【0】開場白： redis提供了復制功能， 實現當一臺數據庫中的數據更新后， 自動將更新的數據同步到其他數據庫上； 這樣即使一條server 發生故障，其他服務器仍然可以繼續提供服務；（為數據生成多個副本并分配到不同的服務器上）

（干貨——這可以理解為水平擴容以提高系統訪問效率） 水平擴容是增加服務器個數， 垂直擴容是服務器個數不增加，而是增加每個服務器容量；

【1】 主redis啟動， redis-server 啟動， 默認端口 6379

redis-server redis.conf?

【2】從redis啟動， 端口 6380? 6381

redis-server --port 6380 --slaveof 192.168.186.100 --protected-mode no

redis-server --port 6381 --slaveof 192.168.186.100 --protected-mode no

【3】客戶端連接

redis-cli -h 192.168.186.100

redis-cli -h 192.168.186.100 -p 6380

redis-cli -h 192.168.186.100 -p 6381

【4】校驗redis的復制功能

192.168.186.100:6379> info replication # Replication role:master connected_slaves:0 master_replid:e808a85991b82c1c266d4b8133f6dd5be56b8828 master_replid2:0000000000000000000000000000000000000000 master_repl_offset:0 second_repl_offset:-1 repl_backlog_active:0 repl_backlog_size:1048576 repl_backlog_first_byte_offset:0 repl_backlog_histlen:0 192.168.186.100:6379> set foo bar // 主數據庫設置值 OK 192.168.186.100:6379> 192.168.186.100:6380> info replication # Replication role:slave master_host:192.168.186.100 master_port:6379 master_link_status:up master_last_io_seconds_ago:8 master_sync_in_progress:0 slave_repl_offset:714 slave_priority:100 slave_read_only:1 connected_slaves:0 master_replid:28c0673df46b0bceda233e58a7a3cd9ae9d5b2e6 master_replid2:0000000000000000000000000000000000000000 master_repl_offset:714 second_repl_offset:-1 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:43 repl_backlog_histlen:672 192.168.186.100:6380> get foo // 從數據庫獲取值 "bar" 192.168.186.100:6380> set foo hello (error) READONLY You can't write against a read only slave. 192.168.186.100:6380> 192.168.186.100:6381> info replication # Replication role:slave master_host:192.168.186.100 master_port:6379 master_link_status:up master_last_io_seconds_ago:5 master_sync_in_progress:0 slave_repl_offset:756 slave_priority:100 slave_read_only:1 connected_slaves:0 master_replid:28c0673df46b0bceda233e58a7a3cd9ae9d5b2e6 master_replid2:0000000000000000000000000000000000000000 master_repl_offset:756 second_repl_offset:-1 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:211 repl_backlog_histlen:546 192.168.186.100:6381> 【說明】

1）默認情況下， 從數據庫是只讀的， 直接修改數據會報錯；?

【4】補充：redis.conf 文件如下：?

