Description

Danga Interactive developed memcached to enhance the speed of LiveJournal.com, a site which was already doing 20 million+ dynamic page views per day for 1 million users with a bunch of webservers and a bunch of database servers. memcached dropped the database load to almost nothing, yielding faster page load times for users, better resource utilization, and faster access to the databases on a memcache miss. memcached optimizes specific high-load serving applications that are designed to take advantage of its versatile no-locking memory access system. Clients are available in several different programming languages, to suit the needs of the specific application. Traditionally this has been used in mod_perl apps to avoid storing large chunks of data in Apache memory, and to share this burden across several machines.

Readme

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Configuration

request-limit
(int) limit of requests a single client can make at one time (memcached option -R) -1 takes memcached default (20)
-1
slab-page-size
(int) Override the size of each slab page in bytes. In mundane words, it adjusts the maximum item size that memcached will accept. You can use the suffixes K and M to specify the size as well, so use 2000000 or 2000K or 2M if you want a maximum size of 2 MB per object. It is not recommended to raise this limit above 1 MB due just to performance reasons. The default value is 1 MB. (memcached option -I) -1 takes the memcached default.
-1
min-item-size
(int) Allocate a minimum of <size> bytes for the item key, value, and flags. The default is 48. If you have a lot of small keys and values, you can get a significant memory efficiency gain with a lower value. If you use a high chunk growth factor (-f option), on the other hand, you may want to increase the size to allow a bigger percentage of your items to fit in the most densely packed (smallest) chunks. (memcached option -n)
-1
disable-large-pages
(string) The charm will will try to use large pages if given more than 2GB of RAM. You may want to disable this behavior. (memcached option -L)
no
disable-cas
(string) disable use of CAS (and reduce the per-item size by 8 bytes)
no
connection-limit
(int) maximum simultaneous connections (memcached option -c)
1024
disable-auto-cleanup
(string) do not remove things automatically from the cache on OOM (memcached option -M)
no
nagios_context
(string) Used by the nrpe-external-master subordinate charm. A string that will be prepended to instance name to set the host name in nagios. So for instance the hostname would be something like: juju-memcached-0 If you're running multiple environments with the same services in them this allows you to differentiate between them.
juju
threads
(int) number of threads to use. default is 4. (memcached option -t)
-1
factor
(float) Use <factor> as the multiplier for computing the sizes of memory chunks that items are stored in. A lower value may result in less wasted memory depending on the total amount of memory available and the distribution of item sizes. The default is 1.25.
1.25
tcp-port
(int) TCP port to listen on. (memcached option -p)
11211
udp-port
(int) UDP port to listen on (memcached option -U)
extra-options
(string) memcached has many other options documented in its man page. You may pass them here as a string which will be appended to memcached's execution.
size
(int) Size of memcache pool in MiB (memcached option -m)
768