A module's state on the bus: buckets from the catalogue, grants, membership (novox/hq ADR 0201)

A manifest names the state it keeps (state) and reads (reads); the controller
asserts a key-value bucket per name on every raise, grants owners write and
readers read (measured against a running server), issues each assignment its
buckets in the membership, and reports buckets nothing declares without
removing them.

internal/broker/jetstream.go

@@ -1,6 +1,7 @@
 package broker
 
 import (
+	"context"
 	"crypto/sha256"
 	"crypto/tls"
 	"crypto/x509"
@@ -12,6 +13,7 @@ import (
 	"time"
 
 	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
 )
 
 // The JetStream side of the controller: the one place the mesh's streams and consumers are
@@ -316,3 +318,50 @@ func retentionOf(r Retention) nats.RetentionPolicy {
 		return nats.LimitsPolicy
 	}
 }
+
+// EnsureBucket creates a module's bucket if it is absent and brings its options to match if it is
+// present (novox/hq ADR 0201).
+//
+// **An update, never a delete and recreate**, for the reason a stream is updated: recreating
+// discards what the bucket holds, and what a module's state holds is data. The mesh's caps are
+// asserted with the owner's options, so a bucket made by hand converges to them.
+func (j *JetStream) EnsureBucket(b Bucket) error {
+	history := b.History
+	if history == 0 {
+		history = 1
+	}
+	js, err := jetstream.New(j.conn)
+	if err != nil {
+		return err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	if _, err := js.CreateOrUpdateKeyValue(ctx, jetstream.KeyValueConfig{
+		Bucket:       b.Bucket(),
+		Description:  b.Why(),
+		History:      uint8(history),
+		TTL:          time.Duration(b.TTLSeconds) * time.Second,
+		MaxValueSize: StateMaxValueBytes,
+		MaxBytes:     StateMaxBytes,
+		Storage:      jetstream.FileStorage,
+	}); err != nil {
+		return fmt.Errorf("asserting bucket %s: %w", b.Bucket(), err)
+	}
+	return nil
+}
+
+// BucketNames is every key-value bucket on the server, the mesh's and anybody else's.
+func (j *JetStream) BucketNames() ([]string, error) {
+	js, err := jetstream.New(j.conn)
+	if err != nil {
+		return nil, err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	lister := js.KeyValueStoreNames(ctx)
+	var out []string
+	for name := range lister.Name() {
+		out = append(out, name)
+	}
+	return out, lister.Error()
+}