My notes from FreeBSD redis install.

# Redis and FreeBSD

## Installing

Install redis FreeBSD port collection:

	$ cd /usr/ports/databases/redis/ && make install clean
	# or with portmaster
	$ portmaster databases/redis

These following programs will be installed with redis:

- `/usr/local/bin/redis-sentinel` the Redis Sentinel executable (monitoring and failover).
- `/usr/local/bin/redis-cli` the command line interface utility to talk with Redis.
- `/usr/local/bin/redis-server` the Redis Server itself.
- `/usr/local/bin/redis-benchmark` used to check Redis performances.

**Redis configuration file**

	/usr/local/etc/redis.conf

**Auto-start Redis at Boot**

To run redis from startup, add `redis_enable="YES"` in your `/etc/rc.conf`.

**Bind Redis to IP**

To bind Redis to a single interface, add the following
line to `/usr/local/etc/redis.conf`:

	bind 127.0.0.1

## Commands

**Stop/Start Redis**

	$ service redis stop
	$ service redis start
	
**Accessing Redis**

	$ telnet localhost 6397

or the Redis CLI client

	$ redis-cli

**Monitor Redis Transactions**

	$ redis-cli monitor

**Server Statistics**

	$ redis-cli INFO

**Changing Runtime Configuration**

	$ redis-cli
	CONFIG GET *

gives you a list of all active configuration variables you can change. The
output might look like this:

	redis 127.0.0.1:6379> CONFIG GET *
	 1) "dir"
	 2) "/var/lib/redis"
	 3) "dbfilename"
	 4) "dump.rdb"
	 5) "requirepass"
	 6) (nil)
	 7) "masterauth"
	 8) (nil)
	 ...

	CONFIG SET timeout 900

Such a change will be effective instantly. When changing values consider
also updating the redis configuration file.

**Multiple Databases**

Redis has a concept of separated namespaces called `databases`.
You can select the database number you want to use with `SELECT`.
By default the database with index 0 is used. So issuing:

	redis 127.0.0.1:6379> SELECT 1
	OK
	redis 127.0.0.1:6379[1]>

switches to the second database. Note how the prompt changed and now
has a `[1]` to indicate the database selection.

To find out how many databases there are you might want to
run `redis-cli` from the shell:

	$ redis-cli INFO | grep ^db
	db0:keys=91,expires=88
	db1:keys=1,expires=0

**Dropping Databases**

To drop the currently selected database run:

	FLUSHDB

to drop all databases at once run:

	FLUSHALL

**Checking for Replication**

To see if the instance is a replication slave or master issue:

	redis 127.0.0.1:6379> INFO
	[...]
	role:master

and watch for the "role" line which shows either `master` or `slave`.

Starting with version 2.8 the `INFO` command also gives you per slave
replication status looking like this:

	slave0:ip=127.0.0.1,port=6380,state=online,offset=281,lag=0

**Enabling Replication**

If you quickly need to set up replication just issue:

	SLAVEOF <IP> <port>

on a machine that you want to become slave of the given IP. It will
immediately get values from the master. Note that this instance will
still be writable. If you want it to be read-only change the redis
config file (only available in most recent version, e.g. not on Debian).

To revert the slave setting run:

	SLAVEOF NO ONE

**Dump Database Backup**

As Redis allows RDB database dumps in background, you can issue a
dump at any time. Just run:

	BGSAVE

When running this command Redis will fork and the new process will dump into
the `dbfilename` configured in the Redis configuration without the original
process being blocked. Of course the fork itself might cause an interruption.

Use `LASTSAVE` to check when the dump file was last updated. For a simple
backup solution just backup the dump file.

If you need a synchronous save run `SAVE` instead of `BGSAVE`.

**Listing Connections**

Starting with version 2.4 you can list connections with:

	CLIENT LIST

and you can terminate connections with:

	CLIENT KILL <IP>:<port>

**Monitoring Traffic**

The propably most useful command compared to memcached where you need to trace
network traffic is the `MONITOR` command which will dump incoming commands in
real time.

	redis 127.0.0.1:6379> MONITOR
	OK
	1371241093.375324 "monitor"
	1371241109.735725 "keys" "*"
	1371241152.344504 "set" "testkey" "1"
	1371241165.169184 "get" "testkey"

**Checking for Keys**

If you want to know if an instance has a key or keys matching some pattern use
`KEYS` instead of `GET` to get an overview.

	redis 127.0.0.1:6379> KEYS test*
	1) "testkey2"
	2) "testkey3"
	3) "testkey"

On production servers use `KEYS` with care as you can limit it and it will
cause a full scan of all keys!

## PHP5-Extension for Redis

	cd /usr/ports/databases/php5-redis/ && make install clean
	# or
	pkg install databases/php5-redis


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## Resources

[Most Important Redis Commands for Sysadmins](http://lzone.de/Most%20Important%20Redis%20Commands%20for%20Sysadmins)