Nameko Redis Keyspace Notifications

Nameko Redis Keyspace Notifications extension.

Usage

This Nameko extension adds the ability to subscribe to events, keys and databases.

Some event examples:

• expire events fired for EXPIRE commands
• expired events fired when a key gets deleted due to expiration

Usage example:

from nameko_rediskn import rediskn, REDIS_PMESSAGE_TYPE


class MyService:

    name = 'my-service'

    @rediskn.subscribe(uri_config_key='MY_REDIS', keys='foo/bar-*')
    def subscriber(self, message):
        if message['type'] != REDIS_PMESSAGE_TYPE:
            return

        event_type = message['data']
        if event_type != 'expired':
            return

        key = message['channel'].split(':')[1]

        # ...

Where subscribe accepts:

• MY_REDIS, which is the attribute name referring to he Redis URI (see the Configuration section below).
• events, keys and dbs as a single value (string) or a list of values to subscribe to. They are all optional but at least one of those arguments must be provided.

For more information, you can check the documentation of the RedisKNEntrypoint entrypoint.

NOTE: this dependency is not "cluster-aware" and fires on all service instances. There are different ways to solve that: using ddebounce is one of them.

Configuration

Nameko configuration file:

# config.yaml

REDIS:
    notification_events: "KEA"
    pubsub_backoff_factor: 3

REDIS_URIS:
    MY_REDIS: "redis://localhost:6380/0"

REDIS[notification_events] is optional and can be omited or just contain None. Otherwise, it must have a valid value for the 'notify-keyspace-events' Redis client configuration attribute. This should be ideally set on the server side, as setting it in one of the Redis clients will affect the rest of them.

REDIS[pubsub_backoff_factor] sets the exponential backoff factor for reconnecting to Redis on errors. If an error occurs while listening for Redis events, we sleep for backoff_factor * 2 ** (n - 1) where n is the number of consecutive errors that have occurred. If omitted, this defaults to 2.

REDIS_URIS follows the config format used by the Nameko Redis dependency provider, where MY_REDIS is just the attribute name refering to the Redis URI of the instance being used.

Tests

RabbitMQ should be up and running on the default URI guest:guest@localhost and using the default ports.

Redis should be also running on the default port.

There are Makefile targets to run both RabbitMQ and Redis docker containers locally using the default ports and configuration:

$ make rabbitmq-container
$ make redis-container

A virtual environment should be set up and up to date:

$ # Create/activate a virtual environment
$ pip install -U pip setuptools wheel

tox can be used to run the tests. It is recomented that all its dependencies, specially virtualenv, are up to date, so that it uses the correct version of libraries like pip, setuptools and wheel:

$ pip install -U --upgrade-strategy=eager tox
$ tox
$ tox -e "py37-namekolatest-redislatest-test"

There are other Makefile targets that can be used to run the tests, but extra dependencies will have to be installed, including this package in develop mode:

$ pip install -U --editable ".[dev]"
$ make test
$ make coverage

A different RabbitMQ URI can be provided overriding the following environment variables: RABBIT_CTL_URI and AMQP_URI.

Additional pytest parameters can be also provided using the ARGS variable:

$ make test RABBIT_CTL_URI=http://guest:guest@localhost:15673 AMQP_URI=amqp://guest:guest@localhost:5673 ARGS='-x -vv --disable-warnings'
$ make coverage RABBIT_CTL_URI=http://guest:guest@localhost:15673 AMQP_URI=amqp://guest:guest@localhost:5673 ARGS='-x -vv --disable-warnings'

Linting

To run linting checks using tox:

$ for env in $(tox -l - | grep linting); do tox -e $env; done

Nameko support

The following Nameko versions are actively supported: 2.11, 2.12.

However, this extension should work from, at least, Nameko 2.6 onwards.

Redis support

The following Redis Python versions are actively supported: 2.10, 3.0, 3.1, 3.2.

Redis 4.0 is actively supported.

Changelog

Consult the CHANGELOG document for fixes and enhancements of each version.

License

The MIT License. See LICENSE for details.