# 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 #################################### 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################################## 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################################## 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 lookback 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 192.168.186.100# 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# 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# 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# 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# 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################################# 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 "/usr/local/redis-4.0.8/logs/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. # 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################################ 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# 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 /usr/local/redis-4.0.8/data################################# REPLICATION ################################## 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. # # 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. # # 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. # 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. 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. # # 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. # # 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. 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. # # 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. # # Note that slaves never free the backlog for timeout, since they may be # promoted to masters later, and should be able to correctly "partially # resynchronize" with the slaves: hence they should always accumulate backlog. # # A value of 0 means to never release the 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. 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.# A Redis master is able to list the address and port of the attached # slaves in different ways. For example the "INFO replication" section # offers this information, which is used, among other tools, by # Redis Sentinel in order to discover slave instances. # Another place where this info is available is in the output of the # "ROLE" command of a master. # # The listed IP and address normally reported by a slave is obtained # in the following way: # # IP: The address is auto detected by checking the peer address # of the socket used by the slave to connect with the master. # # Port: The port is communicated by the slave during the replication # handshake, and is normally the port that the slave is using to # list for connections. # # However when port forwarding or Network Address Translation (NAT) is # used, the slave may be actually reachable via different IP and port # pairs. The following two options can be used by a slave in order to # report to its master a specific set of IP and port, so that both INFO # and ROLE will report those values. # # There is no need to use both the options if you need to override just # the port or the IP address. # # slave-announce-ip 5.5.5.5 # slave-announce-port 1234################################## SECURITY #################################### 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. # # requirepass foobared# 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.################################### CLIENTS ##################################### 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'. # # maxclients 10000############################## MEMORY MANAGEMENT ################################# Set a memory usage limit to 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 or LFU 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'). # # maxmemory <bytes># MAXMEMORY POLICY: how Redis will select what to remove when maxmemory # is reached. You can select among five behaviors: # # volatile-lru -> Evict using approximated LRU among the keys with an expire set. # allkeys-lru -> Evict any key using approximated LRU. # volatile-lfu -> Evict using approximated LFU among the keys with an expire set. # allkeys-lfu -> Evict any key using approximated LFU. # volatile-random -> Remove a random key among the ones 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 evict anything, just return an error on write operations. # # LRU means Least Recently Used # LFU means Least Frequently Used # # Both LRU, LFU and volatile-ttl are implemented using approximated # randomized algorithms. # # 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, LFU 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 more CPU. 3 is faster but not very accurate. # # maxmemory-samples 5############################# LAZY FREEING ##################################### Redis has two primitives to delete keys. One is called DEL and is a blocking # deletion of the object. It means that the server stops processing new commands # in order to reclaim all the memory associated with an object in a synchronous # way. If the key deleted is associated with a small object, the time needed # in order to execute the DEL command is very small and comparable to most other # O(1) or O(log_N) commands in Redis. However if the key is associated with an # aggregated value containing millions of elements, the server can block for # a long time (even seconds) in order to complete the operation. # # For the above reasons Redis also offers non blocking deletion primitives # such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and # FLUSHDB commands, in order to reclaim memory in background. Those commands # are executed in constant time. Another thread will incrementally free the # object in the background as fast as possible. # # DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled. # It's up to the design of the application to understand when it is a good # idea to use one or the other. However the Redis server sometimes has to # delete keys or flush the whole database as a side effect of other operations. # Specifically Redis deletes objects independently of a user call in the # following scenarios: # # 1) On eviction, because of the maxmemory and maxmemory policy configurations, # in order to make room for new data, without going over the specified # memory limit. # 2) Because of expire: when a key with an associated time to live (see the # EXPIRE command) must be deleted from memory. # 3) Because of a side effect of a command that stores data on a key that may # already exist. For example the RENAME command may delete the old key # content when it is replaced with another one. Similarly SUNIONSTORE # or SORT with STORE option may delete existing keys. The SET command # itself removes any old content of the specified key in order to replace # it with the specified string. # 4) During replication, when a slave performs a full resynchronization with # its master, the content of the whole database is removed in order to # load the RDB file just transfered. # # In all the above cases the default is to delete objects in a blocking way, # like if DEL was called. However you can configure each case specifically # in order to instead release memory in a non-blocking way like if UNLINK # was called, using the following configuration directives:lazyfree-lazy-eviction no lazyfree-lazy-expire no lazyfree-lazy-server-del no slave-lazy-flush no############################## 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.appendonly no# The name of the append only file (default: "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".# 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.no-appendfsync-on-rewrite no# 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.auto-aof-rewrite-percentage 100 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# When rewriting the AOF file, Redis is able to use an RDB preamble in the # AOF file for faster rewrites and recoveries. When this option is turned # on the rewritten AOF file is composed of two different stanzas: # # [RDB file][AOF tail] # # When loading Redis recognizes that the AOF file starts with the "REDIS" # string and loads the prefixed RDB file, and continues loading the AOF # tail. # # This is currently turned off by default in order to avoid the surprise # of a format change, but will at some point be used as the default. aof-use-rdb-preamble no################################ 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. 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 an 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.