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02/18/2024, 12:21 PMScout
02/18/2024, 12:21 PMhandle_output
method to specify how and where to write data, and the load_input
method to specify how to retrieve that data for downstream steps.
In your scenario, you want the handle_output
method to write data to a specific path (e.g., repo/branch_asset/asset1
) and then attempt to merge it into another path (e.g., repo/develop/asset1
). If the merge is successful, the next step should read from the merged path.
To achieve this, you could implement custom logic within your I/O manager to handle the merge operation. After writing the data to the initial path in handle_output
, you would perform the merge operation. If the merge is successful, you would need to ensure that the load_input
method of the I/O manager knows to read from the new merged path (repo/develop/asset1
) for the subsequent steps.
Here's a simplified example based on the documentation's guidance on custom I/O managers:
python
from dagster import IOManager, OutputContext, InputContext
class MyCustomIOManager(IOManager):
def handle_output(self, context: OutputContext, obj):
# Write to the initial path
initial_path = f"repo/branch_asset/{context.asset_key.path}"
write_data_to_path(initial_path, obj)
# Attempt to merge into the develop path
develop_path = f"repo/develop/{context.asset_key.path}"
if merge_to_develop(initial_path, develop_path):
# If merge is successful, record the develop path for later retrieval
record_develop_path_for_retrieval(context, develop_path)
def load_input(self, context: InputContext):
# Retrieve the develop path recorded during handle_output
develop_path = retrieve_develop_path_for_retrieval(context)
return read_data_from_path(develop_path)
# Utility functions used by the IOManager
def write_data_to_path(path, data):
# Logic to write data to the specified path
pass
def merge_to_develop(initial_path, develop_path):
# Logic to merge data from initial_path to develop_path
# Return True if merge is successful, False otherwise
pass
def record_develop_path_for_retrieval(context, develop_path):
# Logic to record the develop path for later retrieval by load_input
pass
def retrieve_develop_path_for_retrieval(context):
# Logic to retrieve the develop path recorded by handle_output
pass
def read_data_from_path(path):
# Logic to read data from the specified path
pass
In this example, write_data_to_path
writes the data to the initial path, merge_to_develop
attempts to merge the data intoScout
02/18/2024, 12:21 PMrecord_develop_path_for_retrieval
records the develop path for later retrieval, and read_data_from_path
reads the data from the develop path. Please note that the actual implementation of the merge operation and the recording/retrieval of the develop path would depend on your specific use case and storage backend. You would need to ensure that the record_develop_path_for_retrieval
and retrieve_develop_path_for_retrieval
functions are capable of persisting and accessing the necessary information across different steps or runs of your pipeline. Keep in mind that this is a conceptual example, and you would need to adapt it to fit your specific requirements and the details of your storage system.