H2o KV

A Toy KV Database.

Build & Run Server

Required: Rust 2018 (latest Rust Stable or later versions)

$ make
H2o KV started at 127.0.0.1:30160

Build & Run Client

$ make cli
Connected to h2okv server 127.0.0.1:30160, Ctrl-D to exit
h2okv> get foo
(None)
h2okv> set foo bar
OK
h2okv> get foo
"bar"
h2okv> put first 135
OK
h2okv> scan f
1) "first"
2) "foo"

DB Data Persistence

Each write query would make the whole DB saved into a file named h2okv.data under current working directory. For more details on disk persistence, please see comments in file src/persistence.rs.

H2oKV Protocols

Queries

The query is formed as follow:

+--------+-----+------+--------+----------+
| Header | CMD | Flag | Length | Content  |
+--------+-----+------+--------+----------+
| '\x0c' | 1   | 1    | 2      | Variable |
+--------+-----+------+--------+----------+

Where:

• Header
  • protocol header: always be \x0c for now.
• CMD
  • GET: \x01
  • PUT: \x02 see next protocol table
  • DEL: \x03
  • SCAN: \x04
• Flag
  • Plain Text: \x00
  • GZIP Text: \x01
  • Ciphered Text: \x02 (details TBD)
• Length
  • Two bytes indicating how many bytes the Content part are. LittleEndian.
• Content
  • The KEY bytes for GET, PUT, and DEL
  • The key search pattern for SCAN

Protocol for PUT

+--------+--------+------+------+-----+-------+------+-------+
| Header | CMD    | Flag | KLen | KEY | VLLen | VLen | VALUE |
+--------+--------+------+------+-----+-------+------+-------+
| '\x0c' | '\x02' | 1    | 2    | Var | 1     | Var  | Var   |
+--------+--------+------+------+-----+-------+------+-------+

• KLen
  • Two bytes indicating how many bytes the KEY part are
• KEY
  • The KEY bytes
• VLLen
  • 1 byte indicating how many bytes the VLen part are
• VLen
  • bytes indicating how many bytes the VALUE part are, LittleEndian.
• VALUE
  • The Value bytes

Responses

GET

+--------+------+------+------+-----+---------+
| Header | Stat | Flag | LLen | Len | Content |
+--------+------+------+------+-----+---------+
| '\x0c' | 1    | 1    | 1    | Var | Var     |
+--------+------+------+------+-----+---------+

SCAN

+--------+------+------+-------+-----+-----+-----+-----+-----+
| Header | Stat | Flag | Count | Len | Key | Len | Key | ... |
+--------+------+------+-------+-----+-----+-----+-----+-----+
| '\x0c' | 1    | 1    | 4     | 2   | Var | 2   | Var | ... |
+--------+------+------+-------+-----+-----+-----+-----+-----+

PUT, DEL, All

+--------+------+
| Header | Stat |
+--------+------+
| '\x0c' | 1    |
+--------+------+

• Flag
  • Plain Text: \x00
  • GZIP Text: \x01
  • Ciphered Text: \x02 (details TBD)
• Stat(us)
  • OK: \x00
  • Failed: \x01
  • No such Key: \x02 (for GET)
  • Unknown command: \xFF