Greengrass Lambda failing to start due to log pipe blocked

Question

One of my lambda components is failing to start on an IOT device. Another IOT device received the lambda and it is triggering as expected. The first deployment worked (new IOT device) then subsequent ones failed with the same issues listed below. All the lambda does is log a message when it receives an event on a PUB/SUB topic (testing something out) using Python logger.

The errors I see in the logs (amongst others) are:
* Refusing to execute because the active thread is interrupted
* Error while waiting for LogHandler to fully shutdown.
* Lambda log pipe /opt/greengrass/v2/work/xxxxx/logs/2/warn is blocked, attempting to unblock

Things I've tried:
* I've tried a "reset" on the configuration and deployed a new version of the component, but this doesn't fix the issue.
* I've rebooted the nucleus (running as a service), which also does nothing to the lambda

Any clues as to what's going on and what caused this?

Thanks!

Accepted Answer

If you are starting a new deployment on Greengrass V2 I would advice to use Generic components and not Lambda Functions components.

A generic component is simpler to write and debug and can more easily access devices resources if needed (such as cameras, etc).

All you need to do to trigger some logic on the reception of a message is to create a subscription to the pubsub topic and write the corresponding handler. You can refer to this sample code (from https://docs.aws.amazon.com/greengrass/v2/developerguide/ipc-publish-subscribe.html#ipc-publish-subscribe-examples)

```python
import time
import traceback

from awsiot.greengrasscoreipc.clientv2 import GreengrassCoreIPCClientV2
from awsiot.greengrasscoreipc.model import (
    SubscriptionResponseMessage,
    UnauthorizedError
)

def main():
    topic = 'my/topic';

try:
        ipc_client = GreengrassCoreIPCClientV2()
        # Subscription operations return a tuple with the response and the operation.
        _, operation = ipc_client.subscribe_to_topic(topic=topic, on_stream_event=on_stream_event,
                                                     on_stream_error=on_stream_error)
        print('Successfully subscribed to topic: ' + topic)

# Keep the main thread alive, or the process will exit.
        try:
            while True:
                time.sleep(10)
        except InterruptedError:
            print('Subscribe interrupted.')

# To stop subscribing, close the stream.
        operation.close()
    except UnauthorizedError:
        print('Unauthorized error while subscribing to topic: ' +
              topic, file=sys.stderr)
        traceback.print_exc()
        exit(1)
    except Exception:
        print('Exception occurred', file=sys.stderr)
        traceback.print_exc()
        exit(1)

def on_stream_event(event: SubscriptionResponseMessage) -> None:
    try:
        message = str(event.binary_message.message, 'utf-8')
        topic = event.binary_message.context.topic
        print('Received new message on topic %s: %s' % (topic, message))
    except:
        traceback.print_exc()

def on_stream_error(error: Exception) -> bool:
    print('Received a stream error.', file=sys.stderr)
    traceback.print_exc()
    return False  # Return True to close stream, False to keep stream open.

if __name__ == '__main__':
    main()
```

Greengrass Lambda failing to start due to log pipe blocked

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