深入redis内部--事件处理机制

1. redis事件的定义

maxfd; setsize; *events; *fired; */*定时器事件链表的首部*/ *apidata;

1.1 事件定义

/* File event structure */typedef struct aeFileEvent { int mask; /* one of AE_(READABLE|WRITABLE) */ aeFileProc *rfileProc; aeFileProc *wfileProc; void *clientData;} aeFileEvent;

/* Time event structure */typedef struct aeTimeEvent { long long id; /* time event identifier. */ long when_sec; /* seconds */ long when_ms; /* milliseconds */ aeTimeProc *timeProc; aeEventFinalizerProc *finalizerProc; void *clientData; struct aeTimeEvent *next;} aeTimeEvent;

/* A fired event */typedef struct aeFiredEvent { int fd; int mask;} aeFiredEvent;

2.封装事件处理的实现

3.事件处理的主函数

aeMain(aeEventLoop *->stop = (!eventLoop-> (eventLoop->beforesleep !=->

3.1事件处理过程

aeProcessEvents(aeEventLoop *eventLoop, processed =

</span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; Nothing to do? return ASAP </span><span style="color: #008000;"&gt;*/</span>
<span style="color: #0000ff;"&gt;if</span> (!(flags &amp; AE_TIME_EVENTS) &amp;&amp; !(flags &amp; AE_FILE_EVENTS)) <span style="color: #0000ff;"&gt;return</span> <span style="color: #800080;"&gt;0</span><span style="color: #000000;"&gt;;

</span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; Note that we want call select() even if there are no
 * file events to process as long as we want to process time
 * events,in order to sleep until the next time event is ready
 * to fire. </span><span style="color: #008000;"&gt;*/</span>
<span style="color: #0000ff;"&gt;if</span> (eventLoop->maxfd != -<span style="color: #800080;"&gt;1</span> ||<span style="color: #000000;"&gt;
    ((flags </span>&amp; AE_TIME_EVENTS) &amp;&amp; !(flags &amp;<span style="color: #000000;"&gt; AE_DONT_WAIT))) {
    </span><span style="color: #0000ff;"&gt;int</span><span style="color: #000000;"&gt; j;
    aeTimeEvent </span>*shortest =<span style="color: #000000;"&gt; NULL;
    </span><span style="color: #0000ff;"&gt;struct</span> timeval tv,*<span style="color: #000000;"&gt;tvp;

    </span><span style="color: #0000ff;"&gt;if</span> (flags &amp; AE_TIME_EVENTS &amp;&amp; !(flags &amp;<span style="color: #000000;"&gt; AE_DONT_WAIT))
        shortest </span>=<span style="color: #000000;"&gt; aeSearchNearestTimer(eventLoop);
    </span><span style="color: #0000ff;"&gt;if</span><span style="color: #000000;"&gt; (shortest) {
        </span><span style="color: #0000ff;"&gt;long</span><span style="color: #000000;"&gt; now_sec,now_ms;

