1 Redis內存治理

Redis內存管理相關文件為zmalloc.c/zmalloc.h,其只是對C中內存管理函數做了簡單的封裝,屏蔽了底層平臺的差別,并增加了內存使用情況統計的功能.

void *zmalloc(size_t size) {

// 多申請的一部分內存用于存儲當前分配了多少本身的內存

void *ptr = malloc(size+PREFIX_SIZE);

if (!ptr) zmalloc_oom_handler(size);

#ifdef HAVE_MALLOC_SIZE

update_zmalloc_stat_alloc(zmalloc_size(ptr));

return ptr;

#else

*((size_t*)ptr) = size;

// 內存分派統計

update_zmalloc_stat_alloc(size+PREFIX_SIZE);

return (char*)ptr+PREFIX_SIZE;

#endif

}

內存結構圖示：

2 變亂處理

Redis的事件類型分為時間事件和文件事件,文件事件也便是網絡連接事件.時間事件的處理是在epoll_wait返回處理文件事件后處理的,每次epoll_wait的超時時間都是Redis最近的一個定時器時間.

Redis在進行變亂處理前,首先會進行初始化,初始化的主要邏輯在main/initServer函數中.初始化流程主要做的工作如下：

• 設置旌旗燈號回調函數.

• 創建變亂循環機制,即調用epoll_create.

• 創建服務監聽端口,創建定時變亂,并將這些變亂添加到變亂機制中.

void initServer(void) {

int j;

// 設置信號對應的處置函數

signal(SIGHUP, SIG_IGN);

signal(SIGPIPE, SIG_IGN);

setupSignalHandlers();

...

createSharedObjects();

adjustOpenFilesLimit();

// 創建變亂循環機制,及調用epoll_create創建epollfd用于變亂監聽

server.el = aeCreateEventLoop(server.maxclients+CONFIG_FDSET_INCR);

server.db = zmalloc(sizeof(redisDb)*server.dbnum);

/* Open the TCP listening socket for the user commands. */

// 創立監聽服務端口,socket/bind/listen

if (server.port != 0 &&

listenToPort(server.port,server.ipfd,&server.ipfd_count) == C_ERR)

exit(1);

...

/* Create the Redis databases, and initialize other internal state. */

for (j = 0; j < server.dbnum; j++) {

server.db[j].dict = dictCreate(&dbDictType,NULL);

server.db[j].expires = dictCreate(&keyptrDictType,NULL);

server.db[j].blocking_keys = dictCreate(&keylistDictType,NULL);

server.db[j].ready_keys = dictCreate(&setDictType,NULL);

server.db[j].watched_keys = dictCreate(&keylistDictType,NULL);

server.db[j].eviction_pool = evictionPoolAlloc();

server.db[j].id = j;

server.db[j].avg_ttl = 0;

}

...

/* Create the serverCron() time event, that's our main way to process

* background operations. 創建定時變亂 */

if(aeCreateTimeEvent(server.el, 1, serverCron, NULL, NULL) == AE_ERR) {

serverPanic("Can't create the serverCron time event.");

exit(1);

}

/* Create an event handler for accepting new connections in TCP and Unix

* domain sockets. */

for (j = 0; j < server.ipfd_count; j++) {

if (aeCreateFileEvent(server.el, server.ipfd[j], AE_READABLE,

acceptTcpHandler,NULL) == AE_ERR)

{

serverPanic(

"Unrecoverable error creating server.ipfd file event.");

}

}

// 將變亂加入到變亂機制中,調用鏈為 aeCreateFileEvent/aeApiAddEvent/epoll_ctl

if (server.sofd > 0 && aeCreateFileEvent(server.el,server.sofd,AE_READABLE,

acceptUnixHandler,NULL) == AE_ERR) serverPanic("Unrecoverable error creating server.sofd file event.");

/* Open the AOF file if needed. */

if (server.aof_state == AOF_ON) {

server.aof_fd = open(server.aof_filename,

O_WRONLY|O_APPEND|O_CREAT,0644);

if (server.aof_fd == -1) {

serverLog(LL_WARNING, "Can't open the append-only file: %s",

strerror(errno));

exit(1);

}

}

...

}

變亂處理流程

變亂處理函數鏈：aeMain / aeProcessEvents / aeApiPoll / epoll_wait.

常見的事件機制處理流程是：調用epoll_wait等待事件來臨,然后遍歷每一個epoll_event,提取epoll_event中的events和data域,data域常用來存儲fd或者指針,不過一般的做法是提取出events和data.fd,然后根據fd找到對應的回調函數,fd與對應回調函數之間的映射關系可以存儲在特定的數據結構中,好比數組或者哈希表,然后調用事件回調函數來處理.

Redis中用了一個數組來保留fd與回調函數的映射關系,使用數組的優點就是簡單高效,但是數組一般使用在建立的連接不太多情況,而Redis正好符合這個情況,一般Redis的文件事件大都是客戶端建立的連接,而客戶端的連接個數是一定的,該數量通過配置項maxclients來指定.

static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {

aeApiState *state = eventLoop->apidata;

int retval, numevents = 0;

retval = epoll_wait(state->epfd,state->events,eventLoop->setsize,

tvp 必修 (tvp->tv_sec*1000 + tvp->tv_usec/1000) : -1);

if (retval > 0) {

int j;

numevents = retval;

for (j = 0; j < numevents; j++) {

int mask = 0;

struct epoll_event *e = state->events+j;

if (e->events & EPOLLIN) mask |= AE_READABLE;

if (e->events & EPOLLOUT) mask |= AE_WRITABLE;

if (e->events & EPOLLERR) mask |= AE_WRITABLE;

if (e->events & EPOLLHUP) mask |= AE_WRITABLE;

eventLoop->fired[j].fd = e->data.fd;

eventLoop->fired[j].mask = mask;

