面试将 95% 求职者拒之门外的BAT大数据面试题-附解题方法（文末有福利）
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配置文件Redis.conf注释信息：
1、启动项：
启动Redis要求必须加上配置文件redis.conf路径作为第一参数加载
文档样例：
./redis-server /path/to/redis.conf
2、计量单位：
当需要内存大小时，可以用通常的1k 5GB 4M格式指定内存大小，以此类推：
这些单位不区分大小写，1GB、1gb、1Gb、1gB、都将表示该单位的计量含义
# 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.
3、配置导入
在Spring的学习中，我们可以配置多个Application容器的XML配置，并且使用import标签进行集中导入
或者是结构式的顺序导入，同样的，Redis的配置也允许这么设置
################################## INCLUDES ################################### # 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. # # include /path/to/local.conf # include /path/to/other.conf
导入的声明信息：
include /path/to/local.conf
4、模块加载
用于加载模块的信息，类似上述的导入配置
如果该模块不可用，Redis会自动中止该模块的加载
################################## MODULES ##################################### # Load modules at startup. If the server is not able to load modules # it will abort. It is possible to use multiple loadmodule directives. # # loadmodule /path/to/my_module.so # loadmodule /path/to/other_module.so
5、网络配置
默认情况下，如果没有指定“bind”配置指令，则Redis侦听用于连接服务器上所有可用的网络接口。
可以只监听一个或多个选择的接口 "bind"配置指令，后面跟着一个或多个IP地址。
bind
默认情况下，redis 在 server 上所有有效的网络接口上监听客户端连接。
如果只想让它在一个或多个网络接口上监听，那你就绑定一个IP或者多个IP，多个ip空格分隔即可。
################################## NETWORK ##################################### # By default, if no "bind" configuration directive is specified, Redis listens # for connections from all the network interfaces available on the server. # It is possible to listen to just one or multiple selected interfaces using # the "bind" configuration directive, followed by one or more IP addresses. # # Examples: # # bind 192.168.1.100 10.0.0.1 # bind 127.0.0.1 ::1 # # ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the # internet, binding to all the interfaces is dangerous and will expose the # instance to everybody on the internet. So by default we uncomment the # following bind directive, that will force Redis to listen only into # the IPv4 loopback interface address (this means Redis will be able to # accept connections only from clients running into the same computer it # is running). # # IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES # JUST COMMENT THE FOLLOWING LINE. # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ bind 127.0.0.1
6、受保护模式：
保护模式是一层安全保护，为了避免这种情况访问和利用互联网上开放的Redis实例。
当保护模式开启时，如果：
1）服务器没有使用
“绑定”指令。
2）未配置密码。
服务器只接受来自客户端的连接
IPv4和IPv6环回地址127.0.0.1和：：1，来自Unix域的插座
默认情况下，启用保护模式。
只有在以下情况下才应该禁用它
您确定希望其他主机的客户端连接到Redis。即使没有配置身份验证，也没有一组特定的接口，使用“bind”指令显式列出。
# Protected mode is a layer of security protection, in order to avoid that # Redis instances left open on the internet are accessed and exploited. # # When protected mode is on and if: # # 1) The server is not binding explicitly to a set of addresses using the # "bind" directive. # 2) No password is configured. # # The server only accepts connections from clients connecting from the # IPv4 and IPv6 loopback addresses 127.0.0.1 and ::1, and from Unix domain # sockets. # # By default protected mode is enabled. You should disable it only if # you are sure you want clients from other hosts to connect to Redis # even if no authentication is configured, nor a specific set of interfaces # are explicitly listed using the "bind" directive. protected-mode yes
7、端口号：
# Accept connections on the specified port, default is 6379 (IANA #815344). # If port 0 is specified Redis will not listen on a TCP socket. port 6379
接受指定端口上的连接，默认值为6379（IANA#815344）。
如果指定了端口0，Redis将不会监听TCP套接字。
8、Tcp-backlog
设置tcp的backlog，backlog其实是一个连接队列，backlog队列总和=未完成三次握手队列 + 已经完成三次握手队列。
在高并发环境下你需要一个高backlog值来避免慢客户端连接问题。
注意Linux内核会将这个值减小到/proc/sys/net/core/somaxconn的值，
所以需要确认增大somaxconn和tcp_max_syn_backlog两个值来达到想要的效果
# 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-backlog 511
9、超时设置
当客户端闲置多少秒后关闭连接，如果设置为0表示关闭该功能。
# Unix socket. # # 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) timeout 0
10、TCP 持续连接设置
单位是秒，表示将周期性的使用SO_KEEPALIVE检测客户端是否还处于健康状态，避免服务器一直阻塞，
官方给出的建议值是300S 建议设置成60
# 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 300 seconds, which is the new # Redis default starting with Redis 3.2.1. tcp-keepalive 300
11、通用设置：
################################# GENERAL ##################################### # 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. daemonize yes # If you run Redis from upstart or systemd, Redis can interact with your # supervision tree. Options: # supervised no - no supervision interaction # supervised upstart - signal upstart by putting Redis into SIGSTOP mode # supervised systemd - signal systemd by writing READY=1 to $NOTIFY_SOCKET # supervised auto - detect upstart or systemd method based on # UPSTART_JOB or NOTIFY_SOCKET environment variables # Note: these supervision methods only signal "process is ready." # They do not enable continuous liveness pings back to your supervisor. supervised no # If a pid file is specified, Redis writes it where specified at startup # and removes it at exit. # # When the server runs non daemonized, no pid file is created if none is # specified in the configuration. When the server is daemonized, the pid file # is used even if not specified, defaulting to "/var/run/redis.pid". # # Creating a pid file is best effort: if Redis is not able to create it # nothing bad happens, the server will start and run normally. pidfile /var/run/redis_6379.pid # 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) 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 logfile "" # To enable logging to the system logger, just set ‘syslog-enabled‘ to yes, # and optionally update the other syslog parameters to suit your needs. # syslog-enabled no # Specify the syslog 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 databases 16 # By default Redis shows an ASCII art logo only when started to log to the # standard output and if the standard output is a TTY. Basically this means # that normally a logo is displayed only in interactive sessions. # # However it is possible to force the pre-4.0 behavior and always show a # ASCII art logo in startup logs by setting the following option to yes. always-show-logo yes
