Redis source code analysis-Protocol (notes + supplements)

Note: After Reading redis source code analysis-protocol, I found that the author skipped some simple points, but these simple points are exactly what I didn't understand, so I made some supplements, take notes.

Version: 2.04.

1. Requests format

* Number of parameters CRLF $ length of the first parameter CRLF the length of the first parameter CRLF... $ length of the N parameter CRLF

If you type get a in redis_cli, the request after Protocol assembly is

2\r\n$3\r\nget\r\n$1\r\na\r\n

2. Process

1. readqueryfromclient reads data from Fd: nread = read (FD, C-> querybuf + qblen, readlen );

2. processinputbuffer checks whether it is a telnet request.

2.1 C-> querybuf [0] = '*' --> processmultibulkbuffer.

2.2 Telnet --> processinlinebuffer.

3. processmultibulkbuffer: parses the command and splits the parameters into C-> argc and C-> argv. argc indicates the number of parameters. argv indicates the number of parameters.

Redis_object pointer array.

4. processcommand: When redis server is started, populatecommandtable is called to convert the rediscommandtable array into a hash
Table (server. commands), lookupcommand uses key (get) to find the ing function pointer, as shown below:

struct redisCommand redisCommandTable[] = {    {"get",getCommand,2,"r",0,NULL,1,1,1,0,0},    {"set",setCommand,3,"wm",0,noPreloadGetKeys,1,1,1,0,0},。。。。

5. Call (redisclient * C, int flags): Execute the command function. One of the most important calls I personally feel is C-> cmd-> proc (c ). The preceding C-> cmd = C-> lastcmd = lookupcommand (c-> argv [0]-> PTR) has assigned a rediscommand pointer to cmd. Because it is a GET command. C-> cmd-> proc (c) = getcommand (c ).

typedef void redisCommandProc(redisClient *c);struct redisCommand {    char *name;    redisCommandProc *proc;    int arity;    ..    long long microseconds, calls;};

6. Go to getcommand.

void getCommand(redisClient *c) {    getGenericCommand(c);}int getGenericCommand(redisClient *c) {    ...    if (o->type != REDIS_STRING) {        addReply(c,shared.wrongtypeerr);        return REDIS_ERR;    } else {        addReplyBulk(c,o);        return REDIS_OK;    }}

7. addreplybulk.

void addReplyBulk(redisClient *c, robj *obj) {    addReplyBulkLen(c,obj);    addReply(c,obj);    addReply(c,shared.crlf);}

8. prepareclienttowrite: The write operation is forwarded to the event splitter: sendreplytoclient ,. Write the content of C-> Buf to FD.

References:

1. http://www.hoterran.info/redis_protocol <redis source code analysis-Protocol>