Documentation, examples in README for how to import from S3 to Scylla

[wpaven]

This capability was added in #136 but what needs to be done to make it work? Can we have some documentation please? Sample config.yaml, sample spark-submit, any considerations for the S3 bucket, etc. would be very useful. And any limitations? Import only works with JSON exports correct?

[julienrf]

For now we have documentation in the file config.yaml.example:

scylla-migrator/config.yaml.example

Lines 91 to 122 in ab59858

	# Example for loading from a DynamoDB S3 export (see https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/S3DataExport.Output.html)
	# source:
	# type: dynamodb-s3-export
	# bucket: <bucket-name>
	# # Key of the `manifest-summary.json` object in the bucket
	# manifestKey: <manifest-summary-key>
	# # Key schema and attribute definitions, see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_TableCreationParameters.html
	# tableDescription:
	# attributeDefinitions:
	# - name: <attribute-name>
	# type: <attribute-type> (see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_AttributeDefinition.html)
	# - ...
	# keySchema:
	# - name: <key-name>
	# type: <key-type> (see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_KeySchemaElement.html)
	# - ...
	#
	# # Optional - load from a custom endpoint:
	# endpoint:
	# # Specify the hostname without a protocol
	# host: <host>
	# port: <port>
	# # Optional - specify the region:
	# region: <region>
	#
	# # Optional - static credentials:
	# credentials:
	# accessKey: <user>
	# secretKey: <pass>
	#
	# # Optional - use path-style access in S3 (see https://docs.aws.amazon.com/AmazonS3/latest/userguide/VirtualHosting.html)
	# usePathStyleAccess: true

I will publish the docs on the website soon (related: #116)

[wpaven]

Do you have a sample config.yaml that you can share with me until the docs are published please? I have questions, like is the bucket name the arn resource name for the bucket? Seeing an example of the formats for these attributes would be very helpful.

[wpaven]

thanks @julienrf for pointing out the config.yaml example in the test config https://github.com/scylladb/scylla-migrator/blob/master/tests/src/test/configurations/dynamodb-s3-export-to-alternator-basic.yaml