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redis.c
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/*
* Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "redis.h"
#include "slowlog.h"
#include "bio.h"
#include <time.h>
#include <signal.h>
#include <sys/wait.h>
#include <errno.h>
#include <assert.h>
#include <ctype.h>
#include <stdarg.h>
#include <arpa/inet.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/uio.h>
#include <limits.h>
#include <float.h>
#include <math.h>
#include <sys/resource.h>
#include <sys/utsname.h>
/* Our shared "common" objects */
// 共用共享数组
struct sharedObjectsStruct shared;
/* Global vars that are actually used as constants. The following double
* values are used for double on-disk serialization, and are initialized
* at runtime to avoid strange compiler optimizations. */
double R_Zero, R_PosInf, R_NegInf, R_Nan;
/*================================= Globals ================================= */
/* Global vars */
// 服务器状态
struct redisServer server; /* server global state */
struct redisCommand *commandTable;
/* Our command table.
*
* Every entry is composed of the following fields:
*
* name: a string representing the command name.
* 命令的名称
*
* function: pointer to the C function implementing the command.
* 命令的实现函数
*
* arity: number of arguments, it is possible to use -N to say >= N
* 参数的数量，可以用 -N 表示 >= N
*
* sflags: command flags as string. See below for a table of flags.
* 字符串形式的 FLAG ，用来计算下面的 flags 属性
*
* flags: flags as bitmask. Computed by Redis using the 'sflags' field.
* 位掩码形式的 FLAG ，由 sflags 字符串计算得出
*
* get_keys_proc: an optional function to get key arguments from a command.
* This is only used when the following three fields are not
* enough to specify what arguments are keys.
* 一个可选的函数，用于从命令中取出 key 参数。
* 只在以下三个参数不足以表示 key 参数时使用。
*
* first_key_index: first argument that is a key
* 第一个是 key 的参数
* last_key_index: last argument that is a key
* 最后一个是 key 的参数
* key_step: step to get all the keys from first to last argument. For instance
* in MSET the step is two since arguments are key,val,key,val,...
* 从 first 参数和 last 参数间，获取所有 key 的步数（step）
* 比如说， MSET 命令的格式为 MSET key value [key value ...]
* 它的 step 就为 2
*
* microseconds: microseconds of total execution time for this command.
* 执行这个命令耗费的总微秒数
*
* calls: total number of calls of this command.
* 命令被执行的总次数
*
* The flags, microseconds and calls fields are computed by Redis and should
* always be set to zero.
* microseconds 和 call 由 Redis 计算，总是初始化为 0 。
*
* Command flags are expressed using strings where every character represents
* a flag. Later the populateCommandTable() function will take care of
* populating the real 'flags' field using this characters.
*
* 命令的 FLAG 由 SFLAG 域设置，之后 populateCommandTable() 从 SFLAG 中计算出
* 真正的 FLAG 。
*
* This is the meaning of the flags:
*
* w: write command (may modify the key space).
* 写入命令，可能会修改 key space
*
* r: read command (will never modify the key space).
* 读命令，不修改 key space
*
* m: may increase memory usage once called. Don't allow if out of memory.
* 可能会占用大量内存的命令，调用时对内存占用进行检查
*
* a: admin command, like SAVE or SHUTDOWN.
* 管理员使用的命令
*
* p: Pub/Sub related command.
* 发送/订阅相关的命令
*
* f: force replication of this command, regarless of server.dirty.
* 强制同步这个命令，无视 server.dirty
*
* s: command not allowed in scripts.
* 不允许在脚本中使用的命令
*
* R: random command. Command is not deterministic, that is, the same command
* with the same arguments, with the same key space, may have different
* results. For instance SPOP and RANDOMKEY are two random commands.
* 随机命令，对于同样数据集的同一个命令调用，得出的结果可能是不相同的。
*
* S: Sort command output array if called from script, so that the output
* is deterministic.
* 如果命令在脚本中执行，那么对输出进行排序，从而让输出变得确定起来。
*
* l: Allow command while loading the database.
* 允许在载入数据库时执行的命令
*
* t: Allow command while a slave has stale data but is not allowed to
* server this data. Normally no command is accepted in this condition
* but just a few.
* 允许在附属节点包含过期数据时执行的命令
*
* M: Do not automatically propagate the command on MONITOR.
