redis0.1源码解析之基本原理
本文分析redis的基础原理,暂不做深入分析,后续再详细分析。我们从main函数开始。
int main(int argc, char **argv) {
initServerConfig();
initServer();
aeCreateFileEvent(server.el, server.fd, AE_READABLE, acceptHandler, NULL, NULL)
aeMain(server.el);
return 0;
}
下面就四个函数进行分析。
1 initServerConfig
static void initServerConfig() {
server.dbnum = REDIS_DEFAULT_DBNUM;
server.port = REDIS_SERVERPORT;
server.verbosity = REDIS_DEBUG;
server.maxidletime = REDIS_MAXIDLETIME;
server.saveparams = NULL;
server.logfile = NULL; /* NULL = log on standard output */
server.bindaddr = NULL;
server.glueoutputbuf = 1;
server.daemonize = 0;
server.pidfile = "/var/run/redis.pid";
server.dbfilename = "dump.rdb";
server.requirepass = NULL;
server.shareobjects = 0;
server.maxclients = 0;
ResetServerSaveParams();
appendServerSaveParams(60*60,1); /* save after 1 hour and 1 change */
appendServerSaveParams(300,100); /* save after 5 minutes and 100 changes */
appendServerSaveParams(60,10000); /* save after 1 minute and 10000 changes */
/* Replication related */
server.isslave = 0;
server.masterhost = NULL;
server.masterport = 6379;
server.master = NULL;
server.replstate = REDIS_REPL_NONE;
}
该函数是对redis核心结构体server(struct redisServer server)进行初始化。
2 initServer
static void initServer() {
int j;
// 修改这两个信号的处理函数为忽略,即不处理,如果不设置但又收到这个信号,会导致进程退出
signal(SIGHUP, SIG_IGN);
signal(SIGPIPE, SIG_IGN);
// clients列表,每次收到请求的时候会初始化一个client
server.clients = listCreate();
server.slaves = listCreate();
server.monitors = listCreate();
server.objfreelist = listCreate();
createSharedObjects();
// 创建一个事件循环的结构体
server.el = aeCreateEventLoop();
server.db = zmalloc(sizeof(redisDb)*server.dbnum);
server.sharingpool = dictCreate(&setDictType,NULL);
server.sharingpoolsize = 1024;
// 启动服务器
server.fd = anetTcpServer(server.neterr, server.port, server.bindaddr);
for (j = 0; j < server.dbnum; j++) {
server.db[j].dict = dictCreate(&hashDictType,NULL);
server.db[j].expires = dictCreate(&setDictType,NULL);
server.db[j].id = j;
}
server.cronloops = 0;
server.bgsaveinprogress = 0;
server.lastsave = time(NULL);
server.dirty = 0;
server.usedmemory = 0;
server.stat_numcommands = 0;
server.stat_numconnections = 0;
server.stat_starttime = time(NULL);
// 增加一个定时器
aeCreateTimeEvent(server.el, 1000, serverCron, NULL, NULL);
}
我们主要看initServer函数中的anetTcpServer这个函数。
int anetTcpServer(char *err, int port, char *bindaddr)
{
int s, on = 1;
struct sockaddr_in sa;
if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
anetSetError(err, "socket: %s\n", strerror(errno));
return ANET_ERR;
}
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1) {
anetSetError(err, "setsockopt SO_REUSEADDR: %s\n", strerror(errno));
close(s);
return ANET_ERR;
}
memset(&sa,0,sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(port);
sa.sin_addr.s_addr = htonl(INADDR_ANY);
if (bindaddr) {
if (inet_aton(bindaddr, &sa.sin_addr) == 0) {
anetSetError(err, "Invalid bind address\n");
close(s);
return ANET_ERR;
}
}
if (bind(s, (struct sockaddr*)&sa, sizeof(sa)) == -1) {
anetSetError(err, "bind: %s\n", strerror(errno));
close(s);
return ANET_ERR;
}
if (listen(s, 64) == -1) {
