Redis源码分析（三十五）--- redis.c服务端的实现分析（2）

geelou

在Redis服务端的代码量真的是比较大，如果一个一个API的学习怎么实现，无疑是一种效率很低的做法，所以我今天对服务端的实现代码的学习，重在他的执行流程上，而对于他的模块设计在上一篇中我已经分析过了，不明白的同学可以接着看上篇。所以我学习分析redis服务端的实现也是主要从main函数开始。在分析main执行流程之前，Redis的作者在这里声明了几个变量，这个我们有必要知道一下。

1. /* Our shared "common" objects */  
   
2. /* 共享的对象 */  
   
3. struct sharedObjectsStruct shared;  
   
4.   
   
5. /* Global vars that are actually used as constants. The following double
   
6. * values are used for double on-disk serialization, and are initialized
   
7. * at runtime to avoid strange compiler optimizations. */  
   
8. /* 全局的double类型常量 */  
   
9. double R_Zero, R_PosInf, R_NegInf, R_Nan;  
   
10.   
    
11. /*================================= Globals ================================= */  
    
12.   
    
13. /* Global vars */  
    
14. /* 全局的RedisServer */  
    
15. struct redisServer server; /* server global state */  
    
16.   
    
17. /* Our command table.
    
18. *
    
19. * Every entry is composed of the following fields:
    
20. *
    
21. * name: a string representing the command name.
    
22. * function: pointer to the C function implementing the command.
    
23. * arity: number of arguments, it is possible to use -N to say >= N
    
24. * sflags: command flags as string. See below for a table of flags.
    
25. * flags: flags as bitmask. Computed by Redis using the 'sflags' field.
    
26. * get_keys_proc: an optional function to get key arguments from a command.
    
27. *                This is only used when the following three fields are not
    
28. *                enough to specify what arguments are keys.
    
29. * first_key_index: first argument that is a key
    
30. * last_key_index: last argument that is a key
    
31. * key_step: step to get all the keys from first to last argument. For instance
    
32. *           in MSET the step is two since arguments are key,val,key,val,...
    
33. * microseconds: microseconds of total execution time for this command.
    
34. * calls: total number of calls of this command.
    
35. *
    
36. * The flags, microseconds and calls fields are computed by Redis and should
    
37. * always be set to zero.
    
38. *
    
39. * Command flags are expressed using strings where every character represents
    
40. * a flag. Later the populateCommandTable() function will take care of
    
41. * populating the real 'flags' field using this characters.
    
42. *
    
43. * This is the meaning of the flags:
    
44. *
    
45. * w: write command (may modify the key space).
    
46. * r: read command  (will never modify the key space).
    
47. * m: may increase memory usage once called. Don't allow if out of memory.
    
48. * a: admin command, like SAVE or SHUTDOWN.
    
49. * p: Pub/Sub related command.
    
50. * f: force replication of this command, regardless of server.dirty.
    
51. * s: command not allowed in scripts.
    
52. * R: random command. Command is not deterministic, that is, the same command
    
53. *    with the same arguments, with the same key space, may have different
    
54. *    results. For instance SPOP and RANDOMKEY are two random commands.
    
55. * S: Sort command output array if called from script, so that the output
    
56. *    is deterministic.
    
57. * l: Allow command while loading the database.
    
58. * t: Allow command while a slave has stale data but is not allowed to
    
59. *    server this data. Normally no command is accepted in this condition
    
60. *    but just a few.
    
61. * M: Do not automatically propagate the command on MONITOR.
    
62. * F: Fast command: O(1) or O(log(N)) command that should never delay
    
63. *    its execution as long as the kernel scheduler is giving us time.
    
64. *    Note that commands that may trigger a DEL as a side effect (like SET)
    
65. *    are not fast commands.
    
66. */  
    
67. /* redis命令表格对应关系 */  
    
68. struct redisCommand redisCommandTable[] = {  
    
69.     {"get",getCommand,2,"rF",0,NULL,1,1,1,0,0},  
    
70.     {"set",setCommand,-3,"wm",0,NULL,1,1,1,0,0},  
    
71.     {"setnx",setnxCommand,3,"wmF",0,NULL,1,1,1,0,0},  
    
72.     {"setex",setexCommand,4,"wm",0,NULL,1,1,1,0,0},  
    
73. .....  

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这个命令表相当多，省略了，基本是囊括了所有的可能命令。毕竟服务端都是以上这些命令的响应实现嘛。下面是重点要学习的了，在服务端的执行主程序中，是如何执行的呢，来一个流程框图:

具体的代码实现为如下:

1. int main(int argc, char **argv) {  
   
2.     struct timeval tv;  
   
3.   
   
4.     /* We need to initialize our libraries, and the server configuration. */  
   
5. #ifdef INIT_SETPROCTITLE_REPLACEMENT  
   
6.     spt_init(argc, argv);  
   
7. #endif  
   
8.     setlocale(LC_COLLATE,"");  
   
9.     //启用线程安全模式  
   
10.     zmalloc_enable_thread_safeness();  
    
11.     //启用当发生内存溢出时的handler方法  
    
12.     zmalloc_set_oom_handler(redisOutOfMemoryHandler);  
    
13.     srand(time(NULL)^getpid());  
    
14.     //获取当前时间  
    
15.     gettimeofday(&tv,NULL);  
    
16.     dictSetHashFunctionSeed(tv.tv_sec^tv.tv_usec^getpid());  
    
17.     server.sentinel_mode = checkForSentinelMode(argc,argv);  
    
18.     //初始化服务端的配置  
    
19.     initServerConfig();  
    
20.   
    
