标签归档:redis

Redis CPU使用率过高问题的排查

Redis CPU占用过高会导致所有使用Redis的客户端性能大幅下降,可能的原因中其中一个是大量的请求,尤其是keys命令请求过多,查询流程:

  1. 使用info和monitor命令(这两个命令也可以登录之后使用,不过有可能造成client的crash)

redis-cli -h 192.168.1.2  -a ‘passwd’ info 

Clients

connected_clients:25
client_longest_output_list:0
client_biggest_input_buf:0
blocked_clients:1

Memory

used_memory:24022936
used_memory_human:22.91M
used_memory_rss:27422720
used_memory_rss_human:26.15M
used_memory_peak:76894968
used_memory_peak_human:73.33M
total_system_memory:33566736384
total_system_memory_human:31.26G
used_memory_lua:43008
used_memory_lua_human:42.00K
maxmemory:0
maxmemory_human:0B
maxmemory_policy:noeviction
mem_fragmentation_ratio:1.14
mem_allocator:jemalloc-4.0.3

Persistence

loading:0
rdb_changes_since_last_save:3502
rdb_bgsave_in_progress:0
rdb_last_save_time:1575614696
rdb_last_bgsave_status:ok
rdb_last_bgsave_time_sec:0
rdb_current_bgsave_time_sec:-1
aof_enabled:0
aof_rewrite_in_progress:0
aof_rewrite_scheduled:0
aof_last_rewrite_time_sec:-1
aof_current_rewrite_time_sec:-1
aof_last_bgrewrite_status:ok
aof_last_write_status:ok

Stats

total_connections_received:8119852
total_commands_processed:287772910835
instantaneous_ops_per_sec:23686
total_net_input_bytes:8372810113180
total_net_output_bytes:1471697139442
instantaneous_input_kbps:676.85
instantaneous_output_kbps:129.54
rejected_connections:0
sync_full:0
sync_partial_ok:0
sync_partial_err:0
expired_keys:158935
evicted_keys:0
keyspace_hits:188709502
keyspace_misses:6948953
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:823
migrate_cached_sockets:0

Replication

role:master
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0

CPU

used_cpu_sys:3372080.50
used_cpu_user:404838.31
used_cpu_sys_children:851.85
used_cpu_user_children:5934.84

Cluster

cluster_enabled:0

Keyspace

db0:keys=14078,expires=1209,avg_ttl=150542
db6:keys=878,expires=682,avg_ttl=42691293

redis-cli -h 192.168.1.2 -a ‘ passwd ‘ monitor 

info命令会显示当前的状态,monitor会显示当前的客户端的命令请求;

  1. 使用慢查询 

redis-cli -h 192.168.1.xx  -a ‘ passwd ‘ slowlog get (reset替换get清空旧的log)

这个命令会显示出最近一段时间内的耗时较久的查询。

这几个命令综合起来,基本可以找到是哪些命令频繁调用造成系统繁忙。

一般来说,都是大量调用keys命令并使用通配符造成的。

Redis服务器设置密码后,使用/etc/init.d/redis restart出现(error) NOAUTH Authentication required.

Redis服务器设置密码后,使用/etc/init.d/redis restart出现(error) NOAUTH Authentication required.

#/etc/init.d/redis restart

Stopping …

OK
(error) NOAUTH Authentication required.
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
Waiting for Redis to shutdown …
出现这样的错误信息,redis 这时是没有停止服务的。

可以使用ps -ef | grep redis  查进程号 然后kill 掉,如果在deamon下还需要去删除pid文件,有点繁琐。

解决办法:

用redis-cli 密码登陆(redis-cli -a  password)就OK了。

再用ps -ef | grep redis 可以看到redis进程已经正常退出。

修改redis服务脚本,加入如下所示的红色授权信息即可:

vi /etc/init.d/redis
$CLIEXEC -a “password” -p $REDISPORT shutdown

systemctl管理双redis启动、停止、开机自动启动

systemctl管理双redis启动、停止、开机自动启动
1. 创建服务
用service来管理服务的时候,是在/etc/init.d/目录中创建一个脚本文件,来管理服务的启动和停止,在systemctl中,也类似,文件目录有所不同,在/lib/systemd/system目录下创建一个脚本文件redis_6379.service,里面的内容如下:

[Unit]
Description=Redis
After=network.target

[Service]
ExecStart=/usr/local/bin/redis-server /usr/local/redis/redis_6379.conf  –daemonize no
ExecStop=/usr/local/bin/redis-cli -h 127.0.0.1 -p 6379 shutdown

[Install]
WantedBy=multi-user.target
[Unit] 表示这是基础信息 
Description 是描述
After 是在那个服务后面启动,一般是网络服务启动后启动
[Service] 表示这里是服务信息 
ExecStart 是启动服务的命令
ExecStop 是停止服务的指令
[Install] 表示这是是安装相关信息 
WantedBy 是以哪种方式启动:multi-user.target表明当系统以多用户方式(默认的运行级别)启动时,这个服务需要被自动运行。
更详细的service文件说明请访问:这里

2. 创建软链接
创建软链接是为了下一步系统初始化时自动启动服务

ln -s /lib/systemd/system/redis_6379.service /etc/systemd/system/multi-user.target.wants/redis_6379.service
1
创建软链接就好比Windows下的快捷方式 
ln -s 是创建软链接 
ln -s 原文件 目标文件(快捷方式的决定地址)

如果创建软连接的时候出现异常,不要担心,看看/etc/systemd/system/multi-user.target.wants/ 目录是否正常创建软链接为准,有时候报错只是提示一下,其实成功了。

$ ll /etc/systemd/system/multi-user.target.wants/
total 8
drwxr-xr-x  2 root root 4096 Mar 30 15:46 ./
drwxr-xr-x 13 root root 4096 Mar 13 14:18 ../
lrwxrwxrwx  1 root root   31 Nov 23 14:43 redis_6379.service -> /lib/systemd/system/redis_6379.service
…略…

3. 刷新配置
刚刚配置的服务需要让systemctl能识别,就必须刷新配置

$ systemctl daemon-reload
如果没有权限可以使用sudo
$ sudo systemctl daemon-reload
4. 启动、重启、停止
启动redis

$ systemctl start redis_6379
重启redis

$ systemctl restart redis_6379 
停止redis

$ systemctl stop redis_6379
1
5. 开机自启动
redis服务加入开机启动

$ systemctl enable redis_6379
1
禁止开机启动

$ systemctl disable redis_6379
1
6. 查看状态
查看状态

$ systemctl status redis

● redis_6379.service – Redis
   Loaded: loaded (/usr/lib/systemd/system/redis_6379.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2018-11-12 14:32:32 CST; 2min 30s ago
  Process: 305 ExecStop=/usr/local/redis/bin/redis-cli -h 127.0.0.1 -p 6379 shutdown (code=exited, status=0/SUCCESS)
 Main PID: 335 (redis-server)
   CGroup: /system.slice/redis_6379.service
           └─335 /usr/local/redis/bin/redis-server 127.0.0.1:6379

Nov 12 14:32:32 10-13-35-210 systemd[1]: Started Redis.
Nov 12 14:32:32 10-13-35-210 systemd[1]: Starting Redis…

