py-libp2p

WARNING

py-libp2p is an experimental and work-in-progress repo under heavy development. We do not yet recommend using py-libp2p in production environments.

The Python implementation of the libp2p networking stack

Read more in the documentation on ReadTheDocs. View the change log.

Sponsorship

This project is graciously sponsored by the Ethereum Foundation through Wave 5 of their Grants Program.

Maintainers

The py-libp2p team consists of:

@zixuanzh @alexh @stuckinaboot @robzajac @carver

Development

py-libp2p requires Python 3.7 and the best way to guarantee a clean Python 3.7 environment is with virtualenv

git clone git@github.com:libp2p/py-libp2p.git
cd py-libp2p
virtualenv -p python3.7 venv
. venv/bin/activate
pip install -e .[dev]

Testing Setup

During development, you might like to have tests run on every file save.

Show flake8 errors on file change:

# Test flake8
when-changed -v -s -r -1 libp2p/ tests/ -c "clear; flake8 libp2p tests && echo 'flake8 success' || echo 'error'"

Run multi-process tests in one command, but without color:

# in the project root:
pytest --numprocesses=4 --looponfail --maxfail=1
# the same thing, succinctly:
pytest -n 4 -f --maxfail=1

Run in one thread, with color and desktop notifications:

cd venv
ptw --onfail "notify-send -t 5000 'Test failure ⚠⚠⚠⚠⚠' 'python 3 test on py-libp2p failed'" ../tests ../libp2p

Note that tests/libp2p/test_libp2p.py contains an end-to-end messaging test between two libp2p hosts, which is the bulk of our proof of concept.

Release setup

Releases follow the same basic pattern as releases of some tangentially-related projects, like Trinity. See Trinity's release instructions.

Requirements

The protobuf description in this repository was generated by protoc at version 3.7.1.

Feature Breakdown

py-libp2p aims for conformity with the standard libp2p modules. Below is a breakdown of the modules we have developed, are developing, and may develop in the future.

Legend: :green_apple: Done   :lemon: In Progress   :tomato: Missing   :chestnut: Not planned

Explanation of Basic Two Node Communication

Core Concepts

(non-normative, useful for team notes, not a reference)

Several components of the libp2p stack take part when establishing a connection between two nodes:

1. Host: a node in the libp2p network.
2. Connection: the layer 3 connection between two nodes in a libp2p network.
3. Transport: the component that creates a Connection, e.g. TCP, UDP, QUIC, etc.
4. Streams: an abstraction on top of a Connection representing parallel conversations about different matters, each of which is identified by a protocol ID. Multiple streams are layered on top of a Connection via the Multiplexer.
5. Multiplexer: a component that is responsible for wrapping messages sent on a stream with an envelope that identifies the stream they pertain to, normally via an ID. The multiplexer on the other unwraps the message and routes it internally based on the stream identification.
6. Secure channel: optionally establishes a secure, encrypted, and authenticated channel over the Connection.
7. Upgrader: a component that takes a raw layer 3 connection returned by the Transport, and performs the security and multiplexing negotiation to set up a secure, multiplexed channel on top of which Streams can be opened.

Communication between two hosts X and Y

(non-normative, useful for team notes, not a reference)

Initiate the connection: A host is simply a node in the libp2p network that is able to communicate with other nodes in the network. In order for X and Y to communicate with one another, one of the hosts must initiate the connection. Let's say that X is going to initiate the connection. X will first open a connection to Y. This connection is where all of the actual communication will take place.

Communication over one connection with multiple protocols: X and Y can communicate over the same connection using different protocols and the multiplexer will appropriately route messages for a given protocol to a particular handler function for that protocol, which allows for each host to handle different protocols with separate functions. Furthermore, we can use multiple streams for a given protocol that allow for the same protocol and same underlying connection to be used for communication about separate topics between nodes X and Y.

Why use multiple streams?: The purpose of using the same connection for multiple streams to communicate over is to avoid the overhead of having multiple connections between X and Y. In order for X and Y to differentiate between messages on different streams and different protocols, a multiplexer is used to encode the messages when a message will be sent and decode a message when a message is received. The multiplexer encodes the message by adding a header to the beginning of any message to be sent that contains the stream id (along with some other info). Then, the message is sent across the raw connection and the receiving host will use its multiplexer to decode the message, i.e. determine which stream id the message should be routed to.