Subspace IPC

Next Generation, sub-microsecond latency shared memory IPC.

This is a shared-memory based pub/sub Interprocess Communication system that can be used in robotics and other applications. Why subspace? If your messages are transported between processes on the same computer, they travel through extremely low latency and high bandwidth shared memory buffers, kind of like they are going faster than light (not really, of course). If they go between computers, they are transported over the network at sub-light speed.

It has the following features:

1. Single threaded coroutine based server process written in C++17
2. Coroutine-aware client library, in C++17.
3. Publish/subscribe methodology with multiple publisher and multiple subscribers per channel.
4. No communication with server for message transfer.
5. Message type agnostic transmission – bring your own serialization.
6. Channel types, meaningful to user, not system.
7. Single lock POSIX shared memory channels
8. Both unreliable and reliable communications between publishers and subscribers.
9. Ability to read the next or newest message in a channel.
10. File-descriptor-based event triggers.
11. Automatic UDP discovery and TCP bridging of channels between servers.
12. Shared and weak pointers for message references.
13. Ports to MacOS and Linux, ARM64 and x86_64.
14. Builds using Bazel and uses Abseil and Protocol Buffers from Google.
15. Uses my C++ coroutine library (https://github.com/dallison/cocpp)

See the file docs/subspace.pdf for full documentation.

Building

This uses Google's Bazel to build. You will need to download Bazel to build it. The build also needs some external libraries, but Bazel takes care of downloading them. The .bazelrc file contains some configuration options.

To build on Mac Apple Silicon

bazel build --config=apple_silicon ...

To build on Linux

Subspace really wants to be built using clang. Depending on how your OS is configured, you might need to tell bazel what compiler to use.

CC=clang bazel build ...

It does build with g++ but you will get some compiler warnings about different signed comparisons that clang doesn't care about.

Example: Ubuntu 20.04

Build a minimal set of binaries:

CC=clang bazel build //server:subspace_server //manual_tests:{pub,sub}

Then run each in a separate terminal:

• ./bazel-bin/server/subspace_server
• ./bazel-bin/manual_tests/sub
• ./bazel-bin/manual_tests/pub

Bazel WORKSPACE

Add this to your Bazel WORKSPACE file to get access to this library without downloading it manually.

http_archive(
  name = "subspace",
  urls = ["https://github.com/dallison/subspace/archive/refs/tags/A.B.C.tar.gz"],
  strip_prefix = "subspace-A.B.C",
)

You can also add a sha256 field to ensure a canonical build if you like. Bazel will tell you what to put in for the hash when you first build it.