How to configure an Expectation store in GCS¶
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 a Google Cloud Storage (GCS) bucket.
Prerequisites: This how-to guide assumes that you have already:
Configure your GCP credentials
Check that your environment is configured with the appropriate authentication credentials needed to connect to the GCS bucket where Expectations will be stored.
The Google Cloud Platform documentation describes how to verify your authentication for the Google Cloud API, which includes:
Creating a Google Cloud Platform (GCP) service account,
Verifying authentication by running a simple Google Cloud Storage client library script.
Identify your Data Context Expectations Store
great_expectations.yml, look for the following lines. The configuration tells Great Expectations to look for Expectations in a store called
expectations_storeis set to
expectations_store_name: expectations_store stores: expectations_store: class_name: ExpectationsStore store_backend: class_name: TupleFilesystemStoreBackend base_directory: expectations/
Update your configuration file to include a new store for Expectations on GCS
In our case, the name is set to
expectations_GCS_store, but it can be any name you like. We also need to make some changes to the
class_namewill be set to
projectwill be set to your GCP project,
bucketwill be set to the address of your GCS bucket, and
prefixwill be set to the folder on GCS where Expectation files will be located.
expectations_store_name: expectations_GCS_store stores: expectations_GCS_store: class_name: ExpectationsStore store_backend: class_name: TupleGCSStoreBackend project: '<your_GCP_project_name>' bucket: '<your_GCS_bucket_name>' prefix: '<your_GCS_folder_name>'
Copy existing Expectation JSON files to the GCS bucket. (This step is optional).
One way to copy Expectations into GCS is by using the
gsutil cpcommand, which is part of the Google Cloud SDK. The following example will copy one Expectation,
exp1from a local folder to the GCS bucket. Information on other ways to copy Expectation JSON files, like the Cloud Storage browser in the Google Cloud Console, can be found in the Documentation for Google Cloud.
gsutil cp exp1.json gs://'<your_GCS_bucket_name>'/'<your_GCS_folder_name>' Operation completed over 1 objects/58.8 KiB.
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_storeon the local filesystem and the
expectations_GCS_storewe just configured. This is ok, since Great Expectations will look for Expectations in GCS as long as we set the
expectations_GCS_store, and the config for
expectations_storecan be removed if you would like.
great_expectations store list - name: expectations_store class_name: ExpectationsStore store_backend: class_name: TupleFilesystemStoreBackend base_directory: expectations/ - name: expectations_GCS_store class_name: ExpectationsStore store_backend: class_name: TupleGCSStoreBackend project: '<your_GCP_project_name>' bucket: '<your_GCS_bucket_name>' prefix: '<your_GCS_folder_name>'
Confirm that Expectations can be accessed from GCS by running
great_expectations suite list.
If you followed Step 4, the output should include the Expectation we copied to GCS:
exp1. If you did not copy Expectations to the new Store, you will see a message saying no Expectations were found.
great_expectations suite list 1 Expectation Suite found: - exp1
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