.vscode/ (0, 2022-06-05)
.vscode/settings.json (86, 2022-06-05)
LICENSE (1073, 2022-06-05)
Makefile (1610, 2022-06-05)
connection.c (17650, 2022-06-05)
connection.h (4957, 2022-06-05)
defs.h (1215, 2022-06-05)
fnv.c (232, 2022-06-05)
fnv.h (334, 2022-06-05)
hash_table.c (3520, 2022-06-05)
hash_table.h (2533, 2022-06-05)
lib_demo.c (7113, 2022-06-05)
libmemuncached.c (16951, 2022-06-05)
libmemuncached.h (5054, 2022-06-05)
logger.h (1765, 2022-06-05)
screenshots/ (0, 2022-06-05)
screenshots/libmemcached_screenshot.png (265437, 2022-06-05)
screenshots/telnet_screenshot.png (352117, 2022-06-05)
server.c (4559, 2022-06-05)
utils.h (1770, 2022-06-05)
vector.c (2249, 2022-06-05)
vector.h (2126, 2022-06-05)
# memuncached
_memuncached_ is the worst undistributed memory object caching system.
Its name and description are sarcasticly quoted from [___memcached___](https://memcached.org/)
which is _free & open source, high-performance, distributed memory object caching system_.
The _memory object caching system_ is a in-memory database for storing/caching heavy-to-compute values
to speed up webservers, applications, APIs.
Although I influenced from [___memcached___](https://memcached.org/), I did not implemented their protocol but I designed myself. The commands are selected and slightly changed from [___PHP memcached client documentation___](https://www.php.net/manual/en/class.memcached.php#chunklist_reference).
The software consists of 2 parts: **server**, **client library**.
- As its name, **server** stores key-values in the memory and accepts TCP connections.
- The **client library** is **C library** provides
**connection**, **disconnection**, and **command** implementations.
You can think it like _database client library_.
Since I am developing database-like protocol
I think it is better to write client library
rather than _telnet_ like interactive application.
It is harder than cli because it needs proper way
to handle server responses to provide corresponding
functions (___memuncached\_\*___) for commonds defined in the protocol.
It is written in GNU dialect of ISO C11, _gnu11_.
The _server_ is written first while using _telnet_, so it is fully compatible with _telnet_.
The _server_ handles multiple clients simulataneously thanks to _multithreading_.
Also, I published the full source code at
___[github.com/gokberkakdeniz/memuncached](https://github.com/gokberkakdeniz/memuncached)___.
## Files and Descriptions
- `connection.c, connection.h`: Handles connection. Reads, write, and parses.
- `defs.h`: Global definitions.
- `fnv.c, fnv.h`: Very basic hash function.
- `hash_table.c, hash_table.h`: Thread-safe hash table.
- `lib_demo.c`: libmemuncached demo application.
- `libmemuncached.c, libmemuncached.h`: Client library.
- `logger.h`: Logging macros.
- `Makefile`: To build using make.
- `server.c`: Server main file.
- `utils.h`: Utility functions:
- `vector.c, vector.h`: Thread-safe dynamic array.
## Statistics
The whole project consist of 2.35K~ LoC and 50~ commits since 1st of May 2022.
## Screenshots
## Instructions
### Requirements
- gcc
- make
Tested on `Fedora 35` using `gcc (GCC) 11.3.1 20220421 (Red Hat 11.3.1-2)`, `GNU Make 4.3`.
## Build
- cd _project\_folder_
- make
- Available targets: _all_, _server_, _lib_, _lib\_demo_. Default target: _all_.
## Usage
- Run `./server.o` to start _server_.
- Run `./lib_demo.o` to start _libmemuncached demo application_ which
connects server and executes a few commands.
- Run `telnet localhost 9999` to connect the server via telnet.
## Protocol
- The protocol is ASCII based.
- The transmission is done with TCP.
- The commands are case-insensitive.
- There 3 types of data: **decimal (0)**, **real (1)**, **string (2)**.
- If the command takes payload, its length must be sent.
## Request
There are two types of request:
- Without payload: ```{CMD} {...ARGS}\r\n```
- With payload: ```{CMD} {...ARGS} {LENGTH}\r\n{PAYLOAD}\r\n```
### Examples
```
SET mykey 3 5
abcde
```
```
get mykey
```
## Response
### Format
All responses are in the same format except one optional value, _TYPE_,
which is required for **getter** (get, add) commands.
- ```{CODE} {DESCRIPTION}\r\n{LENGTH} [TYPE]\r\n{PAYLOAD}\0\r\n```
### Examples
```
200 OK
0
```
```
200 OK
3
1.0
```
```
200 OK
28
Client-Count: 1
Key-Count: 0
```
```
400 BAD REQUEST
16
Invalid command.
```
## Responses
- `200 OK`
- `400 BAD REQUEST`
- `404 NOT FOUND`
- `409 KEY EXIST`
- `500 SERVER ERROR`
## Commands
| Command | Arguments | Example Responses | Description |
| ------------------- | --------------------------------------------------------------------------------- | ------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
| ADD | KEY TYPE LENGTH
VALUE |
409 KEY EXIST
0
| Similar to SET but fails if key exists. |
| BYE | - |
200 OK
4
bye.
| Close connection. |
| DEC | KEY [OFFSET=1] [INITIAL=1] |
200 OK
1 0
1
| Decrease the value of KEY by OFFSET.
If the value is empty INITIAL value will be inserted. |
| DEL | KEY |
200 OK
5 2
value
| Deletes the value of the key and returns the value if exist. |
| INC | KEY [OFFSET=1] [INITIAL=1] |
200 OK
3 1
3.5
| Increase the value of KEY by OFFSET.
If the value is empty INITIAL value will be inserted. |
| GET | KEY |
200 OK
4 2
a b\\nc
| Get the value of the key. |
| SET | KEY TYPE LENGTH
VALUE |
200 OK
0
| Set the value of the key. |
| STT | - |
200 OK
28
Client-Count: 1
Key-Count: 0
| Get total key count, client count etc... |
| VER | - |
200 OK
3
1.0
| Get server version. |
## Future Work
### Commands
| Command | Arguments | Example Responses | Description |
| ------------------- | --------------------------------------------------------------------------------- | ------------------------------------------ | -------------------------------------------------- |
| APP | KEY LENGTH
VALUE |
200 OK
0
| Append the value to value identified by given key |
| PRE | KEY LENGTH
VALUE |
200 OK
0
| Prepend the value to value identified by given key |
| KYS | - |
200 OK
10
key1
key2
| Get all keys |
### Others
- Key validation.
- Authentication with username and password
using [___crypt.h___](https://man7.org/linux/man-pages/man3/crypt.3.html).
- Better error handling and reporting for client library
(instead of returning bool, return error codes).
- The telnet/mysql_cli like **client cli**.
## Conclusion
I learnt various topics including network protocol design, concurrency models,
POSIX threads, Linux sockets, client/server model, logging, Makefiles.
I believe that this project made me better programmer since I have never
involved in development of system programming.