* 不要自动将此命令发送到 MONITOR
*/
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},
{"setnx",setnxCommand,3,"wm",0,noPreloadGetKeys,1,1,1,0,0},
{"setex",setexCommand,4,"wm",0,noPreloadGetKeys,1,1,1,0,0},
{"psetex",psetexCommand,4,"wm",0,noPreloadGetKeys,1,1,1,0,0},
{"append",appendCommand,3,"wm",0,NULL,1,1,1,0,0},
{"strlen",strlenCommand,2,"r",0,NULL,1,1,1,0,0},
{"del",delCommand,-2,"w",0,noPreloadGetKeys,1,-1,1,0,0},
{"exists",existsCommand,2,"r",0,NULL,1,1,1,0,0},
{"setbit",setbitCommand,4,"wm",0,NULL,1,1,1,0,0},
{"getbit",getbitCommand,3,"r",0,NULL,1,1,1,0,0},
{"setrange",setrangeCommand,4,"wm",0,NULL,1,1,1,0,0},
{"getrange",getrangeCommand,4,"r",0,NULL,1,1,1,0,0},
{"substr",getrangeCommand,4,"r",0,NULL,1,1,1,0,0},
{"incr",incrCommand,2,"wm",0,NULL,1,1,1,0,0},
{"decr",decrCommand,2,"wm",0,NULL,1,1,1,0,0},
{"mget",mgetCommand,-2,"r",0,NULL,1,-1,1,0,0},
{"rpush",rpushCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"lpush",lpushCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"rpushx",rpushxCommand,3,"wm",0,NULL,1,1,1,0,0},
{"lpushx",lpushxCommand,3,"wm",0,NULL,1,1,1,0,0},
{"linsert",linsertCommand,5,"wm",0,NULL,1,1,1,0,0},
{"rpop",rpopCommand,2,"w",0,NULL,1,1,1,0,0},
{"lpop",lpopCommand,2,"w",0,NULL,1,1,1,0,0},
{"brpop",brpopCommand,-3,"ws",0,NULL,1,1,1,0,0},
{"brpoplpush",brpoplpushCommand,4,"wms",0,NULL,1,2,1,0,0},
{"blpop",blpopCommand,-3,"ws",0,NULL,1,-2,1,0,0},
{"llen",llenCommand,2,"r",0,NULL,1,1,1,0,0},
{"lindex",lindexCommand,3,"r",0,NULL,1,1,1,0,0},
{"lset",lsetCommand,4,"wm",0,NULL,1,1,1,0,0},
{"lrange",lrangeCommand,4,"r",0,NULL,1,1,1,0,0},
{"ltrim",ltrimCommand,4,"w",0,NULL,1,1,1,0,0},
{"lrem",lremCommand,4,"w",0,NULL,1,1,1,0,0},
{"rpoplpush",rpoplpushCommand,3,"wm",0,NULL,1,2,1,0,0},
{"sadd",saddCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"srem",sremCommand,-3,"w",0,NULL,1,1,1,0,0},
{"smove",smoveCommand,4,"w",0,NULL,1,2,1,0,0},
{"sismember",sismemberCommand,3,"r",0,NULL,1,1,1,0,0},
{"scard",scardCommand,2,"r",0,NULL,1,1,1,0,0},
{"spop",spopCommand,2,"wRs",0,NULL,1,1,1,0,0},
{"srandmember",srandmemberCommand,-2,"rR",0,NULL,1,1,1,0,0},
{"sinter",sinterCommand,-2,"rS",0,NULL,1,-1,1,0,0},
{"sinterstore",sinterstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
{"sunion",sunionCommand,-2,"rS",0,NULL,1,-1,1,0,0},
{"sunionstore",sunionstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
{"sdiff",sdiffCommand,-2,"rS",0,NULL,1,-1,1,0,0},
{"sdiffstore",sdiffstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
{"smembers",sinterCommand,2,"rS",0,NULL,1,1,1,0,0},
{"zadd",zaddCommand,-4,"wm",0,NULL,1,1,1,0,0},
{"zincrby",zincrbyCommand,4,"wm",0,NULL,1,1,1,0,0},
{"zrem",zremCommand,-3,"w",0,NULL,1,1,1,0,0},
{"zremrangebyscore",zremrangebyscoreCommand,4,"w",0,NULL,1,1,1,0,0},
{"zremrangebyrank",zremrangebyrankCommand,4,"w",0,NULL,1,1,1,0,0},
{"zunionstore",zunionstoreCommand,-4,"wm",0,zunionInterGetKeys,0,0,0,0,0},
{"zinterstore",zinterstoreCommand,-4,"wm",0,zunionInterGetKeys,0,0,0,0,0},
{"zrange",zrangeCommand,-4,"r",0,NULL,1,1,1,0,0},
{"zrangebyscore",zrangebyscoreCommand,-4,"r",0,NULL,1,1,1,0,0},
{"zrevrangebyscore",zrevrangebyscoreCommand,-4,"r",0,NULL,1,1,1,0,0},
