Aeron


Efficient reliable unicast and multicast message transport.

For details of usage, protocol specification, FAQ, etc. please check out the Wiki.

For those who prefer to watch a video then try Aeron Messaging from StrangeLoop 2014. Things have moved on quite a bit with performance and some features but the basic design still applies.

How do I use Aeron?

1. Java Programming Guide
2. Best Practices Guide

How does Aeron work?

1. Protocol Specification
2. Design Overview
3. Design Principles
4. Flow Control Semantics
5. Media Driver Operation

How do I hack on Aeron?

1. Hacking on Aeron
2. Performance Testing

License (See LICENSE file for full license)

Copyright 2014 Real Logic Limited

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Directory Structure

Client API and common classes

aeron-client

Samples

aeron-samples

Media Driver

aeron-driver

Build

Java Build

You require the following to build Aeron:

• Latest stable Oracle JDK 8

You must first build and install Agrona into the local maven repository

$ ./gradlew

After Agrona is compiled and installed, then you can build Aeron.

Full clean and build of all modules

$ ./gradlew

C++ Build

C++ API is a work in progress and may not build or be stable for usage at this time.

You require the following to build the C++ API for Aeron:

• 2.8 or higher of CMake
• C++11 supported compiler for the supported platform

NOTE: Aeron is supported on Linux, Mac, and Windows. Windows builds require Visual Studio and are being developed with Visual Studio Express 12 with 64-bit builds only. Cygwin, MSys, etc. may work, but are not maintained at this time.

For convenience, a script is provided that does a full clean, build, and test of all targets.

$ ./cppbuild/cppbuild

If you are comfortable with using CMake, then a full clean, build, and test looks like:

$ mkdir -p cppbuild/Debug
$ cd cppbuild/Debug
$ cmake ../..
$ cmake --build . --clean-first
$ ctest

Running Samples

Start up a media driver which will create the data and conductor directories. On Linux, this will probably be at /tmp/aeron.

$ java -cp aeron-samples/build/libs/samples.jar uk.co.real_logic.aeron.driver.MediaDriver

Alternatively, specify the data and conductor directories. The following example uses the shared memory 'directory' on Linux, but you could just as easily point to the regular filesystem.

$ java -cp aeron-samples/build/libs/samples.jar -Daeron.dir.conductor=/dev/shm/aeron/conductor -Daeron.dir.data=/dev/shm/aeron/data uk.co.real_logic.aeron.driver.MediaDriver

You can run the BasicSubscriber from a command line. On Linux, this will be pointing to the /dev/shm shared memory directory, so be sure your MediaDriver is doing the same!

$ java -cp aeron-samples/build/libs/samples.jar uk.co.real_logic.aeron.samples.BasicSubscriber

You can run the BasicPublisher from a command line. On Linux, this will be pointing to the /dev/shm shared memory directory, so be sure your MediaDriver is doing the same!

$ java -cp aeron-samples/build/libs/samples.jar uk.co.real_logic.aeron.samples.BasicPublisher

You can run the AeronStat utility to read system counters from a command line

$ java -cp aeron-samples/build/libs/samples.jar uk.co.real_logic.aeron.samples.AeronStat

Media Driver Packaging

The Media Driver is packaged by the default build into an application that can be found here

aeron-driver/build/distributions/aeron-driver-${VERSION}.zip

Troubleshooting

1. On linux, the subscriber sample throws an exception java.lang.InternalError(a fault occurred in a recent unsafe memory access operation in compiled Java code)

This is actually an out of disk space issue.

To alleviate, check to make sure you have enough disk space.

In the samples, on Linux, this will probably be either at /dev/shm or /tmp/aeron (depending on your settings).

See this thread for a similar problem.

Note: if you are trying to run this inside a Linux Docker, be aware that, by default, Docker only allocates 64 MB to the shared memory space at /dev/shm. However, the samples will quickly outgrow this.

You can work around this issue by running your Docker container in privileged mode and running this command:

mount -t tmpfs -o remount,rw,nosuid,nodev,noexec,relatime,size=1024M tmpfs /dev/shm

This will increase the size of /dev/shm to 1 GB. Hopefully you have enough memory :)