This document includes the new features, enhancements, and fixed issues for the Hazelcast Python Client 4.0.0b1 release.
New Features
- **Hazelcast IMDG 4.0 Changes**: Client protocol enhancements, architectural changes. 217
- **Ownerless Client**: Simpler design to track member leaves and joins to the cluster. 217
- **CP Subsystem Support**: New concurrency APIs including `AtomicLong`, `AtomicReference`, `FencedLock`, `Semaphore`, and `CountDownLatch`. Hazelcast IMDG 4.0 introduces CP Subsystem powered by Raft consensus protocol. It provides CP concurrency primitives with respect to the CAP principle, i.e., they always maintain linearizability and prefer consistency to availability during network partitions and client or server failures. 223, 224, 225, 226, 227
- **Backup Acknowledgment**: Python client now supports backup acks (aka boomerang backups). So far the client was waiting for the sync backups to complete on the member. Boomerang backups decrease the number of network hops, thus improving the performance. 222
- **Paging Predicates**: Support for Paging Predicates which allows you to fetch keys, values, or entries of a map page by page is implemented. 232
Enhancements
- **Configuration Redesign**: Programmatic configuration was simplified. The configuration is now represented with keyword arguments. 219
- **Google Style Docstrings**: Docstrings now follow the Google Python Style Guide to improve the readability. Also, with this change, IDEs are better at showing the type-hints from the docstrings. 221
- **Logging**: Hazelcast Python client was adding custom handlers to the loggers, which is not recommended by the standard library documentation. Custom handlers are now removed and other logging practices recommended by the standard library documentation is followed. 229
- **Performance**: The performance of the client for the non-blocking mode is improved significantly. 242
- **Predicates**: Predicates are now properly documented, have shorter names, and moved from the serialization module. 239
- Some private APIs were exposed to users mistakenly. They are removed from the public API and API documentation. 217, 221
- Serialization of strings is now significantly faster. 217
- Default serialization now supports the native `bytearray` type. 218
- Default serialization now supports Java `UUID` type. 218
- It is now possible to add or remove listeners in a non-blocking way. 248
- Hot path of the client is optimized. 218, 241, 243, 244
- Missing `set_ttl` method is added to the Map. 215
Fixes
- The member list could be broken after Hot Restart enabled member restart. Now the client handles the restart correctly. 231
- Client now handles class definition registrations with the same class id but with different factory ids. 235
- Anchor links were not working on the PyPI. README is converted to reStructuredText format to make them work. 237
- The possible race on handling timers is fixed. 240
Breaking Changes
- AP-based concurrency primitives (`Lock`, `Semaphore`, `AtomicLong`, `AtomicReference`, `CountDownLatch`) were removed from the client. Instead, CP-based versions are implemented. 223, 224, 225, 226, 227
- Programmatic configuration API was changed to work with keyword arguments. Certain configuration options were renamed. Also, the configuration options are now flat. 219
- Logging configuration API was changed according to recommended practices by the standard library. Hazelcast Python client does not add any handlers now. Also, one has to enable logging to see client logs. 229
- Certain predicates are renamed. Also, they are now at the `hazelcast.predicate` module, instead of the `hazelcast.serialization.predicate`. 239
- Some private APIs were exposed to users mistakenly. They are removed from the public API and API documentation. 217, 221
- Adding or removing listeners can be done in a non-blocking way now. Therefore, these APIs are returning `Future[str]` and `Future[bool]` instead of `str` and `bool`. 248
- `hazelcast.exception` module is renamed as `hazelcast.errors`. 217
Known Issues
- Client statistics format in Python client v4.0.0b1 is compatible with Management Center v4.0. Support for format compatible with Management Center v4.2020.08 and newer will be added in one of the upcoming minor releases of the client.