Memcached Tools

About

This is a utility container designed to perform dump and restore of memcached data.

Usage

This cointainer takes (at a minimum) one environment variable, MEMCACHED_SERVERS. This value should be a string of the form "host:port"

Additionally, this container can make use of the link feature of Docker leveraging a destination value of MC. Examples are shown below. There are three primitives available to the container:

• dump - Dump all data in the remote memcached server to /tmp/memcache
• load - Load all data from the path /tmp/memcache to the remote memcached server
• sample - Generate 899 sample keys of the form mykeyXXX and add them to the server

$ mkdir /tmp/test
$ docker run --rm -e MEMCACHED_SERVERS=192.168.1.101:11211 -v /tmp/test:/tmp/memcache brianredbeard/memcache-tools dump

Examples

In this example we will create a memcached container, load it with sample data, verify we can see the values, flush the cache, reload our data, and finally verify that the values match.

Install the memcached server:

$ docker run -p 11211 -d --name memcached jacksoncage/memcache

Load sample data into the container, utilizing a docker link

$ mkdir /tmp/test
$ docker run --rm --link memcached:mc -v /tmp/test:/tmp/memcache brianredbeard/memcache-tools sample

Verify that the data is there

$ docker ps 
CONTAINER ID        IMAGE                         COMMAND             CREATED             STATUS              PORTS                      NAMES
f053e93d69e2        jacksoncage/memcache:latest   bash start.sh       44 seconds ago      Up 41 seconds       0.0.0.0:49154->11211/tcp   memcache  
$ telnet 127.0.0.1 49154
Trying ::1...
Connected to localhost.
Escape character is '^]'.
stats items
STAT items:3:number 899
STAT items:3:age 10
STAT items:3:evicted 0
STAT items:3:evicted_nonzero 0
STAT items:3:evicted_time 0
STAT items:3:outofmemory 0
STAT items:3:tailrepairs 0
STAT items:3:reclaimed 0
STAT items:3:expired_unfetched 0
STAT items:3:evicted_unfetched 0
END
get mykey600
VALUE mykey600 1 49
(dp1
S'lang'
p2
S'python'
p3
sS'value'
p4
I448
s.
END

Here we see that on slab 3 we have 899 values in the cache and that the key mykey600 has the integer value 448 stored inside it's object.

Dump the contents of the cache

$ docker run --rm --link memcached:mc -v /tmp/test:/tmp/memcache brianredbeard/memcache-tools dump

You will find that in /tmp/test there will be 899 files, each with the name of a key. The contents of each file correlate to the respective key on the memcached server.

Flushing the memcached cache

$ telnet 127.0.0.1 49154
Trying ::1...
Connected to localhost.
Escape character is '^]'.
flush_all 1
OK
get mykey600
END

This sets all values to immediately have a one second TTL, effectively expiring the entire cache. Attempting to retrieve the value of mykey600 results in no data returned.

Reload our sample data

$ docker run --rm --link memcached:mc -v /tmp/test:/tmp/memcache brianredbeard/memcache-tools load

At this point our data should be reloaded.

Verification of data

$ telnet 127.0.0.1 49154
Trying ::1...
Connected to localhost.
Escape character is '^]'.
get mykey600
VALUE mykey600 1 49
(dp1
S'lang'
p2
S'python'
p3
sS'value'
p4
I448
s.
END