1, Redis cache database
Redis is an open source using ANSI C language Write, support network, memory based and persistent log type, key value data base . Redis and Memcached are similar, but redis supports more storage value types. Here is a brief introduction to the difference between redis and Memcached
| data base |
Reading and writing efficiency |
data type |
Persistence |
Cluster mode |
Applicable scenario |
| Redis |
10W/S |
K/String List Hash Set SortedSet |
yes |
Redis-Cluster (crc16 algorithm) |
Systems that maintain data integrity and high availability |
| Memcached | >10W/S |
K/V |
no |
Consistency Hash algorithm |
Require more efficiency and accept data loss |
2, Redis installation
Take the installation package of Windows as an example
1. Download the installation package https://github.com/MicrosoftArchive/redis/releases
After downloading, install. After installation, find redis.windows.conf in the root directory of redis installation to modify the configuration according to your own needs. After configuration, find the redis service in the service and start it
| Name | Explain |
| port | Set port number to 6379 by default |
| bind | IP address setting default local 127.0.0.1 |
| tcp-backlog | Maximum capacity of TCP monitoring |
| requirepass | Password settings |
| timeout | Connection recovery policy |
Other configuration description:
Persistence policy:
appendfilename *.aof
1) "appendonly"
2) "yes"
3) "no-appendfsync-on-rewrite"
4) "no"
5) "appendfsync"
6) "everysec"
1) "auto-aof-rewrite-percentage"
2) "100"
3) "auto-aof-rewrite-min-size"
4) "67108864"
#appendfsync always fsync as long as there is newly added data
appendfsync everysec supports delayed fsync
#Append fsync no
Expiration policy:
Six ways of maxmemory policy
Volatile LRU: LRU only for key s with expiration time set (default)
Allkeys lru: delete the key of lru algorithm
Volatile random: randomly delete the expiring key
Allkeys random: random deletion
Volatile TTL: delete expiring
noeviction: never expire, error returned
2. redis visual management tool
Redis Desktop Manager
3, Redis configuration details
# redis profile example # When you need to specify the memory size for a configuration item, you must bring the unit, # The usual format is 1k 5gb 4m, etc # # 1k => 1000 bytes # 1kb => 1024 bytes # 1m => 1000000 bytes # 1mb => 1024*1024 bytes # 1g => 1000000000 bytes # 1gb => 1024*1024*1024 bytes # # Units are not case sensitive. You can write 1K 5GB 4M as well ################################## INCLUDES ################################### # If you have a standard configuration template for all redis server s, # But for some server s, some personalized settings are needed, # You can use include to include some other configuration files, which is very useful for you. # # But please note that the include command cannot be overridden by the config rewrite command # Because redis always takes the last machining line as a configuration command value, you'd better put include at the front of this file, # To avoid overwriting configuration changes at run time, instead, you put it at the back. # # include /path/to/local.conf # include /path/to/other.conf ################################ Commonly used ##################################### # By default, redis does not run as a daemons. If you want it to run in the background, you can change it to yes. # When redis runs as a daemons, it writes a PID to the / var/run/redis.pid file. daemonize no # When redis runs as a daemons, it will write PID to the / var/run/redis.pid file by default, # But you can make your own file location here. pidfile /var/run/redis.pid # Listen to the port number, which is 6379 by default. If you set it to 0, redis will not listen to any client connections on the socket. port 6379 # Maximum capacity of TCP listening # # In a highly concurrent environment, you need to raise this value to avoid slow client connections. # The Linux kernel will silently reduce this value to the value corresponding to / proc/sys/net/core/somaxconn, # So you need to modify these two values to meet your expectations. tcp-backlog 511 # By default, redis listens for client connections on all valid network interfaces on the server. # If you just want it to listen on a network interface, you can bind one IP or multiple IP addresses. # # For example, multiple IP S are separated by spaces: # # bind 192.168.1.100 10.0.0.1 # bind 127.0.0.1 # Specifies the path to the unix socket. # # unixsocket /tmp/redis.sock # unixsocketperm 755 # Specifies how many seconds after a client is idle to close the connection (0 doesn't matter) timeout 0 # tcp heartbeat packet. # # If it is set to non-zero, use so keep to send tcp acks to the client in case of lack of communication with the client. # There are two main reasons why this works: # # 1) 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. # A reasonable value recommended is 60 seconds tcp-keepalive 0 # Define the log level. # These can be the following values: # debug (for development or test phase) # verbose (many rarely useful info, but not a mess like the debug level) # notice (for production environment) # warning (only some important messages are recorded) loglevel notice # Specify the location of the log file logfile "" # To log to the system log, change it to yes, # You can also optionally update other syslog parameters to meet your requirements # syslog-enabled no # Set the identity of syslog. # syslog-ident redis # Set the facility of syslog, which must be a value between USER or LOCAL0-LOCAL7. # syslog-facility local0 # Sets the number of databases. # The default database is DB 0. You can use the select < dbid > command on each connection to select a different database, # But dbid must be a value between 0 and databases - 1 databases 16 ################################ snapshot ################################ # # Save DB to disk: # # Format: save < interval time (seconds) > write times > # # Saves data to disk based on a given time interval and number of writes # # The following example means: # Save if the value of at least one key changes in 900 seconds # If the value of at least 10 key s changes within 300 seconds, save # If the value of at least 10000 key s changes within 60 seconds, save # # Note: you can disable the save function by commenting out all save lines. # You can also disable a null string directly: # save "" save 900 1 save 300 10 save 60 10000 # By default, if the last background save of redis fails, redis will stop accepting write operations, # In this way, users can know in a tough way that data cannot be persisted to disk correctly, # Otherwise, no one will notice the disaster. # # If the background save process is restarted, redis will automatically allow write operations. # # However, if you install