Index > Protocol

Protocol

ROMA protocol is compatible with memcached text-based protocol. Any memcached client libraries allows users to interact with ROMA.

• Protocol
• Storage Command
• set
• add
• replace
• append
• prepend
• cas
• Retrieval Command
• get, gets
• Deletion Command
• delete
• Increment/Decrement
• incr, decr
• Other Command
• balse
• stats, (stat)

Storage Command

set

Purpose

set is a command which stores data in ROMA.

Syntax

 set <key> <flags> <exptime> <bytes> [noreply]\r\n
 <datablock>\r\n 

Semantics

Return Code

After sending the command line and the data block, the client awaits the reply as follows.

• Success

 STORED\r\n 

• Otherwise

 NOT_STORED\r\n

add

Purpose

add is a command which stores data in ROMA, only if ROMA doesn't already hold the data for this key.

Syntax

 add <key> <flags> <exptime> <bytes> [noreply]\r\n
 <datablock>\r\n

Semantics

Return Code

After sending the command line and the data block, the client awaits the reply as follows.

• Success

 STORED\r\n 

• Otherwise

 NOT_STORED\r\n

replace

Purpose

replace is a command which stores data in ROMA, only if ROMA does already hold the data for this key.

Syntax

 replace <key> <flags> <exptime> <bytes> [noreply]\r\n
 <datablock>\r\n

Semantics

Return Code

After sending the command line and the data block, the client awaits the reply as follows.

• Success

 STORED\r\n 

• Otherwise

 NOT_STORED\r\n

append

Purpose

append is a command which adds this data to an existing key after existing data.

Syntax

 append <key> <bytes> [noreply]\r\n
 <datablock>\r\n

Semantics

Return Code

After sending the command line and the data block, the client awaits the reply as follows.

• Success

 STORED\r\n 

• Otherwise

 NOT_STORED\r\n

prepend

Purpose

prepend is a command which adds this data to an existing key before existing data.

Syntax

 prepend <key> <bytes> [noreply]\r\n
 <datablock>\r\n

Semantics

Return Code

After sending the command line and the data block, the client awaits the reply as follows.

• Success

 STORED\r\n 

• Otherwise

 NOT_STORED\r\n

cas

Purpose

cas is a check and set command. ROMA stores this data only if no one else has updated since ROMA last fetched it.

Syntax

 cas <key> <flags> <exptime> <bytes> <cas unqiue> [noreply]\r\n
 <datablock>\r\n 

Semantics

Return Code

After sending the command line and the data block, the client awaits the reply as follows.

• Success

 STORED\r\n 

• The item you are trying to store with a cas command has been modified since you last fetched it.

 EXISTS\r\n

• Otherwise

 NOT_STORED\r\n

Retrieval Command

get, gets

Purpose

get and gets are retrieval commands.

Syntax

 get <key>\r\n

 gets <key>\r\n

Semantics

Return Code

• Each item is sent by the server.

 VALUE <key> <flags> <bytes> [<cas unique>]\r\n 
 <data block>\r\n 

• <key> is the key which is specified the previous command.
• <flags> This values is not used.
• <bytes> is the number of bytes of data block without the delimiting \r\n.
• [<cas unique>] is a unique 64-bit integer. Only if you uses gets command.
• <data block> is the data.

• Finally, the server sends the strings.

 END\r\n 

Deletion Command

delete

Purpose

delete is a command which deletes the data logically.

Syntax

 delete <key> [<time>] [noreply]\r\n 

Semantics

Return Code

After sending the command line, the client awaits the reply as follows.

• Success

 DELETED\r\n

• Otherwise

 NOT_FOUND\r\n

Increment/Decrement

incr, decr

Purpose

incr and decr are commands which increase/decrease the value to existing data.

Syntax

incr <key> <value> [noreply]\r\n

decr <key> <value> [noreply]\r\n

Semantics

Return Code

After sending the command line, the client awaits the reply as follows.

• Success.

 <value>\r\n 

• When the key is not found.

 NOT_FOUND\r\n

Other Command

balse

Purpose

balse is a command which ROMA will be shutdown.

Syntax

balse [<reason>]\r\n

• The server will confirm, you should answer.

Are you sure?(yes/no)\r\n

• yes ROMA will be shutdown immediately.
• no ROMA doesn't do nothing and this connection will close.

Semantics

Return Code

stats, (stat)

Purpose

stats is a command which ROMA informs ROMA's own status.

Syntax

stats\r\n

If you want to show a part of stats, you should use <args> in the regular expression.

stats <args>\r\n

Return Code

Refer to Stats_Information for more detail information about stats command.