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description: This page provides an overview of working with DataHub Volume Assertions | ||
--- | ||
import FeatureAvailability from '@site/src/components/FeatureAvailability'; | ||
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# Volume Assertions | ||
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<FeatureAvailability saasOnly /> | ||
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> ⚠️ The **Volume Assertions** feature is currently in private beta, part of the **Acryl Observe** module, and may only be available to a | ||
> limited set of design partners. | ||
> | ||
> If you are interested in trying it and providing feedback, please reach out to your Acryl Customer Success | ||
> representative. | ||
## Introduction | ||
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Can you remember a time when the meaning of Data Warehouse Table that you depended on fundamentally changed, with little or no notice? | ||
If the answer is yes, how did you find out? We'll take a guess - someone looking at an internal reporting dashboard or worse, a user using your your product, sounded an alarm when | ||
a number looked a bit out of the ordinary. Perhaps your table initially tracked purchases made on your company's e-commerce web store, but suddenly began to include purchases made | ||
through your company's new mobile app. | ||
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There are many reasons why an important Table on Snowflake, Redshift, or BigQuery may change in its meaning - application code bugs, new feature rollouts, | ||
changes to key metric definitions, etc. Often times, these changes break important assumptions made about the data used in building key downstream data products | ||
like reporting dashboards or data-driven product features. | ||
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What if you could reduce the time to detect these incidents, so that the people responsible for the data were made aware of data | ||
issues _before_ anyone else? With Acryl DataHub **Volume Assertions**, you can. | ||
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Acryl DataHub allows users to define expectations about the normal volume, or size, of a particular warehoues Table, | ||
and then monitor those expectations over time as the table grows and changes. | ||
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In this article, we'll cover the basics of monitoring Volume Assertions - what they are, how to configure them, and more - so that you and your team can | ||
start building trust in your most important data assets. | ||
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Let's get started! | ||
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## Support | ||
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Volume Assertions are currently supported for: | ||
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1. Snowflake | ||
2. Redshift | ||
3. BigQuery | ||
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Note that an Ingestion Source _must_ be configured with the data platform of your choice in Acryl DataHub's **Ingestion** | ||
tab. | ||
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> Note that Volume Assertions are not yet supported if you are connecting to your warehouse | ||
> using the DataHub CLI or a Remote Ingestion Executor. | ||
## What is a Volume Assertion? | ||
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A **Volume Assertion** is a configurable Data Quality rule used to monitor a Data Warehouse Table | ||
for unexpected or sudden changes in "volume", or row count. Volume Assertions can be particularly useful when you have frequently-changing | ||
Tables which have a relatively stable pattern of growth or decline. | ||
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For example, imagine that we work for a company with a Snowflake Table that stores user clicks collected from our e-commerce website. | ||
This table is updated with new data on a specific cadence: once per hour (In practice, daily or even weekly are also common). | ||
In turn, there is a downstream Business Analytics Dashboard in Looker that shows important metrics like | ||
the number of people clicking our "Daily Sale" banners, and this dashboard is generated from data stored in our "clicks" table. | ||
It is important that our clicks Table is updated with the correct number of rows each hour, else it could mean | ||
that our downstream metrics dashboard becomes incorrect. The risk of this situation is obvious: our organization | ||
may make bad decisions based on incomplete information. | ||
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In such cases, we can use a **Volume Assertion** that checks whether the Snowflake "clicks" Table is growing in an expected | ||
way, and that there are no sudden increases or sudden decreases in the rows being added or removed from the table. | ||
If too many rows are added or removed within an hour, we can notify key stakeholders and begin to root cause before the problem impacts stakeholders of the data. | ||
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### Anatomy of a Volume Assertion | ||
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At the most basic level, **Volume Assertions** consist of a few important parts: | ||
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1. An **Evaluation Schedule** | ||
2. A **Volume Condition** | ||
2. A **Volume Source** | ||
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In this section, we'll give an overview of each. | ||
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#### 1. Evaluation Schedule | ||
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The **Evaluation Schedule**: This defines how often to check a given warehouse Table for its volume. This should usually | ||
