memcached - performance memory object caching system
memcached [options]
MEMCACHED(8) System Manager's Manual MEMCACHED(8)
NAME
memcached - high-performance memory object caching system
SYNOPSIS
memcached [options]
DESCRIPTION
This manual page documents briefly the memcached memory object caching
daemon.
memcached is a flexible memory object caching daemon designed to alle-
viate database load in dynamic web applications by storing objects in
memory. It's based on libevent to scale to any size needed, and is
specifically optimized to avoid swapping and always use non-blocking
I/O.
OPTIONS
These programs follow the usual GNU command line syntax. A summary of
options is included below.
-s, --unix-socket=<file>
Unix socket path to listen on (disables network support).
-A, --enable-shutdown
Enable ascii "shutdown" command.
-a, --unix-mask=<perms>
Permissions (in octal format) for Unix socket created with -s
option.
-l, --listen=<addr>
Listen on <addr>; default to INADDR_ANY. <addr> may be specified
as host:port. If you don't specify a port number, the value you
specified with -p or -U is used. You may specify multiple
addresses separated by comma or by using -l multiple times. This
is an important option to consider as there is no other way to
secure the installation. Binding to an internal or firewalled
network interface is suggested.
-d, --daemon
Run memcached as a daemon.
-u, --user=<username>
Assume the identity of <username> (only when run as root).
-m, --memory-limit=<num>
Use <num> MB memory max to use for object storage; the default
is 64 megabytes.
-c, --conn-limit=<num>
Use <num> max simultaneous connections; the default is 1024.
-R, --max-reqs-per-event=<num>
This option seeks to prevent client starvation by setting a
limit to the number of sequential requests the server will
process from an individual client connection. Once a connection
has exceeded this value, the server will attempt to process I/O
on other connections before handling any further request from
this connection. The default value for this option is 20.
-k, --lock-memory
Lock down all paged memory. This is a somewhat dangerous option
with large caches, so consult the README and memcached homepage
for configuration suggestions.
-p, --port=<num>
Listen on TCP port <num>, the default is port 11211. 0 means
off.
-U, --udp-port=<num>
Listen on UDP port <num>, the default is port 0, which is off.
-M, --disable-evictions
Disable automatic removal of items from the cache when out of
memory. Additions will not be possible until adequate space is
freed up.
-r, --enable-coredumps
Raise the core file size limit to the maximum allowable.
-f, --slab-growth-factor=<factor>
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.
-n, --slab-min-size=<size>
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.
-C, --disable-cas
Disable the use of CAS (and reduce the per-item size by 8
bytes).
-h, --help
Show the version of memcached and a summary of options.
-v, --verbose
Be verbose during the event loop; print out errors and warnings.
-vv Be even more verbose; same as -v but also print client commands
and responses.
-vvv Be extremely verbose; same of the above and also print internal
state transitions.
-i, --license
Print memcached and libevent licenses.
-P, --pidfile=<filename>
Print pidfile to <filename>, only used under -d option.
-t, --threads=<threads>
Number of threads to use to process incoming requests. This
option is only meaningful if memcached was compiled with thread
support enabled. It is typically not useful to set this higher
than the number of CPU cores on the memcached server. Setting a
high number (64 or more) of worker threads is not recommended.
The default is 4.
-D <char>
Use <char> as the delimiter between key prefixes and IDs. This
is used for per-prefix stats reporting. The default is ":"
(colon). If this option is specified, stats collection is turned
on automatically; if not, then it may be turned on by sending
the "stats detail on" command to the server.
-L, --enable-largepages
Try to use large memory pages (if available). Increasing the
memory page size could reduce the number of TLB misses and
improve the performance. In order to get large pages from the
OS, memcached will allocate the total item-cache in one large
chunk. Only available if supported on your OS.
-b, --listen-backlog=<num>
Set the backlog queue limit to <num> connections. The default is
1024.