daemonize no
是否以守护模式启动，默认为no，配置为yes时以守护模式启动，
这时redis instance会将进程号pid写入默认文件/var/run/redis.pid。
supervised no
可以通过upstart和systemd管理Redis守护进程，这个参数是和具体的操作系统相关的。
pidfile /var/run/redis_6379.pid
配置pid文件路径。当redis以守护模式启动时，
如果没有配置pidfile，pidfile默认值是/var/run/redis.pid 。
loglevel notice
日志级别。可选项有：
debug（记录大量日志信息，适用于开发、测试阶段）；
verbose（较多日志信息）；
notice（适量日志信息，使用于生产环境）；
warning（仅有部分重要、关键信息才会被记录）。
logfile ""
日志文件的位置，当指定为空字符串时，为标准输出，
如果redis已守护进程模式运行，那么日志将会输出到 /dev/null 。
syslog-enabled no
是否把日志记录到系统日志。
syslog-ident
设置系统日志的id 如 syslog-ident redis
databases 16
设置数据库的数目。默认的数据库是DB 0 ，
可以在每个连接上使用select <dbid> 命令选择一个不同的数据库，
dbid是一个介于0到databases - 1 之间的数值。
always-show-logo yes
是否一直显示日志
12、快照 Snap-Shot：
################################ SNAPSHOTTING ################################ # # 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 "" 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. 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. 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. rdbchecksum yes # The filename where to dump the DB dbfilename dump.rdb # Remove RDB files used by replication in instances without persistence # enabled. By default this option is disabled, however there are environments # where for regulations or other security concerns, RDB files persisted on # disk by masters in order to feed replicas, or stored on disk by replicas # in order to load them for the initial synchronization, should be deleted # ASAP. Note that this option ONLY WORKS in instances that have both AOF # and RDB persistence disabled, otherwise is completely ignored. # # An alternative (and sometimes better) way to obtain the same effect is # to use diskless replication on both master and replicas instances. However # in the case of replicas, diskless is not always an option. rdb-del-sync-files no # 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. dir ./
save
保存数据到磁盘。
格式是：save <seconds> <changes> ，
含义是在 seconds 秒之后至少有 changes个keys 发生改变则保存一次。
save 900 1 900秒有一条数据改变就保存 save 300 10 300秒有10条数据改变就保存 save 60 10000 600秒有10000条数据改变就保存
stop-writes-on-bgsave-error
yes 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 好了。
rdbcompression yes
是否在dump .rdb数据库的时候压缩字符串，默认设置为yes。
如果你想节约一些cpu资源的话，可以把它设置为no，这样的话数据集就可能会比较大。
rdbchecksum yes
是否CRC64校验rdb文件，会有一定的性能损失（大概10%）
dbfilename dump.rdb
rdb文件的名字。
12、安全 Security
主要用于访问密码和查看，设置和取消
################################## SECURITY ################################### # Warning: since Redis is pretty fast an outside user can try up to # 1 million passwords per second against a modern box. This means that you # should use very strong passwords, otherwise they will be very easy to break. # Note that because the password is really a shared secret between the client # and the server, and should not be memorized by any human, the password # can be easily a long string from /dev/urandom or whatever, so by using a # long and unguessable password no brute force attack will be possible. # Redis ACL users are defined in the following format: # # user <username> ... acl rules ... # # For example: # # user worker +@list +@connection ~jobs:* on >ffa9203c493aa99 # # The special username "default" is used for new connections. If this user # has the "nopass" rule, then new connections will be immediately authenticated # as the "default" user without the need of any password provided via the # AUTH command. Otherwise if the "default" user is not flagged with "nopass" # the connections will start in not authenticated state, and will require # AUTH (or the HELLO command AUTH option) in order to be authenticated and # start to work. # # The ACL rules that describe what an user can do are the following: # # on Enable the user: it is possible to authenticate as this user. # off Disable the user: it‘s no longer possible to authenticate # with this user, however the already authenticated connections # will still work. # +<command> Allow the execution of that command # -<command> Disallow the execution of that command # +@<category> Allow the execution of all the commands in such category # with valid categories are like @admin, @set, @sortedset, ... # and so forth, see the full list in the server.c file where # the Redis command table is described and defined. # The special category @all means all the commands, but currently # present in the server, and that will be loaded in the future # via modules. # +<command>|subcommand Allow a specific subcommand of an otherwise # disabled command. Note that this form is not # allowed as negative like -DEBUG|SEGFAULT, but # only additive starting with "+". # allcommands Alias for +@all. Note that it implies the ability to execute # all the future commands loaded via the modules system. # nocommands Alias for -@all. # ~<pattern> Add a pattern of keys that can be mentioned as part of # commands. For instance ~* allows all the keys. The pattern # is a glob-style pattern like the one of KEYS. # It