cocagne/python-composable-paxos

Paxos implemented as a set of composable classes

python-composable-paxos

This repository implements the core Paxos algorithm as a set of composable Python classes.

In order to use this module properly, a basic understanding of Paxos is required. The algorithm requires adherence to several messaging rules and that state be saved to persistent media at certain points in the protocol. These classes rely on the enclosing application to supply that behavior and to provide solutions for the implementation-defined aspects of the protocol such as the mechanism to ensure forward progress. The Understanding Paxos paper provides a comprehensive overview of the Paxos algorithm and should provide sufficient context for using this module appropriately.

The advantage to this minimalist approach over more full-featured solutions is flexibility. These classes have no external dependencies and they make no assumptions about the application's operational environment or message handling semantics. All they do is correctly implement the core algorithm in a neat little black box that can be used as a foundational building block for distributed applications.

This module may be installed via "pip install composable-paxos"

python-composable-paxos's Issues

Python 3

In Python 3, namedtuples can't be compared with NoneType.

python-composable-paxos/composable_paxos.py

Line 259 in d5515c2

if msg.proposal_id >= self.promised_id:

self.highest_accepted_id is not initialized in the Proposer class before being used

Here https://github.com/cocagne/python-composable-paxos/blob/master/composable_paxos.py#L216 you are comparing with self.highest_accepted_id, but you initialize it with None here https://github.com/cocagne/python-composable-paxos/blob/master/composable_paxos.py#L134. Maybe you meant self.highest_proposal_id?

Are self.highest_accepted_id and self.highest_proposal_id two logically separate fields?