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https://github.com/dgzlopes/python-liftbridge
WIP: Python client for Liftbridge.
https://github.com/dgzlopes/python-liftbridge
client cloud-native grpc liftbridge messaging nats pubsub python python3 streaming
Last synced: about 2 months ago
JSON representation
WIP: Python client for Liftbridge.
- Host: GitHub
- URL: https://github.com/dgzlopes/python-liftbridge
- Owner: dgzlopes
- License: apache-2.0
- Created: 2019-08-20T14:30:43.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2020-07-05T12:27:06.000Z (over 4 years ago)
- Last Synced: 2024-10-11T22:23:37.162Z (2 months ago)
- Topics: client, cloud-native, grpc, liftbridge, messaging, nats, pubsub, python, python3, streaming
- Language: Python
- Homepage: https://pypi.org/project/python-liftbridge/
- Size: 65.4 KB
- Stars: 10
- Watchers: 6
- Forks: 5
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
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README
# python-liftbridge
[](https://pypi.org/project/python-liftbridge/)
[](https://github.com/dgzlopes/python-liftbridge/blob/master/LICENSE.md)
**This project is under development.**
Python client for [Liftbridge](https://github.com/liftbridge-io/liftbridge), a system that provides lightweight, fault-tolerant message streams for [NATS](https://nats.io).
Liftbridge provides the following high-level features:
- Log-based API for NATS
- Replicated for fault-tolerance
- Horizontally scalable
- Wildcard subscription support
- At-least-once delivery support and message replay
- Message key-value support
- Log compaction by key
## Installation
```
$ pip install python-liftbridge
```
## Basic Usage
```python
from python_liftbridge import Lift, Message, Stream, ErrStreamExists
# Create a Liftbridge client.
client = Lift(ip_address='localhost:9292', timeout=5)
# Create a Liftbridge stream with name "foo-stream"
try:
# create a stream with 5 partitions. default value is 1
client.create_stream(Stream(subject='foo', name='foo-stream', partitions=5))
except ErrStreamExists:
print('This stream already exists!')
# Publish a message to the stream with the name "foo-stream".
client.publish(Message(value='hello', stream='foo-stream'))
# Subscribe to the stream starting from the beginning.
for message in client.subscribe(
Stream(
subject='foo',
name='foo-stream',
subscribe_to_partition=0 # subscribe to specific partition of stream. default value is 0
).start_at_earliest_received(),
):
print("Received: '{}'".format(message.value))
```
### Create Stream
[Streams](https://github.com/liftbridge-io/liftbridge/blob/master/documentation/concepts.md#stream) are a durable message log attached to a NATS subject. They record messages published to the subject for consumption.
Streams have a few key properties: a subject, which is the corresponding NATS subject, a name, which is a human-readable identifier for the stream, and a replication factor, which is the number of nodes the stream should be replicated to for redundancy. Optionally, there is a group which is the name of a load-balance group for the stream to join. Also you can specify partitions count. When there are multiple streams in the same group, messages will be balanced among them.
```python
"""
Create a stream attached to the NATS subject "foo.*" that is replicated to
all the brokers in the cluster. ErrStreamExists is returned if a stream with
the given name already exists for the subject.
"""
client.create_stream(Stream(subject='foo.*', name='my-stream', max_replication=True, partitions=3))
```
### Subscription Start/Replay Options
[Subscriptions](https://github.com/liftbridge-io/liftbridge/blob/master/documentation/concepts.md#subscription) are how Liftbridge streams are consumed. Clients can choose where to start consuming messages from in a stream. This is controlled using options passed to Subscribe.
```python
# Subscribe starting with new messages only.
client.subscribe(
Stream(subject='foo', name='foo-stream')
)
# Subscribe starting with the most recently published value.
client.subscribe(
Stream(subject='foo', name='foo-stream').start_at_earliest_received()
)
# Subscribe starting with the oldest published value.
client.subscribe(
Stream(subject='foo', name='foo-stream').start_at_latest_received()
)
# Subscribe starting at a specific offset.
client.subscribe(
Stream(subject='foo', name='foo-stream').start_at_offset(4)
)
# Subscribe starting at a specific time.
client.subscribe(
Stream(subject='foo', name='foo-stream').start_at_time(datetime.now())
)
# Subscribe starting at a specific amount of time in the past.
client.subscribe(
Stream(subject='foo', name='foo-stream').start_at_time_delta(timedelta(days=1))
)
# Subscribe specific partition
client.subscribe(
Stream(subject='foo', name='foo-stream', subscribe_to_partition=2).start_at_latest_received()
)
```
### Publishing
A publish API is provided to make it easy to write messages to streams. This includes a number of options for decorating messages with metadata like a message key.
Keys are used by Liftbridge's log compaction. When enabled, Liftbridge streams will retain only the last message for a given key.
```python
# Publish a message with a key
client.publish(Message(stream='foo-stream', value='Hello', key='key'))
```
Also, it is possible to publish a message to the NATS subject (and, in turn, any streams that match the subject).
```python
# Publish a message to the NATS subject
client.publish_to_subject(Message(subject='foo', value='Hello foo'))
```
And you can publish message to specific stream partition.
```python
# Publish a message to the NATS subject
client.publish_to_subject(Message(subject='foo', value='Hello foo', partition=3))
```
#### Publishing Directly with NATS
Since Liftbridge is an extension of [NATS](https://github.com/nats-io/gnatsd), a [NATS client](https://github.com/nats-io/nats.py) can also be used to publish messages. This means existing NATS publishers do not need any changes for messages to be consumed in Liftbridge.
## How to contribute
1. Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug.
2. Fork [the repository](https://github.com/dgzlopes/python-liftbridge) on GitHub to start making your changes to the master branch (or branch off of it).
3. Write a test which shows that the bug was fixed or that the feature works as expected.
4. Send a [pull request](https://help.github.com/en/articles/creating-a-pull-request-from-a-fork) and bug [me](https://github.com/dgzlopes) until it gets merged and published.
Some things on the backlog:
- [ ] Add documentation (Sphynx)
- [ ] Add CI (CircleCI or TravisCI)
- [ ] Add tests
- [ ] Add code coverage
- [x] Add TLS support for gRPC
- [ ] Add message headers support
- [ ] Add message ACK support (scaffolding is already done)
- [x] Add method to close connection
- [ ] Add async client
- [ ] Add gRPC connection pool
- [x] Add logging (and remove all the random prints)
- [ ] Add proper docstrings
- [x] Add version file
- [ ] Add Contributing.md and explanation of the workflow (pyenv,tox,make,pre-commit...)
- [ ] Improve fetch metadata
- [ ] Improve error handling
- [x] Add to the makefile run-liftbridge using Docker [container](https://github.com/dgzlopes/liftbridge-docker)
- [ ] Better instrumentation/observability (OpenCensus support?)