其他端口,复制一份

redis_6379

重启redis时没有用root用户,结果dump.rdb文件停止更新,bgsave命令报错

原因:
1.dump.rdb文件所在的文件夹权限没有开通导致dump.rdb文件停止更新此时修改redis数据时会报错原因是默认配置 stop-writes-on-bgsaveerror yes当bgsave出错时数据将不能修改如下操作后可以更新数据: config set stop-writes-on-bgsaveerror nodump.rdb文件也恢复更新
2.当redis的内存占用比较大时在上述操作后dump.rdb文件仍然停止更新并且slave服务器也不能同步原因是操作系统的vm.overcommit_memory配置(配置说明在最后)如下操作:
echo 1 > /proc/sys/vm/overcommit_memory
后dump.rdb文件恢复更新。slave也可以同步数据了。
3.当使用root用户启动redis时没有上述问题

vm.overcommit_memory 表示内核在分配内存时候做检查的方式。这个变量可以取到0,1,2三个值。对取不同的值时的处理方式都定义在内核源码 mm/mmap.c 的 __vm_enough_memory 函数中。
取 1 的时候 : 此时宏为 OVERCOMMIT_ALWAYS函数直接 return 0分配成功。
取 2 的时候:  此时宏为 OVERCOMMIT_NEVER内核计算:内存总量×vm.overcommit_ratio/100+SWAP 的总量如果申请空间超过此数值则分配失败。vm.overcommit_ratio 的默认值为50。
取 0 的时候: 此时宏为 OVERCOMMIT_GUESS内核计算:NR_FILE_PAGES 总量+SWAP总量+slab中可以释放的内存总量如果申请空间超过此数值则将此数值与空闲内存总量减掉 totalreserve_pages(?) 的总量相加。如果申请空间依然超过此数值则分配失败。
以上为粗略描述在实际计算时如果非root进程则在计算时候会保留3%的空间而root进程则没有该限制。详细过程可看源码。

Redis Bgrewriteaof 命令 – 异步执行一个 AOF(AppendOnly File) 文件重写操作

Redis Bgrewriteaof 命令用于异步执行一个 AOF(AppendOnly File) 文件重写操作。重写会创建一个当前 AOF 文件的体积优化版本。

即使 Bgrewriteaof 执行失败,也不会有任何数据丢失,因为旧的 AOF 文件在 Bgrewriteaof 成功之前不会被修改。

注意:从 Redis 2.4 开始, AOF 重写由 Redis 自行触发, BGREWRITEAOF 仅仅用于手动触发重写操作。

语法

redis Bgrewriteaof 命令基本语法如下:

	
  1. redis 127.0.0.1:6379> BGREWRITEAOF

可用版本

>= 1.0.0

返回值

反馈信息。

实例

	
  1. redis 127.0.0.1:6379>
  2. Background append only file rewriting started

Redis Save 与 BGSAVE 的区别

一,save保存数据到磁盘的方式:

Redis Save 命令执行一个同步保存操作,将当前 Redis 实例的所有数据快照(snapshot)以 RDB 文件的形式保存到硬盘。

语法
redis Save 命令基本语法如下:

redis 127.0.0.1:6379> SAVE

返回值

保存成功时返回 OK 。

 

二,BGSAVE保存数据到磁盘的方式:

BGSAVE 命令执行之后立即返回 OK ,然后 Redis fork 出一个新子进程,原来的 Redis 进程(父进程)继续处理客户端请求,而子进程则负责将数据保存到磁盘,然后退出。

客户端可以通过 LASTSAVE 命令查看相关信息,判断 BGSAVE 命令是否执行成功。

 

时间复杂度:

O(N), N 为要保存到数据库中的 key 的数量。

案例:

redis> BGSAVE
Background saving started

 

 

三,结论

SAVE  保存是阻塞主进程,客户端无法连接redis,等SAVE完成后,主进程才开始工作,客户端可以连接

BGSAVE  是fork一个save的子进程,在执行save过程中,不影响主进程,客户端可以正常链接redis,等子进程fork执行save完成后,通知主进程,子进程关闭。很明细BGSAVE方式比较适合线上的维护操作,两种方式的使用一定要了解清楚在谨慎选择。

1.Master写内存快照,save命令调度rdbSave函数,会阻塞主线程的工作,当快照比较大时对性能影响是非常大的,会间断性暂停服务,所以Master最好不要写内存快照。

 

2.Master AOF持久化,如果不重写AOF文件,这个持久化方式对性能的影响是最小的,但是AOF文件会不断增大,AOF文件过大会影响Master重启的恢复速度。

 

3.Master调用BGREWRITEAOF重写AOF文件,AOF在重写的时候会占大量的CPU和内存资源,导致服务load过高,出现短暂服务暂停现象。

下面是我的一个实际项目的情况,大概情况是这样的:一个Master,4个Slave,没有Sharding机制,仅是读写分离,Master负责写入操作和AOF日志备份,AOF文件大概5G,Slave负责读操作,当Master调用BGREWRITEAOF时,Master和Slave负载会突然陡增,Master的写入请求基本上都不响应了,持续了大概5分钟,Slave的读请求过也半无法及时响应,Master和Slave的服务器负载图如下:

 

Master Server load:

 

Slave server load: 

 

上面的情况本来不会也不应该发生的,是因为以前Master的这个机器是Slave,在上面有一个shell定时任务在每天的上午10点调用BGREWRITEAOF重写AOF文件,后来由于Master机器down了,就把备份的这个Slave切成Master了,但是这个定时任务忘记删除了,就导致了上面悲剧情况的发生,原因还是找了几天才找到的。

 

no-appendfsync-on-rewrite的配置设为yes可以缓解这个问题,设置为yes表示rewrite期间对新写操作不fsync,暂时存在内存中,等rewrite完成后再写入。最好是不开启Master的AOF备份功能。

 

4.Redis主从复制的性能问题,第一次Slave向Master同步的实现是:Slave向Master发出同步请求,Master先dump出rdb文件,然后将rdb文件全量传输给slave,然后Master把缓存的命令转发给Slave,初次同步完成。第二次以及以后的同步实现是:Master将变量的快照直接实时依次发送给各个Slave。不管什么原因导致Slave和Master断开重连都会重复以上过程。Redis的主从复制是建立在内存快照的持久化基础上,只要有Slave就一定会有内存快照发生。虽然Redis宣称主从复制无阻塞,但由于磁盘io的限制,如果Master快照文件比较大,那么dump会耗费比较长的时间,这个过程中Master可能无法响应请求,也就是说服务会中断,对于关键服务,这个后果也是很可怕的。

 

以上1.2.3.4根本问题的原因都离不开系统io瓶颈问题,也就是硬盘读写速度不够快,主进程 fsync()/write() 操作被阻塞。

 

5.单点故障问题,由于目前Redis的主从复制还不够成熟,所以存在明显的单点故障问题,这个目前只能自己做方案解决,如:主动复制,Proxy实现Slave对Master的替换等,这个也是Redis作者目前比较优先的任务之一,作者的解决方案思路简单优雅,详情可见
Redis Sentinel design draft http://redis.io/topics/sentinel-spec

 

总结:

1.Master最好不要做任何持久化工作,包括内存快照和AOF日志文件,特别是不要启用内存快照做持久化。

2.如果数据比较关键,某个Slave开启AOF备份数据,策略为每秒同步一次。

3.为了主从复制的速度和连接的稳定性,Slave和Master最好在同一个局域网内。

4.尽量避免在压力较大的主库上增加从库

5.为了Master的稳定性,主从复制不要用图状结构,用单向链表结构更稳定,即主从关系为:Master<–Slave1<–Slave2<–Slave3…….,这样的结构也方便解决单点故障问题,实现Slave对Master的替换,也即,如果Master挂了,可以立马启用Slave1做Master,其他不变。

php安装swoole扩展

swoole是一个PHP的异步、并行、高性能网络通信引擎,使用纯C语言编写,提供了PHP语言的异步多线程服务器,异步TCP/UDP网络客户端,异步MySQL,异步Redis,数据库连接池,AsyncTask,消息队列,毫秒定时器,异步文件读写,异步DNS查询。
Swoole内置了Http/WebSocket服务器端/客户端、Http2.0服务器端。
Swoole可以广泛应用于互联网、移动通信、企业软件、云计算、网络游戏、物联网(IOT)、车联网、智能家居等领域。 使用PHP+Swoole作为网络通信框架,可以使企业IT研发团队的效率大大提升,更加专注于开发创新产品。

注意事项:
1、server.php中的ip地址必须是外网可访问地址 123.57.232.99,不能为localhost

1、安装

# wget https://github.com/swoole/swoole-src/archive/swoole-1.7.6-stable.tar.gz

# tar zxvf swoole-1.7.6-stable.tar.gz

# cd swoole-src-swoole-1.7.6-stable

# /usr/local/php/bin/phpize

  1. #./configure  --enable-zip --with-php-config=/usr/local/php/bin/php-config 
  2. # make
  3. # make install

提示:
Build complete.
Don’t forget to run ‘make test’.

