--- date: 2022-02-20 --- - [整体概述](#%E6%95%B4%E4%BD%93%E6%A6%82%E8%BF%B0) - [客户端属性](#%E5%AE%A2%E6%88%B7%E7%AB%AF%E5%B1%9E%E6%80%A7) - [套接字描述符](#%E5%A5%97%E6%8E%A5%E5%AD%97%E6%8F%8F%E8%BF%B0%E7%AC%A6) - [标志](#%E6%A0%87%E5%BF%97) - [输入缓冲区](#%E8%BE%93%E5%85%A5%E7%BC%93%E5%86%B2%E5%8C%BA) - [命名及命令参数](#%E5%91%BD%E5%90%8D%E5%8F%8A%E5%91%BD%E4%BB%A4%E5%8F%82%E6%95%B0) - [命令的实现函数](#%E5%91%BD%E4%BB%A4%E7%9A%84%E5%AE%9E%E7%8E%B0%E5%87%BD%E6%95%B0) - [输出缓冲区](#%E8%BE%93%E5%87%BA%E7%BC%93%E5%86%B2%E5%8C%BA) - [客户端的创建与关闭](#%E5%AE%A2%E6%88%B7%E7%AB%AF%E7%9A%84%E5%88%9B%E5%BB%BA%E4%B8%8E%E5%85%B3%E9%97%AD) - [创建普通客户端](#%E5%88%9B%E5%BB%BA%E6%99%AE%E9%80%9A%E5%AE%A2%E6%88%B7%E7%AB%AF) - [关闭普通客户端](#%E5%85%B3%E9%97%AD%E6%99%AE%E9%80%9A%E5%AE%A2%E6%88%B7%E7%AB%AF) - [参考链接](#%E5%8F%82%E8%80%83%E9%93%BE%E6%8E%A5) - [Redis 源码简洁剖析系列](#redis-%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97) - [我的公众号](#%E6%88%91%E7%9A%84%E5%85%AC%E4%BC%97%E5%8F%B7) # 整体概述 Redis 一个服务器可以和多个客户端建立网络连接，每个客户端都可以向服务器发送命令请求，服务器接收客户端的命令，处理后将结果返回给客户端。 Redis 的文件事件处理器使用 `I/O 多路复用`，Redis 使用`单线程单进程`处理命令请求，与多个客户端进行网络通信。 ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220220101513.png?x-oss-process=style/yano) 每个连接了 Redis 服务器的客户端，服务器都建立了一个 `redisClient` 结构的`客户端状态`，保存了客户端当前的状态信息，以及执行相关功能时用到的数据结构。 Redis 服务器状态结构的 clients 属性是一个链表，保存了所有与服务器连接的客户端状态。 ```c struct redisServer { …… // 保存了所有客户端状态的链表 list *clients; …… }; ``` ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221084841.png?x-oss-process=style/yano) # 客户端属性 先贴一下 client 完整的数据结构： ```c typedef struct client { uint64_t id; /* Client incremental unique ID. */ connection *conn; int resp; /* RESP protocol version. Can be 2 or 3. */ redisDb *db; /* Pointer to currently SELECTed DB. */ robj *name; /* As set by CLIENT SETNAME. */ sds querybuf; /* Buffer we use to accumulate client queries. */ size_t qb_pos; /* The position we have read in querybuf. */ sds pending_querybuf; /* If this client is flagged as master, this buffer represents the yet not applied portion of the replication stream that we are receiving from the master. */ size_t querybuf_peak; /* Recent (100ms or more) peak of querybuf size. */ int argc; /* Num of arguments of current command. */ robj **argv; /* Arguments of current command. */ int original_argc; /* Num of arguments of original command if arguments were rewritten. */ robj **original_argv; /* Arguments of original command if arguments were rewritten. */ size_t argv_len_sum; /* Sum of lengths of objects in argv list. */ struct redisCommand *cmd, *lastcmd; /* Last command executed. */ user *user; /* User associated with this connection. If the user is set to NULL the connection can do anything (admin). */ int reqtype; /* Request protocol type: PROTO_REQ_* */ int multibulklen; /* Number of multi bulk arguments left to read. */ long bulklen; /* Length of bulk argument in multi bulk request. */ list *reply; /* List of reply objects to send to the client. */ unsigned long long reply_bytes; /* Tot bytes of objects in reply list. */ size_t sentlen; /* Amount of bytes already sent in the current buffer or object being sent. */ time_t ctime; /* Client creation time. */ long duration; /* Current command duration. Used for measuring latency of blocking/non-blocking cmds */ time_t lastinteraction; /* Time of the last interaction, used for timeout */ time_t obuf_soft_limit_reached_time; uint64_t flags; /* Client flags: CLIENT_* macros. */ int