How to configure an Expectation store in Amazon S3

By default, newly profiled Expectations are stored in JSON format in the expectations/ subdirectory of your great_expectations/ folder. This guide will help you configure Great Expectations to store them in an Amazon S3 bucket.

Prerequisites: This how-to guide assumes that you have already:

  • Configured a Data Context.

  • Configured an Expectations Suite.

  • Installed boto3 in your local environment.

  • Identified the S3 bucket and prefix where Expectations will be stored.

Steps

  1. Configure boto3 to connect to the Amazon S3 bucket where Expectations will be stored.

    Instructions on how to set up boto3 with AWS can be found at boto3’s documentation site.

  2. Identify your Data Context Expectations Store

    In your great_expectations.yml , look for the following lines. The configuration tells Great Expectations to look for Expectations in a store called expectations_store. The base_directory for expectations_store is set to expectations/ by default.

    expectations_store_name: expectations_store
    
    stores:
        expectations_store:
            class_name: ExpectationsStore
            store_backend:
                class_name: TupleFilesystemStoreBackend
                base_directory: expectations/
    
  3. Update your configuration file to include a new store for Expectations on S3.

    In our case, the name is set to expectations_S3_store, but it can be any name you like. We also need to make some changes to the store_backend settings. The class_name will be set to TupleS3StoreBackend, bucket will be set to the address of your S3 bucket, and prefix will be set to the folder where Expectation files will be located.

    Warning

    If you are also storing Validations in S3 or DataDocs in S3, please ensure that the prefix values are disjoint and one is not a substring of the other.

    expectations_store_name: expectations_S3_store
    
    stores:
        expectations_S3_store:
            class_name: ExpectationsStore
            store_backend:
                class_name: TupleS3StoreBackend
                bucket: '<your_s3_bucket_name>'
                prefix: '<your_s3_bucket_folder_name>'
    
  4. Copy existing Expectation JSON files to the S3 bucket. (This step is optional).

    One way to copy Expectations into Amazon S3 is by using the aws s3 sync command. As mentioned earlier, the base_directory is set to expectations/ by default. In the example below, two Expectations, exp1 and exp2 are copied to Amazon S3. Your output should looks something like this:

    aws s3 sync '<base_directory>' s3://'<your_s3_bucket_name>'/'<your_s3_bucket_folder_name>'
    
    upload: ./exp1.json to s3://'<your_s3_bucket_name>'/'<your_s3_bucket_folder_name>'/exp1.json
    upload: ./exp2.json to s3://'<your_s3_bucket_name>'/'<your_s3_bucket_folder_name>'/exp2.json
    
  5. Confirm that the new Expectations store has been added by running great_expectations store list.

    Notice the output contains two Expectation stores: the original expectations_store on the local filesystem and the expectations_S3_store we just configured. This is ok, since Great Expectations will look for Expectations in the S3 bucket as long as we set the expectations_name variable to expectations_S3_store.

    great_expectations store list
    
    - name: expectations_store
    class_name: ExpectationsStore
    store_backend:
        class_name: TupleFilesystemStoreBackend
        base_directory: expectations/
    
    - name: expectations_S3_store
    class_name: ExpectationsStore
    store_backend:
        class_name: TupleS3StoreBackend
        bucket: '<your_s3_bucket_name>'
        prefix: '<your_s3_bucket_folder_name>'
    
  6. Confirm that Expectations can be accessed from Amazon S3 by running great_expectations suite list.

    If you followed Step 4, The output should include the 2 Expectations we copied to Amazon S3: exp1 and exp2. If you did not copy Expectations to the new Store, you will see a message saying no expectations were found.

    great_expectations suite list
    
    2 Expectation Suites found:
     - exp1
     - exp2
    

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