Installing shared extensions: /usr/lib64/php/modules/
说明安装成功

2、php加载swoole扩展

extension=/xxx/xxx/php5.6/lib/php/extensions/no-debug-non-zts-20131226/swoole.so

3、重启服务
service php-fpm restart

4、测试,查看phpinfo信息,如下图所示:

5、代码测试

server.php代码:

# telnet 123.57.232.99 55152 
  • 1

Trying 123.57.232.99…
Connected to 123.57.232.99.
Escape character is ‘^]’.
rr
Swoole: rr
测试
Swoole: 测试

官网方式参考(php7.2.19)使用了这个方式:

安装Swoole框架和扩展

Swoole扩展

到GitHub首页下载Swoole扩展源码,地址:https://github.com/swoole/swoole-src 下载后按照标准的PHP扩展编译方式进行编译和安装。一般是

phpize
./configure
make install 

编译安装完后,修改php.ini加入extension=swoole.so开启swoole扩展。也可以通过dl(‘swoole.so’)动态载入,推荐修改php.ini。


下载swoole_framework源码,地址:https://github.com/swoole/framework。放置到您的workspace目录中即可。swoole_framework是PHP代码,只需要require/include即可,无需编译和安装。

redis 3.2.10 安装和主从配置

1. 下载 redis

wget http://download.redis.io/releases/redis-3.2.9.tar.gz

2. 解压

tar xzf redis-3.2.9.tar.gz

3. 进入 src 目录

cd redis-3.2.9

4. make

5. make test && make install

6. 如果出现 tcl 需要安装 yum -y install tcl

7. make install

8.注意 rdb 目录 和 save 配置 ,dir 目录指定文件存档目录, bind 指定ip

9. 修改密码 requirepass 修改

10. 指定启动目录 redis-server /etc/redis.conf

11. slave 机器安装 redis

12. slave 机器 redis.conf 修改 slaveof 和  masterauth

13. 重启

14. info 查看信息

master:

slave:


./redis-cli -p <修改的端口号> -a <修改的密码> shutdown

redis配置详解

##redis配置详解

# Redis configuration file example.
#
# Note that in order to read the configuration file, Redis must be
# started with the file path as first argument:
#
# ./redis-server /path/to/redis.conf

# Note on units: when memory size is needed, it is possible to specify
# it in the usual form of 1k 5GB 4M and so forth:
#
# 1k => 1000 bytes
# 1kb => 1024 bytes
# 1m => 1000000 bytes
# 1mb => 1024*1024 bytes
# 1g => 1000000000 bytes
# 1gb => 1024*1024*1024 bytes
#
# units are case insensitive so 1GB 1Gb 1gB are all the same.

################################## INCLUDES ###################################
################################## 包含     ###################################

# Include one or more other config files here.  This is useful if you
# have a standard template that goes to all Redis servers but also need
# to customize a few per-server settings.  Include files can include
# other files, so use this wisely.
#
# Notice option “include” won’t be rewritten by command “CONFIG REWRITE”
# from admin or Redis Sentinel. Since Redis always uses the last processed
# line as value of a configuration directive, you’d better put includes
# at the beginning of this file to avoid overwriting config change at runtime.
#
# If instead you are interested in using includes to override configuration
# options, it is better to use include as the last line.
#
# 假如说你有一个可用于所有的 redis server 的标准配置模板,
# 但针对某些 server 又需要一些个性化的设置,
# 你可以使用 include 来包含一些其他的配置文件,这对你来说是非常有用的。
#
# 但是要注意哦,include 是不能被 config rewrite 命令改写的
# 由于 redis 总是以最后的加工线作为一个配置指令值,所以你最好是把 include 放在这个文件的最前面,
# 以避免在运行时覆盖配置的改变,相反,你就把它放在后面
# include /path/to/local.conf
# include /path/to/other.conf

################################ GENERAL  #####################################
################################ 常用     #####################################

# By default Redis does not run as a daemon. Use ‘yes’ if you need it.
# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
# 默认情况下 redis 不是作为守护进程运行的,如果你想让它在后台运行,你就把它改成 yes。
# 当redis作为守护进程运行的时候,它会写一个 pid 到 /var/run/redis.pid 文件里面。
daemonize yes

# When running daemonized, Redis writes a pid file in /var/run/redis.pid by
# default. You can specify a custom pid file location here.
# 当 Redis 以守护进程的方式运行的时候,Redis 默认会把 pid 文件放在/var/run/redis.pid
# 可配置到其他地址,当运行多个 redis 服务时,需要指定不同的 pid 文件和端口
# 指定存储Redis进程号的文件路径
pidfile /var/run/redis.pid

# Accept connections on the specified port, default is 6379.
# If port 0 is specified Redis will not listen on a TCP socket.
# 端口,默认端口是6379,生产环境中建议更改端口号,安全性更高
# 如果你设为 0 ,redis 将不在 socket 上监听任何客户端连接。
port 9966

# TCP listen() backlog.
#
# In high requests-per-second environments you need an high backlog in order
# to avoid slow clients connections issues. Note that the Linux kernel
# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
# in order to get the desired effect.
# TCP 监听的最大容纳数量
# 此参数确定了TCP连接中已完成队列(完成三次握手之后)的长度,
# 当系统并发量大并且客户端速度缓慢的时候,你需要把这个值调高以避免客户端连接缓慢的问题。
# Linux 内核会一声不响的把这个值缩小成 /proc/sys/net/core/somaxconn 对应的值,默认是511,而Linux的默认参数值是128。
# 所以可以将这二个参数一起参考设定,你以便达到你的预期。
#  
tcp-backlog 511

# By default Redis listens for connections from all the network interfaces
# available on the server. It is possible to listen to just one or multiple
# interfaces using the “bind” configuration directive, followed by one or
# more IP addresses.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1
# 有时候为了安全起见,redis一般都是监听127.0.0.1 但是有时候又有同网段能连接的需求,当然可以绑定0.0.0.0 用iptables来控制访问权限,或者设置redis访问密码来保证数据安全

# 不设置将处理所有请求,建议生产环境中设置,有个误区:bind是用来限制外网IP访问的,其实不是,限制外网ip访问可以通过iptables;如:-A INPUT -s 10.10.1.0/24 -p tcp -m state –state NEW -m tcp –dport 9966 -j ACCEPT ;
# 实际上,bind ip 绑定的是redis所在服务器网卡的ip,当然127.0.0.1也是可以的
#如果绑定一个外网ip,就会报错:Creating Server TCP listening socket xxx.xxx.xxx.xxx:9966: bind: Cannot assign requested address

# bind 127.0.0.1
bind 127.0.0.1 10.10.1.3

# 假设绑定是以上ip,使用 netstat -anp|grep 9966 会发现,这两个ip被bind,其中10.10.1.3是服务器网卡的ip
# tcp        0      0 10.10.1.3:9966         0.0.0.0:*                   LISTEN      11188/redis-server  
# tcp        0      0 127.0.0.1:9966         0.0.0.0:*                   LISTEN      11188/redis-server 

# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
#
# unixsocket /tmp/redis.sock
# unixsocketperm 700

# Close the connection after a client is idle for N seconds (0 to disable)
# 客户端和Redis服务端的连接超时时间,默认是0,表示永不超时。
timeout 0

# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 60 seconds.

