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Redis Command Compatibility

This section describes DCS's compatibility with Redis commands, including supported commands, disabled commands, unsupported scripts and commands of later Redis versions, and restrictions on command usage.

For more information about the command syntax, visit the Redis official website.

DCS for Redis instances support most Redis commands. Any client compatible with the Redis protocol can access DCS.

  • For security purposes, some Redis commands are disabled in DCS. For details, see Commands Disabled by DCS for Redis 3.0 <dcs-ug-180522002__section0341135531914>.
  • Some Redis commands have usage restrictions, which are described in Other Command Usage Restrictions <dcs-ug-180522002__section834293511127>.
  • Some Redis commands are supported by cluster DCS instances for multi-key operations in the same slot. For details, see Table 4 <dcs-ug-180522002__table7589193113396>.

Commands Supported by DCS for Redis 3.0

The following lists commands supported by DCS for Redis 3.0.

Note

Commands available since later Redis versions are not supported by earlier versions. Run a command on redis-cli to check whether it is supported by DCS for Redis. If the message "(error) ERR unknown command" is returned, the command is not supported.

Table 1 Commands supported by DCS for Redis 3.0
Category Command
Key DEL, DUMP, EXISTS, EXPIRE, MOVE, PERSISI, PTTL, RANDOMKEY, RENAME, RENAMENX, RESTORE, SORT, TTL, TYPE, SCAN, OBJIECT
String APPEND, BITCOUNT, BITOP, BITPOS, DECR, DECRBY, GET, GETRANGE, GETSET, INCR, INCRBY, INCRBYFLOAT, MGET, MSET, MSETNX, PSETEX, SET, SETBIT, SETEX, SETNX, SETRANGE, STRLEN
Hash HDEL, HEXISTS, HGET, HGETALL, HINCRBY, HINCRBYFLOAT, HKEYS, HMGET, HMSET, HSET, HSETNX, HVALS, HSCAN
List

BLPOP, BRPOP, BRPOPLRUSH, LINDEX, LINSERT, LLEN, LPOP, LPUSHX, LRANGE, LREM, LSET, LTRIM, RPOP, RPOPLPU, RPOPLPUSH, RPUSH, RPUSHX

Note

Proxy Cluster Redis 3.0 instances do not support BLPOP, BRPOP, and BRPOPLRUSH commands.
Set SADD, SCARD, SDIFF, SDIFFSTORE, SINTER, SINTERSTORE, SISMEMBER, SMEMBERS, SMOVE, SPOP, SRANDMEMBER, SREM, SUNION, SUNIONSTORE, SSCAN
Sorted set ZADD, ZCARD, ZCOUNT, ZINCRBY, ZRANGE, ZRANGEBYSCORE, ZRANK, ZREMRANGEBYRANK, ZREMRANGEBYCORE, ZREVRANGE, ZREVRANGEBYSCORE, ZREVRANK, ZSCORE, ZUNIONSTORE, ZINTERSTORE, ZSCAN, ZRANGEBYLEX
HyperLogLog PFADD, PFCOUNT, PFMERGE
Pub/Sub PSUBSCRIBE, PUBLISH, PUBSUB, PUNSUBSCRIBE, SUBSCRIBE, UNSUBSCRIBE
Transaction DISCARD, EXEC, MULTI, UNWATCH, WATCH
Connection AUTH, ECHO, PING, QUIT, SELECT
Server

FLUSHALL, FLUSHDB, DBSIZE, TIME, INFO, KEYS, CLIENT KILL, CLIENT LIST, CLIENT GETNAME, CLIENT SETNAME, CONFIG GET, MONITOR, SLOWLOG, ROLE

