Redis源码分析：Event-driven programming library |yfkiss
Event-driven programminglibray，提到这个，很容易想到如雷贯耳的libevent库（libeven封装了以下三种事件的响应:IO事件,定时器事件,信号事件）。redis的没有采用庞大的libevent库，而是自己写了一个，牺牲了一些平台通用性，但是性能非常强劲。memcache采用了libevent，有人认为这是redis的优于性能比memcache性能。没有测试过，保留意见。
x相关源码：ae.h ae.c
networking.c anet.cnet.hae_epoll.c ae_select.c ae_kqueue.c
ae.h、ae.c ：event library具体实现
networking.c ： 与客户端的交互
anet.h anet.c ： 网络通信
ae_epoll.c ae_select.c ae_kqueue.c: 不同系统多路IO封装
ae_epoll.c ： linux平台
ae_select.c ：unix平台
ae_kqueue.c : BSD、APPLE
ae.c多路IO选择：
#ifdef __linux__
#define HAVE_EPOLL 1
#endif
#if (defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_6)) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined (__NetBSD__)
#define HAVE_KQUEUE 1
#endif
#ifdef HAVE_EPOLL
#include "ae_epoll.c"
#else
#ifdef HAVE_KQUEUE
#include "ae_kqueue.c"
#else
#include "ae_select.c"
#endif
#endif
多路IO封装（以ae_epoll.c为例）：
aeApiCreate：创建句柄（epoll_create）
aeApiFree：关闭句柄（close）
aeApiAddEvent：事件添加（epoll_ctl）
aeApiDelEvent：事件删除（epoll_ctl）
aeApiPoll：等待事件发生（epoll_wait）
网络简要说明：
1. 初始化server, 等待客户端连接，并注册事件，回调函数acceptTcpHandler/acceptUnixHandler
if (server.ipfd > 0 && aeCreateFileEvent(server.el,server.ipfd,AE_READABLE,
acceptTcpHandler,NULL) == AE_ERR) oom("creating file event");
if (server.sofd > 0 && aeCreateFileEvent(server.el,server.sofd,AE_READABLE,
acceptUnixHandler,NULL) == AE_ERR) oom("creating file event");2. 回调函数acceptTcpHandler/acceptUnixHandler
在监听到新连接请求时，接收连接，创建redisClient对象，并注册事件（回调函数readQueryFromClient）
void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
redisClient *c = (redisClient*) privdata;
char buf;
int nread;
REDIS_NOTUSED(el);
REDIS_NOTUSED(mask);
nread = read(fd, buf, REDIS_IOBUF_LEN);
if (nread == -1) {
if (errno == EAGAIN) {
nread = 0;
} else {
redisLog(REDIS_VERBOSE, "Reading from client: %s",strerror(errno));
freeClient(c);
return;
}
} else if (nread == 0) {
redisLog(REDIS_VERBOSE, "Client closed connection");
freeClient(c);
return;
}
if (nread) {
c->querybuf = sdscatlen(c->querybuf,buf,nread);
c->lastinteraction = time(NULL);
} else {
return;
}
if (sdslen(c->querybuf) > server.client_max_querybuf_len) {
sds ci = getClientInfoString(c), bytes = sdsempty();
bytes = sdscatrepr(bytes,c->querybuf,64);
redisLog(REDIS_WARNING,"Closing client that reached max query buffer length: %s (qbuf initial bytes: %s)", ci, bytes);
sdsfree(ci);
sdsfree(bytes);
freeClient(c);
return;
}
processInputBuffer(c);
}3. 客户端请求处理：
在接收到客户端请求数据后，首先对请求进行解析，解析完成后反馈请求
void processInputBuffer(redisClient *c) {
/* Keep processing while there is something in the input buffer */
while(sdslen(c->querybuf)) {
/* Immediately abort if the client is in the middle of something. */
if (c->flags & REDIS_BLOCKED || c->flags & REDIS_IO_WAIT) return;
/* REDIS_CLOSE_AFTER_REPLY closes the connection once the reply is
* written to the client. Make sure to not let the reply grow after
* this flag has been set (i.e. don't process more commands). */
if (c->flags & REDIS_CLOSE_AFTER_REPLY) return;
/* Determine request type when unknown. */
if (!c->reqtype) {
if (c->querybuf == '*') {
c->reqtype = REDIS_REQ_MULTIBULK;
} else {
c->reqtype = REDIS_REQ_INLINE;
}
}
if (c->reqtype == REDIS_REQ_INLINE) {
if (processInlineBuffer(c) != REDIS_OK) break;
} else if (c->reqtype == REDIS_REQ_MULTIBULK) {
if (processMultibulkBuffer(c) != REDIS_OK) break;
} else {
redisPanic("Unknown request type");
}
/* Multibulk processing could see a <= 0 length. */
if (c->argc == 0) {
resetClient(c);
} else {
/* Only reset the client when the command was executed. */
if (processCommand(c) == REDIS_OK)
resetClient(c);
}
}
}在请求处理完成后，反馈结果.
int processCommand(redisClient *c) {
.......