-B, --protocol=<proto>
Specify the binding protocol to use. By default, the server
will autonegotiate client connections. By using this option,
you can specify the protocol clients must speak. Possible
options are "auto" (the default, autonegotiation behavior),
"ascii" and "binary".
-I, --max-item-size=<size>
Override the default size of each slab page. The default size is
1mb. Default value for this parameter is 1m, minimum is 1k, max
is 1G (1024 * 1024 * 1024). Adjusting this value changes the
item size limit.
-S, --enable-sasl
Turn on SASL authentication. This option is only meaningful if
memcached was compiled with SASL support enabled.
-F, --disable-flush-all
Disables the "flush_all" command. The cmd_flush counter will
increment, but clients will receive an error message and the
flush will not occur.
-X, --disable-dumping
Disables the "stats cachedump" and "lru_crawler metadump" com-
mands.
-o, --extended=<options>
Comma separated list of extended or experimental options. See -h
or wiki for up to date list.
-V, --version
print version and exit
SERVICE MANAGEMENT FACILITY
memcached package for Solaris (service/memcached) includes files neces-
sary to register with the Service Management Facility described in
SMF(7). The following procedure describes the steps to automate the
service management using memcached.
1. Add other parameters to be passed to the memcached service
instance.
example: specify the server to use 1024 MB of memory
example% svccfg
svc:> select memcached
svc:/application/database/memcached> setprop memcached/options=("-m" "1024")
svc:/application/database/memcached> quit
example% svcadm refresh memcached
Note -
The arguments cannot be passed as a single string because of a
limitation in svccfg.
2. Enable memcached .
example% svcadm enable memcached
The state of the service instance changes to online, and the
memcached service instance must be started:
example% svcs memcached
STATE STIME FMRI
online 1:19:15 svc:/application/database/memcached:default
3. To disable shutdown and automatic restart of memcached ser-
vice instance,
example% svcadm disable memcached
USER AUTHORIZATIONS
You can use RBAC(7) to authorize otherwise non-privileged users to man-
age memcached services. To let a user named myuser change memcached
value properties and manage memcached service states, add the following
line to /etc/user_attr:
myuser::::type=role;profiles=Memcached Administration,All
PACKAGE CONTENTS
The memcached package consists of the memcached server and man pages
for the server.
Client libraries can be made available by installing other packages.
The memcached server is based on the memcached open-source software
available from http://www.danga.com/memcached/.
SECURITY
When the memcached server is started, it listens for network requests
on a TCP port and/or a UDP port. It is important for the security of
the network that you protect this port, for example, by blocking access
to this port in a firewall.
The default TCP port number to use is 11211.
You may use the -p option to set another TCP port number. There is no
default UDP port number. You can use the -U option to set a UDP port
number.
If you are running memcached on a server with multiple network inter-
faces, you can restrict vulnerability by binding memcached to a single
interface by using the -l option.
Caution -
Note that memcached was designed for speed and not for security.
There is no authentication of requests that go in to the memcached
servers, and communication is not encrypted. The network that your
memcached servers and clients run within should be safe-guarded
against network attacks.
LICENSE
The memcached daemon is copyright Danga Interactive and is distributed
under the BSD license. Note that daemon clients are licensed sepa-
rately.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+-------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-------------------+
|Availability | service/memcached |
+---------------+-------------------+
|Stability | Uncommitted |
+---------------+-------------------+
SEE ALSO
The README file that comes with memcached
libmemcached(3libmemcached)
https://www.memcached.org
AUTHOR
The memcached daemon was written by Anatoly Vorobey <mellon@pobox.com>
and Brad Fitzpatrick <brad@danga.com> and the rest of the crew of Danga
Interactive https://www.danga.com
NOTES
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from http://memcached.org/files/mem-
cached-1.6.9.tar.gz.
Further information about this software can be found on the open source
community website at http://memcached.org/.
April 11, 2005 MEMCACHED(8)