Note

  • Proxy Cluster Redis 3.0 instances do not support CLIENT commands, including CLIENT KILL, CLIENT GETNAME, CLIENT LIST, CLIENT SETNAME, CLIENT PAUSE, and CLIENT REPLY.
  • Proxy Cluster Redis 3.0 instances do not support the MONITOR command.
Scripting EVAL, EVALSHA, SCRIPT EXISTS, SCRIPT FLUSH, SCRIPT KILL, SCRIPT LOAD
Geo GEOADD, GEOHASH, GEOPOS, GEODIST, GEORADIUS, GEORADIUSBYMEMBER

Commands Disabled by DCS for Redis 3.0

Redis APIs of single-node and master/standby DCS instances are compatible with open-source Redis for data access. For ease of use and security purposes, some management operations cannot be initiated from a Redis client. Related commands are listed in Table 2 <dcs-ug-180522002__table31856418216>.

Table 2 Redis commands disabled in single-node and master/standby Redis 3.0 instances
Command Description
Key
MIGRATE Transfers a key from one Redis instance to another.
Server
SLAVEOF Changes the replication settings of a replica on the fly.
SHUTDOWN Stops all the clients and quits the Redis process.
LASTSAVE Returns the time of the last successful data persistence to disk.
DEBUG commands Debugging command that should not be used by clients.
COMMAND Returns array reply of details about all Redis commands.
SAVE Performs a synchronous save on disk, producing a point in time snapshot of all the data inside the Redis instance, in the form of an RDB file.
BGSAVE Asynchronously saves the database on disk.
BGREWRITEAOF Starts an Append Only File (AOF) rewrite process.

In additional to these commands, Proxy Cluster Redis 3.0 instances do not support the commands listed in Table 3 <dcs-ug-180522002__table122021410155210>.

Table 3 Redis commands disabled in Proxy Cluster Redis 3.0 instances
Command Description
Server
SYNC An internal command used for full replication.
PSYNC An internal command used for partial replication.
MONITOR Streams back every command processed by the Redis server for debugging.
CLIENT commands CLIENT KILL, CLIENT GETNAME, CLIENT LIST, CLIENT SETNAME, CLIENT PAUSE, and CLIENT REPLY.
OBJECT Debugging command that should not be used by clients.
ROLE Returns the role of the instance node.
Transaction
DISCARD Flushes all previously queued commands in a transaction.
EXEC Executes all previously queued commands in a transaction.
MULTI Marks the start of a transaction block.
UNWATCH Flushes all the previously watched keys for a transaction.
WATCH Marks the given key or keys to be watched. If the key or keys are modified by other commands before WATCH is executed, the transaction is interrupted.
Connection
SELECT Selects the Redis database. Note: Parameters of the SELECT command can only be set to 0.
Keys
MOVE Moves key of the currently selected database to the specified destination database.
Cluster
CLUSTER Used for cluster management.
codis (Proxy Cluster)
TIME Returns the current server time.
SLOTSINFO Returns the number of slots and the size of each slot in Redis.
SLOTSDEL Deletes all key-value pairs in multiple slots in Redis.
SLOTSMGRTSLOT Randomly migrates a key-value pair in a slot to the destination.
SLOTSMGRTONE Migrates a specified key-value pair to the destination.
SLOTSCHECK

Checks whether slots meet the following consistency requirements:

  • All the keys in the slots have a corresponding value in the database.
  • All the keys in the database have a value in the corresponding slot.
SLOTSMGRTTAGSLOT Migrates all key-value pairs with the same tag as a randomly selected key in a slot.
SLOTSMGRTTAGONE Migrates all key-value pairs with the same tag as a specified key.
List
BLPOP The blocking version of LPOP because it blocks the connection when there are no elements to pop from any of the given lists until the specified timeout has expired or a non-empty element is popped.
BRPOP The blocking version of RPOP because it blocks the connection when there are no elements to pop from any of the given lists until the specified timeout has expired or a non-empty element is popped.
BRPOPLPUSH The blocking variant of RPOPLPUSH. When source contains elements, this command behaves exactly like RPOPLPUSH.