}

}

return numevents;

}

int aeProcessEvents(aeEventLoop *eventLoop, int flags)

{

numevents = aeApiPoll(eventLoop, tvp);

for (j = 0; j < numevents; j++) {

// 從eventLoop->events數組中查找對應的回調函數

aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];

int mask = eventLoop->fired[j].mask;

int fd = eventLoop->fired[j].fd;

int rfired = 0;

/* note the fe->mask & mask & ... code: maybe an already processed

* event removed an element that fired and we still didn't

* processed, so we check if the event is still valid. */

if (fe->mask & mask & AE_READABLE) {

rfired = 1;

fe->rfileProc(eventLoop,fd,fe->clientData,mask);

}

if (fe->mask & mask & AE_WRITABLE) {

if (!rfired || fe->wfileProc != fe->rfileProc)

fe->wfileProc(eventLoop,fd,fe->clientData,mask);

}

processed++;

}

...

}

文件變亂的監聽

Redis監聽端口的變亂回調函數鏈是：acceptTcpHandler / acceptCommonHandler / createClient / aeCreateFileEvent / aeApiAddEvent / epoll_ctl.

在Reids監聽事件處理流程中,會將客戶端的連接fd添加到事件機制中,并設置其回調函數為readQueryFromClient,該函數負責處理客戶端的命令哀求.

命令處置流程

命令處理流程鏈是：readQueryFromClient / processInputBuffer / processCommand / call / 對應命令的回調函數(c->cmd->proc),好比get key命令的處理回調函數為getCommand.getCommand的執行流程是先到client對應的數據庫字典中根據key來查找數據,然后根據響應消息格式將查詢結果填充到響應消息中.

IT進修就選優就業

3 如何添加自界說命令

如安在Redis中添加自定的命令呢?其中只需要改動以下幾個地方就行了,比如自定義命令random xxx,然后返回redis: xxx,因為hello xxx和get key類似,所以就依葫蘆畫瓢.random命令用來返回一個小于xxx的隨機值.

首先在redisCommandTable數組中添加自界說的命令,redisCommandTable數組界說在server.c中.然后在getCommand界說處后面添加randomCommand的界說,getCommand界說在t_string.c中.最后在server.h中添加helloCommand的聲明.整個修改patch文件如下,代碼基于redis-2.8.9版本.

From 5304020683078273c1bc6cc9666dab95efa18607 Mon Sep 17 00:00:00 2001

From: luoxn28 <luoxn28@163.com>

Date: Fri, 30 Jun 2017 04:43:47 -0700

Subject: [PATCH] add own command: random num

---

src/server.c | 3 ++-

src/server.h | 1 +

src/t_string.c | 44 ++++++++++++++++++++++++++++++++++++++++++++

3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/server.c b/src/server.c

index 609f396..e040104 100644

--- a/src/server.c

+++ b/src/server.c

@@ -296,7 +296,8 @@ struct redisCommand redisCommandTable[] = {

{"pfdebug",pfdebugCommand,-3,"w",0,NULL,0,0,0,0,0},

{"post",securityWarningCommand,-1,"lt",0,NULL,0,0,0,0,0},

{"host:",securityWarningCommand,-1,"lt",0,NULL,0,0,0,0,0},

- {"latency",latencyCommand,-2,"aslt",0,NULL,0,0,0,0,0}

+ {"latency",latencyCommand,-2,"aslt",0,NULL,0,0,0,0,0},

+ {"random",randomCommand,2,"rF",0,NULL,1,1,1,0,0}

};

struct evictionPoolEntry *evictionPoolAlloc(void);

diff --git a/src/server.h b/src/server.h

index 3fa7c3a..427ac92 100644

--- a/src/server.h

+++ b/src/server.h

@@ -1485,6 +1485,7 @@ void setnxCommand(client *c);

void setexCommand(client *c);

void psetexCommand(client *c);

void getCommand(client *c);

+void randomCommand(client *c);

void delCommand(client *c);

void existsCommand(client *c);

void setbitCommand(client *c);

diff --git a/src/t_string.c b/src/t_string.c

index 8c737c4..df4022d 100644

--- a/src/t_string.c

+++ b/src/t_string.c

@@ -173,6 +173,50 @@ void getCommand(client *c) {

getGenericCommand(c);

}

+static bool checkRandomNum(char *num)

+{

+ char *c = num;

+

+ while (*c != '\0') {

+ if (!(('0' <= *c) && (*c <= '9'))) {

+ return false;

+ }

+ c++;

+ }

+

+ return true;

+}

+

+/**

+ * command: random n

+ * return a random num < n, if n <= 0, return 0

+ * @author: luoxiangnan

+ */

+void randomCommand(client *c)

+{

+ char buff[64] = {0};

+ int num = 0;

+ robj *o = NULL;

+

+ if (!checkRandomNum(c->argv[1]->ptr)) {

+ o = createObject(OBJ_STRING, sdsnewlen("sorry, it's not a num :(",

+ strlen("sorry, it's not a num :(")));

+ addReplyBulk(c, o);

+ return;

+ }

+

+ sscanf(c->argv[1]->ptr, "%d", &num);

+ if (num > 0) {

+ num = random() % num;

+ } else {

+ num = 0;

+ }

+

+ sprintf(buff, "%s %d", "redis: ", num);

+ o = createObject(OBJ_STRING, sdsnewlen(buff, strlen(buff)));

+ addReplyBulk(c, o);

+}

+

void getsetCommand(client *c) {

if (getGenericCommand(c) == C_ERR) return;

c->argv[2] = tryObjectEncoding(c->argv[2]);

--

1.8.3.1

成果如下所示：

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