Greengrass IPC without Greengrass V2?

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Platform/OS/Device
What are you running the sdk on?
Ubuntu.

Describe the question
I'm unclear on the functionality of the newly released Greengrass IPC part of this SDK. Is it possible to use this to publish messages from a non-Greengrass process? The documentation here - https://docs.aws.amazon.com/greengrass/v2/developerguide/ipc-publish-subscribe.html - seems to only demonstrate using this SDK within Greengrass.

[Kriechi]

You should be able to talk to Greengrass v2 from any process - as long as you know the path to the local socket and the authtoken. Both are available as environment variable: AWS_GG_NUCLEUS_DOMAIN_SOCKET_FILEPATH_FOR_COMPONENT and SVCUID.

I did a quick test with a different non-root Linux user and a regular python process started from my shell (instead of a component deployed through GGv2). And it works.

See this PR for an example and an improved / simplified connection creation: #144

[afwilkin]

@Kriechi

Quick couple of questions:

1. Is this only GGv2 compliant, or can this be used with GGv1 as well?
2. I keep getting an error when trying to create IPCUtils() object. I am able to import the modules, but the object IPCUtils() can not be found

[Kriechi]

@afwilkin as far as I know, the IPC was introduced with Greengrass v2.
For your IPCUtils, I would suggest opening a new issue so core team can help you. Make sure to include a full set of steps and error message, tracebacks, etc.

[jmklix]

1. Yes, Greengrass v1 does not have support for IPC

Subscriptions

In AWS IoT Greengrass V1, subscriptions specify where Lambda functions receive event messages to consume as function payloads. Functions subscribe to local publish/subscribe messages and AWS IoT Core MQTT messages.

In AWS IoT Greengrass V2, components manage their own subscriptions to local publish/subscribe and AWS IoT Core MQTT messages. In the component recipe, you define authorization policies to specify which topics the component can use to communicate. In component code, you can use interprocess communication (IPC) for local publish/subscribe messaging and AWS IoT Core MQTT messaging. For more information, see Use the AWS IoT Device SDK for interprocess communication (IPC).

2. Can you include more details about the error that you are getting and how you are trying to use IPCUtils() object.

[jmklix]

There is a currently a PR for an IPC example. If you haven't already you might want to take a look at it to see if it helps your implementation.

[lacteolus]

You should be able to talk to Greengrass v2 from any process - as long as you know the path to the local socket and the authtoken. Both are available as environment variable: AWS_GG_NUCLEUS_DOMAIN_SOCKET_FILEPATH_FOR_COMPONENT and SVCUID.

I did a quick test with a different non-root Linux user and a regular python process started from my shell (instead of a component deployed through GGv2). And it works.

See this PR for an example and an improved / simplified connection creation: #144

What is a proper way of getting these environment variables? As I understand they are only available within GG environment. AWS_GG_NUCLEUS_DOMAIN_SOCKET_FILEPATH_FOR_COMPONENT is static so it can be merely hardcoded in external script. Is SVCUID generated once GG software is installed or is it updated automatically and periodically?
And a few additional issues:

1. When ipc_greengrass.py example runs as standalone process (not as a component) with those two variables provided, it raises awsiot.greengrasscoreipc.model.UnauthorizedError error when it tries to publish a message. Connection itself is established successfully.
2. try: result = op.get_response().result(timeout=5.0) print("successfully published message:", result) except Exception as e: print("failed to publish message:", e) code doesn't show any exeption details. Just a Failed to publish message:
3. Can be this ipc_greengrass.py example be used as a lamda component? It seems that in this case it is also unable to publish messages to IoT core topic.

[jmklix]

Copy from aws forums:

Hi,

3 (Using IPC and internal GG topics directly) should not be used as your are basically breaking the Greengrass authentication and authorization system's intent. It certainly can be done that way, but I would really caution against it. Either # 1 or # 2 makes the most sense to me; so much sense in fact that we've already implemented an example of this solution https://github.com/aws-greengrass/aws-greengrass-component-examples/tree/main/mqtt-bridge.
This example code must be treated exactly as that, an example. It does not implement any security above username+password and has very minimal error handling. You can have a look at it to give you a head start, but I would tell you to not deploy it as-is into a production environment as it has not been tested to those standards.

Hope that helps,
Michael Dombrowski