# tcp 心跳包。
#
# 如果设置为非零,则在与客户端缺乏通讯的时候使用 SO_KEEPALIVE 发送 tcp acks 给客户端。
# 这个之所有有用,主要由两个原因:
#
# 1) 防止死的 peers
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# 推荐一个合理的值就是60秒
tcp-keepalive 0

# Specify the server verbosity level.
# This can be one of:
# debug (a lot of information, useful for development/testing)
# verbose (many rarely useful info, but not a mess like the debug level)
# notice (moderately verbose, what you want in production probably)
# warning (only very important / critical messages are logged)
# 日志记录等级,4个可选值debug,verbose,notice,warning
# 可以是下面的这些值:
# debug (适用于开发或测试阶段)
# verbose (many rarely useful info, but not a mess like the debug level)
# notice (适用于生产环境)
# warning (仅仅一些重要的消息被记录)
loglevel notice

# Specify the log file name. Also the empty string can be used to force
# Redis to log on the standard output. Note that if you use standard
# output for logging but daemonize, logs will be sent to /dev/null
#配置 log 文件地址,默认打印在命令行终端的窗口上,也可设为/dev/null屏蔽日志、
logfile “/data/logs/redis/redis.log”

# To enable logging to the system logger, just set ‘syslog-enabled’ to yes,
# and optionally update the other syslog parameters to suit your needs.
# 要想把日志记录到系统日志,就把它改成 yes,
# 也可以可选择性的更新其他的syslog 参数以达到你的要求
# syslog-enabled no

# Specify the syslog identity.
# 设置 syslog 的 identity。
# syslog-ident redis

# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# syslog-facility local0

# Set the number of databases. The default database is DB 0, you can select
# a different one on a per-connection basis using SELECT <dbid> where
# dbid is a number between 0 and ‘databases’-1
# 可用的数据库数,默认值为16,默认数据库为0,数据库范围在0-(database-1)之间
databases 16

################################ SNAPSHOTTING  ################################
################################ 快照          ################################
#
# Save the DB on disk:
#
#   save <seconds> <changes>
#
#   Will save the DB if both the given number of seconds and the given
#   number of write operations against the DB occurred.
#
#   In the example below the behaviour will be to save:
#   after 900 sec (15 min) if at least 1 key changed
#   after 300 sec (5 min) if at least 10 keys changed
#   after 60 sec if at least 10000 keys changed
#
#   Note: you can disable saving completely by commenting out all “save” lines.
#
#   It is also possible to remove all the previously configured save
#   points by adding a save directive with a single empty string argument
#   like in the following example:
#
#   save “”
# 在 900 秒内最少有 1 个 key 被改动,或者 300 秒内最少有 10 个 key 被改动,又或者 60 秒内最少有 1000 个 key 被改动,以上三个条件随便满足一个,就触发一次保存操作。

#    if(在60秒之内有10000个keys发生变化时){
#      进行镜像备份
#    }else if(在300秒之内有10个keys发生了变化){
#      进行镜像备份
#    }else if(在900秒之内有1个keys发生了变化){
#      进行镜像备份
#    }

save 900 1
save 300 10
save 60 10000

# By default Redis will stop accepting writes if RDB snapshots are enabled
# (at least one save point) and the latest background save failed.
# This will make the user aware (in a hard way) that data is not persisting
# on disk properly, otherwise chances are that no one will notice and some
#:/ disaster will happen.
#
# If the background saving process will start working again Redis will
# automatically allow writes again.
#
# However if you have setup your proper monitoring of the Redis server
# and persistence, you may want to disable this feature so that Redis will
# continue to work as usual even if there are problems with disk,
# permissions, and so forth.
# 默认情况下,如果 redis 最后一次的后台保存失败,redis 将停止接受写操作,
# 这样以一种强硬的方式让用户知道数据不能正确的持久化到磁盘,
# 否则就会没人注意到灾难的发生。
#
# 如果后台保存进程重新启动工作了,redis 也将自动的允许写操作。
#
# 然而你要是安装了靠谱的监控,你可能不希望 redis 这样做,那你就改成 no 好
stop-writes-on-bgsave-error yes

# Compress string objects using LZF when dump .rdb databases?
# For default that’s set to ‘yes’ as it’s almost always a win.
# If you want to save some CPU in the saving child set it to ‘no’ but
# the dataset will likely be bigger if you have compressible values or keys.
# 在进行备份时,是否进行压缩
# 是否在 dump .rdb 数据库的时候使用 LZF 压缩字符串
# 默认都设为 yes
# 如果你希望保存子进程节省点 cpu ,你就设置它为 no ,
# 不过这个数据集可能就会比较大
rdbcompression yes

# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.    
# 读取和写入的时候是否支持CRC64校验,默认是开启的
rdbchecksum yes

# The filename where to dump the DB
# 备份文件的文件名
dbfilename dump.rdb

# The working directory.
#
# The DB will be written inside this directory, with the filename specified
# above using the ‘dbfilename’ configuration directive.
#
# The Append Only File will also be created inside this directory.
#
# Note that you must specify a directory here, not a file name.
# 数据库备份的文件放置的路径
# 路径跟文件名分开配置是因为 Redis 备份时,先会将当前数据库的状态写入到一个临时文件
# 等备份完成时,再把该临时文件替换为上面所指定的文件
# 而临时文件和上面所配置的备份文件都会放在这个指定的路径当中
# 默认值为 ./
dir /data/data/redis/

################################# REPLICATION #################################
################################# 主从复制    #################################
# Master-Slave replication. Use slaveof to make a Redis instance a copy of
# another Redis server. A few things to understand ASAP about Redis replication.
#
# 1) Redis replication is asynchronous, but you can configure a master to
#    stop accepting writes if it appears to be not connected with at least
#    a given number of slaves.
# 2) Redis slaves are able to perform a partial resynchronization with the
#    master if the replication link is lost for a relatively small amount of
#    time. You may want to configure the replication backlog size (see the next
#    sections of this file) with a sensible value depending on your needs.
# 3) Replication is automatic and does not need user intervention. After a
#    network partition slaves automatically try to reconnect to masters
#    and resynchronize with them.
#
# 设置该数据库为其他数据库的从数据库
# slaveof <masterip> <masterport> 当本机为从服务时,设置主服务的IP及端口
# slaveof <masterip> <masterport>

# If the master is password protected (using the “requirepass” configuration
# directive below) it is possible to tell the slave to authenticate before
# starting the replication synchronization process, otherwise the master will
# refuse the slave request.
#
# 指定与主数据库连接时需要的密码验证
# masterauth <master-password> 当本机为从服务时,设置访问master服务器的密码
# masterauth <master-password>

# When a slave loses its connection with the master, or when the replication
# is still in progress, the slave can act in two different ways:
#
# 1) if slave-serve-stale-data is set to ‘yes’ (the default) the slave will
#    still reply to client requests, possibly with out of date data, or the
#    data set may just be empty if this is the first synchronization.
#
# 2) if slave-serve-stale-data is set to ‘no’ the slave will reply with
#    an error “SYNC with master in progress” to all the kind of commands
#    but to INFO and SLAVEOF.
#
# 当slave服务器和master服务器失去连接后,或者当数据正在复制传输的时候,如果此参数值设置“yes”,slave服务器可以继续接受客户端的请求,否则,会返回给请求的客户端如下信息“SYNC with master in progress”,除了INFO,SLAVEOF这两个命令
slave-serve-stale-data yes

# You can configure a slave instance to accept writes or not. Writing against
# a slave instance may be useful to store some ephemeral data (because data
# written on a slave will be easily deleted after resync with the master) but
# may also cause problems if clients are writing to it because of a
# misconfiguration.
#
# Since Redis 2.6 by default slaves are read-only.
#
# Note: read only slaves are not designed to be exposed to untrusted clients
# on the internet. It’s just a protection layer against misuse of the instance.
# Still a read only slave exports by default all the administrative commands
# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
# security of read only slaves using ‘rename-command’ to shadow all the
# administrative / dangerous commands.
# 是否允许slave服务器节点只提供读服务
slave-read-only yes

# Replication SYNC strategy: disk or socket.
#
# ——————————————————-
# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
# ——————————————————-
#
# New slaves and reconnecting slaves that are not able to continue the replication
# process just receiving differences, need to do what is called a “full
# synchronization”. An RDB file is transmitted from the master to the slaves.
# The transmission can happen in two different ways:
#
# 1) Disk-backed: The Redis master creates a new process that writes the RDB
#                 file on disk. Later the file is transferred by the parent
#                 process to the slaves incrementally.
# 2) Diskless: The Redis master creates a new process that directly writes the
#              RDB file to slave sockets, without touching the disk at all.
#
# With disk-backed replication, while the RDB file is generated, more slaves
# can be queued and served with the RDB file as soon as the current child producing
# the RDB file finishes its work. With diskless replication instead once
# the transfer starts, new slaves arriving will be queued and a new transfer
# will start when the current one terminates.
#
# When diskless replication is used, the master waits a configurable amount of
# time (in seconds) before starting the transfer in the hope that multiple slaves
# will arrive and the transfer can be parallelized.
#
# With slow disks and fast (large bandwidth) networks, diskless replication
# works better.
repl-diskless-sync no

# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that transfers the RDB via socket
# to the slaves.
#
# This is important since once the transfer starts, it is not possible to serve
# new slaves arriving, that will be queued for the next RDB transfer, so the server
# waits a delay in order to let more slaves arrive.
#
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
repl-diskless-sync-delay 5

# Slaves send PINGs to server in a predefined interval. It’s possible to change
# this interval with the repl_ping_slave_period option. The default value is 10
# seconds.
#
# Slaves 在一个预定义的时间间隔内发送 ping 命令到 server 。
# 你可以改变这个时间间隔。默认为 10 秒。
# repl-ping-slave-period 10

# The following option sets the replication timeout for:
#
# 1) Bulk transfer I/O during SYNC, from the point of view of slave.
# 2) Master timeout from the point of view of slaves (data, pings).
# 3) Slave timeout from the point of view of masters (REPLCONF ACK pings).
#
# It is important to make sure that this value is greater than the value
# specified for repl-ping-slave-period otherwise a timeout will be detected
# every time there is low traffic between the master and the slave.
#
# 设置主从复制过期时间
# 这个值一定要比 repl-ping-slave-period 大
# repl-timeout 60

# Disable TCP_NODELAY on the slave socket after SYNC?
#
# If you select “yes” Redis will use a smaller number of TCP packets and
# less bandwidth to send data to slaves. But this can add a delay for
# the data to appear on the slave side, up to 40 milliseconds with
# Linux kernels using a default configuration.
#
# If you select “no” the delay for data to appear on the slave side will
# be reduced but more bandwidth will be used for replication.
#
# By default we optimize for low latency, but in very high traffic conditions
# or when the master and slaves are many hops away, turning this to “yes” may
# be a good idea.
# 指定向slave同步数据时,是否禁用socket的NO_DELAY选 项。若配置为“yes”,则禁用NO_DELAY,则TCP协议栈会合并小包统一发送,这样可以减少主从节点间的包数量并节省带宽,但会增加数据同步到 slave的时间。若配置为“no”,表明启用NO_DELAY,则TCP协议栈不会延迟小包的发送时机,这样数据同步的延时会减少,但需要更大的带宽。 通常情况下,应该配置为no以降低同步延时,但在主从节点间网络负载已经很高的情况下,可以配置为yes。
repl-disable-tcp-nodelay no

# Set the replication backlog size. The backlog is a buffer that accumulates
# slave data when slaves are disconnected for some time, so that when a slave
# wants to reconnect again, often a full resync is not needed, but a partial
# resync is enough, just passing the portion of data the slave missed while
# disconnected.
#
# The bigger the replication backlog, the longer the time the slave can be
# disconnected and later be able to perform a partial resynchronization.
#
# The backlog is only allocated once there is at least a slave connected.
#
# 设置主从复制容量大小。这个 backlog 是一个用来在 slaves 被断开连接时
# 存放 slave 数据的 buffer,所以当一个 slave 想要重新连接,通常不希望全部重新同步,
# 只是部分同步就够了,仅仅传递 slave 在断开连接时丢失的这部分数据。
#
# The biggest the replication backlog, the longer the time the slave can be
# disconnected and later be able to perform a partial resynchronization.
# 这个值越大,salve 可以断开连接的时间就越长。

# repl-backlog-size 1mb

# After a master has no longer connected slaves for some time, the backlog
# will be freed. The following option configures the amount of seconds that
# need to elapse, starting from the time the last slave disconnected, for
# the backlog buffer to be freed.
#
# A value of 0 means to never release the backlog.
#
# 在某些时候,master 不再连接 slaves,backlog 将被释放。
# 如果设置为 0 ,意味着绝不释放 backlog 。
# repl-backlog-ttl 3600

# The slave priority is an integer number published by Redis in the INFO output.
# It is used by Redis Sentinel in order to select a slave to promote into a
# master if the master is no longer working correctly.
#
# A slave with a low priority number is considered better for promotion, so
# for instance if there are three slaves with priority 10, 100, 25 Sentinel will
# pick the one with priority 10, that is the lowest.
#
# However a special priority of 0 marks the slave as not able to perform the
# role of master, so a slave with priority of 0 will never be selected by
# Redis Sentinel for promotion.
#
# By default the priority is 100.
# 指定slave的优先级。在不只1个slave存在的部署环境下,当master宕机时,Redis
# Sentinel会将priority值最小的slave提升为master。
# 这个值越小,就越会被优先选中,需要注意的是,
# 若该配置项为0,则对应的slave永远不会自动提升为master。
slave-priority 100

# It is possible for a master to stop accepting writes if there are less than
# N slaves connected, having a lag less or equal than M seconds.
#
# The N slaves need to be in “online” state.
#
# The lag in seconds, that must be <= the specified value, is calculated from
# the last ping received from the slave, that is usually sent every second.
#
# This option does not GUARANTEE that N replicas will accept the write, but
# will limit the window of exposure for lost writes in case not enough slaves
# are available, to the specified number of seconds
#
# For example to require at least 3 slaves with a lag <= 10 seconds use:
#
# min-slaves-to-write 3
# min-slaves-max-lag 10
#
# Setting one or the other to 0 disables the feature.
#
# By default min-slaves-to-write is set to 0 (feature disabled) and
# min-slaves-max-lag is set to 10.

################################## SECURITY ###################################
################################## 安全     ###################################

# Require clients to issue AUTH <PASSWORD> before processing any other
# commands.  This might be useful in environments in which you do not trust
# others with access to the host running redis-server.
#
# This should stay commented out for backward compatibility and because most
# people do not need auth (e.g. they run their own servers).
#
# Warning: since Redis is pretty fast an outside user can try up to
# 150k passwords per second against a good box. This means that you should
# use a very strong password otherwise it will be very easy to break.
#
# 设置连接redis的密码
# redis速度相当快,一个外部用户在一秒钟进行150K次密码尝试,需指定强大的密码来防止暴力破解
requirepass set_enough_strong_passwd

# Command renaming.
#
# It is possible to change the name of dangerous commands in a shared
# environment. For instance the CONFIG command may be renamed into something
# hard to guess so that it will still be available for internal-use tools
# but not available for general clients.
#
# Example:
#
# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
#
# It is also possible to completely kill a command by renaming it into
# an empty string:
#
# rename-command CONFIG “”
#
# Please note that changing the name of commands that are logged into the
# AOF file or transmitted to slaves may cause problems.
# 重命名一些高危命令,用来禁止高危命令
rename-command FLUSHALL ZYzv6FOBdwflW2nX
rename-command CONFIG aI7zwm1GDzMMrEi
rename-command EVAL S9UHPKEpSvUJMM
rename-command FLUSHDB D60FPVDJuip7gy6l

################################### LIMITS ####################################
################################### 限制   ####################################

# Set the max number of connected clients at the same time. By default
# this limit is set to 10000 clients, however if the Redis server is not
# able to configure the process file limit to allow for the specified limit
# the max number of allowed clients is set to the current file limit
# minus 32 (as Redis reserves a few file descriptors for internal uses).
#
# Once the limit is reached Redis will close all the new connections sending
# an error ‘max number of clients reached’.
#
# 限制同时连接的客户数量,默认是10000
# 当连接数超过这个值时,redis 将不再接收其他连接请求,客户端尝试连接时将收到 error 信息
# maxclients 10000

