def _releaseId(self, msgId):
        """
        Release message ID to the pool.

        @param msgId: message ID, no longer on the wire
        @type msgId: C{str}
        """
        self._uuids.append(msgId)
        if len(self._uuids) > 2 * self.UUID_POOL_GEN_SIZE:
            self._uuids[-self.UUID_POOL_GEN_SIZE:] = []
Release message ID to the pool.

        @param msgId: message ID, no longer on the wire
        @type msgId: C{str}