This patch modifies the Python Paho MQTT library to use the selectors module instead of legacy select method for handling I/O operations. The motivation for this change is to overcome the maximum file descriptor limit imposed by the select method, which restricts the number of simultaneous connections that can be handled when running multiple Paho MQTT clients in the same process.
The selectors module provides a high-level, platform-independent way to manage I/O events and supports various mechanisms like epoll, kqueue, or poll where available. Unlike select, these mechanisms:
- Avoid the hard limit of 1024 file descriptors on many operating systems.
- Provide better scalability, especially for testing purposes when there's a need of handling a large number of connections.
- Offer a small performance boost in scenarios with many idle or low-traffic connections.
- Replaced the
selectsystem call with theselectorsmodule to manage socket operations. - Maintained backward compatibility with the existing library interface (Paho version >= 2.0).
- Added an extra parameter to pass a threading event, enabling the parent thread to trigger an exit from the event loop.
To use the patched version:
- Clone or download the patched library.
- Replace the existing Paho MQTT library in your project with the patched version.
- Use the library, no additional configuration is required.