db: don't configure WAL failover if ReadOnly

In ReadOnly mode, don't bother to set up the WAL failover manager if not in
ReadOnly mode. In ReadOnly mode we'll never create a WAL, so there's no need to
set up the failover manager. The failover manager writes a secondary identifier
file during initialization.

Author: jbowens

open.go

@@ -351,7 +351,7 @@ func Open(dirname string, opts *Options) (db *DB, err error) {
 			return nil, err
 		}
 	}
-	if opts.WALFailover != nil {
+	if !opts.ReadOnly && opts.WALFailover != nil {
 		walOpts.Secondary = opts.WALFailover.Secondary
 		// Lock the secondary WAL directory, if distinct from the data directory
 		// and primary WAL directory.