# traffic-shm

**Repository Path**: johnnie_walker/traffic-shm

## Basic Information

- **Project Name**: traffic-shm
- **Description**: No description available
- **Primary Language**: Java
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2024-09-05
- **Last Updated**: 2024-09-05

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# **traffic-shm**  [![logo](https://github.com/peptos/traffic-shm/raw/master/logo.png "logo")](https://github.com/peptos/traffic-shm "logo")


## Overview
traffic-shm (Shared Memory) is a Java based message library, which is designed for interprocess communication (IPC) on the same server.


## Features
### 1. Pure Java
Shared memory is an efficient mechanism for interprocess communication. Memory mapped files offer a dynamical memory management
feature that allows applications to access files on disk in the same way they attach the shared segment of physical memory to their virtual address spaces.

**traffic-shm** provides a pure java implementation using *sun.misc.Unsafe* and *FileChannel*, JDK 1.6+ is required.

### 2. Cross-Platform

*alignment:* 4-bytes aligned
*byteorder:* big-endian

Most of the major operating systems like Linux, macOS, Windows, AIX and HP-UX are supported.

Note:
- set **-Xmpas:on** on HP-UX
- set **--add-opens=java.base/jdk.internal.misc=ALL-UNNAMED** option to support JDK 9+

### 3. Async Mode:
#### 3.1 Lock-Free
With non-blocking algorithm, implementation of multi-producer/single-consumer and multi-producer/multi-consumer concurrent queue, **traffic-shm** could be use to build a real-time system with high throughput and low latency.

#### 3.2 Message Ordering

**traffic-shm** provides a FIFO queue which is ONCE-AND-ONLY-ONCE guaranteed.
cursor is forward only, once a message is delivered successfully, message is AUTOMATIC ACKNOWLEDGEMENT which means that a message is acknowledged as soon as the receiver gets it.

### 4. Sync Mode:
#### 4.1 Segmental Lock
offer a multi-producer/single-consumer concurrent data structure

## Data Structure Layout
**Async Mode:**
![Async](https://github.com/peptos/traffic-shm/raw/master/async.png)

## Getting Started

***Async:***

*Reader:*

	Queue queue = Queue.map("/Users/peptos/ashm", 2000L);;

	while (running) {
		Block block = queue.poll();
		if (block != null) {
			System.out.println(new String(block.getPayload(), "UTF-8"));
		} else {
			Util.pause(10);
		}
	}
	
	queue.close();
	

*Writer:*

	Queue queue = Queue.attach("/Users/peptos/ashm");

	String string = "hello, world";
	byte[] bytes = string.getBytes("UTF-8");
	System.out.println(queue.offer(new Block(bytes)));

	queue.close();