{"zcount",zcountCommand,4,"r",0,NULL,1,1,1,0,0},
{"zrevrange",zrevrangeCommand,-4,"r",0,NULL,1,1,1,0,0},
{"zcard",zcardCommand,2,"r",0,NULL,1,1,1,0,0},
{"zscore",zscoreCommand,3,"r",0,NULL,1,1,1,0,0},
{"zrank",zrankCommand,3,"r",0,NULL,1,1,1,0,0},
{"zrevrank",zrevrankCommand,3,"r",0,NULL,1,1,1,0,0},
{"hset",hsetCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hsetnx",hsetnxCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hget",hgetCommand,3,"r",0,NULL,1,1,1,0,0},
{"hmset",hmsetCommand,-4,"wm",0,NULL,1,1,1,0,0},
{"hmget",hmgetCommand,-3,"r",0,NULL,1,1,1,0,0},
{"hincrby",hincrbyCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hincrbyfloat",hincrbyfloatCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hdel",hdelCommand,-3,"w",0,NULL,1,1,1,0,0},
{"hlen",hlenCommand,2,"r",0,NULL,1,1,1,0,0},
{"hkeys",hkeysCommand,2,"rS",0,NULL,1,1,1,0,0},
{"hvals",hvalsCommand,2,"rS",0,NULL,1,1,1,0,0},
{"hgetall",hgetallCommand,2,"r",0,NULL,1,1,1,0,0},
{"hexists",hexistsCommand,3,"r",0,NULL,1,1,1,0,0},
{"incrby",incrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
{"decrby",decrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
{"incrbyfloat",incrbyfloatCommand,3,"wm",0,NULL,1,1,1,0,0},
{"getset",getsetCommand,3,"wm",0,NULL,1,1,1,0,0},
{"mset",msetCommand,-3,"wm",0,NULL,1,-1,2,0,0},
{"msetnx",msetnxCommand,-3,"wm",0,NULL,1,-1,2,0,0},
{"randomkey",randomkeyCommand,1,"rR",0,NULL,0,0,0,0,0},
{"select",selectCommand,2,"r",0,NULL,0,0,0,0,0},
{"move",moveCommand,3,"w",0,NULL,1,1,1,0,0},
{"rename",renameCommand,3,"w",0,renameGetKeys,1,2,1,0,0},
{"renamenx",renamenxCommand,3,"w",0,renameGetKeys,1,2,1,0,0},
{"expire",expireCommand,3,"w",0,NULL,1,1,1,0,0},
{"expireat",expireatCommand,3,"w",0,NULL,1,1,1,0,0},
{"pexpire",pexpireCommand,3,"w",0,NULL,1,1,1,0,0},
{"pexpireat",pexpireatCommand,3,"w",0,NULL,1,1,1,0,0},
{"keys",keysCommand,2,"rS",0,NULL,0,0,0,0,0},
{"dbsize",dbsizeCommand,1,"r",0,NULL,0,0,0,0,0},
{"auth",authCommand,2,"rs",0,NULL,0,0,0,0,0},
{"ping",pingCommand,1,"r",0,NULL,0,0,0,0,0},
{"echo",echoCommand,2,"r",0,NULL,0,0,0,0,0},
{"save",saveCommand,1,"ars",0,NULL,0,0,0,0,0},
{"bgsave",bgsaveCommand,1,"ar",0,NULL,0,0,0,0,0},
{"bgrewriteaof",bgrewriteaofCommand,1,"ar",0,NULL,0,0,0,0,0},
{"shutdown",shutdownCommand,-1,"ar",0,NULL,0,0,0,0,0},
{"lastsave",lastsaveCommand,1,"r",0,NULL,0,0,0,0,0},
{"type",typeCommand,2,"r",0,NULL,1,1,1,0,0},
{"multi",multiCommand,1,"rs",0,NULL,0,0,0,0,0},
{"exec",execCommand,1,"sM",0,NULL,0,0,0,0,0},
{"discard",discardCommand,1,"rs",0,NULL,0,0,0,0,0},
{"sync",syncCommand,1,"ars",0,NULL,0,0,0,0,0},
{"replconf",replconfCommand,-1,"ars",0,NULL,0,0,0,0,0},
{"flushdb",flushdbCommand,1,"w",0,NULL,0,0,0,0,0},
{"flushall",flushallCommand,1,"w",0,NULL,0,0,0,0,0},
{"sort",sortCommand,-2,"wm",0,NULL,1,1,1,0,0},
{"info",infoCommand,-1,"rlt",0,NULL,0,0,0,0,0},
{"monitor",monitorCommand,1,"ars",0,NULL,0,0,0,0,0},
{"ttl",ttlCommand,2,"r",0,NULL,1,1,1,0,0},
{"pttl",pttlCommand,2,"r",0,NULL,1,1,1,0,0},
{"persist",persistCommand,2,"w",0,NULL,1,1,1,0,0},
{"slaveof",slaveofCommand,3,"ast",0,NULL,0,0,0,0,0},
{"debug",debugCommand,-2,"as",0,NULL,0,0,0,0,0},
