How did memcached get on my Mac OSX system?


-rwxr-xr-x  1 root  wheel  153968 Mar  4  2014 /usr/bin/memcached


cat /System/Library/LaunchDaemons/com.danga.memcached.plist
 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict> 
    <key>Label</key> <string>memcached</string>
 
    <key>ProgramArguments</key>
    <array>
      <string>/usr/bin/memcached</string>
      <string>-l</string> <string>127.0.0.1</string>
      <string>-t</string> <string>4</string>
      <string>-m</string> <string>64</string>
    </array>
 
    <key>Disabled</key> <true/> 
    <key>KeepAlive</key> <true/> 
    <key>UserName</key> <string>daemon</string> 
    <key>GroupName</key> <string>daemon</string>
 
  </dict>
</plist>

> memcached -h
memcached 1.4.13
-p <num>      TCP port number to listen on (default: 11211)
-U <num>      UDP port number to listen on (default: 11211, 0 is off)
-s <file>     UNIX socket path to listen on (disables network support)
-a <mask>     access mask for UNIX socket, in octal (default: 0700)
-l <addr>     interface to listen on (default: INADDR_ANY, all addresses)
              <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
-d            run as a daemon
-r            maximize core file limit
-u <username> assume identity of  (only when run as root)
-m <num>      max memory to use for items in megabytes (default: 64 MB)
-M            return error on memory exhausted (rather than removing items)
-c <num>      max simultaneous connections (default: 1024)
-k            lock down all paged memory.  Note that there is a
              limit on how much memory you may lock.  Trying to
              allocate more than that would fail, so be sure you
              set the limit correctly for the user you started
              the daemon with (not for -u <username> user;
              under sh this is done with 'ulimit -S -l NUM_KB').
-v            verbose (print errors/warnings while in event loop)
-vv           very verbose (also print client commands/reponses)
-vvv          extremely verbose (also print internal state transitions)
-h            print this help and exit
-i            print memcached and libevent license
-P <file>     save PID in , only used with -d option
-f <factor>   chunk size growth factor (default: 1.25)
-n <bytes>    minimum space allocated for key+value+flags (default: 48)
-L            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.
-D <char>     Use  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.
-t <num>      number of threads to use (default: 4)
-R            Maximum number of requests per event, limits the number of
              requests process for a given connection to prevent 
              starvation (default: 20)
-C            Disable use of CAS
-b            Set the backlog queue limit (default: 1024)
-B            Binding protocol - one of ascii, binary, or auto (default)
-I            Override the size of each slab page. Adjusts max item size
              (default: 1mb, min: 1k, max: 128m)
-o            Comma separated list of extended or experimental options
              - (EXPERIMENTAL) maxconns_fast: immediately close new connections if over maxconns limit
              - hashpower: An integer multiplier for how large the hash table should be. 
                Can be grown at runtime if not big enough.
                Set this based on "STAT hash_power_level" before a restart

Connecting to Memcached server with telnet

telnet <hostname> <port>
Example: telnet local 11211


If Memcached server sends ERROR or CLIENT_ERROR, something is wrong with the command, if it's SERVER_ERROR, server itself is in trouble

Retrieval Commands

Parameters :
<key> : the key of the data stored to retrieve
<key>* mean you can request value of multiple keys separated by whitespace

These commands return :
VALUE <flag> <bytes>␤<data> (see the following for explanation of <bytes> and <flag>)
END indicate the end of response

Get

Get value from key
get <key>*

get key
VALUE key 0 4
data
END

Gets

Get value from key along with a cas token (to use with cas command)
gets <key>*

get key
VALUE key 0 4
data
END


Storage Commands

Parameters :
<key> : the key of the data stored
<flags> : 32-bit unsigned integer that the server store with the data (provided by the user), and return along the data when the item is retrieved
<exptime> : expiration time in seconds, 0 mean no delay, if exptime is superior to 30 day, Memcached will use it as a UNIX timestamps for expiration
<bytes> : number of bytes in the data block
<cas unique> : unique 64-bit value of an existing entry (retrieved with gets command) to use with cas command
[noreply] : optional parameter that inform the server to not send the reply

These commands can return :
STORED to indicate success
NOT_STORED indicate that the data was not stored because condition for "add" or "replace" command wasn't met, or the item is in a delete queue
EXISTS indicate that the item you are trying to store with "cas" command has been modified since last fetch
NOT_FOUND indicate that the item did not exist or has been deleted

