Log snapshots

Run evaluations and send the results.

To visualize data in the Evidently ML monitoring interface, you must capture data and model metrics as Evidently JSON snapshots.

What is snapshot?

Snapshots are JSON summaries of data and model performance for a given period. They contain metrics, data summaries, test results, and supporting render data. You pick what exactly goes in a snapshot: this also determines what you can alert on.

By sending multiple snapshots to the Project (e.g., hourly, daily, or weekly), you create a data source for monitoring Panels. You can plot trends over time by parsing values from individual snapshots.

You can:

  • Send the snapshots sequentially (e.g., hourly or daily data summaries).

  • Send one-off snapshots after specific evaluations (e.g., results of CI/CD checks).

  • Backdate your snapshots (e.g., log model quality after you get the labels).

  • Add multiple snapshots for the same period (e.g., for shadow and production models).

Snapshots vs. Reports. The snapshot functionality is directly based on the Evidently Reports and Test Suites. Put simply, a snapshot is a JSON "version" of the Evidently Report or Test Suite. To learn the basics, check the Get Started Tutorial or a Report and Test Suite User Guide. Browse Presets, Metrics and Tests to see available checks.

How it works

Here is the general workflow.

1. Connect to a Project in your workspace where you want to send the snapshots.

project = ws.get_project("PROJECT_ID")

2. Define and compute a snapshot.

  • Create a Report or Test Suite object. Define the metrics or tests.

  • Pass the current dataset you want to evaluate or profile.

  • Optional: pass the column_mapping to define the data schema. (Required for model quality or text data checks to map target, prediction, text columns, etc.).

  • Optional: pass the reference dataset. (Required for drift data drift checks).

  • Optional: pass parameters for metric calculations and/or test conditions.

For monitoring, you can also add tags and timestamp to your snapshots.

  1. Send the snapshot. After you compute the Report or Test Suite, use the add_report or add_test_suite methods to send them to a corresponding Project in your workspace.

Collector service. To compute snapshots in near real-time, you can also configure a collector service.

Send snapshots

Send a Report. To create and send a Report with data summaries for a single dataset batch1:

data_report = Report(
data_report.run(reference_data=None, current_data=batch1)
ws.add_report(project.id, data_report)

Send a Test Suite. To create and send Test Suite with data drift checks, passing current and reference data:

drift_checks = TestSuite(tests=[
drift_checks.run(reference_data=reference_batch, current_data=batch1)
ws.add_test_suite(project.id, drift_checks)

Send a snapshot. The add_report or add_test_suite methods generate snapshots automatically. If you already have a snapshot (e.g., a previously saved Report), you can load it to Python and add to your Project:

ws.add_snapshot(project.id, snapshot.load("data_drift_snapshot.json"))

Snapshot size. A single upload to Evidently Cloud should not exceed 50MB for free trial users or 500MB for Pro plan. This limitation applies to the size of the resulting JSON, not the dataset itself. For example, a data drift report for 50 columns and 10,000 rows of current and reference data results in a snapshot of approximately 1MB. (For 100 columns x 10,000 rows: ~ 3.5MB; for 100 columns x 100,000 rows: ~ 9MB). However, the size varies depending on the metrics or tests used.

Add timestamp

Each snapshot is associated with a single timestamp. By default, Evidently will assign the datetime.now() using the Report/Test Suite computation time based on the user time zone.

You can also add your own timestamp:

data_drift_report = Report(

Evidently won't automatically use DateTime columns from your data. You can manually specify the snapshot timestamp to match the last value of the DateTime column in your dataset:

data_drift_report = Report(

Since you can assign arbitrary timestamps, you can log snapshots asynchronously or with a delay (for example, after you receive ground truth).

Add tags and metadata

You can include tags and metadata in snapshots. This is useful for search and data filtering for monitoring Panels.

Examples of when to use tags include:

  • You have production/shadow or champion/challenger models.

  • You compute snapshots with different reference datasets (for example, to compare distribution drift week-by-week and month-by-month).

  • You have data for multiple models of the same type inside a Project.

  • You capture snapshots for multiple segments in your data.

  • You want to tag individual Reports in a Project, e.g., datasheet card, a model card, etc.

Custom tags. Pass any custom Tags as a list:

data_drift_report = Report(
	tags=["groupA", "shadow"],

Custom metadata. Pass metadata as a Python dictionary in key:value pairs:

data_drift_report = Report(
	metadata = {
	"deployment": "shadow",
	"status": "production",

Default metadata. Use built-in metadata fields model_id, reference_id, batch_size, dataset_id:

data_drift_report = Report(

Add Tags to existing Reports.. You can add Tags to a previously generated Report or Test Suite:


Delete snapshots

To delete snapshots in the Workspace ws, pass the Project ID and snapshot ID. You can see the snapshot ID on the Report or Test Suite page.

ws.delete_snapshot(project_id, snapshot_id)

What's next?

Once you've sent data to the Project, you can add monitoring Panels and Tabs.

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