# Don’t use more memory than the specified amount of bytes.
# When the memory limit is reached Redis will try to remove keys
# according to the eviction policy selected (see maxmemory-policy).
#
# If Redis can’t remove keys according to the policy, or if the policy is
# set to ‘noeviction’, Redis will start to reply with errors to commands
# that would use more memory, like SET, LPUSH, and so on, and will continue
# to reply to read-only commands like GET.
#
# This option is usually useful when using Redis as an LRU cache, or to set
# a hard memory limit for an instance (using the ‘noeviction’ policy).
#
# WARNING: If you have slaves attached to an instance with maxmemory on,
# the size of the output buffers needed to feed the slaves are subtracted
# from the used memory count, so that network problems / resyncs will
# not trigger a loop where keys are evicted, and in turn the output
# buffer of slaves is full with DELs of keys evicted triggering the deletion
# of more keys, and so forth until the database is completely emptied.
#
# In short… if you have slaves attached it is suggested that you set a lower
# limit for maxmemory so that there is some free RAM on the system for slave
# output buffers (but this is not needed if the policy is ‘noeviction’).
#
# 设置redis能够使用的最大内存。
# 达到最大内存设置后,Redis会先尝试清除已到期或即将到期的Key(设置过expire信息的key)
# 在删除时,按照过期时间进行删除,最早将要被过期的key将最先被删除
# 如果已到期或即将到期的key删光,仍进行set操作,那么将返回错误
# 此时redis将不再接收写请求,只接收get请求。
# maxmemory的设置比较适合于把redis当作于类似memcached 的缓存来使用
# maxmemory <bytes>

# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
# is reached. You can select among five behaviors:
#
# volatile-lru -> remove the key with an expire set using an LRU algorithm
# allkeys-lru -> remove any key according to the LRU algorithm
# volatile-random -> remove a random key with an expire set
# allkeys-random -> remove a random key, any key
# volatile-ttl -> remove the key with the nearest expire time (minor TTL)
# noeviction -> don’t expire at all, just return an error on write operations
#
# Note: with any of the above policies, Redis will return an error on write
#       operations, when there are no suitable keys for eviction.
#
#       At the date of writing these commands are: set setnx setex append
#       incr decr rpush lpush rpushx lpushx linsert lset rpoplpush sadd
#       sinter sinterstore sunion sunionstore sdiff sdiffstore zadd zincrby
#       zunionstore zinterstore hset hsetnx hmset hincrby incrby decrby
#       getset mset msetnx exec sort
#
# The default is:
#
# maxmemory-policy noeviction

# LRU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can tune it for speed or
# accuracy. For default Redis will check five keys and pick the one that was
# used less recently, you can change the sample size using the following
# configuration directive.
#
# The default of 5 produces good enough results. 10 Approximates very closely
# true LRU but costs a bit more CPU. 3 is very fast but not very accurate.
#
# maxmemory-samples 5

############################## APPEND ONLY MODE ###############################

# By default Redis asynchronously dumps the dataset on disk. This mode is
# good enough in many applications, but an issue with the Redis process or
# a power outage may result into a few minutes of writes lost (depending on
# the configured save points).
#
# The Append Only File is an alternative persistence mode that provides
# much better durability. For instance using the default data fsync policy
# (see later in the config file) Redis can lose just one second of writes in a
# dramatic event like a server power outage, or a single write if something
# wrong with the Redis process itself happens, but the operating system is
# still running correctly.
#
# AOF and RDB persistence can be enabled at the same time without problems.
# If the AOF is enabled on startup Redis will load the AOF, that is the file
# with the better durability guarantees.
#
# Please check http://redis.io/topics/persistence for more information.

# redis 默认每次更新操作后会在后台异步的把数据库镜像备份到磁盘,但该备份非常耗时,且备份不宜太频繁
# redis 同步数据文件是按上面save条件来同步的
# 如果发生诸如拉闸限电、拔插头等状况,那么将造成比较大范围的数据丢失
# 所以redis提供了另外一种更加高效的数据库备份及灾难恢复方式
# 开启append only 模式后,redis 将每一次写操作请求都追加到appendonly.aof 文件中
# redis重新启动时,会从该文件恢复出之前的状态。
# 但可能会造成 appendonly.aof 文件过大,所以redis支持BGREWRITEAOF 指令,对appendonly.aof重新整理,默认是不开启的。

appendonly no

# The name of the append only file (default: “appendonly.aof”)
# 默认为appendonly.aof。
appendfilename “appendonly.aof”

# The fsync() call tells the Operating System to actually write data on disk
# instead of waiting for more data in the output buffer. Some OS will really flush
# data on disk, some other OS will just try to do it ASAP.
#
# Redis supports three different modes:
#
# no: don’t fsync, just let the OS flush the data when it wants. Faster.
# always: fsync after every write to the append only log. Slow, Safest.
# everysec: fsync only one time every second. Compromise.
#
# The default is “everysec”, as that’s usually the right compromise between
# speed and data safety. It’s up to you to understand if you can relax this to
# “no” that will let the operating system flush the output buffer when
# it wants, for better performances (but if you can live with the idea of
# some data loss consider the default persistence mode that’s snapshotting),
# or on the contrary, use “always” that’s very slow but a bit safer than
# everysec.
#
# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
#
# If unsure, use “everysec”.

# 设置对 appendonly.aof 文件进行同步的频率,有三种选择always、everysec、no,默认是everysec表示每秒同步一次。
# always 表示每次有写操作都进行同步,everysec 表示对写操作进行累积,每秒同步一次。
# no表示等操作系统进行数据缓存同步到磁盘,都进行同步,everysec 表示对写操作进行累积,每秒同步一次
# appendfsync always
# appendfsync everysec
# appendfsync no

# When the AOF fsync policy is set to always or everysec, and a background
# saving process (a background save or AOF log background rewriting) is
# performing a lot of I/O against the disk, in some Linux configurations
# Redis may block too long on the fsync() call. Note that there is no fix for
# this currently, as even performing fsync in a different thread will block
# our synchronous write(2) call.
#
# In order to mitigate this problem it’s possible to use the following option
# that will prevent fsync() from being called in the main process while a
# BGSAVE or BGREWRITEAOF is in progress.
#
# This means that while another child is saving, the durability of Redis is
# the same as “appendfsync none”. In practical terms, this means that it is
# possible to lose up to 30 seconds of log in the worst scenario (with the
# default Linux settings).
#
# If you have latency problems turn this to “yes”. Otherwise leave it as
# “no” that is the safest pick from the point of view of durability.
# 指定是否在后台aof文件rewrite期间调用fsync,默认为no,表示要调用fsync(无论后台是否有子进程在刷盘)。Redis在后台写RDB文件或重写afo文件期间会存在大量磁盘IO,此时,在某些linux系统中,调用fsync可能会阻塞。
no-appendfsync-on-rewrite yes

# Automatic rewrite of the append only file.
# Redis is able to automatically rewrite the log file implicitly calling
# BGREWRITEAOF when the AOF log size grows by the specified percentage.
#
# This is how it works: Redis remembers the size of the AOF file after the
# latest rewrite (if no rewrite has happened since the restart, the size of
# the AOF at startup is used).
#
# This base size is compared to the current size. If the current size is
# bigger than the specified percentage, the rewrite is triggered. Also
# you need to specify a minimal size for the AOF file to be rewritten, this
# is useful to avoid rewriting the AOF file even if the percentage increase
# is reached but it is still pretty small.
#
# Specify a percentage of zero in order to disable the automatic AOF
# rewrite feature.
# 指定Redis重写aof文件的条件,默认为100,表示与上次rewrite的aof文件大小相比,当前aof文件增长量超过上次afo文件大小的100%时,就会触发background rewrite。若配置为0,则会禁用自动rewrite
auto-aof-rewrite-percentage 100

# 指定触发rewrite的aof文件大小。若aof文件小于该值,即使当前文件的增量比例达到auto-aof-rewrite-percentage的配置值,也不会触发自动rewrite。即这两个配置项同时满足时,才会触发rewrite。
auto-aof-rewrite-min-size 64mb

# An AOF file may be found to be truncated at the end during the Redis
# startup process, when the AOF data gets loaded back into memory.
# This may happen when the system where Redis is running
# crashes, especially when an ext4 filesystem is mounted without the
# data=ordered option (however this can’t happen when Redis itself
# crashes or aborts but the operating system still works correctly).
#
# Redis can either exit with an error when this happens, or load as much
# data as possible (the default now) and start if the AOF file is found
# to be truncated at the end. The following option controls this behavior.
#
# If aof-load-truncated is set to yes, a truncated AOF file is loaded and
# the Redis server starts emitting a log to inform the user of the event.
# Otherwise if the option is set to no, the server aborts with an error
# and refuses to start. When the option is set to no, the user requires
# to fix the AOF file using the “redis-check-aof” utility before to restart
# the server.
#
# Note that if the AOF file will be found to be corrupted in the middle
# the server will still exit with an error. This option only applies when
# Redis will try to read more data from the AOF file but not enough bytes
# will be found.
aof-load-truncated yes

