AWS SageMaker - What is Channel?

What is exactly channel in AWS SageMaker?

SageMaker Documentation - Channel

A channel is a named input source that training algorithms can consume.

Input Data Configuration

For example, suppose that you specify three data channels (train, evaluation, and validation) in your request.

Is it a location where data for either training or validation or test is stored? Or a mechanism such as UNIX pipe by which data is feed into SageMaker runtime for consumption?

Where is the term defined?

The Channel in the Sage Maker, is the source of the Input data for a training a machine learning model. Channels define how training data is fed into a SageMaker training job.

Lets Take the an example, You have two input channel (train and test): You will have 2 Environment variable

• SM_CHANNEL_TRAIN: For the path to the directory with input data for TRAIN Channel.
• Similarly for test (SM_CHANNEL_TEST).

Check this document for the variables of SM: https://github.com/aws/sagemaker-training-toolkit/blob/master/ENVIRONMENT_VARIABLES.md

Each channel specifies the following:

• Data Source – The location of the dataset (e.g., an Amazon S3 bucket).
• Content Type – The format of the data (e.g., CSV, JSON, Parquet, or RecordIO).
• Compression Type – Whether the data is compressed (e.g., None or Gzip).
• Input Mode – How SageMaker accesses the data:
  • File – Downloads the data to the training instance.
  • Pipe – Streams the data in real time (useful for large datasets).
• Record Wrapping (Optional) – Used for formats like RecordIO or TFRecord.

Ref Doc: https://docs.aws.amazon.com/sagemaker/latest/APIReference/API_Channel.html

Example Config for Channel:

training_channel = {
    "ChannelName": "train",
    "DataSource": {
        "S3DataSource": {
            "S3DataType": "S3Prefix",
            "S3Uri": "s3://your-bucket/train-data/",
            "S3DataDistributionType": "FullyReplicated",
        }
    },
    "ContentType": "text/csv",
    "CompressionType": "None",
    "InputMode": "File"
}

In short: The Channel is a way to define the source or path for the input data in Sage Maker