anetSetError(err, "listen: %s\n", strerror(errno));
close(s);
return ANET_ERR;
}
return s;
}
这个函数的逻辑就是经典的网络socket编程流程。最后通过listen函数,启动服务器。。
3 aeCreateFileEvent(server.el, server.fd, AE_READABLE, acceptHandler, NULL, NULL)
int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
aeFileProc *proc, void *clientData,
aeEventFinalizerProc *finalizerProc)
{
aeFileEvent *fe;
fe = zmalloc(sizeof(*fe));
if (fe == NULL) return AE_ERR;
fe->fd = fd;
fe->mask = mask;
fe->fileProc = proc;
fe->finalizerProc = finalizerProc;
fe->clientData = clientData;
fe->next = eventLoop->fileEventHead;
eventLoop->fileEventHead = fe;
return AE_OK;
}
aeCreateFileEvent函数在事件驱动那篇文章分析过,他就封装一个结构体,然后在事件循环的时候注册到事件驱动模块(本版本是使用select函数)。这里是注册可读事件,回调函数是acceptHandler。
4 aeMain
void aeMain(aeEventLoop *eventLoop)
{
eventLoop->stop = 0;
while (!eventLoop->stop)
aeProcessEvents(eventLoop, AE_ALL_EVENTS);
}
该函数在事件驱动文章也分析过,就是注册事件到事件驱动模块,然后开始等待事件发生,接着处理回调,根据3的分析,当有连接到来,会执行acceptHandler。
static void acceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
int cport, cfd;
char cip[128];
redisClient *c;
// 调用accept摘下一个请求
cfd = anetAccept(server.neterr, fd, cip, &cport);
// 创建一个client
if ((c = createClient(cfd)) == NULL) {
//
}
}
该函数摘下一个请求的节点,然后创建一个client处理该请求。
static redisClient *createClient(int fd) {
redisClient *c = zmalloc(sizeof(*c));
anetNonBlock(NULL,fd);
anetTcpNoDelay(NULL,fd);
if (!c) return NULL;
selectDb(c,0);
c->fd = fd;
c->querybuf = sdsempty();
c->argc = 0;
c->argv = NULL;
c->bulklen = -1;
c->sentlen = 0;
c->flags = 0;
c->lastinteraction = time(NULL);
c->authenticated = 0;
c->replstate = REDIS_REPL_NONE;
if ((c->reply = listCreate()) == NULL) oom("listCreate");
listSetFreeMethod(c->reply,decrRefCount);
listSetDupMethod(c->reply,dupClientReplyValue);
if (aeCreateFileEvent(server.el, c->fd, AE_READABLE,
readQueryFromClient, c, NULL) == AE_ERR) {
freeClient(c);
return NULL;
}
if (!listAddNodeTail(server.clients,c)) oom("listAddNodeTail");
return c;
}
我们接着看aeCreateFileEvent(server.el, c->fd, AE_READABLE,readQueryFromClient, c, NULL)这一句,在accept的fd(和客户端通信的fd)上注册可读事件(即等待客户端发送数据过来),然后执行readQueryFromClient。readQueryFromClient函数主要是读取客户端发送过来的数据,然后调processCommand。
static int processCommand(redisClient *c) {
struct redisCommand *cmd;
long long dirty;
// 退出命令
if (!strcasecmp(c->argv[0]->ptr,"quit")) {
freeClient(c);
return 0;
}
// 根据客户端的命令找到对应的命令配置
cmd = lookupCommand(c->argv[0]->ptr);
// ...
// 执行对应的处理函数
cmd->proc(c);
return 1;
}
上面函数根据用户发送的命令执行对应的函数。redis的命令配置表为。
static struct redisCommand cmdTable[] = {
{"get",getCommand,2,REDIS_CMD_INLINE},
...
};
假设客户端发送的是get命令,则执行的函数为getCommand。
static void getCommand(redisClient *c) {
// 读取客户端发送的数据
robj *o = lookupKeyRead(c->db,c->argv[1]);
addReply(c,o);
}
static void addReply(redisClient *c, robj *obj) {
aeCreateFileEvent(server.el, c->fd, AE_WRITABLE, sendReplyToClient, c, NULL)
}
给客户端fd注册可写事件,准备给客户端回复信息。事件触发时执行的函数是sendReplyToClient。
static void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask) {
redisClient *c = privdata;
//...
nwritten = write(fd, ((char*)o->ptr)+c->sentlen, objlen - c->sentlen);
}
发送回包给客户端。
这就是redis启动到处理客户端信息的整体流程。