Redis is a TCP server and supports request/response protocol. In Redis, a request is accomplished with the following steps −

• The client sends a query to the server, and reads from the socket, usually in a blocking way, for the server response.

• The server processes the command and sends the response back to the client.

Meaning of Pipelining

The basic meaning of pipelining is, the client can send multiple requests to the server without waiting for the replies at all, and finally reads the replies in a single step.

Example

To check the Redis pipelining, just start the Redis instance and type the following command in the terminal.

$(echo -en "PINGrn SET tutorial redisrnGET tutorialrnINCR
visitorrnINCR visitorrnINCR visitorrn"; sleep 10) | nc localhost 6379
+PONG
+OK
redis
:1
:2
:3

In the above example, we will check Redis connection by using PING command. We have set a string named tutorial with value redis. Later, we get that keys value and increment the visitor number three times. In the result, we can see that all commands are submitted to Redis once, and Redis provides the output of all commands in a single step.

Benefits of Pipelining

The benefit of this technique is a drastically improved protocol performance. The speedup gained by pipelining ranges from a factor of five for connections to localhost up to a factor of at least one hundred over slower internet connections.

Redis accepts clients’ connections on the configured listening TCP port and on the Unix socket, if enabled. When a new client connection is accepted, the following operations are performed −

• The client socket is put in non-blocking state since Redis uses multiplexing and non-blocking I/O.

• The TCP_NODELAY option is set in order to ensure that we don”t have delays in our connection.

• A readable file event is created so that Redis is able to collect the client queries as soon as new data is available to be read on the socket.

Maximum Number of Clients

In Redis config (redis.conf), there is a property called maxclients, which describes the maximum number of clients that can connect to Redis.

Following is the basic syntax of command.

config get maxclients

1) "maxclients"
2) "10000"

By default, this property is set to 10000 (depending upon the maximum number of file descriptors limit of OS), although you can change this property.

Example

In the following example, we have set the maximum number of clients to 100000, while starting the server.

redis-server --maxclients 100000

Client Commands

Redis benchmark is the utility to check the performance of Redis by running n commands simultaneously.

Syntax

Following is the basic syntax of Redis benchmark.

redis-benchmark [option] [option value]

Example

Following example checks Redis by calling 100000 commands.

redis-benchmark -n 100000

PING_INLINE: 141043.72 requests per second
PING_BULK: 142857.14 requests per second
SET: 141442.72 requests per second
GET: 145348.83 requests per second
INCR: 137362.64 requests per second
LPUSH: 145348.83 requests per second
LPOP: 146198.83 requests per second
SADD: 146198.83 requests per second
SPOP: 149253.73 requests per second
LPUSH (needed to benchmark LRANGE): 148588.42 requests per second
LRANGE_100 (first 100 elements): 58411.21 requests per second
LRANGE_300 (first 300 elements): 21195.42 requests per second
LRANGE_500 (first 450 elements): 14539.11 requests per second
LRANGE_600 (first 600 elements): 10504.20 requests per second
MSET (10 keys): 93283.58 requests per second

Following is a list of available options in Redis benchmark.

Example

Following example shows the multiple usage options in Redis benchmark utility.

redis-benchmark -h 127.0.0.1 -p 6379 -t set,lpush -n 100000 -q

SET: 146198.83 requests per second
LPUSH: 145560.41 requests per second

Redis server commands are basically used to manage Redis server.

Example

Following example explains how we can get all statistics and information about the server.

redis 127.0.0.1:6379> INFO

# Server
redis_version:2.8.13
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:c2238b38b1edb0e2
redis_mode:standalone
os:Linux 3.5.0-48-generic x86_64
arch_bits:64
multiplexing_api:epoll
gcc_version:4.7.2
process_id:3856
run_id:0e61abd297771de3fe812a3c21027732ac9f41fe
tcp_port:6379
uptime_in_seconds:11554
uptime_in_days:0 hz:10
lru_clock:16651447
config_file:

# Clients
connected_clients:1
client_longest_output_list:0
client_biggest_input_buf:0
blocked_clients:0

# Memory
used_memory:589016
used_memory_human:575.21K
used_memory_rss:2461696
used_memory_peak:667312
used_memory_peak_human:651.67K
used_memory_lua:33792
mem_fragmentation_ratio:4.18
mem_allocator:jemalloc-3.6.0

# Persistence
loading:0
rdb_changes_since_last_save:3
rdb_bgsave_in_progress:0
rdb_last_save_time:1409158561
rdb_last_bgsave_status:ok
rdb_last_bgsave_time_sec:0
rdb_current_bgsave_time_sec:-1
aof_enabled:0
aof_rewrite_in_progress:0
aof_rewrite_scheduled:0
aof_last_rewrite_time_sec:-1
aof_current_rewrite_time_sec:-1
aof_last_bgrewrite_status:ok
aof_last_write_status:ok

# Stats
total_connections_received:24
total_commands_processed:294
instantaneous_ops_per_sec:0
rejected_connections:0
sync_full:0
sync_partial_ok:0
sync_partial_err:0
expired_keys:0
evicted_keys:0
keyspace_hits:41
keyspace_misses:82
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:264

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

# CPU
used_cpu_sys:10.49
used_cpu_user:4.96
used_cpu_sys_children:0.00
used_cpu_user_children:0.01

# Keyspace
db0:keys = 94,expires = 1,avg_ttl = 41638810
db1:keys = 1,expires = 0,avg_ttl = 0
db3:keys = 1,expires = 0,avg_ttl = 0

Redis Server Commands

Following table lists some basic commands related to Redis server.