Set

Store key/value pair in Memcached

set <key> <flags> <exptime> <bytes> [noreply]<value>

set key 0 900 4
data
STORED

Add

Store key/value pair in Memcached, but only if the server doesn't already hold data for this key

add <key> <flags> <exptime> <bytes> [noreply]<value>

add key 0 900 2
10
STORED

Replace

Store key/value pair in Memcached, but only if the server already hold data for this key

replace <key> <flags> <exptime> <bytes> [noreply]<value>

replace key 0 900 2
10
STORED

Append

Add value to an existing key after existing data
Append does not take <flags> or <exptime> parameters but you must provide them !

append <key> <flags> <exptime> <bytes> [noreply]<value>

append key 0 900 2
10
STORED

Prepend

Add value to an existing key before existing data
Prepend does not take <flags> or <exptime> parameters but you must provide them !

prepend <key> <flags> <exptime> <bytes> [noreply]<value>

prepend key 0 900 2
10
STORED

Cas

Store data only if no one else has updated since the last fetch, determined with the cas tokem from gets command
cas <key> <flags> <exptime> <bytes> <cas unique> [noreply]

cas key 0 900 2 <cas unique>
10
STORED


Delete Command

Parameters :
<key> : the key to delete
[<time>] : optional time in second before real deletion of item
[noreply] : optional parameter that inform the server to not send the reply

These command can return :
DELETED to indicate success
NOT_FOUND indicate that the item did not exist or has been deleted

Delete

Store key/value pair in Memcached

delete <key> [<time>] [noreply]

delete key
DELETED


Increment/Decrement Commands

Parameters :
<key> : the key to delete
<value> : the amount to increase/decrease the item.
[noreply] : optional parameter that inform the server to not send the reply

These command can return :
NOT_FOUND indicate that the item did not exist or has been deleted
<value> increment and decrement return the result

Increment

Increment value associated with key in Memcached, item must exist, increment command will not create it
The limit of increment is the 64 bit mark

incr <key> <value> [noreply]

incr key 12
56

Decrement

Decrement value associated with key in Memcached, item must exist, decrement command will not create it
If you try to decrement a value bellow 0, value will stay at 0

decr <key> <value> [noreply]

decr key 12
44


Touch Command

Parameters :
<key> : the key to delete
<exptime> : is expiration time. Works the same as with the update commands (set/add/etc). This replaces the existing expiration time.
[noreply] : optional parameter that inform the server to not send the reply

These command can return :
NOT_FOUND indicate that the item did not exist or has been deleted
TOUCHED to indicate success

Touch

The "touch" command is used to update the expiration time of an existing item without fetching it.

touch <key> <exptime> [noreply]

touch key 1800
TOUCHED


Statistics Commands

Parameters :
<args> : argument to stats command

These command can return various stats that we will explain in the following

Basic stats

Return general-purpose statistics like uptime, version, memory occupation, ...

stats

stats
STAT pid 106796
STAT uptime 5696
STAT time 1274397461
STAT version 1.4.5
STAT pointer_size 32
...
STAT total_items 344512124
STAT evictions 0
END

Items stats

Return items statistics, will display items statistics (count, age, eviction, ...) organized by slabs ID

stats items

stats
STAT items:1:number 1125
STAT items:1:age 426
STAT items:1:evicted 0
STAT items:1:evicted_nonzero 0
STAT items:1:evicted_time 0
STAT items:1:outofmemory 0
STAT items:1:tailrepairs 0
...
STAT items:42:tailrepairs 0
END

Slabs stats

Return slabs statistics, will display slabs statistics (size, memory usage, commands count, ...) organized by slabs ID

stats slabs

stats
STAT 1:chunk_size 80
STAT 1:chunks_per_page 13107
STAT 1:total_pages 1
STAT 1:total_chunks 13107
STAT 1:used_chunks 1125
...
STAT active_slabs 25
STAT total_malloced 10485600
END


Misc Commands

Flush_all

Flush the server key/value pair (invalidating them) after a optional [<time>] period
It always return OK

flush_all [<time>] [noreply]

flush_all 10
OK

Version

Return the Memcached server version

version

version
VERSION 1.4.5

Verbosity

Change the verbosity ouptut of Memcached server
It always return OK

verbosity <level> [noreply]

verbosity 2
OK

Quit

Server close connection when receiving this command

quit

quit


For any advanced need Memcached text protocol can be found here

Other Memcached Resources

You can find a lot of Memcached resources on Memcached resources page.

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