################################ LUA SCRIPTING  ###############################

# Max execution time of a Lua script in milliseconds.
#
# If the maximum execution time is reached Redis will log that a script is
# still in execution after the maximum allowed time and will start to
# reply to queries with an error.
#
# When a long running script exceeds the maximum execution time only the
# SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
# used to stop a script that did not yet called write commands. The second
# is the only way to shut down the server in the case a write command was
# already issued by the script but the user doesn’t want to wait for the natural
# termination of the script.
#
# Set it to 0 or a negative value for unlimited execution without warnings.
# 一个Lua脚本最长的执行时间,单位为毫秒,如果为0或负数表示无限执行时间,默认为5000
lua-time-limit 5000

################################ REDIS CLUSTER  ###############################
#
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# WARNING EXPERIMENTAL: Redis Cluster is considered to be stable code, however
# in order to mark it as “mature” we need to wait for a non trivial percentage
# of users to deploy it in production.
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#
# Normal Redis instances can’t be part of a Redis Cluster; only nodes that are
# started as cluster nodes can. In order to start a Redis instance as a
# cluster node enable the cluster support uncommenting the following:
#
# cluster-enabled yes

# Every cluster node has a cluster configuration file. This file is not
# intended to be edited by hand. It is created and updated by Redis nodes.
# Every Redis Cluster node requires a different cluster configuration file.
# Make sure that instances running in the same system do not have
# overlapping cluster configuration file names.
#
# cluster-config-file nodes-6379.conf

# Cluster node timeout is the amount of milliseconds a node must be unreachable
# for it to be considered in failure state.
# Most other internal time limits are multiple of the node timeout.
#
# cluster-node-timeout 15000

# A slave of a failing master will avoid to start a failover if its data
# looks too old.
#
# There is no simple way for a slave to actually have a exact measure of
# its “data age”, so the following two checks are performed:
#
# 1) If there are multiple slaves able to failover, they exchange messages
#    in order to try to give an advantage to the slave with the best
#    replication offset (more data from the master processed).
#    Slaves will try to get their rank by offset, and apply to the start
#    of the failover a delay proportional to their rank.
#
# 2) Every single slave computes the time of the last interaction with
#    its master. This can be the last ping or command received (if the master
#    is still in the “connected” state), or the time that elapsed since the
#    disconnection with the master (if the replication link is currently down).
#    If the last interaction is too old, the slave will not try to failover
#    at all.
#
# The point “2” can be tuned by user. Specifically a slave will not perform
# the failover if, since the last interaction with the master, the time
# elapsed is greater than:
#
#   (node-timeout * slave-validity-factor) + repl-ping-slave-period
#
# So for example if node-timeout is 30 seconds, and the slave-validity-factor
# is 10, and assuming a default repl-ping-slave-period of 10 seconds, the
# slave will not try to failover if it was not able to talk with the master
# for longer than 310 seconds.
#
# A large slave-validity-factor may allow slaves with too old data to failover
# a master, while a too small value may prevent the cluster from being able to
# elect a slave at all.
#
# For maximum availability, it is possible to set the slave-validity-factor
# to a value of 0, which means, that slaves will always try to failover the
# master regardless of the last time they interacted with the master.
# (However they’ll always try to apply a delay proportional to their
# offset rank).
#
# Zero is the only value able to guarantee that when all the partitions heal
# the cluster will always be able to continue.
#
# cluster-slave-validity-factor 10

# Cluster slaves are able to migrate to orphaned masters, that are masters
# that are left without working slaves. This improves the cluster ability
# to resist to failures as otherwise an orphaned master can’t be failed over
# in case of failure if it has no working slaves.
#
# Slaves migrate to orphaned masters only if there are still at least a
# given number of other working slaves for their old master. This number
# is the “migration barrier”. A migration barrier of 1 means that a slave
# will migrate only if there is at least 1 other working slave for its master
# and so forth. It usually reflects the number of slaves you want for every
# master in your cluster.
#
# Default is 1 (slaves migrate only if their masters remain with at least
# one slave). To disable migration just set it to a very large value.
# A value of 0 can be set but is useful only for debugging and dangerous
# in production.
#
# cluster-migration-barrier 1

# By default Redis Cluster nodes stop accepting queries if they detect there
# is at least an hash slot uncovered (no available node is serving it).
# This way if the cluster is partially down (for example a range of hash slots
# are no longer covered) all the cluster becomes, eventually, unavailable.
# It automatically returns available as soon as all the slots are covered again.
#
# However sometimes you want the subset of the cluster which is working,
# to continue to accept queries for the part of the key space that is still
# covered. In order to do so, just set the cluster-require-full-coverage
# option to no.
#
# cluster-require-full-coverage yes

# In order to setup your cluster make sure to read the documentation
# available at http://redis.io web site.

################################## SLOW LOG ###################################

# The Redis Slow Log is a system to log queries that exceeded a specified
# execution time. The execution time does not include the I/O operations
# like talking with the client, sending the reply and so forth,
# but just the time needed to actually execute the command (this is the only
# stage of command execution where the thread is blocked and can not serve
# other requests in the meantime).
#
# You can configure the slow log with two parameters: one tells Redis
# what is the execution time, in microseconds, to exceed in order for the
# command to get logged, and the other parameter is the length of the
# slow log. When a new command is logged the oldest one is removed from the
# queue of logged commands.

# The following time is expressed in microseconds, so 1000000 is equivalent
# to one second. Note that a negative number disables the slow log, while
# a value of zero forces the logging of every command.
slowlog-log-slower-than 10000

# There is no limit to this length. Just be aware that it will consume memory.
# You can reclaim memory used by the slow log with SLOWLOG RESET.
slowlog-max-len 128

################################ LATENCY MONITOR ##############################

# The Redis latency monitoring subsystem samples different operations
# at runtime in order to collect data related to possible sources of
# latency of a Redis instance.
#
# Via the LATENCY command this information is available to the user that can
# print graphs and obtain reports.
#
# The system only logs operations that were performed in a time equal or
# greater than the amount of milliseconds specified via the
# latency-monitor-threshold configuration directive. When its value is set
# to zero, the latency monitor is turned off.
#
# By default latency monitoring is disabled since it is mostly not needed
# if you don’t have latency issues, and collecting data has a performance
# impact, that while very small, can be measured under big load. Latency
# monitoring can easily be enabled at runtime using the command
# “CONFIG SET latency-monitor-threshold <milliseconds>” if needed.
latency-monitor-threshold 0

############################# EVENT NOTIFICATION ##############################

# Redis can notify Pub/Sub clients about events happening in the key space.
# This feature is documented at http://redis.io/topics/notifications
#
# For instance if keyspace events notification is enabled, and a client
# performs a DEL operation on key “foo” stored in the Database 0, two
# messages will be published via Pub/Sub:
#
# PUBLISH __keyspace@0__:foo del
# PUBLISH __keyevent@0__:del foo
#
# It is possible to select the events that Redis will notify among a set
# of classes. Every class is identified by a single character:
#
#  K     Keyspace events, published with __keyspace@<db>__ prefix.
#  E     Keyevent events, published with __keyevent@<db>__ prefix.
#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, …
#  $     String commands
#  l     List commands
#  s     Set commands
#  h     Hash commands
#  z     Sorted set commands
#  x     Expired events (events generated every time a key expires)
#  e     Evicted events (events generated when a key is evicted for maxmemory)
#  A     Alias for g$lshzxe, so that the “AKE” string means all the events.
#
#  The “notify-keyspace-events” takes as argument a string that is composed
#  of zero or multiple characters. The empty string means that notifications
#  are disabled.
#
#  Example: to enable list and generic events, from the point of view of the
#           event name, use:
#
#  notify-keyspace-events Elg
#
#  Example 2: to get the stream of the expired keys subscribing to channel
#             name __keyevent@0__:expired use:
#
#  notify-keyspace-events Ex
#
#  By default all notifications are disabled because most users don’t need
#  this feature and the feature has some overhead. Note that if you don’t
#  specify at least one of K or E, no events will be delivered.
notify-keyspace-events “”

