Redis命令處理過程源碼解析

void processInputBuffer(client *c) {
    ......
    //循環遍歷輸入緩沖區，獲取命令參數,調用processMultibulkBuffer解析命令參數和長度
    while(sdslen(c->querybuf)) {
        if (c->reqtype == PROTO_REQ_INLINE) {
            if (processInlineBuffer(c) != C_OK) break;//處理telnet方式的內聯命令
        } else if (c->reqtype == PROTO_REQ_MULTIBULK) {
            if (processMultibulkBuffer(c) != C_OK) break; //解析命令參數和長度暫存到客戶端結構體中
        } else {
            serverPanic("Unknown request type");
        }
    }    
}

//解析命令參數和長度暫存到客戶端結構體中
int processMultibulkBuffer(client *c) {
    //定位到行尾
    newline = strchr(c->querybuf,'\r');
    //解析命令請求參數數目，並存儲在客戶端對象的c->multibulklen字段
    serverAssertWithInfo(c,NULL,c->querybuf[0] == '*');
    ok = string2ll(c->querybuf+1,newline-(c->querybuf+1),&ll);
    c->multibulklen = ll;
    pos = (newline-c->querybuf)+2;//記錄已解析命令的請求長度resp的長度
    /* Setup argv array on client structure */
    //分配請求參數存儲空間
    c->argv = zmalloc(sizeof(robj*)*c->multibulklen);
    
    // 開始循環解析每個請求參數
    while(c->multibulklen) {
        ......
        newline = strchr(c->querybuf+pos,'\r');
        if (c->querybuf[pos] != '$') {
            return C_ERR;
        ok = string2ll(c->querybuf+pos+1,newline-(c->querybuf+pos+1),&ll);
        pos += newline-(c->querybuf+pos)+2;
        c->bulklen = ll;//字符串參數長度暫存在客戶端對象的bulklen字段
        
        //讀取該長度的參數內容，並創建字符串對象，同時更新待解析參數multibulklen
        c->argv[c->argc++] =createStringObject(c->querybuf+pos,c->bulklen);
        pos += c->bulklen+2;
        c->multibulklen--;
    }

void processInputBuffer(client *c) {
    
    ......
     //調用processCommand來處理命令
     if (processCommand(c) == C_OK) {
         ......
     }
}

//處理命令函數
int processCommand(client *c) {
    //校驗是否是quit命令
    if (!strcasecmp(c->argv[0]->ptr,"quit")) {
        addReply(c,shared.ok);
        c->flags |= CLIENT_CLOSE_AFTER_REPLY;
        return C_ERR;
    }
    //調用lookupCommand，查看該命令是否存在
    c->cmd = c->lastcmd = lookupCommand(c->argv[0]->ptr);
    if (!c->cmd) {
        flagTransaction(c);
        addReplyErrorFormat(c,"unknown command '%s'",
            (char*)c->argv[0]->ptr);
        return C_OK;
    //檢查用戶權限
    if (server.requirepass && !c->authenticated && c->cmd->proc != authCommand)
    {
        addReply(c,shared.noautherr);
    //還有很多檢查，不一一列舉，比如集群/持久化/復制等
    /* 真正執行命令 */
    if (c->flags & CLIENT_MULTI &&
        c->cmd->proc != execCommand && c->cmd->proc != discardCommand &&
        c->cmd->proc != multiCommand && c->cmd->proc != watchCommand)
        queueMultiCommand(c);
        //將結果寫入outbuffer
        addReply(c,shared.queued);
    } 
// 調用execCommand執行命令
void execCommand(client *c) {
    call(c,CMD_CALL_FULL);//調用call執行命令
//調用execCommand調用call執行命令
void call(client *c, int flags) {
    start = ustime();
    c->cmd->proc(c);//執行命令
    duration = ustime()-start;
    //如果是慢查詢，記錄慢查詢
    if (flags & CMD_CALL_SLOWLOG && c->cmd->proc != execCommand) {
        char *latency_event = (c->cmd->flags & CMD_FAST) ?
                              "fast-command" : "command";
        latencyAddSampleIfNeeded(latency_event,duration/1000);
        //記錄到慢日志中
        slowlogPushEntryIfNeeded(c,c->argv,c->argc,duration);
    //更新統計信息：當前命令執行時間和調用次數
    if (flags & CMD_CALL_STATS) {
        c->lastcmd->microseconds += duration;
        c->lastcmd->calls++;

int processCommand(client *c) {
    ......
    //將結果寫入outbuffer
    addReply(c,shared.queued);
    ......
    
}
//將結果寫入outbuffer
void addReply(client *c, robj *obj) {
    //調用listAddNodeHead將客戶端添加到服務端結構體的client_pending_write鏈表，以便後續能快速查找出哪些客戶端有數據需要發送
    if (prepareClientToWrite(c) != C_OK) return;
    
    //然後添加字符串到輸出緩沖區
    if (_addReplyToBuffer(c,obj->ptr,sdslen(obj->ptr)) != C_OK)
        //如果添加失敗，則添加到輸出鏈表中
        _addReplyObjectToList(c,obj); 
}

void beforeSleep(struct aeEventLoop *eventLoop) {
    ......
     /* Handle writes with pending output buffers. */
    handleClientsWithPendingWrites();
}

//回復客戶端命令函數
int handleClientsWithPendingWrites(void) {
    listIter li;
    listNode *ln;
    int processed = listLength(server.clients_pending_write);
    listRewind(server.clients_pending_write,&li);
    while((ln = listNext(&li))) {
        client *c = listNodeValue(ln);
        c->flags &= ~CLIENT_PENDING_WRITE;
        listDelNode(server.clients_pending_write,ln);
        /* 發送客戶端數據 */
        if (writeToClient(c->fd,c,0) == C_ERR) continue;
        /* If there is nothing left, do nothing. Otherwise install
         * the write handler. */
         //如果數據量很大，一次性沒有發送完成，則進行添加文件事件，監聽當前客戶端socket文件描述符的可寫事件即可
        if (clientHasPendingReplies(c) &&
            aeCreateFileEvent(server.el, c->fd, AE_WRITABLE,
                sendReplyToClient, c) == AE_ERR)
        {
            freeClientAsync(c);
        }
    }
    return processed;