Introduction
High availability of MySQL servers can be achieved through 'MySQL
Fabric' which is basically a system for managing a farm of servers.
To deploy Fabric , there has been the requirement to have connectors
which are Fabric aware. The requests for supporting basic connectors
are frequent and this is where MySQL Router comes into the picture.
With Router, connectors no longer need to be Fabric aware. They can
communicate with Fabric through Router, just as they communicate with
standalone MySQL servers.
In this blog, we shall focus on how exactly we can integrate Fabric
with Router.
Fabric Cache
MySQL Router includes the 'Fabric Cache' plugin which essentially
caches high-availability group and shard information from Fabric.
This is similar to how a Fabric-aware connector would cache such
information. This Router plugin thus maintains the connection between
a client application and Fabric.
Hands On
Let us start by setting up high-availability groups
of mysql servers with the help of Fabric :
a) MySQL Fabric is currently shipped as part of MySQL Utilities,
which can be downloaded from :
https://dev.mysql.com/downloads/utilities
.
b) Make sure that a set of mysql servers is running. (In this example
we assume the servers are running on the local machine, and server
ports start at 13002)
c) Configure the fabric.cfg file with the proper username and
password values to start. Make sure the storage section is pointed to
a valid mysql server :
[storage]
address = localhost:13002
d) Start Fabric as :
mysqlfabric manage setup
mysqlfabric manage start
e) Create a high availability group of mysql servers, and promote one
server to be the primary :
mysqlfabric group create my_group1
mysqlfabric group add my_group1 localhost:13003
mysqlfabric group add my_group1 localhost:13004
mysqlfabric group add my_group1 localhost:13005
mysqlfabric group promote my_group1 –slave_id=localhost:13003
f) Execute a group lookup_servers command to make sure that the HA group
is setup properly.
Now we can proceed to setup MySQL Router :
a) Download MySQL Router from http://dev.mysql.com/downloads/router/
and install.
b) Create a configuration file for router , say as follows :
[fabric_cache]
address = 127.0.0.1:32275
user = admin
[routing:fabric_read_write]
bind_address = 127.0.0.1:7002
destinations = fabric+cache:///group/my_group1
mode = read-write
[routing:fabric_read_only]
bind_address = 127.0.0.1:7003
destinations = fabric+cache:///group/my_group1
mode = read-only
Here, the address 127.0.0.1:32275 and user admin correspond to
[protocol.mysql] section of the fabric config file.
Two routing services 'fabric_read_write' and 'fabric_read_only' have
been defined. Client applications which use
bind_address=127.0.0.1:7002 would be connected to the primary server
(which is read_write) of the HA group : 'my_group1' and those which
use bind_address=127.0.0.1:7003 would be connected to the secondary
servers (which are read_only) of the HA group : 'my_group1' in a
round-robin fashion.
c) Now as the Router is installed and the config file is ready, we
are good to start it and connect to the Fabric group.
Start Router :
./mysqlrouter --config=<path to router config file> 
d) Now, we use a mysql client to connect to the bind_address of the router, which would make the connection to the Fabric group.
./mysql --host=127.0.0.1 --port=7002 (Will be routed to the primary server of my_group1)
./mysql --host=127.0.0.1 --port=7003 (Will be routed to one secondary server of my_group1) 
./mysql --host=127.0.0.1 --port=7003 (Will be routed to the other secondary server of my_group1)
In this way, client applications can communicate with a highly-available farm of mysql servers using Router, without Fabric aware connectors.
To learn more about MySQL High-availability solution, visit :
http://mysqlhighavailability.com/
To learn more about MySQL Router, visit :
http://using-mysqlrouter.blogspot.in/
