Memcached is free and open source, high performance distributed
memory object caching system, generic in nature, but intended for use in speeding up dynamic web
applications by alleviating database load.
Memcached is an in-memory key value store for small chunks of
arbitrary data storage (strings, objects) from results of database calls, API
calls, or for page rendering. Memcached is simple yet powerful. Its simple
design promotes quick deployment, ease of deployment and solves many problems
facing large data caches. Its API is available for most popular languages.
Memcache installation on windows
You can unzip the folder and paste at suitable place in your
computer. For installation , you can run following command :
When you open your task manager, you can watch this memcached
service running in your computer.
Congratulations! J you have installed memcached in your system.
Memcached installation on Unix based system.
1. Lets walk through some steps and commands on unix based system
Download link : http://www.memcached.org/files/memcached-1.4.20.tar.gz
1. To start memcache on unix :
shell> memcached
or sh memcached.sh
2.
By default, memcached uses
the following settings:
·
Memory allocation of 64MB
·
Listens for connections on all network interfaces,
using port 11211
·
Supports a maximum of 1024 simultaneous connections.
Typically, you would specify the full combination of options that
you want when starting memcached, and normally provide a startup script to
handle the initialization of memcached.For example, the following line starts
memcached with a maximum of 1024MB RAM for the cache,listening on port 11211 on
the IP address 192.168.0.110, running as a background daemon:
shell> memcached -d -m 1024 -p 11211 -l 192.168.0.110
3.
-l interface
Specify a network interface/address to listen for connections. The
default is to listen on all available address (INADDR_ANY).
shell> memcached -l 192.168.0.110
Support for IPv6 address support was added in memcached 1.2.5.
-p port
Specify the TCP port to use for connections. Default is 18080.
shell> memcached -p 18080
4. If you start memcached as root, use the -u option to specify
the user for executing memcached:
shell> memcached -u memcache
You can use the output of the vmstat command to get the free
memory, as shown in free column:
shell> vmstat
5. -c connections
Specify the maximum number of simultaneous connections to the
memcached service. The default is 1024.
shell> memcached -c 2048
6. -t threads
Specify the number of threads to use when processing incoming
requests.
By default, memcached is configured to use 4 concurrent threads.
The threading improves the performance of storing and retrieving data in the
cache, using a locking system to prevent different threads overwriting or
updating the same values. To increase or decrease the number of threads, use
the -t option:
shell> memcached -t 8
7-d
Run memcached as a daemon (background) process:
shell> memcached -d
8 -r
Maximize the size of the core file limit. In the event of a
failure, this attempts to dump the entire memory space to disk as a core file,
up to any limits imposed by setrlimit.
9.-M
Return an error to the client when the memory has been exhausted.
This replaces the normal behavior of removing older items from the cache to
make way for new items.
10.-k
Lock down all paged memory. This reserves the memory before use,
instead of allocating new slabs of memory as new items are stored in the cache.
Note
There is a user-level limit on how much memory you can lock.
Trying to allocate more than the available memory fails. You can set the limit
for the user you started the daemon with (not for the -u user user) within the
shell by using ulimit -S -l NUM_KB
11.-v
Verbose mode. Prints errors and warnings while executing the main
event loop.
12.-vv
Very verbose mode. In addition to information printed by -v, also
prints each client command and the response.
13.
-vvv
Extremely verbose mode. In addition to information printed by -vv,
also show the internal state transitions.
14.-h
Print the help message and exit.
15.-i
Print the memcached and libevent license.
16.-I mem
Specify the maximum size permitted for storing an object within
the memcached instance. The size supports a unit postfix (k for kilobytes, m
for megabytes). For example, to increase the maximum supported object size to
32MB:
shell> memcached -I 32m
The maximum object size you can specify is 128MB, the default
remains at 1MB.
This option was added in 1.4.2.
17.-b
Set the backlog queue limit. The backlog queue configures how many
network connections can be waiting to be processed by memcached. Increasing this
limit may reduce errors received by the client that it is not able to connect
to the memcached instance, but does not improve the performance of the server.
The default is 1024.
18.-P pidfile
Save the process ID of the memcached instance into file.
19.-f
Set the chunk size growth factor. When allocating new memory
chunks, the allocated size of new chunks is determined by multiplying the
default slab size by this factor.
To see the effects of this option without extensive testing, use
the -vv command-line option to show the calculated slab sizes. For more
information, see Section 15.6.2.8, “memcached Logs”.
20.-n bytes
The minimum space allocated for the key+value+flags information.
The default is 48 bytes.
21.-L
On systems that support large memory pages, enables large memory
page use. Using large memory pages enables memcached to allocate the item cache
in one large chunk, which can improve the performance by reducing the number
misses when accessing memory.
22.-C
Disable the use of compare and swap (CAS) operations.
This option was added in memcached 1.3.x.
23.-D char
Set the default character to be used as a delimiter between the
key prefixes and IDs. This is used for the per-prefix statistics reporting (see
Section 15.6.4, “Getting memcached Statistics”). The default is the colon (:).
If this option is used, statistics collection is turned on automatically. If
not used, you can enable stats collection by sending the stats detail on
command to the server.
This option was added in memcached 1.3.x.
24.-R num
Sets the maximum number of requests per event process. The default
is 20.
25.-B protocol
Set the binding protocol, that is, the default memcached protocol
support for client connections. Options are ascii, binary or auto. Automatic
(auto) is the default.
This option was added in memcached 1.4.0.
Lets finish configuration related talks here and move to some hard
core java programming for availaing
caching.