authenticated; /* Needed when the default user requires auth. */ int replstate; /* Replication state if this is a slave. */ int repl_put_online_on_ack; /* Install slave write handler on first ACK. */ int repldbfd; /* Replication DB file descriptor. */ off_t repldboff; /* Replication DB file offset. */ off_t repldbsize; /* Replication DB file size. */ sds replpreamble; /* Replication DB preamble. */ long long read_reploff; /* Read replication offset if this is a master. */ long long reploff; /* Applied replication offset if this is a master. */ long long repl_ack_off; /* Replication ack offset, if this is a slave. */ long long repl_ack_time;/* Replication ack time, if this is a slave. */ long long repl_last_partial_write; /* The last time the server did a partial write from the RDB child pipe to this replica */ long long psync_initial_offset; /* FULLRESYNC reply offset other slaves copying this slave output buffer should use. */ char replid[CONFIG_RUN_ID_SIZE+1]; /* Master replication ID (if master). */ int slave_listening_port; /* As configured with: REPLCONF listening-port */ char *slave_addr; /* Optionally given by REPLCONF ip-address */ int slave_capa; /* Slave capabilities: SLAVE_CAPA_* bitwise OR. */ multiState mstate; /* MULTI/EXEC state */ int btype; /* Type of blocking op if CLIENT_BLOCKED. */ blockingState bpop; /* blocking state */ long long woff; /* Last write global replication offset. */ list *watched_keys; /* Keys WATCHED for MULTI/EXEC CAS */ dict *pubsub_channels; /* channels a client is interested in (SUBSCRIBE) */ list *pubsub_patterns; /* patterns a client is interested in (SUBSCRIBE) */ sds peerid; /* Cached peer ID. */ sds sockname; /* Cached connection target address. */ listNode *client_list_node; /* list node in client list */ listNode *paused_list_node; /* list node within the pause list */ RedisModuleUserChangedFunc auth_callback; /* Module callback to execute * when the authenticated user * changes. */ void *auth_callback_privdata; /* Private data that is passed when the auth * changed callback is executed. Opaque for * Redis Core. */ void *auth_module; /* The module that owns the callback, which is used * to disconnect the client if the module is * unloaded for cleanup. Opaque for Redis Core.*/ /* If this client is in tracking mode and this field is non zero, * invalidation messages for keys fetched by this client will be send to * the specified client ID. */ uint64_t client_tracking_redirection; rax *client_tracking_prefixes; /* A dictionary of prefixes we are already subscribed to in BCAST mode, in the context of client side caching. */ /* In clientsCronTrackClientsMemUsage() we track the memory usage of * each client and add it to the sum of all the clients of a given type, * however we need to remember what was the old contribution of each * client, and in which categoty the client was, in order to remove it * before adding it the new value. */ uint64_t client_cron_last_memory_usage; int client_cron_last_memory_type; /* Response buffer */ int bufpos; char buf[PROTO_REPLY_CHUNK_BYTES]; } client; ``` ## 套接字描述符 ```c typedef struct client { …… // 记录客户端正在使用的套接字描述符 int fd; …… } ``` ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220220104015.png?x-oss-process=style/yano) ## 标志 客户端的标志属性 flags 记录了`客户端的角色`（role），以及客户端目前所处的状态： ```c typedef struct redisClient { // ... int flags; // ... } redisClient; ``` 具体值可参考：[《Redis 