@Override
    public GuacamoleSession remove(String authToken) {

        // There are no null auth tokens
        if (authToken == null)
            return null;

        // Attempt to retrieve only if non-null
        return sessionMap.remove(authToken);

    }
Iterates through all active sessions, evicting those sessions which
are beyond the session timeout, or are marked as invalid. Internal
errors which would otherwise stop the session eviction process are
caught, logged, and the process is allowed to proceed.
guacamole/src/main/java/org/apache/guacamole/rest/auth/HashTokenSessionMap.java