How can I create a sensor that watches an S3 bucket for a new file and then kicks of an asset materialization for that new asset?

To create a sensor that watches an S3 bucket for a new file and then kicks off an asset materialization, you can use Dagster's sensor functionality. Sensors in Dagster are used to run a job or materialize an asset in response to specific events, such as a new file arriving in a specific location like an Amazon S3 bucket. Here's a high-level overview of the steps you would take to create such a sensor, based on the documentation: 1. Define a sensor function that checks the S3 bucket for new files. You can use the

boto3

library (AWS SDK for Python) to interact with the S3 bucket and list objects to detect new files. 2. In the sensor function, compare the list of files in the bucket with a stored cursor or timestamp to determine if there are new files since the last check. 3. If new files are detected, create a

RunRequest

for each new file. The

RunRequest

should include the necessary

run_config

to specify the file to be processed and any other relevant job configuration. 4. Associate the sensor with a job that materializes the asset. The job should be defined to handle the processing of the file and materialize the asset as needed. 5. Deploy the sensor so that it periodically checks the S3 bucket and triggers the job when new files are found. The documentation provides an example of a sensor that monitors S3 keys and triggers runs based on new keys detected. While the documentation does not provide a complete code example specifically for watching an S3 bucket and triggering an asset materialization, you can use the concepts and methods described in the Sensors documentation to implement this functionality. Please note that the specifics of the sensor's implementation, such as how to interact with S3, how to define the job, and how to configure the

RunRequest

, will depend on your particular use case and the structure of your Dagster project. If you need a more detailed example or guidance, you may want to refer to the Sensors documentation and the examples provided there.

Could you show me an example code for this?