Invalidate all the memcache data without restart the service

You can invalidate all existing cache items using the flush_all command. This command does not pause the server, as it returns immediately. It does not free up or flush memory at all, it just causes all items to expire. You can send flush_all command using any one of the following method:

nc command – The nc (also know as netcat) utility is used for just about anything under the sun involving TCP or UDP.
telnet command – The telnet command is used to communicate with another host using the TELNET protocol.

netcat (nc) Command Example To Flush Contents Of Memcached Server

The nc (netcat) command is a simple unix utility which reads and writes data across network connections, using TCP or UDP protocol. It can simply connect to the memcached instance and and invalidate all existing cache:

echo 'flush_all' | nc localhost 11211

OR
echo 'flush_all' | netcat localhost 11211

OR

nc 192.168.1.10 11211 <<< "flush_all"

Where,

192.168.1.10 – memcached server instance
localhost – memcached server instance
11211 – memcached server port.

Telnet Command Example To Flush Contents Of Memcached Server

Type the following command:
telnet your-memcached-server-ip PORT

In this example connect to 192.168.1.10 11211 and issue the flush_all command as follows:

$ telnet 192.168.1.10 11211

Sample outputs:

Trying 192.168.1.10...
Connected to 192.168.1.10
Escape character is ‘^]’.
flush_all
OK
quit
Connection to 192.168.1.10 closed by foreign host.