pop-beacon 1

A system to continually watch interfaces for events and forward them respectively

A system to continually watch interfaces for events and forward them respectively through the event bus

INSTALLATION

pip install pop-beacon

USAGE

beacon is mainly an app-merge component for larger projects. However, it includes a script that can be useful for testing your beacons. This testing script will listen to all beacons and print out events that any of them receive. A listener iterates over the internal beacon queues and prints everything that gets posted to them. The the outputter to format the printed data can be specified with –output.

beacon_test --output json

TESTING

Install beacon locally with testing libraries:

$ git clone [e-mail]:saltstack/pop/beacon.git
$ pip install -e beacon -r requirements-test.txt

If you have a rabbitmq-server binary installed via your system’s package manager, the pika tests won’t be skipped. Start a local rabbitmq-server with the default parameters:

sudo rabbitmq-server

Run the tests with pytest:

$ pytest beacon/tests

ACCT PROFILES

beacon will read credentials that are encrypted using the acct system. To use this system, create a yaml file that has the plaintext credentials and information needed to connect with the various beacon plugins. For example, to connect to a rabbitmq server, or any amqp implementation, have a profile in your acct credentials file that specifies the “pika” acct plugin:

credentials.yml

pika:
  profile_name:
    host: localhost
    port: 5672
    username: XXXXXXXXXXXX
    password: XXXXXXXXXXXX
    beacon_channels:
      - channel1
      - channel2

Next use the acct command to encrypt this file using the fernet algorithm:

$ acct credentials.yml
New encrypted file created at: credentials.yml.fernet
The file was encrypted with this key:
YeckEnWEGOjBDVxxytw13AsdLgquzhCtFHOs7kDsna8=

The acct information can now be stored in environment variables:

$ export ACCT_FILE = $PWD/credentials.yml.fernet
$ export ACCT_KEY = "YeckEnWEGOjBDVxxytw13AsdLgquzhCtFHOs7kDsna8="

They can also be used on the command line:

$ beacon_test --acct-file=credentials.yml.fernet --acct-key="YeckEnWEGOjBDVxxytw13AsdLgquzhCtFHOs7kDsna8="

INTEGRATION

Your own app can extend acct’s command line interface to use the –acct-file and –acct-key options for beacon:

my_project/conf.py

CLI_CONFIG = {
    "acct_file": {"source": "acct", "os": "ACCT_FILE"},
    "acct_key": {"source": "acct", "os": "ACCT_KEY"},
    "beacon_profiles": {"source": "beacon"},
}

In your own project, you can vertically merge beacon and extend it with your own beacon plugins:

my_project/conf.py

DYNE = {
    "acct": ["acct"],
    "beacon": ["beacon"],
    "my_project": ["my_project"],
}

Create the directory my_project/beacon and add your beacon plugins there.

Beacon plugins need a function called “listen” that is an asynchronous generator.

my_project/beacon/my_plugin.py

from typing import AsyncGenerator

async def listen(hub) -> AsyncGenerator:
    async for event in my_queue:
        yield event

The “listen” function can optionally have a ctx parameter if your beacon plugin requires login credentials. The ctx parameter will be automatically be populated by acct and evbus if a profile that specifies your plugin is included in the encrypted acct file.

my_project/beacon/my_plugin.py

from typing import AsyncGenerator

async def listen(hub, ctx) -> AsyncGenerator:
    if not ctx.connected:
        return

    # Many message queues have named channels that can be specified
    # Create a listener for every channel on this connection
    # A listener is another function that returns an async generator
    channel_listeners = [await ctx.connection.channel_listener(channel) for channel in ctx.channels]
    # Use hub.pop.loop.as_yielded to combine all the channel async generators into a single async generator
    generator = hub.pop.loop.as_yielded(channel_listeners)

    # Listen for events as they come from any of the channels
    async for event in generator:
        yield event

Create the directory my_project/acct/beacon and add your acct plugins there. acct plugins need to implement a gather function, which reads the appropriate information from hub.acct.PROFILES and turns it into processed profile information in hub.acct.SUB_PROFILES. This processing can include operations such as opening a connection to a remote server.

my_project/acct/beacon/my_plugin.py

async def gather(hub):
    """
    Get [my_plugin] profiles from an encrypted file

    Example:

    .. code-block:: yaml

        my_plugin:
          profile_name:
            host: localhost
            port: 12345
            username: XXXXXXXXXXXX
            password: XXXXXXXXXXXX
            beacon_channels:
              - channel1
              - channel2
    """
    sub_profiles = {}
    for profile, ctx in hub.acct.PROFILES.get("my_plugin", {}).items():
        # Create a connection through [some_library] for each of the profiles
        sub_profiles[profile] = {
            "connected": False,
            "connection": await some_library.connect(**ctx),
            "channels": ctx.pop("beacon_channels", []),
        }
    # Return these to be automatically processed by acct and injected into the `ctx` parameter of appropriate beacon publish calls.
    return sub_profiles

Add beacon startup code to your project’s initializer:

my_project/my_project/init.py

def __init__(hub):
    # Horizontally merge the beacon dynamic namespace into your project
    hub.pop.sub.add(dyne_name="beacon")

def cli(hub):
    # Load the config from beacon onto hub.OPT
    hub.pop.config.load(["my_project", "beacon", "evbus", "acct"], cli="my_project")

    # Create the asyncio loop
    hub.pop.loop.create()

    # Create the beacon coroutine
    coro = hub.beacon.init.start(
        format_plugin=hub.OPT.beacon.format,
        acct_file=hub.OPT.acct.acct_file,
        acct_key=hub.OPT.acct.acct_key,
        beacon_profiles=hub.OPT.beacon.beacon_profiles,
    )

    # Start the main beacon listener
    hub.pop.Loop.run_until_complete(coro)