Restricted Redis Commands

Some Redis commands are supported by cluster DCS instances for multi-key operations in the same slot. For details, see Table 4 <dcs-ug-180522002__table7589193113396>.

Table 4 Redis commands restricted in cluster DCS instances.
Category Description
Set
SINTER Returns the members of the set resulting from the intersection of all the given sets.
SINTERSTORE Equal to SINTER, but instead of returning the result set, it is stored in destination.
SUNION Returns the members of the set resulting from the union of all the given sets.
SUNIONSTORE Equal to SUNION, but instead of returning the result set, it is stored in destination.
SDIFF Returns the members of the set resulting from the difference between the first set and all the successive sets.
SDIFFSTORE Equal to SDIFF, but instead of returning the result set, it is stored in destination.
SMOVE Moves member from the set at source to the set at destination.
Sorted Set
ZUNIONSTORE Computes the union of numkeys sorted sets given by the specified keys.
ZINTERSTORE Computes the intersection of numkeys sorted sets given by the specified keys.
HyperLogLog
PFCOUNT Returns the approximated cardinality computed by the HyperLogLog data structure stored at the specified variable.
PFMERGE Merges multiple HyperLogLog values into a unique value.
Key
RENAME Renames key to newkey.
RENAMENX Renames key to newkey if newkey does not yet exist.
BITOP Performs a bitwise operation between multiple keys (containing string values) and stores the result in the destination key.
RPOPLPUSH Returns and removes the last element (tail) of the list stored at source, and pushes the element at the first element (head) of the list stored at destination.
String
MSETNX Sets the given keys to their respective values.

Note

While running commands that take a long time to run, such as FLUSHALL, DCS instances may not respond to other commands and change to the faulty state. After the command finishes executing, the instance will return to normal.

Other Command Usage Restrictions

Key commands:

In case of a large amount of cached data, running a Keys command may block the execution of other commands for a long time or occupy exceptionally large memory. Therefore, when running a Keys command, describe the exact pattern and do not use fuzzy keys *. keys * can be used during commissioning or when the number of keys does not exceed 5 million. Otherwise, the service cannot run properly.

Server commands:

  • While running commands that take a long time to run, such as FLUSHALL, DCS instances may not respond to other commands and change to the faulty state. After the command finishes executing, the instance will return to normal.
  • When the FLUSHDB or FLUSHALL command is run, execution of other service commands may be blocked for a long time in case of a large amount of cached data.

EVAL and EVALSHA commands:

  • When the EVAL or EVALSHA command is run, at least one key must be contained in the command parameter. Otherwise, the error message "ERR eval/evalsha numkeys must be bigger than zero in redis cluster mode" is displayed.
  • When the EVAL or EVALSHA command is run, a cluster DCS Redis instance uses the first key to compute slots. Ensure that the keys to be operated in your code are in the same slot. For details, visit http://redis.io/commands.
  • For the EVAL command:
    • You are advised to learn the Lua script features of Redis before running the EVAL command. For details, see https://redis.io/commands/eval.
    • The execution timeout time of a Lua script is 5 seconds. Time-consuming statements such as long-time sleep and large loop statements should be avoided.
    • When calling a Lua script, do not use random functions to specify keys. Otherwise, the execution results are inconsistent on the master and standby nodes.

Others:

  • The time limit for executing a Redis command is 15 seconds. To prevent other services from failing, a master/replica switchover will be triggered after the command execution times out.

  • Proxy Cluster DCS Redis instances created before July 10, 2018 must be upgraded to support the following commands:

    SINTER, SDIFF, SUNION, PFCOUNT, PFMERGE, SINTERSTORE, SUNIONSTORE, SDIFFSTORE, SMOVE, ZUNIONSTORE, ZINTERSTORE, EVAL, EVALSHA, BITOP, RENAME, RENAMENX, RPOPLPUSH, MSETNX, SCRIPT LOAD, SCRIPT KILL, SCRIPT EXISTS, SCRIPT FLUSH.