be configured to match the expected change frequency of the Table, although it can also be less frequently depending | ||
on the requirements. You can also specify specific days of the week, hours in the day, or even | ||
minutes in an hour. | ||
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#### 2. Volume Condition | ||
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The **Volume Condition**: This defines the type of condition that we'd like to monitor, or when the Assertion | ||
should result in failure. | ||
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There are a 2 different categories of conditions: **Total** Volume and **Change** Volume. | ||
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_Total_ volume conditions are those which are defined against the point-in-time total row count for a table. They allow you to specify conditions like: | ||
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1. **Table has too many rows**: The table should always have less than 1000 rows | ||
2. **Table has too few rows**: The table should always have more than 1000 rows | ||
3. **Table row count is outside a range**: The table should always have between 1000 and 2000 rows. | ||
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_Change_ volume conditions are those which are defined against the growth or decline rate of a table, measured between subsequent checks | ||
of the table volume. They allow you to specify conditions like: | ||
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1. **Table growth is too fast**: When the table volume is checked, it should have < 1000 more rows than it had during the previous check. | ||
2. **Table growth is too slow**: When the table volume is checked, it should have > 1000 more rows than it had during the previous check. | ||
3. **Table growth is outside a range**: When the table volume is checked, it should have between 1000 and 2000 more rows than it had during the previous check. | ||
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For change volume conditions, both _absolute_ row count deltas and relative percentage deltas are supported for identifying | ||
table that are following an abnormal pattern of growth. | ||
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#### 3. Volume Source | ||
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The **Volume Source**: This is the mechanism that Acryl DataHub should use to determine the table volume (row count). The supported | ||
source types vary by the platform, but generally fall into these categories: | ||
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- **Information Schema**: A system Table that is exposed by the Data Warehouse which contains live information about the Databases | ||
and Tables stored inside the Data Warehouse, including their row count. It is usually efficient to check, but can in some cases be slightly delayed to update | ||
once a change has been made to a table. | ||
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- **Query**: A `COUNT(*)` query is used to retrieve the latest row count for a table, with optional SQL filters applied (depending on platform). | ||
This can be less efficient to check depending on the size of the table. This approach is more portable, as it does not involve | ||
system warehouse tables, it is also easily portable across Data Warehouse and Data Lake providers. | ||
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Volume Assertions also have an off switch: they can be started or stopped at any time with the click of button. | ||
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## Creating a Volume Assertion | ||
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### Prerequisites | ||
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1. **Permissions**: To create or delete Volume Assertions for a specific entity on DataHub, you'll need to be granted the | ||
`Edit Assertions` and `Edit Monitors` privileges for the entity. This is granted to Entity owners by default. | ||
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2. **Data Platform Connection**: In order to create a Volume Assertion, you'll need to have an **Ingestion Source** configured to your | ||
Data Platform: Snowflake, BigQuery, or Redshift under the **Integrations** tab. | ||
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Once these are in place, you're ready to create your Volume Assertions! | ||
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### Steps | ||
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1. Navigate to the Table that to monitor for volume | ||
2. Click the **Validations** tab | ||
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<p align="center"> | ||
<img width="90%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/freshness/profile-validation-tab.png"/> | ||
</p> | ||
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3. Click **+ Create Assertion** | ||
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<p align="center"> | ||
<img width="90%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/volume/assertion-builder-volume-choose-type.png"/> | ||
</p> | ||
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4. Choose **Volume** | ||
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5. Configure the evaluation **schedule**. This is the frequency at which the assertion will be evaluated to produce a pass or fail result, and the times | ||
when the table volume will be checked. | ||
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6. Configure the evaluation **condition type**. This determines the cases in which the new assertion will fail when it is evaluated. | ||
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<p align="center"> | ||