Redis SAVE command is used to create a backup of the current Redis database.

Syntax

Following is the basic syntax of redis SAVE command.

127.0.0.1:6379> SAVE

Example

Following example creates a backup of the current database.

127.0.0.1:6379> SAVE
OK

This command will create a dump.rdb file in your Redis directory.

Restore Redis Data

To restore Redis data, move Redis backup file (dump.rdb) into your Redis directory and start the server. To get your Redis directory, use CONFIG command of Redis as shown below.

127.0.0.1:6379> CONFIG get dir
1) "dir"
2) "/user/tutorialspoint/redis-2.8.13/src"

In the output of the above command /user/tutorialspoint/redis-2.8.13/src is the directory, where Redis server is installed.

Bgsave

To create Redis backup, an alternate command BGSAVE is also available. This command will start the backup process and run this in the background.

Example

127.0.0.1:6379> BGSAVE
Background saving started

Redis transactions allow the execution of a group of commands in a single step. Following are the two properties of Transactions.

• All commands in a transaction are sequentially executed as a single isolated operation. It is not possible that a request issued by another client is served in the middle of the execution of a Redis transaction.

• Redis transaction is also atomic. Atomic means either all of the commands or none are processed.

Sample

Redis transaction is initiated by command MULTI and then you need to pass a list of commands that should be executed in the transaction, after which the entire transaction is executed by EXEC command.

redis 127.0.0.1:6379> MULTI
OK
List of commands here
redis 127.0.0.1:6379> EXEC

Example

Following example explains how Redis transaction can be initiated and executed.

redis 127.0.0.1:6379> MULTI
OK
redis 127.0.0.1:6379> SET tutorial redis
QUEUED
redis 127.0.0.1:6379> GET tutorial
QUEUED
redis 127.0.0.1:6379> INCR visitors
QUEUED
redis 127.0.0.1:6379> EXEC
1) OK
2) "redis"
3) (integer) 1

Redis Transaction Commands

Following table shows some basic commands related to Redis transactions.

Redis scripting is used to evaluate scripts using the Lua interpreter. It is built into Redis starting from version 2.6.0. The command used for scripting is EVAL command.

Syntax

Following is the basic syntax of EVAL command.

redis 127.0.0.1:6379> EVAL script numkeys key [key ...] arg [arg ...]

Example

Following example explains how Redis scripting works.

redis 127.0.0.1:6379> EVAL "return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}" 2 key1
key2 first second
1) "key1"
2) "key2"
3) "first"
4) "second"

Redis Scripting Commands

Following table lists some basic commands related to Redis Scripting.

Redis database can be secured, such that any client making a connection needs to authenticate before executing a command. To secure Redis, you need to set the password in the config file.

Example

Following example shows the steps to secure your Redis instance.

127.0.0.1:6379> CONFIG get requirepass
1) "requirepass"
2) ""

By default, this property is blank, which means no password is set for this instance. You can change this property by executing the following command.

127.0.0.1:6379> CONFIG set requirepass "tutorialspoint"
OK
127.0.0.1:6379> CONFIG get requirepass
1) "requirepass"
2) "tutorialspoint"

After setting the password, if any client runs the command without authentication, then (error) NOAUTH Authentication required. error will return. Hence, the client needs to use AUTH command to authenticate himself.

Syntax

Following is the basic syntax of AUTH command.

127.0.0.1:6379> AUTH password

Example

127.0.0.1:6379> AUTH "tutorialspoint"
OK
127.0.0.1:6379> SET mykey "Test value"
OK
127.0.0.1:6379> GET mykey
"Test value"

Redis connection commands are basically used to manage client connections with Redis server.

Example

Following example explains how a client authenticates itself to Redis server and checks whether the server is running or not.

redis 127.0.0.1:6379> AUTH "password"
OK
redis 127.0.0.1:6379> PING
PONG

Redis Connection Commands

Following table lists some basic commands related to Redis connections.

Redis Pub/Sub implements the messaging system where the senders (in redis terminology called publishers) sends the messages while the receivers (subscribers) receive them. The link by which the messages are transferred is called channel.

In Redis, a client can subscribe any number of channels.

Example

Following example explains how publish subscriber concept works. In the following example, one client subscribes a channel named ‘redisChat’.

redis 127.0.0.1:6379> SUBSCRIBE redisChat
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "redisChat"
3) (integer) 1

Now, two clients are publishing the messages on the same channel named ‘redisChat’ and the above subscribed client is receiving messages.

redis 127.0.0.1:6379> PUBLISH redisChat "Redis is a great caching technique"
(integer) 1
redis 127.0.0.1:6379> PUBLISH redisChat "Learn redis by tutorials point"
(integer) 1
1) "message"
2) "redisChat"
3) "Redis is a great caching technique"
1) "message"
2) "redisChat"
3) "Learn redis by tutorials point"

Redis PubSub Commands

Following table lists some basic commands related to Redis Pub/Sub.