/* Exec the command */
if (c->flags & REDIS_MULTI &&
c->cmd->proc != execCommand && c->cmd->proc != discardCommand &&
c->cmd->proc != multiCommand && c->cmd->proc != watchCommand)
{
queueMultiCommand(c);
addReply(c,shared.queued);
} else {
if (server.vm_enabled && server.vm_max_threads > 0 &&
blockClientOnSwappedKeys(c)) return REDIS_ERR;
call(c);
}
return REDIS_OK;
}void addReply(redisClient *c, robj *obj) {
if (_installWriteEvent(c) != REDIS_OK) return;
redisAssert(!server.vm_enabled || obj->storage == REDIS_VM_MEMORY);
/* This is an important place where we can avoid copy-on-write
* when there is a saving child running, avoiding touching the
* refcount field of the object if it's not needed.
*
* If the encoding is RAW and there is room in the static buffer
* we'll be able to send the object to the client without
* messing with its page. */
if (obj->encoding == REDIS_ENCODING_RAW) {
if (_addReplyToBuffer(c,obj->ptr,sdslen(obj->ptr)) != REDIS_OK)
_addReplyObjectToList(c,obj);
} else {
/* FIXME: convert the long into string and use _addReplyToBuffer()
* instead of calling getDecodedObject. As this place in the
* code is too performance critical. */
obj = getDecodedObject(obj);
if (_addReplyToBuffer(c,obj->ptr,sdslen(obj->ptr)) != REDIS_OK)
_addReplyObjectToList(c,obj);
decrRefCount(obj);
}
}int _installWriteEvent(redisClient *c) {
if (c->fd <= 0) return REDIS_ERR;
if (c->bufpos == 0 && listLength(c->reply) == 0 &&
(c->replstate == REDIS_REPL_NONE ||
c->replstate == REDIS_REPL_ONLINE) &&
aeCreateFileEvent(server.el, c->fd, AE_WRITABLE,
sendReplyToClient, c) == AE_ERR) return REDIS_ERR;
return REDIS_OK;
}Redis执行完客户端请求后，会调用addReply，在addReply中调用installWriteEvent来注册一个事件，并绑定事件处理函数sendReplyToClient，用来把数据发送到client。
4.主循环
处理定时事件和注册事件
void aeMain(aeEventLoop *eventLoop) {
eventLoop->stop = 0;
while (!eventLoop->stop) {
if (eventLoop->beforesleep != NULL)
eventLoop->beforesleep(eventLoop);
aeProcessEvents(eventLoop, AE_ALL_EVENTS);
}
}beforesleep通过aeSetBeforeSleepProc定义，主要是特殊处理vm和aof相关的请求
int aeProcessEvents(aeEventLoop *eventLoop, int flags)
{
int processed = 0, numevents;
/* Nothing to do? return ASAP */
if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
/* 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. */
if (eventLoop->maxfd != -1 ||
((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
int j;
aeTimeEvent *shortest = NULL;
struct timeval tv, *tvp;
if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
shortest = aeSearchNearestTimer(eventLoop);
if (shortest) {
long now_sec, now_ms;
/* Calculate the time missing for the nearest
* timer to fire. */
aeGetTime(&now_sec, &now_ms);
tvp = &tv;
tvp->tv_sec = shortest->when_sec - now_sec;
if (shortest->when_ms < now_ms) {
tvp->tv_usec = ((shortest->when_ms+1000) - now_ms)*1000;
tvp->tv_sec --;
} else {
tvp->tv_usec = (shortest->when_ms - now_ms)*1000;
}
if (tvp->tv_sec < 0) tvp->tv_sec = 0;
if (tvp->tv_usec < 0) tvp->tv_usec = 0;
} else {
/* If we have to check for events but need to return
* ASAP because of AE_DONT_WAIT we need to se the timeout
* to zero */
if (flags & AE_DONT_WAIT) {
tv.tv_sec = tv.tv_usec = 0;
tvp = &tv;
} else {
/* Otherwise we can block */
tvp = NULL; /* wait forever */
}
}
numevents = aeApiPoll(eventLoop, tvp);
for (j = 0; j < numevents; j++) {
aeFileEvent *fe = &eventLoop->events.fd];
int mask = eventLoop->fired.mask;
int fd = eventLoop->fired.fd;
int rfired = 0;
/* note the fe->mask & mask & ... 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. */
if (fe->mask & mask & AE_READABLE) {
rfired = 1;
fe->rfileProc(eventLoop,fd,fe->clientData,mask);
}
if (fe->mask & mask & AE_WRITABLE) {
if (!rfired || fe->wfileProc != fe->rfileProc)
fe->wfileProc(eventLoop,fd,fe->clientData,mask);
}
processed++;
}
}
/* Check time events */
if (flags & AE_TIME_EVENTS)
processed += processTimeEvents(eventLoop);
return processed; /* return the number of processed file/time events */
}rfileProc和wfileProc即注册事件时定义的回调函数
作者：yfkiss 发表于2011-12-13 23:33:27 原文链接
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