redis是多線(xiàn)程的，你會(huì)問(wèn)如何確認(rèn)，其實(shí)很簡(jiǎn)單，用gdb確認(rèn)即可，我服務(wù)器上的剛好有部署redis，它的進(jìn)程pid為26716。

[root@rookie_centos myXxl]# gdb -p 26716
[Thread debugging using libthread_db enabled]
Loaded symbols for /lib64/libpthread.so.0
Reading symbols from /lib64/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib64/libc.so.6
Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
0x00007f6e8faa81c3 in epoll_wait () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.209.el6_9.2.x86_64
(gdb) bt
#0  0x00007f6e8faa81c3 in epoll_wait () from /lib64/libc.so.6
#1  0x000000000042491e in aeApiPoll (eventLoop=0x7f6e894340a0, flags=11) at ae_epoll.c:112
#2  aeProcessEvents (eventLoop=0x7f6e894340a0, flags=11) at ae.c:404
#3  0x0000000000424d3b in aeMain (eventLoop=0x7f6e894340a0) at ae.c:464
#4  0x000000000042d902 in main (argc=<value optimized out>, argv=0x7ffe660d3dd8) at server.c:3865
(gdb) info threads
  4 Thread 0x7f6e893ff700 (LWP 26718)  0x00007f6e8fd5e68c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
  3 Thread 0x7f6e889fe700 (LWP 26719)  0x00007f6e8fd5e68c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
  2 Thread 0x7f6e87ffd700 (LWP 26720)  0x00007f6e8fd5e68c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
* 1 Thread 0x7f6e9060c740 (LWP 26716)  0x00007f6e8faa81c3 in epoll_wait () from /lib64/libc.so.6
(gdb) 

正如上面一樓所說(shuō)redis采用的是reactor的并發(fā)模型，也就是主線(xiàn)程使用io復(fù)用對(duì)多個(gè)客戶(hù)端進(jìn)行監(jiān)聽(tīng)，有請(qǐng)求過(guò)來(lái)時(shí)，喚醒工作線(xiàn)程來(lái)做讀io操作讀取客戶(hù)的請(qǐng)求數(shù)據(jù)，工作線(xiàn)程處理完請(qǐng)求向主線(xiàn)程注冊(cè)寫(xiě)請(qǐng)求，客戶(hù)端io可寫(xiě)時(shí)主線(xiàn)程喚醒工作線(xiàn)程，工作線(xiàn)程再進(jìn)行寫(xiě)io操作把應(yīng)答發(fā)送給客戶(hù)端。主線(xiàn)程通過(guò)條件變量來(lái)喚醒工作線(xiàn)程，從上面gdb的輸出可以看出工作線(xiàn)程都是調(diào)用pthread_cond_wait后被掛起，在等待主線(xiàn)程的喚醒，主線(xiàn)程則調(diào)用epoll_wait這個(gè)高效的io復(fù)用函數(shù)在等待客戶(hù)端的請(qǐng)求。

Redis的網(wǎng)絡(luò)模型是一個(gè)單線(xiàn)程epoll模型，但是不見(jiàn)得處理過(guò)程始終單進(jìn)程哦，有些處理可能會(huì)阻塞服務(wù)器，還是會(huì)開(kāi)進(jìn)程處理的：比如在保存RDB文件時(shí)候，https://github.com/antirez/redis/blob/unstable/src/rdb.c#L1059，還有sentinel，https://github.com/antirez/redis/blob/unstable/src/sentinel.c#L754

在 redis 實(shí)戰(zhàn) 里邊是有談到這個(gè)問(wèn)題,但是其實(shí)問(wèn)題的本質(zhì)還是 UNIX IO 模型的運(yùn)用,建議看一下UNIX 網(wǎng)絡(luò)編程 第六章 IO復(fù)用.說(shuō)到具體的實(shí)現(xiàn)可以看一下 reactor 模式 .