{"config",configCommand,-2,"ar",0,NULL,0,0,0,0,0},
{"subscribe",subscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},
{"unsubscribe",unsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
{"psubscribe",psubscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},
{"punsubscribe",punsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
{"publish",publishCommand,3,"pflt",0,NULL,0,0,0,0,0},
{"watch",watchCommand,-2,"rs",0,noPreloadGetKeys,1,-1,1,0,0},
{"unwatch",unwatchCommand,1,"rs",0,NULL,0,0,0,0,0},
{"cluster",clusterCommand,-2,"ar",0,NULL,0,0,0,0,0},
{"restore",restoreCommand,-4,"awm",0,NULL,1,1,1,0,0},
{"migrate",migrateCommand,-6,"aw",0,NULL,0,0,0,0,0},
{"asking",askingCommand,1,"r",0,NULL,0,0,0,0,0},
{"dump",dumpCommand,2,"ar",0,NULL,1,1,1,0,0},
{"object",objectCommand,-2,"r",0,NULL,2,2,2,0,0},
{"client",clientCommand,-2,"ar",0,NULL,0,0,0,0,0},
{"eval",evalCommand,-3,"s",0,zunionInterGetKeys,0,0,0,0,0},
{"evalsha",evalShaCommand,-3,"s",0,zunionInterGetKeys,0,0,0,0,0},
{"slowlog",slowlogCommand,-2,"r",0,NULL,0,0,0,0,0},
{"script",scriptCommand,-2,"ras",0,NULL,0,0,0,0,0},
{"time",timeCommand,1,"rR",0,NULL,0,0,0,0,0},
{"bitop",bitopCommand,-4,"wm",0,NULL,2,-1,1,0,0},
{"bitcount",bitcountCommand,-2,"r",0,NULL,1,1,1,0,0}
};
/*============================ Utility functions ============================ */
/* Low level logging. To use only for very big messages, otherwise
* redisLog() is to prefer. */
void redisLogRaw(int level, const char *msg) {
const int syslogLevelMap[] = { LOG_DEBUG, LOG_INFO, LOG_NOTICE, LOG_WARNING };
const char *c = ".-*#";
FILE *fp;
char buf[64];
int rawmode = (level & REDIS_LOG_RAW);
level &= 0xff; /* clear flags */
if (level < server.verbosity) return;
fp = (server.logfile == NULL) ? stdout : fopen(server.logfile,"a");
if (!fp) return;
if (rawmode) {
fprintf(fp,"%s",msg);
} else {
int off;
struct timeval tv;
gettimeofday(&tv,NULL);
off = strftime(buf,sizeof(buf),"%d %b %H:%M:%S.",localtime(&tv.tv_sec));
snprintf(buf+off,sizeof(buf)-off,"%03d",(int)tv.tv_usec/1000);
fprintf(fp,"[%d] %s %c %s\n",(int)getpid(),buf,c[level],msg);
}
fflush(fp);
if (server.logfile) fclose(fp);
if (server.syslog_enabled) syslog(syslogLevelMap[level], "%s", msg);
}
/* Like redisLogRaw() but with printf-alike support. This is the funciton that
* is used across the code. The raw version is only used in order to dump
* the INFO output on crash. */
void redisLog(int level, const char *fmt, ...) {
va_list ap;
char msg[REDIS_MAX_LOGMSG_LEN];
if ((level&0xff) < server.verbosity) return;
va_start(ap, fmt);
vsnprintf(msg, sizeof(msg), fmt, ap);
va_end(ap);
redisLogRaw(level,msg);
}
/* Log a fixed message without printf-alike capabilities, in a way that is
* safe to call from a signal handler.
*
* We actually use this only for signals that are not fatal from the point
* of view of Redis. Signals that are going to kill the server anyway and
* where we need printf-alike features are served by redisLog(). */
void redisLogFromHandler(int level, const char *msg) {
int fd;
char buf[64];
if ((level&0xff) < server.verbosity ||
(server.logfile == NULL && server.daemonize)) return;
fd = server.logfile ?