        </span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; Calculate the time missing for the nearest
         * timer to fire. </span><span style="color: #008000;"&gt;*/</span><span style="color: #000000;"&gt;
        aeGetTime(</span>&amp;now_sec,&amp;<span style="color: #000000;"&gt;now_ms);
        tvp </span>= &amp;<span style="color: #000000;"&gt;tv;
        tvp</span>->tv_sec = shortest->when_sec -<span style="color: #000000;"&gt; now_sec;
        </span><span style="color: #0000ff;"&gt;if</span> (shortest->when_ms <<span style="color: #000000;"&gt; now_ms) {
            tvp</span>->tv_usec = ((shortest->when_ms+<span style="color: #800080;"&gt;1000</span>) - now_ms)*<span style="color: #800080;"&gt;1000</span><span style="color: #000000;"&gt;;
            tvp</span>->tv_sec --<span style="color: #000000;"&gt;;
        } </span><span style="color: #0000ff;"&gt;else</span><span style="color: #000000;"&gt; {
            tvp</span>->tv_usec = (shortest->when_ms - now_ms)*<span style="color: #800080;"&gt;1000</span><span style="color: #000000;"&gt;;
        }
        </span><span style="color: #0000ff;"&gt;if</span> (tvp->tv_sec < <span style="color: #800080;"&gt;0</span>) tvp->tv_sec = <span style="color: #800080;"&gt;0</span><span style="color: #000000;"&gt;;
        </span><span style="color: #0000ff;"&gt;if</span> (tvp->tv_usec < <span style="color: #800080;"&gt;0</span>) tvp->tv_usec = <span style="color: #800080;"&gt;0</span><span style="color: #000000;"&gt;;
    } </span><span style="color: #0000ff;"&gt;else</span><span style="color: #000000;"&gt; {
        </span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; If we have to check for events but need to return
         * ASAP because of AE_DONT_WAIT we need to set the timeout
         * to zero </span><span style="color: #008000;"&gt;*/</span>
        <span style="color: #0000ff;"&gt;if</span> (flags &amp;<span style="color: #000000;"&gt; AE_DONT_WAIT) {
            tv.tv_sec </span>= tv.tv_usec = <span style="color: #800080;"&gt;0</span><span style="color: #000000;"&gt;;
            tvp </span>= &amp;<span style="color: #000000;"&gt;tv;
        } </span><span style="color: #0000ff;"&gt;else</span><span style="color: #000000;"&gt; {
            </span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; Otherwise we can block </span><span style="color: #008000;"&gt;*/</span><span style="color: #000000;"&gt;
            tvp </span>= NULL; <span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; wait forever </span><span style="color: #008000;"&gt;*/</span><span style="color: #000000;"&gt;
        }
    }

    numevents </span>=<span style="color: #000000;"&gt; aeApiPoll(eventLoop,tvp);
    </span><span style="color: #0000ff;"&gt;for</span> (j = <span style="color: #800080;"&gt;0</span>; j < numevents; j++<span style="color: #000000;"&gt;) {
        aeFileEvent </span>*fe = &amp;eventLoop->events[eventLoop-><span style="color: #000000;"&gt;fired[j].fd];
        </span><span style="color: #0000ff;"&gt;int</span> mask = eventLoop-><span style="color: #000000;"&gt;fired[j].mask;
        </span><span style="color: #0000ff;"&gt;int</span> fd = eventLoop-><span style="color: #000000;"&gt;fired[j].fd;
        </span><span style="color: #0000ff;"&gt;int</span> rfired = <span style="color: #800080;"&gt;0</span><span style="color: #000000;"&gt;;

    </span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; note the fe->mask &amp; mask &amp; ... code: maybe an already processed
         * event removed an element that fired and we still didn't
         * processed,so we check if the event is still valid. </span><span style="color: #008000;"&gt;*/</span>
        <span style="color: #0000ff;"&gt;if</span> (fe->mask &amp; mask &amp;<span style="color: #000000;"&gt; AE_READABLE) {
            rfired </span>= <span style="color: #800080;"&gt;1</span><span style="color: #000000;"&gt;;
            fe</span>->rfileProc(eventLoop,fd,fe-><span style="color: #000000;"&gt;clientData,mask);
        }
        </span><span style="color: #0000ff;"&gt;if</span> (fe->mask &amp; mask &amp;<span style="color: #000000;"&gt; AE_WRITABLE) {
            </span><span style="color: #0000ff;"&gt;if</span> (!rfired || fe->wfileProc != fe-><span style="color: #000000;"&gt;rfileProc)
                fe</span>->wfileProc(eventLoop,mask);
        }
        processed</span>++<span style="color: #000000;"&gt;;
    }
}
</span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; Check time events </span><span style="color: #008000;"&gt;*/</span>
<span style="color: #0000ff;"&gt;if</span> (flags &amp;<span style="color: #000000;"&gt; AE_TIME_EVENTS)
    processed </span>+=<span style="color: #000000;"&gt; processTimeEvents(eventLoop);

</span><span style="color: #0000ff;"&gt;return</span> processed; <span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; return the number of processed file/time events </span><span style="color: #008000;"&gt;*/</span><span style="color: #000000;"&gt;

