Redis 記憶體管理與事件處理
1 Redis記憶體管理
Redis記憶體管理相關檔為zmalloc.c/zmalloc.h,其只是對C中記憶體管理函數做了簡單的封裝,遮罩了底層平臺的差異,並增加了記憶體使用情況統計的功能。
void *zmalloc(size_t size) {
// 多申請的一部分記憶體用於存儲當前分配了多少自己的記憶體
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;
// 記憶體分配統計
update_zmalloc_stat_alloc(size+PREFIX_SIZE);
return (char*)ptr+PREFIX_SIZE;
#endif
}
記憶體佈局圖示:
2 事件處理
Redis的事件類型分為時間事件和檔事件,檔事件也就是網路連接事件。時間事件的處理是在epoll_wait返回處理檔事件後處理的,每次epoll_wait的超時時間都是Redis最近的一個計時器時間。
Redis在進行事件處理前,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:
設置信號回呼函數。
創建事件迴圈機制,
創建服務監聽埠,創建定時事件,並將這些事件添加到事件機制中。
void initServer(void) {
int j;
// 設置信號對應的處理函數
signal(SIGHUP, SIG_IGN);
signal(SIGPIPE, SIG_IGN);
setupSignalHandlers();
...
createSharedObjects();
adjustOpenFilesLimit();
// 創建事件迴圈機制,及調用epoll_create創建epollfd用於事件監聽
server.el = aeCreateEventLoop(server.maxclients+CONFIG_FDSET_INCR);
server.db = zmalloc(sizeof(redisDb)*server.dbnum);
/* Open the TCP listening socket for the user commands. */
// 創建監聽服務埠,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. 創建定時事件 */
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.");
}
}
// 將事件加入到事件機制中,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);
}
}
...
}
事件處理流程
事件處理函數鏈: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,然後遍歷每一個epoll_event,提取epoll_event中的events和data域,data域常用來存儲fd或者指標,
Redis中用了一個陣列來保存fd與回呼函數的映射關係,使用陣列的優點就是簡單高效,但是陣列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的檔事件大都是用戶端建立的連接,
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 ? (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陣列中查找對應的回呼函數
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++;
}
...
}
文件事件的監聽
Redis監聽埠的事件回呼函數鏈是:acceptTcpHandler / acceptCommonHandler / createClient / aeCreateFileEvent / aeApiAddEvent / epoll_ctl。
在Reids監聽事件處理流程中,會將用戶端的連接fd添加到事件機制中,並設置其回呼函數為readQueryFromClient,該函數負責處理用戶端的命令請求。
命令處理流程
命令處理流程鏈是:readQueryFromClient / processInputBuffer / processCommand / call / 對應命令的回呼函數(c->cmd->proc),比如get key命令的處理回呼函數為getCommand。getCommand的執行流程是先到client對應的資料庫字典中根據key來查找資料,
IT學習就選優就業
3 如何添加自訂命令
如何在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,比如自訂命令random xxx,然後返回redis: xxx,因為hello xxx和get key類似,所以就依葫蘆畫瓢。
首先在redisCommandTable陣列中添加自訂的命令,redisCommandTable陣列定義在server.c中。然後在getCommand定義處後面添加randomCommand的定義,getCommand定義在t_string.c中。最後在server.h中添加helloCommand的聲明。整個修改patch檔如下,代碼基於redis-2.8.9版本。
From 5304020683078273c1bc6cc9666dab95efa18607 Mon Sep 17 00:00:00 2001
From: luoxn28
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 != ' ') {
+ if (!(('0' <= *c)="" &&="" (*c="">=><= '9')))="">=>
+ return false;
+ }
+ c++;
+ }
+
+ return true;
+}
+
+/**
+ * command: random n
+ * return a random num < n,="" if="" n=""><= 0,="" return="">=>
+ * @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
結果如下所示:
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