open(server.logfile, O_APPEND|O_CREAT|O_WRONLY, 0644) :
STDOUT_FILENO;
if (fd == -1) return;
ll2string(buf,sizeof(buf),getpid());
if (write(fd,"[",1) == -1) goto err;
if (write(fd,buf,strlen(buf)) == -1) goto err;
if (write(fd," | signal handler] (",20) == -1) goto err;
ll2string(buf,sizeof(buf),time(NULL));
if (write(fd,buf,strlen(buf)) == -1) goto err;
if (write(fd,") ",2) == -1) goto err;
if (write(fd,msg,strlen(msg)) == -1) goto err;
if (write(fd,"\n",1) == -1) goto err;
err:
if (server.logfile) close(fd);
}
/* Return the UNIX time in microseconds */
// 返回以微秒为格式的 UNIX 时间
long long ustime(void) {
struct timeval tv;
long long ust;
gettimeofday(&tv, NULL);
ust = ((long long)tv.tv_sec)*1000000;
ust += tv.tv_usec;
return ust;
}
/* Return the UNIX time in milliseconds */
// 返回以毫秒为单位的 UNIX 时间
long long mstime(void) {
return ustime()/1000;
}
/* After an RDB dump or AOF rewrite we exit from children using _exit() instead of
* exit(), because the latter may interact with the same file objects used by
* the parent process. However if we are testing the coverage normal exit() is
* used in order to obtain the right coverage information. */
// 如果在测试中，使用 exit 退出 RDB 或 AOF 程序的子进程，
// 运行情况下，使用 _exit
void exitFromChild(int retcode) {
#ifdef COVERAGE_TEST
exit(retcode);
#else
_exit(retcode);
#endif
}
/*====================== Hash table type implementation ==================== */
/* This is an hash table type that uses the SDS dynamic strings libary as
* keys and radis objects as values (objects can hold SDS strings,
* lists, sets). */
void dictVanillaFree(void *privdata, void *val)
{
DICT_NOTUSED(privdata);
zfree(val);
}
void dictListDestructor(void *privdata, void *val)
{
DICT_NOTUSED(privdata);
listRelease((list*)val);
}
int dictSdsKeyCompare(void *privdata, const void *key1,
const void *key2)
{
int l1,l2;
DICT_NOTUSED(privdata);
l1 = sdslen((sds)key1);
l2 = sdslen((sds)key2);
if (l1 != l2) return 0;
return memcmp(key1, key2, l1) == 0;
}
/* A case insensitive version used for the command lookup table and other
* places where case insensitive non binary-safe comparison is needed. */
int dictSdsKeyCaseCompare(void *privdata, const void *key1,
const void *key2)
{
DICT_NOTUSED(privdata);
return strcasecmp(key1, key2) == 0;
}
void dictRedisObjectDestructor(void *privdata, void *val)
{
DICT_NOTUSED(privdata);
if (val == NULL) return; /* Values of swapped out keys as set to NULL */
decrRefCount(val);
}
void dictSdsDestructor(void *privdata, void *val)
{
DICT_NOTUSED(privdata);
sdsfree(val);
}
int dictObjKeyCompare(void *privdata, const void *key1,
const void *key2)
{
const robj *o1 = key1, *o2 = key2;
return dictSdsKeyCompare(privdata,o1->ptr,o2->ptr);
}
unsigned int dictObjHash(const void *key) {
const robj *o = key;
return dictGenHashFunction(o->ptr, sdslen((sds)o->ptr));
}
unsigned int dictSdsHash(const void *key) {
return dictGenHashFunction((unsigned char*)key, sdslen((char*)key));
}
unsigned int dictSdsCaseHash(const void *key) {
return dictGenCaseHashFunction((unsigned char*)key, sdslen((char*)key));
}
int dictEncObjKeyCompare(void *privdata, const void *key1,
const void *key2)
{
robj *o1 = (robj*) key1, *o2 = (robj*) key2;
int cmp;
if (o1->encoding == REDIS_ENCODING_INT &&
o2->encoding == REDIS_ENCODING_INT)
return o1->ptr == o2->ptr;
o1 = getDecodedObject(o1);
o2 = getDecodedObject(o2);
cmp = dictSdsKeyCompare(privdata,o1->ptr,o2->ptr);
decrRefCount(o1);
decrRefCount(o2);
return cmp;
}
unsigned int dictEncObjHash(const void *key) {
robj *o = (robj*) key;
if (o->encoding == REDIS_ENCODING_RAW) {
return dictGenHashFunction(o->ptr, sdslen((sds)o->ptr));
} else {
if (o->encoding == REDIS_ENCODING_INT) {
char buf[32];
int len;
len = ll2string(buf,32,(long)o->ptr);
return dictGenHashFunction((unsigned char*)buf, len);
} else {
unsigned int hash;
o = getDecodedObject(o);
hash = dictGenHashFunction(o->ptr, sdslen((sds)o->ptr));
decrRefCount(o);
return hash;
}
}
}
/* Sets type hash table */
dictType setDictType = {
dictEncObjHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictEncObjKeyCompare, /* key compare */
dictRedisObjectDestructor, /* key destructor */
NULL /* val destructor */
};
/* Sorted sets hash (note: a skiplist is used in addition to the hash table) */
dictType zsetDictType = {
dictEncObjHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictEncObjKeyCompare, /* key compare */
dictRedisObjectDestructor, /* key destructor */
NULL /* val destructor */
};
/* Db->dict, keys are sds strings, vals are Redis objects. */
dictType dbDictType = {
dictSdsHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCompare, /* key compare */
dictSdsDestructor, /* key destructor */
dictRedisObjectDestructor /* val destructor */
};
/* server.lua_scripts sha (as sds string) -> scripts (as robj) cache. */
dictType shaScriptObjectDictType = {
dictSdsCaseHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCaseCompare, /* key compare */
dictSdsDestructor, /* key destructor */
dictRedisObjectDestructor /* val destructor */
};
/* Db->expires */
dictType keyptrDictType = {
dictSdsHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCompare, /* key compare */
NULL, /* key destructor */
NULL /* val destructor */
};
/* Command table. sds string -> command struct pointer. */
dictType commandTableDictType = {
dictSdsCaseHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCaseCompare, /* key compare */
dictSdsDestructor, /* key destructor */
NULL /* val destructor */
};
/* Hash type hash table (note that small hashes are represented with zimpaps) */
dictType hashDictType = {
dictEncObjHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictEncObjKeyCompare, /* key compare */
dictRedisObjectDestructor, /* key destructor */
dictRedisObjectDestructor /* val destructor */
};
/* Keylist hash table type has unencoded redis objects as keys and
* lists as values. It's used for blocking operations (BLPOP) and to
* map swapped keys to a list of clients waiting for this keys to be loaded. */
dictType keylistDictType = {
dictObjHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictObjKeyCompare, /* key compare */
dictRedisObjectDestructor, /* key destructor */
dictListDestructor /* val destructor */
};
/* Cluster nodes hash table, mapping nodes addresses 1.2.3.4:6379 to
* clusterNode structures. */
dictType clusterNodesDictType = {
dictSdsHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCompare, /* key compare */
dictSdsDestructor, /* key destructor */
NULL /* val destructor */
};
/* Migrate cache dict type. */
dictType migrateCacheDictType = {
dictSdsHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCompare, /* key compare */
dictSdsDestructor, /* key destructor */
NULL /* val destructor */
};
/*
* 检查字典节点的使用率是否低于系统允许的最小比率
*
* 是的话返回 1 ，否则返回 0 。
*/
int htNeedsResize(dict *dict) {
long long size, used;
// 已用节点数
size = dictSlots(dict);
// 可用节点数
used = dictSize(dict);
// 哈希表大小大于 DICT_HT_INITIAL_SIZE
// 并且空间的占用百分比为 10% 时
// 返回真
return (size && used && size > DICT_HT_INITIAL_SIZE &&
(used*100/size < REDIS_HT_MINFILL));
}
/* If the percentage of used slots in the HT reaches REDIS_HT_MINFILL
* we resize the hash table to save memory */
/*
* 如果字典的使用空间比率低于 REDIS_HT_MINFILL
* 那么将字典的大小缩小，让 USED/BUCKETS 的比率 <= 1
*/
void tryResizeHashTables(void) {
int j;
for (j = 0; j < server.dbnum; j++) {
// 缩小 key space
if (htNeedsResize(server.db[j].dict))
dictResize(server.db[j].dict);
// 缩小 expire space
if (htNeedsResize(server.db[j].expires))
dictResize(server.db[j].expires);
}
}
/* Our hash table implementation performs rehashing incrementally while
* we write/read from the hash table. Still if the server is idle, the hash
* table will use two tables for a long time. So we try to use 1 millisecond
* of CPU time at every serverCron() loop in order to rehash some key. */
/*
* 在 Redis Cron 中调用，对数据库中第一个遇到的、可以进行 rehash 的哈希表
* 进行 1 毫秒的渐进式 rehash
*/
void incrementallyRehash(void) {
int j;
for (j = 0; j < server.dbnum; j++) {
/* Keys dictionary */
if (dictIsRehashing(server.db[j].dict)) {
dictRehashMilliseconds(server.db[j].dict,1);
break; /* already used our millisecond for this loop... */
}
/* Expires */
if (dictIsRehashing(server.db[j].expires)) {
dictRehashMilliseconds(server.db[j].expires,1);
break; /* already used our millisecond for this loop... */
}
}
}
/* This function is called once a background process of some kind terminates,
* as we want to avoid resizing the hash tables when there is a child in order
* to play well with copy-on-write (otherwise when a resize happens lots of
* memory pages are copied). The goal of this function is to update the ability
* for dict.c to resize the hash tables accordingly to the fact we have o not
* running childs. */
// 在执行保存时关闭对数据库的 rehash
// 避免 copy-on-write 问题
void updateDictResizePolicy(void) {
if (server.rdb_child_pid == -1 && server.aof_child_pid == -1)
dictEnableResize();
else
dictDisableResize();
}
/* ======================= Cron: called every 100 ms ======================== */
// 在新版中，已经可以设置 HZ 的时间了
/* Try to expire a few timed out keys. The algorithm used is adaptive and
* will use few CPU cycles if there are few expiring keys, otherwise
* it will get more aggressive to avoid that too much memory is used by
* keys that can be removed from the keyspace. */
/*
* 主动清除过期 key
*/
void activeExpireCycle(void) {
int j, iteration = 0;
long long start = ustime(), timelimit;
/* We can use at max REDIS_EXPIRELOOKUPS_TIME_PERC percentage of CPU time
* per iteration. Since this function gets called with a frequency of
* REDIS_HZ times per second, the following is the max amount of
* microseconds we can spend in this function. */
// 这个函数可以使用的时长（毫秒）
timelimit = 1000000*REDIS_EXPIRELOOKUPS_TIME_PERC/REDIS_HZ/100;
if (timelimit <= 0) timelimit = 1;
for (j = 0; j < server.dbnum; j++) {
int expired;
redisDb *db = server.db+j;
/* Continue to expire if at the end of the cycle more than 25%
* of the keys were expired. */
do {
unsigned long num = dictSize(db->expires);
unsigned long slots = dictSlots(db->expires);
long long now = mstime();
/* When there are less than 1% filled slots getting random
* keys is expensive, so stop here waiting for better times...
