memcached.js

memcached.js is inspired in memcached server. This implementation has only a subset of commands from the original. Commands currently support are listed below

The server is useful if you want a simple memcached server that integrates with your existing node.js infrastructure, otherwise use the original memcached which is a very lightweight.

Usage

Run Server

$ yarn start

memcached.js will run, by default, on port 11211. For a custom port, please set PORT environment variable from console.

Run client

For test the server you can use any memcached client, otherwise you can connect using telnet running this command. telnet <ip-address> <port> e.g:

$ telnet localhost 11211

Server Commands

memcached.js accepts the following commands, based on the original commands:

Retrieval commands:

• get
• gets

Storage commands:

• set
• add
• replace
• append
• prepend
• cas

Storage

There are a few storage commands that start with a header like this:

<command> <key> <flags> <exptime> <bytes>\r\n

for cas implementation need extra value

cas <key> <flags> <exptime> <bytes> <cas unique>

• <command> is set, add, replace, cas, append or prepend.

• <key> is a string that will identify the element.

• <flags> is a 16-bit integer to store with the value.

• <exptime> is expiration time in seconds.

• <bytes> is the length of the data in bytes.

• <cas unique> is a unique 64-bit value of an existing entry.

Clients should use the value returned from the "gets" command

when issuing "cas" updates.

Afterwards the server will expect the data block:

<data>\r\n

with a length of <bytes>.

The server will respond with:

• STORED\r\n to indicate success.

• NOT_STORED\r\n to indicate failure.

• EXISTS\r\n to indicate that the item you are trying to store with a "cas" command has been modified since you last fetched it.

• NOT_FOUND\r\n to indicate that the item you are trying to store with a "cas" command did not exist.

Retrieval

The commands get and gets have the following syntax:

get <key>\r\n

where <key> is a string that identifies a pair KEY VALUE already storaged

After this command, the client expects zero or more items, each of which is received as a text line followed by a data block. After all the items have been transmitted, the server sends the string

END\r\n

to indicate the end of a response.

Each item sent by the server looks like this:

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

• <key> is the key for the item being sent

• <flags> is the flags value set by the storage command

• <bytes> is the length of the data block to follow, not including its delimiting \r\n

• <cas unique> is a unique 64-bit integer that uniquely identifies this specific item.

• <data block> is the data for this item.

Store sample command

set kevin 0 300 0\r\n
to-moovitr\r\n

the server responds with STORED\r\n.

Error sample commands

if you run command not supported, you will recibe ERROR\r\n, example command:

$ store\r\n

If you run a supported command, but with incorrect number of params, you will recibe CLIENT_ERROR bad command line format\r\n, example command:

$ add kevin 0 300

Testing

For execute the tests just run:

 $ yarn test

References

• protocol.txt