设计与实现-客户端属性》](http://redisbook.com/preview/client/redis_client_property.html)，flag 例子： ```c # 客户端是一个主服务器 REDIS_MASTER # 客户端正在被列表命令阻塞 REDIS_BLOCKED # 客户端正在执行事务，但事务的安全性已被破坏 REDIS_MULTI | REDIS_DIRTY_CAS # 客户端是一个从服务器，并且版本低于 Redis 2.8 REDIS_SLAVE | REDIS_PRE_PSYNC # 这是专门用于执行 Lua 脚本包含的 Redis 命令的伪客户端 # 它强制服务器将当前执行的命令写入 AOF 文件，并复制给从服务器 REDIS_LUA_CLIENT | REDIS_FORCE_AOF | REDIS_FORCE_REPL ``` ## 输入缓冲区 客户端状态的输入缓冲区用于保存`客户端发送的命令请求`： ```c typedef struct redisClient { // ... sds querybuf; // ... } redisClient; ``` 如果客户端向服务器发送了以下命令请求： ```c SET key value ``` 客户端状态的 querybuf 属性将是一个包含以下内容的 SDS 值： ```c *3\r\n$3\r\nSET\r\n$3\r\nkey\r\n$5\r\nvalue\r\n ``` 展示了这个 SDS 值以及 querybuf 属性的样子： ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221082404.png) ## 命名及命令参数 在服务器将客户端发送的命令请求保存到客户端状态的 `querybuf` 后，服务器会分析该命令，将得到的命令参数、命令参数的个数分别保存到客户端状态的 `argv` 属性和 `argc` 属性中： ```c typedef struct redisClient { // ... robj **argv; int argc; // ... } redisClient; ``` ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221083136.png?x-oss-process=style/yano) ## 命令的实现函数 当服务器从协议内容中分析并得出 argv 属性和 argc 属性的值之后， 服务器将根据项 argv[0] 的值，在命令表中查找命令所对应的命令实现函数。 当程序在命令表中成功找到 argv[0] 所对应的 `redisCommand` 结构时， 它会将客户端状态的 `cmd 指针`指向这个结构： ```c typedef struct redisClient { // ... struct redisCommand *cmd; // ... } redisClient; ``` ```c struct redisCommand { char *name; redisCommandProc *proc; int arity; char *sflags; /* Flags as string representation, one char per flag. */ uint64_t flags; /* The actual flags, obtained from the 'sflags' field. */ /* Use a function to determine keys arguments in a command line. * Used for Redis Cluster redirect. */ redisGetKeysProc *getkeys_proc; /* What keys should be loaded in background when calling this command? */ int firstkey; /* The first argument that's a key (0 = no keys) */ int lastkey; /* The last argument that's a key */ int keystep; /* The step between first and last key */ long long microseconds, calls, rejected_calls, failed_calls; int id; /* Command ID. This is a progressive ID starting from 0 that is assigned at runtime, and is used in order to check ACLs. A connection is able to execute a given command if the user associated to the connection has this command bit set in the bitmap of allowed commands. */ }; ``` 每个命令所对应的处理函数在是下面的 table： ```c struct redisCommand redisCommandTable[] = { {"module",moduleCommand,-2, "admin no-script", 0,NULL,0,0,0,0,0,0}, {"get",getCommand,2, "read-only fast @string", 0,NULL,1,1,1,0,0,0}, {"getex",getexCommand,-2, "write fast @string", 0,NULL,1,1,1,0,0,0}, …… } ``` ## 输出缓冲区 保存执行命令所得的`命令回复`。 ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221084219.png?x-oss-process=style/yano) 客户端的`固定大小缓冲区`由 `buf` 和 `bufpos` 两个属性组成： ```c typedef struct redisClient { // ... char buf[REDIS_REPLY_CHUNK_BYTES]; // 记录了 buf 数组目前已使用的字节数量 int bufpos; // ... } redisClient; ``` `可变大小缓冲区`由 `reply 链表`和一个或多个字符串对象组成： ```c typedef struct redisClient { // ... list *reply; // ... } redisClient; ``` 通过使用链表来连接多个字符串对象， 服务器可以为客户端保存一个非常长的命令回复， 而不必受到固定大小缓冲区 16 KB 大小的限制。展示了一个包含三个字符串对象的 reply 链表。 ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221084752.png?x-oss-process=style/yano) # 客户端的创建与关闭 ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221085412.png?x-oss-process=style/yano) ## 创建普通客户端 使用 connect 函数连接到服务器，服务器调用连接事件处理器，为客户端创建对应的客户端状态，并将其添加到服务器状态结构 clients 链表的末尾。 ![](http://yano.oss-cn-beijing.aliyuncs.com/blog/20220221202740.png?x-oss-process=style/yano) ## 关闭普通客户端 关闭普通客户端的原因： - 客户端进程退出或被杀死，客户端与服务端的网络连接被关闭 - 客户端向服务端发送了不符合协议格式的命令请求 - 客户端成为了 CLIENT KILL 命令的目标 - 客户端的空转时间超过 timeout 配置选项的值 - 客户端发送的命令请求大小，超过了深入缓冲区的限制大小（默认为 1GB） - 服务端返回给客户端的数据超过了输出缓冲区的限制大小 # 参考链接 - [《Redis 设计与实现-客户端属性》](http://redisbook.com/preview/client/redis_client_property.html) # Redis 源码简洁剖析系列 - [Redis 7.0.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%207.0.md) - [Redis 源码简洁剖析 01 - 环境配置.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2001%20-%20%E7%8E%AF%E5%A2%83%E9%85%8D%E7%BD%AE.md) - [Redis 源码简洁剖析 02 - SDS 字符串.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2002%20-%20SDS%20%E5%AD%97%E7%AC%A6%E4%B8%B2.md) - [Redis 源码简洁剖析 03 - Dict Hash 基础.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2003%20-%20Dict%20Hash%20%E5%9F%BA%E7%A1%80.md) - [Redis 源码简洁剖析 04 - Sorted Set 有序集合.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2004%20-%20Sorted%20Set%20%E6%9C%89%E5%BA%8F%E9%9B%86%E5%90%88.md) - [Redis 源码简洁剖析 05 - ziplist 压缩列表.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2005%20-%20ziplist%20%E5%8E%8B%E7%BC%A9%E5%88%97%E8%A1%A8.md) - [Redis 源码简洁剖析 06 - quicklist 和 listpack.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2006%20-%20quicklist%20%E5%92%8C%20listpack.md) - [Redis 源码简洁剖析 07 - main 函数启动.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2007%20-%20main%20%E5%87%BD%E6%95%B0%E5%90%AF%E5%8A%A8.md) - [Redis 源码简洁剖析 08 - epoll.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2008%20-%20epoll.md) - [Redis 源码简洁剖析 09 - Reactor 模型.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2009%20-%20Reactor%20%E6%A8%A1%E5%9E%8B.md) - [Redis 源码简洁剖析 10 - aeEventLoop 及事件.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2010%20-%20aeEventLoop%20%E5%8F%8A%E4%BA%8B%E4%BB%B6.md) - [Redis 源码简洁剖析 11 - 主 IO 线程及 Redis 6.0 多 IO 线程.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2011%20-%20%E4%B8%BB%20IO%20%E7%BA%BF%E7%A8%8B%E5%8F%8A%20Redis%206.0%20%E5%A4%9A%20IO%20%E7%BA%BF%E7%A8%8B.md) - [Redis 源码简洁剖析 12 - 一条命令的处理过程.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2012%20-%20%E4%B8%80%E6%9D%A1%E5%91%BD%E4%BB%A4%E7%9A%84%E5%A4%84%E7%90%86%E8%BF%87%E7%A8%8B.md) - [Redis 源码简洁剖析 13 - RDB 文件.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2013%20-%20RDB%20%E6%96%87%E4%BB%B6.md) - [Redis 源码简洁剖析 14 - Redis 持久化.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2014%20-%20Redis%20%E6%8C%81%E4%B9%85%E5%8C%96.md) - [Redis 源码简洁剖析 15 - AOF.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2015%20-%20AOF.md) - [Redis 源码简洁剖析 16 - 客户端.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2016%20-%20%E5%AE%A2%E6%88%B7%E7%AB%AF.md) - [Redis 源码简洁剖析 17 - 服务器.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2017%20-%20%E6%9C%8D%E5%8A%A1%E5%99%A8.md) - [Redis 源码简洁剖析 18 - 复制、哨兵 Sentinel.md](https://github.com/LjyYano/Thinking_in_Java_MindMapping/tree/master/%E7%BC%96%E7%A8%8B/Redis%20%E6%BA%90%E7%A0%81%E5%89%96%E6%9E%90%E7%B3%BB%E5%88%97/Redis%20%E6%BA%90%E7%A0%81%E7%AE%80%E6%B4%81%E5%89%96%E6%9E%90%2018%20-%20%E5%A4%8D%E5%88%B6%E3%80%81%E5%93%A8%E5%85%B5%20Sentinel.md) [Java 编程思想-最全思维导图-GitHub 下载链接](https://github.com/LjyYano/Thinking_in_Java_MindMapping)，需要的小伙伴可以自取~ 原创不易，希望大家转载时请先联系我，并标注原文链接。 # 我的公众号 coding 笔记、读书笔记、点滴记录，以后的文章也会同步到公众号（Coding Insight）中，大家关注^_^ 我的博客地址：[博客主页](https://yano-nankai.notion.site/yano-nankai/Yano-Space-ff42bde7acd1467eb3ae63dc0d4a9f8c)。 ![](http://yano.oss-cn-beijing.aliyuncs.com/2019-07-29-qrcode_for_gh_a26ce4572791_258.jpg)