* The dictionary will be resized asap. */
// 过期字典里只有 %1 位置被占用，调用随机 key 的消耗比较高
// 等 key 多一点再来
if (num && slots > DICT_HT_INITIAL_SIZE &&
(num*100/slots < 1)) break;
/* The main collection cycle. Sample random keys among keys
* with an expire set, checking for expired ones. */
// 从过期字典中随机取出 key ，检查它是否过期
expired = 0; // 被删除 key 计数
if (num > REDIS_EXPIRELOOKUPS_PER_CRON) // 最多每次可查找的次数
num = REDIS_EXPIRELOOKUPS_PER_CRON;
while (num--) {
dictEntry *de;
long long t;
// 随机查找带有 TTL 的 key ，看它是否过期
// 如果数据库为空，跳出
if ((de = dictGetRandomKey(db->expires)) == NULL) break;
t = dictGetSignedIntegerVal(de);
if (now > t) {
// 已过期
sds key = dictGetKey(de);
robj *keyobj = createStringObject(key,sdslen(key));
propagateExpire(db,keyobj);
dbDelete(db,keyobj);
decrRefCount(keyobj);
expired++;
server.stat_expiredkeys++;
}
}
/* We can't block forever here even if there are many keys to
* expire. So after a given amount of milliseconds return to the
* caller waiting for the other active expire cycle. */
// 每次进行 16 次循环之后，检查时间是否超过，如果超过，则退出
iteration++;
if ((iteration & 0xf) == 0 && /* check once every 16 cycles. */
(ustime()-start) > timelimit) return;
} while (expired > REDIS_EXPIRELOOKUPS_PER_CRON/4);
}
}
/*
* 更新服务器的 LRU 时间
*/
void updateLRUClock(void) {
server.lruclock = (server.unixtime/REDIS_LRU_CLOCK_RESOLUTION) &
REDIS_LRU_CLOCK_MAX;
}
/* Add a sample to the operations per second array of samples. */
void trackOperationsPerSecond(void) {
long long t = mstime() - server.ops_sec_last_sample_time;
long long ops = server.stat_numcommands - server.ops_sec_last_sample_ops;
long long ops_sec;
ops_sec = t > 0 ? (ops*1000/t) : 0;
server.ops_sec_samples[server.ops_sec_idx] = ops_sec;
server.ops_sec_idx = (server.ops_sec_idx+1) % REDIS_OPS_SEC_SAMPLES;
server.ops_sec_last_sample_time = mstime();
server.ops_sec_last_sample_ops = server.stat_numcommands;
}
/* Return the mean of all the samples. */
long long getOperationsPerSecond(void) {
int j;
long long sum = 0;
for (j = 0; j < REDIS_OPS_SEC_SAMPLES; j++)
sum += server.ops_sec_samples[j];
return sum / REDIS_OPS_SEC_SAMPLES;
}
/* Check for timeouts. Returns non-zero if the client was terminated */
/*
* 检查客户端连接是否超时
*
* 客户端被终止时返回 1 ，未过时返回 0 。
*/
int clientsCronHandleTimeout(redisClient *c) {
time_t now = server.unixtime;
if (server.maxidletime &&
!(c->flags & REDIS_SLAVE) && /* no timeout for slaves */
!(c->flags & REDIS_MASTER) && /* no timeout for masters */
!(c->flags & REDIS_BLOCKED) && /* no timeout for BLPOP */
dictSize(c->pubsub_channels) == 0 && /* no timeout for pubsub */
listLength(c->pubsub_patterns) == 0 &&
(now - c->lastinteraction > server.maxidletime))
{
redisLog(REDIS_VERBOSE,"Closing idle client");
freeClient(c);
return 1;
} else if (c->flags & REDIS_BLOCKED) {
// 返回空白回复给阻塞超时的客户端
if (c->bpop.timeout != 0 && c->bpop.timeout < now) {
addReply(c,shared.nullmultibulk);
unblockClientWaitingData(c);
}
}
return 0;
}
/* The client query buffer is an sds.c string that can end with a lot of
* free space not used, this function reclaims space if needed.
