memdb

memdb is a simple key-value in-memory database. Just for learning.

Features

• in-memory key-value store
• eviction policies like LFU, LRU
• TTL (per key)
• concurrent
• HTTP/CLI access

Running DB

Running the command

memdb --port 9300 --eviction-policy LRU

Data structures

This database will contain some data structures that will store data:

• Strings: single key-value
• Hash: multiple key-value data
• Set: a collection of not repeating values

HTTP Specification

The path represent the data structure to use, for example: /key, /hash, /set and the HTTP method the action

Key

Creating/Replacing a key

POST /key

STATUS:
201: When new Item
200: When Item already exists
400: bad input data

BODY:
{
    "key": "",
    "value": ""
}

RESPONSE:
{
    "affected_keys": 0,
}

Getting a key

GET /key/{key}

STATUS:
200: success response
204 (no content): item does not exists

RESPONSE (when 200):
{
    "value": ""
}

Deleting a key

DELETE /key/{key}

STATUS:
200: success response

RESPONSE:
{
    "affected_keys": 0,
}

Hash

Creating/Replacing a hash

POST /hash

STATUS:
201: When new Item
200: When Item already exists
400: bad input data

BODY:
{
    "key": "",
    "value": {
        "key1": "",
        "key2": ""
    }
}

RESPONSE:
{
    "affected_keys": 1,
}

Adding/Replacing the hash properties

PUT /hash/{key}

STATUS:
200: Succes response
400: bad input data
404: key not found

BODY:
{
    "value": {
        "key1": "",
        "key2": ""
    }
}

RESPONSE:
{
    "affected_keys": 1,
}

Getting a hash

GET /hash/{key}

STATUS:
200: success response
204 (no content): item does not exists

RESPONSE (when 200):
{
    "value": {
        "key1": "",
        "key2": ""
    }
}

Deleting a hash

DELETE /hash/{key}

STATUS:
200: success response

RESPONSE:
{
    "affected_keys": 0,
}

Deleting hash properties (can delete multiple keys separated by spaces)

DELETE /hash/{key}?keys={key, ...}

STATUS:
200: success response

RESPONSE:
{
    "affected_keys": 0,
}

CLI Specification

Defines how to use memdb by using the CLI

Key

Creating/Updating a key

KEY {keyname} SET {value}

Getting a key

KEY {keyname} GET

Deleting a key

KEY {keyname} DEL

Hash

Creating/Replacing the hash (can set multiple key-values separated by spaces)

HASH {keyname} SET {key} {value} ...

Adding/Replacing the hash properties (can set multiple key-values separated by spaces)

HASH {keyname} PUT {key} {value} ...

Getting a hash

HASH {keyname} GET

Deleting a hash

HASH {keyname} DEL

Deleting hash keys (can delete multiple keys separated by spaces)

HASH {keyname} DEL {key} ...