############################### ADVANCED CONFIG ###############################

# Hashes are encoded using a memory efficient data structure when they have a
# small number of entries, and the biggest entry does not exceed a given
# threshold. These thresholds can be configured using the following directives.
# 当hash中包含超过指定元素个数并且最大的元素没有超过临界时,
# hash将以一种特殊的编码方式(大大减少内存使用)来存储,这里可以设置这两个临界值
hash-max-ziplist-entries 512
hash-max-ziplist-value 64

# Similarly to hashes, small lists are also encoded in a special way in order
# to save a lot of space. The special representation is only used when
# you are under the following limits:
# list数据类型多少节点以下会采用去指针的紧凑存储格式。
# list数据类型节点值大小小于多少字节会采用紧凑存储格式。
list-max-ziplist-entries 512
list-max-ziplist-value 64

# Sets have a special encoding in just one case: when a set is composed
# of just strings that happen to be integers in radix 10 in the range
# of 64 bit signed integers.
# The following configuration setting sets the limit in the size of the
# set in order to use this special memory saving encoding.
# set数据类型内部数据如果全部是数值型,且包含多少节点以下会采用紧凑格式存储。
set-max-intset-entries 512

# Similarly to hashes and lists, sorted sets are also specially encoded in
# order to save a lot of space. This encoding is only used when the length and
# elements of a sorted set are below the following limits:

# zsort数据类型多少节点以下会采用去指针的紧凑存储格式。
# zsort数据类型节点值大小小于多少字节会采用紧凑存储格式。
zset-max-ziplist-entries 128
zset-max-ziplist-value 64

# HyperLogLog sparse representation bytes limit. The limit includes the
# 16 bytes header. When an HyperLogLog using the sparse representation crosses
# this limit, it is converted into the dense representation.
#
# A value greater than 16000 is totally useless, since at that point the
# dense representation is more memory efficient.
#
# The suggested value is ~ 3000 in order to have the benefits of
# the space efficient encoding without slowing down too much PFADD,
# which is O(N) with the sparse encoding. The value can be raised to
# ~ 10000 when CPU is not a concern, but space is, and the data set is
# composed of many HyperLogLogs with cardinality in the 0 – 15000 range.
hll-sparse-max-bytes 3000

# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
# order to help rehashing the main Redis hash table (the one mapping top-level
# keys to values). The hash table implementation Redis uses (see dict.c)
# performs a lazy rehashing: the more operation you run into a hash table
# that is rehashing, the more rehashing “steps” are performed, so if the
# server is idle the rehashing is never complete and some more memory is used
# by the hash table.
#
# The default is to use this millisecond 10 times every second in order to
# actively rehash the main dictionaries, freeing memory when possible.
#
# If unsure:
# use “activerehashing no” if you have hard latency requirements and it is
# not a good thing in your environment that Redis can reply from time to time
# to queries with 2 milliseconds delay.
#
# use “activerehashing yes” if you don’t have such hard requirements but
# want to free memory asap when possible.

# Redis将在每100毫秒时使用1毫秒的CPU时间来对redis的hash表进行重新hash,可以降低内存的使用
# 当你的使用场景中,有非常严格的实时性需要,不能够接受Redis时不时的对请求有2毫秒的延迟的话,把这项配置为no。
# 如果没有这么严格的实时性要求,可以设置为yes,以便能够尽可能快的释放内存
activerehashing yes

# The client output buffer limits can be used to force disconnection of clients
# that are not reading data from the server fast enough for some reason (a
# common reason is that a Pub/Sub client can’t consume messages as fast as the
# publisher can produce them).
#
# The limit can be set differently for the three different classes of clients:
#
# normal -> normal clients including MONITOR clients
# slave  -> slave clients
# pubsub -> clients subscribed to at least one pubsub channel or pattern
#
# The syntax of every client-output-buffer-limit directive is the following:
#
# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
#
# A client is immediately disconnected once the hard limit is reached, or if
# the soft limit is reached and remains reached for the specified number of
# seconds (continuously).
# So for instance if the hard limit is 32 megabytes and the soft limit is
# 16 megabytes / 10 seconds, the client will get disconnected immediately
# if the size of the output buffers reach 32 megabytes, but will also get
# disconnected if the client reaches 16 megabytes and continuously overcomes
# the limit for 10 seconds.
#
# By default normal clients are not limited because they don’t receive data
# without asking (in a push way), but just after a request, so only
# asynchronous clients may create a scenario where data is requested faster
# than it can read.
#
# Instead there is a default limit for pubsub and slave clients, since
# subscribers and slaves receive data in a push fashion.
#
# Both the hard or the soft limit can be disabled by setting them to zero.
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60

# Redis calls an internal function to perform many background tasks, like
# closing connections of clients in timeout, purging expired keys that are
# never requested, and so forth.
#
# Not all tasks are performed with the same frequency, but Redis checks for
# tasks to perform according to the specified “hz” value.
#
# By default “hz” is set to 10. Raising the value will use more CPU when
# Redis is idle, but at the same time will make Redis more responsive when
# there are many keys expiring at the same time, and timeouts may be
# handled with more precision.
#
# The range is between 1 and 500, however a value over 100 is usually not
# a good idea. Most users should use the default of 10 and raise this up to
# 100 only in environments where very low latency is required.
hz 10

# When a child rewrites the AOF file, if the following option is enabled
# the file will be fsync-ed every 32 MB of data generated. This is useful
# in order to commit the file to the disk more incrementally and avoid
# big latency spikes.
# aof rewrite过程中,是否采取增量文件同步策略,默认为“yes”。 rewrite过程中,每32M数据进行一次文件同步,这样可以减少aof大文件写入对磁盘的操作次数
aof-rewrite-incremental-fsync yes

# redis数据存储
redis的存储分为内存存储、磁盘存储和log文件三部分,配置文件中有三个参数对其进行配置。
save seconds updates,save配置,指出在多长时间内,有多少次更新操作,就将数据同步到数据文件。可多个条件配合,默认配置了三个条件。
appendonly yes/no ,appendonly配置,指出是否在每次更新操作后进行日志记录,如果不开启,可能会在断电时导致一段时间内的数据丢失。因为redis本身同步数据文件是按上面的save条件来同步的,所以有的数据会在一段时间内只存在于内存中。
appendfsync no/always/everysec ,appendfsync配置,no表示等操作系统进行数据缓存同步到磁盘,always表示每次更新操作后手动调用fsync()将数据写到磁盘,everysec表示每秒同步一次。

redis编译错误:Test replication partial resync: no backlog in tests/integration/replication-psync.tcl

下午配置一台centos服务器,编译redis, 运行make test 报了这样的一个错误:

!!! WARNING The following tests failed:
*** [err]: Test replication partial resync: ok psync (diskless: yes, reconnect: 1) in tests/integration/replication-psync.tcl
Expected condition ‘[s -1 sync_partial_ok] > 0’ to be true ([s -1 sync_partial_ok] > 0)
Cleanup: may take some time… OK
make[1]: *** [test] Error 1
make[1]: Leaving directory `/usr/local/src/redis-3.2.1/src’
make: *** [test] Error 2

■ 解决办法:

1,只用单核运行 make test:

taskset -c 1 sudo make test


2,更改 tests/integration/replication-psync.tcl 文件:

vi tests/integration/replication-psync.tcl

把对应报错的那段代码中的 after后面的数字,从100改成 500。我个人觉得,这个参数貌似是等待的毫秒数。


编辑文件tests/integration/replication-psync.tcl

然后找到after 100 把此值修改成200或者300。重新执行make test就可以了



same issue on

Linux sie 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt20-1+deb8u4 (2016-02-29) x86_64 GNU/Linux

was able to pass all tests ONLY when using single CPU core using:

taskset -c 0 sudo make test

is it OK to run the server anyway?