feat: publish assignment rosters atomically

server/store/assignment_sql.go

@@ -86,6 +86,44 @@ func SaveAssignment(ctx context.Context, db *sql.DB, assignment DurableAssignmen
 	return nil
 }
 
+// SaveAssignments publishes a complete signed roster atomically. Assignment
+// readiness is a match boundary: exposing only some players would let the
+// control plane tell different participants incompatible stories after a
+// transient database failure.
+func SaveAssignments(ctx context.Context, db *sql.DB, assignments []DurableAssignment) error {
+	if db == nil || len(assignments) == 0 {
+		return fmt.Errorf("invalid assignment batch")
+	}
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+	seen := make(map[string]struct{}, len(assignments))
+	for _, assignment := range assignments {
+		if err := validateDurableAssignment(assignment); err != nil {
+			return err
+		}
+		key := assignment.MatchID + "\x00" + assignment.PlayerID
+		if _, ok := seen[key]; ok {
+			return fmt.Errorf("duplicate assignment in batch")
+		}
+		seen[key] = struct{}{}
+		result, err := tx.ExecContext(ctx, AssignmentUpsertSQL, assignment.MatchID, assignment.PlayerID, assignment.AllocationID, assignment.ServerID, assignment.Slot, assignment.Region, assignment.ClientBuild, assignment.ProtocolVersion, assignment.Transport, assignment.Endpoint, assignment.JoinAuthorisation, assignment.ManifestDigest, assignment.ExpiresAt, assignment.Revision)
+		if err != nil {
+			return err
+		}
+		changed, err := result.RowsAffected()
+		if err != nil {
+			return err
+		}
+		if changed != 1 {
+			return fmt.Errorf("assignment persistence conflict")
+		}
+	}
+	return tx.Commit()
+}
+
 func GetAssignment(ctx context.Context, db *sql.DB, playerID, matchID string, now time.Time) (DurableAssignment, error) {
 	if db == nil || playerID == "" || matchID == "" || now.IsZero() {
 		return DurableAssignment{}, fmt.Errorf("invalid assignment recovery arguments")

server/store/assignment_sql_test.go

@@ -29,3 +29,12 @@ func TestAssignmentStoreRejectsInvalidRecoveryAndManifestInputs(t *testing.T) {
 		t.Fatal("out-of-range slot accepted")
 	}
 }
+
+func TestAssignmentStoreRejectsInvalidBatches(t *testing.T) {
+	if err := SaveAssignments(nil, nil, nil); err == nil {
+		t.Fatal("nil database/empty batch accepted")
+	}
+	if err := SaveAssignments(nil, nil, []DurableAssignment{{MatchID: "match-1", PlayerID: "player-1"}}); err == nil {
+		t.Fatal("invalid assignment batch accepted")
+	}
+}