ass="identifier">ptime</span> <span class="identifier">m_last_store_time</span><span class="special">;</span>
    <span class="comment">// The collected data writing interval</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">time_duration</span> <span class="identifier">m_write_interval</span><span class="special">;</span>

<span class="keyword">public</span><span class="special">:<