Serverless platforms provide massive parallelism with very high elasticity and fine-grained billing. Because of these properties, they are increasingly used for stateful, distributed jobs at large scales. However, a major limitation of the commonly used platforms is communication: Individual functions cannot communicate directly and using external storage or databases for ephemeral data can be slow and expensive. We present FMI, the FaaS Message Interface, to overcome this limitation. FMI is an easy-to-use, high-performance framework for general-purpose communication in Function as a Service platforms. It supports different communication channels (including direct communication with our TCP NAT hole punching system), a model-driven channel selection according to performance or cost, and provides optimized collective implementations that exploit characteristics of the different channels. In our experiments, FMI can speed up communication for a distributed machine learning job by up to 1,200x, while reducing cost at the same time by factors of up to 365. It provides a simple interface and can be integrated into existing codebases with a few minor changes.

• C++17 or higher
• Boost
• AWS SDK for C++
• hiredis
• TCPunch

• Clone this repository
• Add to your CMakeLists.txt:

add_subdirectory(path_to_repo/FMI/)

target_link_libraries(${PROJECT_NAME} PRIVATE FMI)
target_include_directories(${PROJECT_NAME} PRIVATE ${FMI_INCLUDE_DIRS})

• Integrate the library into your project:

#include <Communicator.h>
...
FMI::Communicator comm(peer_id, num_peers, "config/fmi.json", "MyApp", 512);

• Clone this repository

cd python
mkdir build
cd build
cmake ..
make

• fmi.so gets created in the python/build directory. You can copy it into your Python module path or include the build directory via PYTHONPATH. The library can then be integrated into your project:

import fmi
comm = fmi.Communicator(peer_id, num_peers, "config/fmi.json", "MyApp", 512);

The Docker images FMI-build-docker contain all necessary dependencies and set up the environment for you. See the repo for details.

For even easier deployment, we provide AWS CloudFormation templates to create Lambda layers in python/aws. Simply run sam build and sam deploy --guided in the folder corresponding to your Python version, which creates a Lambda layer in your account that can be added to your function. As soon as you added the layer, you can simply use import fmi and work with the library.

C++ sample code for the library is available at tests/communicator.cpp, the usage from Python is demonstrated in python/tests/client.py.

The architecture of the system including a comparison with existing systems and benchmarks is documented in the paper preprint FMI: Fast and Cheap Message Passing for Serverless Functions. More details can be found in the thesis FMI: The FaaS Message Interface.

A technical documentation of the system (for people that want to extend it) is available at fmi.opencore.ch.

• Marcin Copik (ETH Zurich) - maintainer.
• Roman Böhringer (OpenCoreCH) - main author of FMI.