A page reads the bucket bound once and stops at its time budget, one value at least; an unknown verb is told by its code (issue 1966)

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

node-tools/internal/bus/state.go

@@ -145,21 +145,72 @@ type StatePage struct {
 	Next    string       `json:"next,omitempty"`
 }
 
-// StatePage reads the values in key order after `after` in one pass, as many as fit maxBytes (each key and value) and
-// at least one, so a bundle asks one request for many values, where StateGet is one request each. It is a read like
-// StateGet: served to the owner and to every reader, and writes nothing. Next is the last key given when more follow.
-func (c *Conn) StatePage(module, name, after string, maxBytes int) (StatePage, error) {
-	keys, err := c.StateKeys(module, name)
+// StatePageBudget is the time a page spends reading when the asker names none: well under the 30 s a reader waits.
+const StatePageBudget = 10 * time.Second
+
+// PageClock is the time a page's budget counts by, replaced by a test.
+var PageClock = time.Now
+
+// StatePage reads the values in key order after `after` in one pass, as many as fit maxBytes (each key and value),
+// stopping when budget is spent, at least one value, so a bundle asks one request for many values, where StateGet
+// is one request each. Access is checked once and the bucket bound once. It is a read like StateGet: served to the
+// owner and to every reader, and writes nothing. Next is the last key given when more follow.
+func (c *Conn) StatePage(module, name, after string, maxBytes int, budget time.Duration) (StatePage, error) {
+	s, err := c.issuedState(module, name)
 	if err != nil {
 		return StatePage{}, err
 	}
+	if budget <= 0 {
+		budget = StatePageBudget
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), StateTimeout)
+	defer cancel()
+	var keys []string
+	var get func(key string) (*StateEntry, error)
+	if s.PerNode {
+		fam := c.family(s)
+		if keys, err = fam.Keys(ctx); err != nil {
+			return StatePage{}, err
+		}
+		get = func(key string) (*StateEntry, error) {
+			e, err := fam.Get(ctx, key)
+			if err != nil || e == nil {
+				return nil, err
+			}
+			return &StateEntry{Key: e.Key(), Value: valueOf(e.Value()), Revision: e.Revision(), At: e.Created().UTC()}, nil
+		}
+	} else {
+		kv, err := c.bucket(ctx, s)
+		if err != nil {
+			return StatePage{}, err
+		}
+		if keys, err = keysOf(ctx, kv); err != nil {
+			return StatePage{}, err
+		}
+		get = func(key string) (*StateEntry, error) {
+			e, err := kv.Get(ctx, key)
+			if errors.Is(err, jetstream.ErrKeyNotFound) {
+				return nil, nil
+			}
+			if err != nil {
+				return nil, err
+			}
+			return &StateEntry{Key: e.Key(), Value: valueOf(e.Value()), Revision: e.Revision(), At: e.Created().UTC()}, nil
+		}
+	}
+	sort.Strings(keys)
 	page := StatePage{Entries: []StateEntry{}}
+	started := PageClock()
 	size := 0
 	for _, k := range keys {
 		if after != "" && k <= after {
 			continue
 		}
-		e, err := c.StateGet(module, name, k)
+		if len(page.Entries) > 0 && PageClock().Sub(started) >= budget {
+			page.Next = page.Entries[len(page.Entries)-1].Key
+			break
+		}
+		e, err := get(k)
 		if err != nil {
 			return StatePage{}, err
 		}

node-tools/internal/runtime/runtime.go

@@ -1024,8 +1024,15 @@ type stateAsked struct {
 	// After and MaxBytes are a `page`'s start key and its size in keys and values (zero is a megabyte).
 	After    string `json:"after"`
 	MaxBytes int    `json:"max_bytes"`
+	// BudgetMS is the time a `page` may spend reading, in milliseconds (zero is the runtime's own, well under 30 s).
+	BudgetMS int `json:"budget_ms"`
 }
 
+// unknownVerb is an answer with the JSON-RPC code of a method not found, which a bundle tells by its code.
+type unknownVerb struct{ error }
+
+func (unknownVerb) ErrorCode() int { return -32601 }
+
 // State answers a bundle's `get`, `put`, `delete`, `keys`, `page`, `create`, `update`, `history` and `info` on its
 // module's state (ADR 0201, ADR 0259, ADR 0307); `create` and `put` take `ttl_seconds`, a key's own time to live,
 // whose end every watch hears as an `expire` (issue 1952). The runtime refuses, with the reason, a state the module was not issued and a write to one it only reads.
@@ -1051,7 +1058,7 @@ func (b *moduleBus) State(verb string, params json.RawMessage) (json.RawMessage,
 		if asked.MaxBytes <= 0 {
 			asked.MaxBytes = 1 << 20
 		}
-		page, err := conn.StatePage(b.module, asked.State, asked.After, asked.MaxBytes)
+		page, err := conn.StatePage(b.module, asked.State, asked.After, asked.MaxBytes, time.Duration(asked.BudgetMS)*time.Millisecond)
 		if err != nil {
 			return nil, err
 		}
@@ -1118,7 +1125,7 @@ func (b *moduleBus) State(verb string, params json.RawMessage) (json.RawMessage,
 		}
 		answer = map[string]any{"revision": revision}
 	default:
-		return nil, fmt.Errorf("the runtime answers no mesh/state.%s", verb)
+		return nil, unknownVerb{fmt.Errorf("the runtime answers no mesh/state.%s", verb)}
 	}
 	return json.Marshal(answer)
 }

node-tools/internal/runtime/state_history_test.go

@@ -132,8 +132,9 @@ func TestAKeysHistoryIsEveryValueKeptOldestFirst(t *testing.T) {
 	}
 }
 
-// A module the bucket was not issued to is refused its history with the reason, as it is a get.
-func TestAKeysHistoryIsRefusedToAModuleNotIssuedTheState(t *testing.T) {
+// A module the bucket was not issued to is refused its history, and a page, with the reason, as it is a get; the
+// owner and a reader are served a page.
+func TestAKeysHistoryAndAPageOfAStateAreServedToOwnerAndReaderAndRefusedToAModuleNotIssuedIt(t *testing.T) {
 	owner, reader, other := historyBuses(t)
 	if _, err := ask(owner, "put", map[string]any{"state": "issues", "key": "1", "value": 1}); err != nil {
 		t.Fatal(err)
@@ -179,6 +180,15 @@ func TestAKeysHistoryIsRefusedToAModuleNotIssuedTheState(t *testing.T) {
 			}
 		}
 	}
+	// A page stops when its time budget is spent, after one value at least, and says where it goes on.
+	step := time.Time{}
+	bus.PageClock = func() time.Time { step = step.Add(11 * time.Second); return step }
+	defer func() { bus.PageClock = time.Now }()
+	raw, err := ask(owner, "page", map[string]any{"state": "issues", "max_bytes": 1 << 20, "budget_ms": 10000})
+	var cut page
+	if err != nil || json.Unmarshal(raw, &cut) != nil || len(cut.Entries) != 1 || cut.Next != "1" {
+		t.Fatalf("a page past its budget = %s, %v", raw, err)
+	}
 	if _, err := ask(other, "page", map[string]any{"state": "issues.issues"}); err == nil {
 		t.Errorf("a page given to a module not issued the state")
 	}