21.     /* We need to init sentinel right now as parsing the configuration file
    
22.      * in sentinel mode will have the effect of populating the sentinel
    
23.      * data structures with master nodes to monitor. */  
    
24.     //初始化服务端的模式  
    
25.     if (server.sentinel_mode) {  
    
26.         initSentinelConfig();  
    
27.         initSentinel();  
    
28.     }  
    
29.   
    
30.     if (argc >= 2) {  
    
31.         int j = 1; /* First option to parse in argv[] */  
    
32.         sds options = sdsempty();  
    
33.         char *configfile = NULL;  
    
34.   
    
35.         /* Handle special options --help and --version */  
    
36.         if (strcmp(argv[1], "-v") == 0 ||  
    
37.             strcmp(argv[1], "--version") == 0) version();  
    
38.         if (strcmp(argv[1], "--help") == 0 ||  
    
39.             strcmp(argv[1], "-h") == 0) usage();  
    
40.         if (strcmp(argv[1], "--test-memory") == 0) {  
    
41.             if (argc == 3) {  
    
42.                 memtest(atoi(argv[2]),50);  
    
43.                 exit(0);  
    
44.             } else {  
    
45.                 fprintf(stderr,"Please specify the amount of memory to test in megabytes.\n");  
    
46.                 fprintf(stderr,"Example: ./redis-server --test-memory 4096\n\n");  
    
47.                 exit(1);  
    
48.             }  
    
49.         }  
    
50.   
    
51.         /* First argument is the config file name? */  
    
52.         if (argv[j][0] != '-' || argv[j][1] != '-')  
    
53.             configfile = argv[j++];  
    
54.         /* All the other options are parsed and conceptually appended to the
    
55.          * configuration file. For instance --port 6380 will generate the
    
56.          * string "port 6380\n" to be parsed after the actual file name
    
57.          * is parsed, if any. */  
    
58.         while(j != argc) {  
    
59.             if (argv[j][0] == '-' && argv[j][1] == '-') {  
    
60.                 /* Option name */  
    
61.                 if (sdslen(options)) options = sdscat(options,"\n");  
    
62.                 options = sdscat(options,argv[j]+2);  
    
63.                 options = sdscat(options," ");  
    
64.             } else {  
    
65.                 /* Option argument */  
    
66.                 options = sdscatrepr(options,argv[j],strlen(argv[j]));  
    
67.                 options = sdscat(options," ");  
    
68.             }  
    
69.             j++;  
    
70.         }  
    
71.         if (server.sentinel_mode && configfile && *configfile == '-') {  
    
72.             redisLog(REDIS_WARNING,  
    
73.                 "Sentinel config from STDIN not allowed.");  
    
74.             redisLog(REDIS_WARNING,  
    
75.                 "Sentinel needs config file on disk to save state.  Exiting...");  
    
76.             exit(1);  
    
77.         }  
    
78.         if (configfile) server.configfile = getAbsolutePath(configfile);  
    
79.         resetServerSaveParams();  
    
80.         //加载服务端的配置，根据config配置文件来加载  
    
81.         loadServerConfig(configfile,options);  
    
82.         sdsfree(options);  
    
83.     } else {  
    
84.         redisLog(REDIS_WARNING, "Warning: no config file specified, using the default config. In order to specify a config file use %s /path/to/%s.conf", argv[0], server.sentinel_mode ? "sentinel" : "redis");  
    
85.     }  
    
86.     //是否开启守护进程  
    
87.     if (server.daemonize) daemonize();  
    
88.     initServer();  
    
89.     if (server.daemonize) createPidFile();  
    
90.     redisSetProcTitle(argv[0]);  
    
91.     redisAsciiArt();  
    
92.   
    
93.     if (!server.sentinel_mode) {  
    
94.         /* Things not needed when running in Sentinel mode. */  
    
95.         redisLog(REDIS_WARNING,"Server started, Redis version " REDIS_VERSION);  
    
96.     #ifdef __linux__  
    
97.         linuxOvercommitMemoryWarning();  
    
98.     #endif  
    
99.         loadDataFromDisk();  
    
100.         if (server.ipfd_count > 0)  
     
101.             redisLog(REDIS_NOTICE,"The server is now ready to accept connections on port %d", server.port);  
     
102.         if (server.sofd > 0)  
     
103.             redisLog(REDIS_NOTICE,"The server is now ready to accept connections at %s", server.unixsocket);  
     
104.     } else {  
     
105.         sentinelIsRunning();  
     
106.     }  
     
107.   
     
108.     /* Warning the user about suspicious maxmemory setting. */  
     
109.     if (server.maxmemory > 0 && server.maxmemory < 1024*1024) {  
     
110.         redisLog(REDIS_WARNING,"WARNING: You specified a maxmemory value that is less than 1MB (current value is %llu bytes). Are you sure this is what you really want?", server.maxmemory);  
     
111.     }  
     
112.       
     
113.     //事件加载之前调用的beforeSleep方法  
     
114.     aeSetBeforeSleepProc(server.el,beforeSleep);  
     
115.     //开启事件驱动循环  
     
116.     aeMain(server.el);  
     
117.     aeDeleteEventLoop(server.el);  
     
118.     return 0;  
     
119. }  

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方法非常简单命令，有人估计比较纳闷了，为什么没有连接操作呢，Client和Server不是要有连接操作的嘛，在这里为什么会没有呢，因为那些是客户端的主动进行的操作，所以服务端的main操作相对简单很多。


转自：http://blog.csdn.net/androidlushangderen/article/details/40918041
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