memcached server

Memcached is an open source, high-performance, distributed memory object caching system. For more information check out the official memcached github repository.

Contents

1. Instructions
2. Supported commands
3. Usage
4. Environment variables

Instructions

Run server

The server runs in the 11211 port by default

• Download zip file

• Unzip

• Set environment variables using an .env file (see the Environment variables section)

• Open terminal

• Go to project location

• Run the following commands:

  npm install
  node index.js
  

Run client

• Open terminal

• Run the following command:

  telnet localhost 1337
  

Run tests

• Open terminal

• Go to project location

• Run the following command:

  npm test
  

Run code coverage

• Open terminal

• Go to project location

• Run the following command:

  npm run coverage
  

Supported commands

Storage

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

Retrieval

• get
• gets

Usage

Storage

The sytntax goes like this:

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

where:

• <command> is one of the following: set, add, replace, append or prepend.

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

• <flags> is a 32-bit integer that will be stored alongside the value.

• <exptime> is the expiration time in seconds.

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

• [noreply] is an optional string that removes the reply from the server.

Note: the cas command is equal to the previously mentioned but with an extra parameter <unique_cas_key> which is a unique 64-bit integer.

After the previous has been sent, the server will be expecting data in the following fashion:

<data>\r\n

where <data> must have a length of <bytes>.

The server can respond with:

• STORED\r\n in case of success.

and one of the following in case of failure:

• NOT_STORED\r\n

• NOT_FOUND\r\n

• EXISTS\r\n

• ERROR\r\n

• CLIENT_ERROR bad data chunk\r\nERROR\r\n

• CLIENT_ERROR bad command line format\r\n

Examples

Set

set key 0 1200 2
333
CLIENT_ERROR bad data chunk
ERROR

Add

add key 0 1200 2
23
STORED

Replace

replace key 0 30 3 noreply
333

Append

append other_key 0 1200 5
hello
NOT_STORED   

Prepend

prepend other_key 0 1200 11 noreply
helloworld!

Cas

cas key 0 1200 9 1
memcached
STORED        

Retrieval

For the retrieval commands the sytntax is shorter:

<command> <key_1> <key2> <key_3>...<key_n>\r\n

where:

• <command> is one of the following: get or gets.

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

The server can respond with:

• VALUE <key> <flags> <bytes>\r\n<value>\r\nEND\r\n in case the key in the get commands exists.

and the following in case of a successful gets request:

• VALUE <key> <flags> <bytes> <cas>\r\n<value>\r\nEND\r\n in case the key in the gets commands exists.

or in case the key doesn't exist:

• END\r\n

and one of the following in case of failure:

• ERROR\r\n

• CLIENT_ERROR bad data chunk\r\nERROR\r\n

Examples

Get

get key
VALUE key 0 2
25
END

Gets

gets key
VALUE key 0 2 1
25
END

Environment variables

The server uses 3 environment variables:

<PORT>, <IP> and <MAX_CONNECTIONS>

If not provided, the default values are 1337, 0.0.0.0 and 5 respectively.