*
* The funciton always returns 0 as it never terminates the client. */
// 收缩查询缓存的空间
int clientsCronResizeQueryBuffer(redisClient *c) {
size_t querybuf_size = sdsAllocSize(c->querybuf);
time_t idletime = server.unixtime - c->lastinteraction;
/* There are two conditions to resize the query buffer:
* 1) Query buffer is > BIG_ARG and too big for latest peak.
* 2) Client is inactive and the buffer is bigger than 1k. */
if (((querybuf_size > REDIS_MBULK_BIG_ARG) &&
(querybuf_size/(c->querybuf_peak+1)) > 2) ||
(querybuf_size > 1024 && idletime > 2))
{
/* Only resize the query buffer if it is actually wasting space. */
if (sdsavail(c->querybuf) > 1024) {
c->querybuf = sdsRemoveFreeSpace(c->querybuf);
}
}
/* Reset the peak again to capture the peak memory usage in the next
* cycle. */
c->querybuf_peak = 0;
return 0;
}
/*
* 客户端常规任务
*
* 检查连接是否超时，以及清理多余的查询缓存
*/
void clientsCron(void) {
/* Make sure to process at least 1/(REDIS_HZ*10) of clients per call.
* Since this function is called REDIS_HZ times per second we are sure that
* in the worst case we process all the clients in 10 seconds.
* In normal conditions (a reasonable number of clients) we process
* all the clients in a shorter time. */
int numclients = listLength(server.clients);
int iterations = numclients/(REDIS_HZ*10);
// 最多执行 50 个迭代
if (iterations < 50)
iterations = (numclients < 50) ? numclients : 50;
while(listLength(server.clients) && iterations--) {
redisClient *c;
listNode *head;
/* Rotate the list, take the current head, process.
* This way if the client must be removed from the list it's the
* first element and we don't incur into O(N) computation. */
// 将处理的客户端调到表头，
// 这样在要删除客户端时，复杂度就是 O(1) 而不是 O(N) 了
listRotate(server.clients);
head = listFirst(server.clients);
c = listNodeValue(head);
/* The following functions do different service checks on the client.
* The protocol is that they return non-zero if the client was
* terminated. */
// 检查客户端是否超时，如果是的话，删除它的连接
// 如果客户端正因 BLPOP/BRPOP/BLPOPRPUSH 阻塞，那么检查阻塞是否超时，
// 是的话就退出阻塞状态
if (clientsCronHandleTimeout(c)) continue;
// 释放客户端查询缓存多余的空间
if (clientsCronResizeQueryBuffer(c)) continue;
}
}
/* This is our timer interrupt, called REDIS_HZ times per second.
* 时间中断器，调用间隔为 REDIS_HZ 。
*
* Here is where we do a number of things that need to be done asynchronously.
* For instance:
*
* 以下是需要异步地完成的工作：
*
* - Active expired keys collection (it is also performed in a lazy way on
* lookup).
* 主动回收过期的键
*
* - Software watchdong.
* WATCHDOG
*
* - Update some statistic.
* 更新统计信息
*
* - Incremental rehashing of the DBs hash tables.
* 对数据库进行渐进式 REHASH
*
* - Triggering BGSAVE / AOF rewrite, and handling of terminated children.
* 触发 BGSAVE 、 AOF 重写，并处理随之而来的子进程中介
*
* - Clients timeout of differnet kinds.
* 各种类型的客户端超时
*
* - Replication reconnection.
* 重连复制节点
*
* - Many more...
* 等等
*
* Everything directly called here will be called REDIS_HZ times per second,
* so in order to throttle execution of things we want to do less frequently
* a macro is used: run_with_period(milliseconds) { .... }
*
* 因为在这个函数中直接调用的函数都会以 REDIS_HZ 频率调用，
* 为了调整部分函数执行的频率，使用了 run_with_period(ms) { ... }
* 来修改代码的执行频率
*/
int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
int j;
REDIS_NOTUSED(eventLoop);
REDIS_NOTUSED(id);
REDIS_NOTUSED(clientData);
/* Software watchdog: deliver the SIGALRM that will reach the signal
* handler if we don't return here fast enough. */
if (server.watchdog_period) watchdogScheduleSignal(server.watchdog_period);
/* We take a cached value of the unix time in the global state because
* with virtual memory and aging there is to store the current time
* in objects at every object access, and accuracy is not needed.
* To access a global var is faster than calling time(NULL) */
// 将 UNIX 时间保存在服务器状态中，减少对 time(NULL) 的调用，加速。
server.unixtime = time(NULL);
// 对执行命令的时间进行采样分析
run_with_period(100) trackOperationsPerSecond();
/* We have just 22 bits per object for LRU information.
* So we use an (eventually wrapping) LRU clock with 10 seconds resolution.
* 2^22 bits with 10 seconds resoluton is more or less 1.5 years.
*
* Note that even if this will wrap after 1.5 years it's not a problem,
* everything will still work but just some object will appear younger
* to Redis. But for this to happen a given object should never be touched
* for 1.5 years.