public boolean completeSyncFuture(
        ClassicGroupMember member,
        SyncGroupResponseData response
    ) {
        if (member.isAwaitingSync()) {
            member.awaitingSyncFuture().complete(response);
            member.setAwaitingSyncFuture(null);
            return true;
        }
        return false;
    }
Complete a member's sync future.

@param member    the member.
@param response  the sync response to complete the future with.
@return true if a sync future actually completes.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/classic/ClassicGroup.java