}

processTimeEvents(aeEventLoop * processed = * =

</span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; If the system clock is moved to the future,and then set back to the
 * right value,time events may be delayed in a random way. Often this
 * means that scheduled operations will not be performed soon enough.
 *
 * Here we try to detect system clock skews,and force all the time
 * events to be processed ASAP when this happens: the idea is that
 * processing events earlier is less dangerous than delaying them
 * indefinitely,and practice suggests it is. </span><span style="color: #008000;"&gt;*/</span>
<span style="color: #0000ff;"&gt;if</span> (now < eventLoop-><span style="color: #000000;"&gt;lastTime) {
    te </span>= eventLoop-><span style="color: #000000;"&gt;timeEventHead;
    </span><span style="color: #0000ff;"&gt;while</span><span style="color: #000000;"&gt;(te) {
        te</span>->when_sec = <span style="color: #800080;"&gt;0</span><span style="color: #000000;"&gt;;
        te </span>= te-><span style="color: #000000;"&gt;next;
    }
}
eventLoop</span>->lastTime =<span style="color: #000000;"&gt; now;

te </span>= eventLoop-><span style="color: #000000;"&gt;timeEventHead;
maxId </span>= eventLoop->timeEventNextId-<span style="color: #800080;"&gt;1</span><span style="color: #000000;"&gt;;
</span><span style="color: #0000ff;"&gt;while</span><span style="color: #000000;"&gt;(te) {
    </span><span style="color: #0000ff;"&gt;long</span><span style="color: #000000;"&gt; now_sec,now_ms;
    </span><span style="color: #0000ff;"&gt;long</span> <span style="color: #0000ff;"&gt;long</span><span style="color: #000000;"&gt; id;

    </span><span style="color: #0000ff;"&gt;if</span> (te->id ><span style="color: #000000;"&gt; maxId) {
        te </span>= te-><span style="color: #000000;"&gt;next;
        </span><span style="color: #0000ff;"&gt;continue</span><span style="color: #000000;"&gt;;
    }
    aeGetTime(</span>&amp;now_sec,&amp;<span style="color: #000000;"&gt;now_ms);
    </span><span style="color: #0000ff;"&gt;if</span> (now_sec > te->when_sec ||<span style="color: #000000;"&gt;
        (now_sec </span>== te->when_sec &amp;&amp; now_ms >= te-><span style="color: #000000;"&gt;when_ms))
    {
        </span><span style="color: #0000ff;"&gt;int</span><span style="color: #000000;"&gt; retval;

        id </span>= te-><span style="color: #000000;"&gt;id;
        retval </span>= te->timeProc(eventLoop,id,te-><span style="color: #000000;"&gt;clientData);
        processed</span>++<span style="color: #000000;"&gt;;
        </span><span style="color: #008000;"&gt;/*</span><span style="color: #008000;"&gt; After an event is processed our time event list may
         * no longer be the same,so we restart from head.
         * Still we make sure to don't process events registered
         * by event handlers itself in order to don't loop forever.
         * To do so we saved the max ID we want to handle.
         *
         * FUTURE OPTIMIZATIONS:
         * Note that this is NOT great algorithmically. Redis uses
         * a single time event so it's not a problem but the right
         * way to do this is to add the new elements on head,and
         * to flag deleted elements in a special way for later
         * deletion (putting references to the nodes to delete into
         * another linked list). </span><span style="color: #008000;"&gt;*/</span>
        <span style="color: #0000ff;"&gt;if</span> (retval !=<span style="color: #000000;"&gt; AE_NOMORE) {
            aeAddMillisecondsToNow(retval,</span>&amp;te->when_sec,&amp;te-><span style="color: #000000;"&gt;when_ms);
        } </span><span style="color: #0000ff;"&gt;else</span><span style="color: #000000;"&gt; {
            aeDeleteTimeEvent(eventLoop,id);
        }
        te </span>= eventLoop-><span style="color: #000000;"&gt;timeEventHead;
    } </span><span style="color: #0000ff;"&gt;else</span><span style="color: #000000;"&gt; {
        te </span>= te-><span style="color: #000000;"&gt;next;
    }
}
</span><span style="color: #0000ff;"&gt;return</span><span style="color: #000000;"&gt; processed;

}

深入redis内部--事件处理机制

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