is possible to specify multiple patterns. # allkeys Alias for ~* # resetkeys Flush the list of allowed keys patterns. # ><password> Add this passowrd to the list of valid password for the user. # For example >mypass will add "mypass" to the list. # This directive clears the "nopass" flag (see later). # <<password> Remove this password from the list of valid passwords. # nopass All the set passwords of the user are removed, and the user # is flagged as requiring no password: it means that every # password will work against this user. If this directive is # used for the default user, every new connection will be # immediately authenticated with the default user without # any explicit AUTH command required. Note that the "resetpass" # directive will clear this condition. # resetpass Flush the list of allowed passwords. Moreover removes the # "nopass" status. After "resetpass" the user has no associated # passwords and there is no way to authenticate without adding # some password (or setting it as "nopass" later). # reset Performs the following actions: resetpass, resetkeys, off, # -@all. The user returns to the same state it has immediately # after its creation. # # ACL rules can be specified in any order: for instance you can start with # passwords, then flags, or key patterns. However note that the additive # and subtractive rules will CHANGE MEANING depending on the ordering. # For instance see the following example: # # user alice on +@all -DEBUG ~* >somepassword # # This will allow "alice" to use all the commands with the exception of the # DEBUG command, since +@all added all the commands to the set of the commands # alice can use, and later DEBUG was removed. However if we invert the order # of two ACL rules the result will be different: # # user alice on -DEBUG +@all ~* >somepassword # # Now DEBUG was removed when alice had yet no commands in the set of allowed # commands, later all the commands are added, so the user will be able to # execute everything. # # Basically ACL rules are processed left-to-right. # # For more information about ACL configuration please refer to # the Redis web site at https://redis.io/topics/acl # ACL LOG # # The ACL Log tracks failed commands and authentication events associated # with ACLs. The ACL Log is useful to troubleshoot failed commands blocked # by ACLs. The ACL Log is stored in memory. You can reclaim memory with # ACL LOG RESET. Define the maximum entry length of the ACL Log below. acllog-max-len 128 # Using an external ACL file # # Instead of configuring users here in this file, it is possible to use # a stand-alone file just listing users. The two methods cannot be mixed: # if you configure users here and at the same time you activate the exteranl # ACL file, the server will refuse to start. # # The format of the external ACL user file is exactly the same as the # format that is used inside redis.conf to describe users. # # aclfile /etc/redis/users.acl # IMPORTANT NOTE: starting with Redis 6 "requirepass" is just a compatiblity # layer on top of the new ACL system. The option effect will be just setting # the password for the default user. Clients will still authenticate using # AUTH <password> as usually, or more explicitly with AUTH default <password> # if they follow the new protocol: both will work. # # requirepass foobared # Command renaming (DEPRECATED). # # ------------------------------------------------------------------------ # WARNING: avoid using this option if possible. Instead use ACLs to remove # commands from the default user, and put them only in some admin user you # create for administrative purposes. # ------------------------------------------------------------------------ # # 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 "" # the Redis web site at https://redis.io/topics/acl # ACL LOG # # The ACL Log tracks failed commands and authentication events associated # with ACLs. The ACL Log is useful to troubleshoot failed commands blocked # by ACLs. The ACL Log is stored in memory. You can reclaim memory with # ACL LOG RESET. Define the maximum entry length of the ACL Log below. acllog-max-len 128 # Using an external ACL file # # Instead of configuring users here in this file, it is possible to use # a stand-alone file just listing users. The two methods cannot be mixed: # if you configure users here and at the same time you activate the exteranl # ACL file, the server will refuse to start. # # The format of the external ACL user file is exactly the same as the # format that is used inside redis.conf to describe users. # # aclfile /etc/redis/users.acl # IMPORTANT NOTE: starting with Redis 6 "requirepass" is just a compatiblity # layer on top of the new ACL system. The option effect will be just setting # the password for the default user. Clients will still authenticate using # AUTH <password> as usually, or more explicitly with AUTH default <password> # if they follow the new protocol: both will work. # # requirepass foobared # Command renaming (DEPRECATED). # # ------------------------------------------------------------------------ # WARNING: avoid using this option if possible. Instead use ACLs to remove # commands from the default user, and put them only in some admin user you # create for administrative purposes. # ------------------------------------------------------------------------ # # 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 replicas may cause problems.
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