########################## CLUSTER DOCKER/NAT support ######################### In certain deployments, Redis Cluster nodes address discovery fails, because # addresses are NAT-ted or because ports are forwarded (the typical case is # Docker and other containers). # # In order to make Redis Cluster working in such environments, a static # configuration where each node knows its public address is needed. The # following two options are used for this scope, and are: # # * cluster-announce-ip # * cluster-announce-port # * cluster-announce-bus-port # # Each instruct the node about its address, client port, and cluster message # bus port. The information is then published in the header of the bus packets # so that other nodes will be able to correctly map the address of the node # publishing the information. # # If the above options are not used, the normal Redis Cluster auto-detection # will be used instead. # # Note that when remapped, the bus port may not be at the fixed offset of # clients port + 10000, so you can specify any port and bus-port depending # on how they get remapped. If the bus-port is not set, a fixed offset of # 10000 will be used as usually. # # Example: # # cluster-announce-ip 10.1.1.5 # cluster-announce-port 6379 # cluster-announce-bus-port 6380################################## 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. hash-max-ziplist-entries 512 hash-max-ziplist-value 64# Lists are also encoded in a special way to save a lot of space. # The number of entries allowed per internal list node can be specified # as a fixed maximum size or a maximum number of elements. # For a fixed maximum size, use -5 through -1, meaning: # -5: max size: 64 Kb <-- not recommended for normal workloads # -4: max size: 32 Kb <-- not recommended # -3: max size: 16 Kb <-- probably not recommended # -2: max size: 8 Kb <-- good # -1: max size: 4 Kb <-- good # Positive numbers mean store up to _exactly_ that number of elements # per list node. # The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size), # but if your use case is unique, adjust the settings as necessary. list-max-ziplist-size -2# Lists may also be compressed. # Compress depth is the number of quicklist ziplist nodes from *each* side of # the list to *exclude* from compression. The head and tail of the list # are always uncompressed for fast push/pop operations. Settings are: # 0: disable all list compression # 1: depth 1 means "don't start compressing until after 1 node into the list, # going from either the head or tail" # So: [head]->node->node->...->node->[tail] # [head], [tail] will always be uncompressed; inner nodes will compress. # 2: [head]->[next]->node->node->...->node->[prev]->[tail] # 2 here means: don't compress head or head->next or tail->prev or tail, # but compress all nodes between them. # 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail] # etc. list-compress-depth 0# 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-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: 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. 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# Client query buffers accumulate new commands. They are limited to a fixed # amount by default in order to avoid that a protocol desynchronization (for # instance due to a bug in the client) will lead to unbound memory usage in # the query buffer. However you can configure it here if you have very special # needs, such us huge multi/exec requests or alike. # # client-query-buffer-limit 1gb# In the Redis protocol, bulk requests, that are, elements representing single # strings, are normally limited ot 512 mb. However you can change this limit # here. # # proto-max-bulk-len 512mb# 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-incremental-fsync yes# Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good # idea to start with the default settings and only change them after investigating # how to improve the performances and how the keys LFU change over time, which # is possible to inspect via the OBJECT FREQ command. # # There are two tunable parameters in the Redis LFU implementation: the # counter logarithm factor and the counter decay time. It is important to # understand what the two parameters mean before changing them. # # The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis # uses a probabilistic increment with logarithmic behavior. Given the value # of the old counter, when a key is accessed, the counter is incremented in # this way: # # 1. A random number R between 0 and 1 is extracted. # 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1). # 3. The counter is incremented only if R < P. # # The default lfu-log-factor is 10. This is a table of how the frequency # counter changes with a different number of accesses with different # logarithmic factors: # # +--------+------------+------------+------------+------------+------------+ # | factor | 100 hits | 1000 hits | 100K hits | 1M hits | 10M hits | # +--------+------------+------------+------------+------------+------------+ # | 0 | 104 | 255 | 255 | 255 | 255 | # +--------+------------+------------+------------+------------+------------+ # | 1 | 18 | 49 | 255 | 255 | 255 | # +--------+------------+------------+------------+------------+------------+ # | 10 | 10 | 18 | 142 | 255 | 255 | # +--------+------------+------------+------------+------------+------------+ # | 100 | 8 | 11 | 49 | 143 | 255 | # +--------+------------+------------+------------+------------+------------+ # # NOTE: The above table was obtained by running the following commands: # # redis-benchmark -n 1000000 incr foo # redis-cli object freq foo # # NOTE 2: The counter initial value is 5 in order to give new objects a chance # to accumulate hits. # # The counter decay time is the time, in minutes, that must elapse in order # for the key counter to be divided by two (or decremented if it has a value # less <= 10). # # The default value for the lfu-decay-time is 1. A Special value of 0 means to # decay the counter every time it happens to be scanned. # # lfu-log-factor 10 # lfu-decay-time 1########################### ACTIVE DEFRAGMENTATION ####################### # # WARNING THIS FEATURE IS EXPERIMENTAL. However it was stress tested # even in production and manually tested by multiple engineers for some # time. # # What is active defragmentation? # ------------------------------- # # Active (online) defragmentation allows a Redis server to compact the # spaces left between small allocations and deallocations of data in memory, # thus allowing to reclaim back memory. # # Fragmentation is a natural process that happens with every allocator (but # less so with Jemalloc, fortunately) and certain workloads. Normally a server # restart is needed in order to lower the fragmentation, or at least to flush # away all the data and create it again. However thanks to this feature # implemented by Oran Agra for Redis 4.0 this process can happen at runtime # in an "hot" way, while the server is running. # # Basically when the fragmentation is over a certain level (see the # configuration options below) Redis will start to create new copies of the # values in contiguous memory regions by exploiting certain specific Jemalloc # features (in order to understand if an allocation is causing fragmentation # and to allocate it in a better place), and at the same time, will release the # old copies of the data. This process, repeated incrementally for all the keys # will cause the fragmentation to drop back to normal values. # # Important things to understand: # # 1. This feature is disabled by default, and only works if you compiled Redis # to use the copy of Jemalloc we ship with the source code of Redis. # This is the default with Linux builds. # # 2. You never need to enable this feature if you don't have fragmentation # issues. # # 3. Once you experience fragmentation, you can enable this feature when # needed with the command "CONFIG SET activedefrag yes". # # The configuration parameters are able to fine tune the behavior of the # defragmentation process. If you are not sure about what they mean it is # a good idea to leave the defaults untouched.# Enabled active defragmentation # activedefrag yes# Minimum amount of fragmentation waste to start active defrag # active-defrag-ignore-bytes 100mb# Minimum percentage of fragmentation to start active defrag # active-defrag-threshold-lower 10# Maximum percentage of fragmentation at which we use maximum effort # active-defrag-threshold-upper 100# Minimal effort for defrag in CPU percentage # active-defrag-cycle-min 25# Maximal effort for defrag in CPU percentage # active-defrag-cycle-max 75

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