reliable monitoring, you may not want redis to do so. Then you can change it to no. stop-writes-on-bgsave-error yes # Whether to use LZF to compress string when dump. RDB database # All set to yes by default # If you want to save subprocesses to save cpu, you set it to no, # But this data set may be larger rdbcompression yes # Check rdb file or not rdbchecksum yes # Set the file location of dump dbfilename dump.rdb # working directory # For example, the dbfilename above only specifies the file name, # But it will be written to this directory. This configuration item must be a directory, not a filename. dir ./ ################################# Master slave replication ################################# # Master-slave replication. Use slavof to make a redis instance a copy of another reids instance. # Note that this only needs to be configured on the slave. # # slaveof <masterip> <masterport> # If the master needs password authentication, set it here # masterauth <master-password> # When a slave loses contact with the master or replication is in progress, # There are two possible manifestations of slave: # # 1) If yes, slave will still answer the client's request, but the returned data may be outdated, # Or the data may be empty at the first synchronization # # 2) If no, when you execute commands other than info he salveof, # slave will return a "SYNC with master in progress" error, # slave-serve-stale-data yes # You can configure whether a slave entity accepts write operations. # It may be useful for a slave instance to store some transient data through write operations, # Because it is easier to write data to slave than to resynchronize data from master. # However, if the client writes due to a wrong configuration, it may cause some problems. # # Since redis version 2.6, the 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. # Note: read only slaves are not designed to be exposed to untrusted clients on the internet. # It's just a layer of protection for misused instances. slave-read-only yes # Slave sends ping command to server in a predefined time interval. # You can change the time interval. The default is 10 seconds. # # repl-ping-slave-period 10 # The following option sets the replication timeout for: # Set master-slave replication expiration time # # 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. # This value must be greater than repl Ping slave period # # 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 primary and secondary replication capacity size. This backlog is used when slaves is disconnected # The buffer that stores the slave data, so when a slave wants to reconnect, it usually does not want to resynchronize all of them, # Only partial synchronization is enough, only passing the data that is lost when the slave is disconnected. # # The biggest the replication backlog, the longer the time the slave can be # disconnected and later be able to perform a partial resynchronization. # The higher the value, the longer it takes for a salve to disconnect. # # 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. # In some cases, the master will no longer connect to the slaves, and the backlog will be released. # # A value of 0 means to never release the backlog. # If set to 0, it means never release the backlog. # # repl-backlog-ttl 3600 # When the master fails to work normally, Redis Sentinel will select a new master from the slaves, # The smaller the value is, the higher the priority will be. But if it is 0, it means that the slave cannot be selected. # # The default 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 GUARANTEES 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 ################################### # 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. # # Set authentication password # 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. ################################### limit #################################### # 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 maximum limit is reached, redis will close all new connections # And send a 'max number of clients reached' error. # # maxclients 10000 # If you set this value, when the cache data capacity reaches this value, redis will select # eviction policy to remove some keys. # # If redis cannot remove keys according to the policy, or the policy is set to 'noeviction', # redis will start to respond to errors to commands, such as set, lpush, etc, # And continue to respond to read-only commands, such as 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'). # # Maximum memory used # maxmemory <bytes> # You have five options for the maximum memory strategy. # # volatile-lru -> remove the key with an expire set using an LRU algorithm # Volatile LRU - > use the LRU algorithm to remove key s that contain expiration settings. # allkeys-lru -> remove any key accordingly to the LRU algorithm # Allkeys LRU - > remove all keys according to 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 # Noeviction - > do not let any key expire, just return an error to the write operation # # Note: with any of the above policies, Redis will return an error on write # operations, when there are not suitable keys for eviction. # # At the date of writing this 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. 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 to wait 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 ################################ 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 exceed 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 commands was # already issue by the script but the user don'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 colony ############################### # # Enable or disable clusters # 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 does 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 # 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 ############################# Event notification ############################## # Redis can notify Pub/Sub clients about events happening in the key space. # This feature is documented at http://redis.io/topics/keyspace-events # # 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 # by zero or multiple characters. The empty string means that notifications # are disabled at all. # # 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 # 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-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 happens 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 # active rehashing 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 form 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 # slave -> slave clients and MONITOR 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 accordingly 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