ace", seats, nil); err == nil {
+		t.Errorf("no readings read as an empty list")
 	}
 }
 
@@ -99,11 +101,11 @@ func TestBackupFromTheSeatsAndTheData(t *testing.T) {
 func TestAFailedAskKeepsTheLastBackupPaths(t *testing.T) {
 	f := newFake(t)
 	m := f.machine()
-	m.TakeBackupWith("ace", func(string, any) (json.RawMessage, error) {
+	m.TakeBackupWith("ace", func(string) ([]health.Reading, error) {
 		return nil, errors.New("no responders")
 	}, noHolders)
 	f.backup("restic", "/storage/restic")
-	m.TakeBackupWith("ace", func(string, any) (json.RawMessage, error) {
+	m.TakeBackupWith("ace", func(string) ([]health.Reading, error) {
 		return nil, errors.New("timeout")
 	}, func() (map[string][]byte, error) { return backupHolders("ace", "restic"), nil })
 	var b BackupFromBus
@@ -152,12 +154,12 @@ func TestAStaleOrUnknownBackupListIsSaidWithItsAge(t *testing.T) {
 		t.Errorf("an unknown backup list is not a warning in the health: %+v", h)
 	}
 
-	ok := func(key string, body any) (json.RawMessage, error) {
-		return json.RawMessage(`{"answer":{"data":[{"machine":"hs","module":"restic","path":"/srv/restic"}]}}`), nil
+	ok := func(string) ([]health.Reading, error) {
+		return readingsOfPaths("hs", map[string]string{"restic/repository": "/srv/restic"}), nil
 	}
 	m.TakeBackupWith("hs", ok, func() (map[string][]byte, error) { return backupHolders("hs", "restic"), nil })
 	now = now.Add(2 * time.Hour)
-	m.TakeBackupWith("hs", func(string, any) (json.RawMessage, error) { return nil, errors.New("the bus did not answer") },
+	m.TakeBackupWith("hs", func(string) ([]health.Reading, error) { return nil, errors.New("the bus did not answer") },
 		func() (map[string][]byte, error) { return backupHolders("hs", "restic"), nil })
 	s := m.Pass(context.Background(), nil)
 	said := strings.Join(append(append([]string{}, s.Said...), s.Warnings...), "\n")
@@ -177,3 +179,13 @@ func backupHolders(node, module string) map[string][]byte {
 }
 
 func noHolders() (map[string][]byte, error) { return nil, errors.New("the state is not read yet") }
+
+// readingsOfPaths is disk-load's readings of one node's items, by "<module>/<item>", each at its path.
+func readingsOfPaths(node string, items map[string]string) []health.Reading {
+	var out []health.Reading
+	for k, p := range items {
+		module, item, _ := strings.Cut(k, "/")
+		out = append(out, health.Reading{V: 1, Node: node, PlacedDataItem: catalogue.PlacedDataItem{Module: module, ID: item, Path: p}})
+	}
+	return out
+}

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

@@ -4,7 +4,7 @@ package main
 
 import (
 	"context"
-	"encoding/json"
+	"git.novox.be/novox/mesh-sdk/go/health"
 	"strings"
 	"testing"
 )
@@ -63,12 +63,10 @@ func TestAFailedReloadIsTriedAgainWhenNothingElseAsks(t *testing.T) {
 	}
 }
 
-func TestBackupFromRefusesAnAnswerWithoutADataList(t *testing.T) {
+func TestBackupFromRefusesNoReadingsAtAll(t *testing.T) {
 	seats := backupHolders("ace", "restic")
-	for _, data := range []string{`{"answer":{}}`, `{"answer":{"data":null}}`} {
-		if _, paths, err := BackupFrom("ace", seats, json.RawMessage(data)); err == nil {
-			t.Errorf("%s was read as the empty list %v: never \"nothing to fear\"", data, paths)
-		}
+	if _, paths, err := BackupFrom("ace", seats, []health.Reading{}); err == nil {
+		t.Errorf("no readings were read as the empty list %v: never \"nothing to fear\"", paths)
 	}
 }
 

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

@@ -16,11 +16,13 @@ import (
 	"os"
 	"os/signal"
 	"sort"
+	"strings"
 	"syscall"
 	"time"
 
 	stdio "git.novox.be/novox/mesh-sdk/go"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
 )
 
 // ExportsState is the state the exports are kept in on the bus; MountsState the `mounts` modules' state,
@@ -89,9 +91,30 @@ func ShareExports(m *Machine) {
 	}
 }
 
-// askBus calls a seat's verb over the bus as this module, through the runtime.
-func askBus(key string, body any) (json.RawMessage, error) {
-	return stdio.Ask(key, body)
+// readingsOf reads disk-load's readings of one machine's data items, every key `<node>.<module>.<item>`.
+func readingsOf(node string) ([]health.Reading, error) {
+	state := stdio.State(health.ReadingsRead)
+	names, err := state.Keys()
+	if err != nil {
+		return nil, err
+	}
+	var out []health.Reading
+	for _, k := range names {
+		if !strings.HasPrefix(k, node+".") {
+			continue
+		}
+		e, err := state.Get(k)
+		if err != nil {
+			return nil, err
+		}
+		if e == nil {
+			continue
+		}
+		if r, err := health.DecodeReading(e.Value); err == nil {
+			out = append(out, r)
+		}
+	}
+	return out, nil
 }
 
 // seatHolderKeys reads the placement seat's state of who holds which seat, every key.

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

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/json"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
 	"os"
 	"regexp"
 	"sort"
@@ -138,7 +139,7 @@ func TestTheManifestCarriesGrantsTheRosterTheWantsAndTheRemovalOrder(t *testing.
 	if err := json.Unmarshal([]byte(raw), &full); err != nil {
 		t.Fatal(err)
 	}
-	if len(full.Reads) != 2 || full.Reads[0] != delivery.SeatHoldersRead || full.Reads[1] != MountsState {
+	if len(full.Reads) != 3 || full.Reads[0] != health.ReadingsRead || full.Reads[1] != delivery.SeatHoldersRead || full.Reads[2] != MountsState {
 		t.Errorf("reads: %v", full.Reads)
 	}
 	roster := full.Facts["machines"]

modules/nfs-server/go.mod

@@ -2,4 +2,4 @@ module nfsserver
 
 go 1.26.0
 
-require git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029220947-f9a496d3e121
+require git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029221656-196c5b6af277

modules/nfs-server/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029220947-f9a496d3e121 h1:OsA1v6n736a7RqEV8Nkip8pf5ILMbzj0PWuKqcBOhK0=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029220947-f9a496d3e121/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029221656-196c5b6af277 h1:ajjsH4MWcx45MGYASjUSRQKhLzEringuk3TA0oxZRCU=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029221656-196c5b6af277/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/klauspost/compress v1.20.0 h1:a3C1ke2ohxFymNlb2HWAHjDeKCI90scRskErZkR0ezA=
 github.com/klauspost/compress v1.20.0/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
 github.com/nats-io/nats.go v1.54.0 h1:vsXoOxjHp/GmPUN+EcI7uOf/uB+iAP+kEsAFNQN0yzA=

modules/nfs-server/module.json

@@ -48,12 +48,10 @@
     }
   ],
   "reads": [
+    "disk-load.readings",
     "mesh-delivery-assigner.seat-holders",
     "mounts.shares"
   ],
-  "invokes": [
-    "seat:mesh-controller.data"
-  ],
   "config": {
     "shares": {
       "type": "string",