<img width="45%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/volume/assertion-builder-volume-condition-type.png"/> | ||
</p> | ||
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7. (Optional) Click **Advanced** to customize the volume **source**. This is the mechanism that will be used to obtain the table | ||
row count metric. Each Data Platform supports different options including Information Schema and Query. | ||
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<p align="center"> | ||
<img width="45%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/volume/assertion-builder-volume-select-source-type.png"/> | ||
</p> | ||
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- **Information Schema**: Check the Data Platform system metadata tables to determine the table row count. | ||
- **Query**: Issue a `COUNT(*)` query to the table to determine the row count. | ||
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8. Click **Next** | ||
9. Configure actions that should be taken when the Volume Assertion passes or fails | ||
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<p align="left"> | ||
<img width="45%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/freshness/assertion-builder-actions.png"/> | ||
</p> | ||
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- **Raise incident**: Automatically raise a new DataHub `Volume` Incident for the Table whenever the Volume Assertion is failing. This | ||
may indicate that the Table is unfit for consumption. Configure Slack Notifications under **Settings** to be notified when | ||
an incident is created due to an Assertion failure. | ||
- **Resolve incident**: Automatically resolved any incidents that were raised due to failures in this Volume Assertion. Note that | ||
any other incidents will not be impacted. | ||
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10. Click **Save**. | ||
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And that's it! DataHub will now begin to monitor your Volume Assertion for the table. | ||
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To view the time of the next Volume Assertion evaluation, simply click **Volume** and then click on your | ||
new Assertion: | ||
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<p align="center"> | ||
<img width="40%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/freshness/assertion-next-evaluation-time.png"/> | ||
</p> | ||
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Once your assertion has run, you will begin to see Success or Failure status for the Table | ||
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<p align="center"> | ||
<img width="90%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/volume/profile-passing-volume-assertions-expanded.png"/> | ||
</p> | ||
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## Stopping a Volume Assertion | ||
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In order to temporarily stop the evaluation of a Volume Assertion: | ||
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1. Navigate to the **Validations** tab of the Table with the assertion | ||
2. Click **Volume** to open the Volume Assertions list | ||
3. Click the three-dot menu on the right side of the assertion you want to disable | ||
4. Click **Stop** | ||
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<p align="left"> | ||
<img width="25%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/freshness/manage-assertion-menu.png"/> | ||
</p> | ||
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To resume the Volume Assertion, simply click **Turn On**. | ||
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<p align="center"> | ||
<img width="90%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/freshness/stopped-assertion.png"/> | ||
</p> | ||
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## Smart Assertions ⚡ | ||
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As part of the **Acryl Observe** module, Acryl DataHub also provides **Smart Assertions** out of the box. These are | ||
dynamic, AI-powered Volume Assertions that you can use to monitor the volume of important warehouse Tables, without | ||
requiring any manual setup. | ||
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If Acryl DataHub is able to detect a pattern in the volume of a Snowflake, Redshift, or BigQuery Table, you'll find | ||
a recommended Smart Assertion under the `Validations` tab on the Table profile page: | ||
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<p align="center"> | ||
<img width="90%" src="https://raw.githubusercontent.com/datahub-project/static-assets/main/imgs/observe/freshness/smart-assertion.png"/> | ||
</p> | ||
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In order to enable it, simply click **Turn On**. From this point forward, the Smart Assertion will check for changes on a cadence | ||
based on the Table history. | ||
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Don't need it anymore? Smart Assertions can just as easily be turned off by clicking the three-dot "more" button and then **Stop**. | ||
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## Creating Volume Assertions via API | ||
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Under the hood, Acryl DataHub implements Volume Assertion Monitoring using two "entity" concepts: | ||
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- **Assertion**: The specific expectation for volume, e.g. "The table was changed int the past 7 hours" | ||
or "The table is changed on a schedule of every day by 8am". This is the "what". | ||
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- **Monitor**: The process responsible for evaluating the Assertion on a given evaluation schedule and using specific | ||
mechanisms. This is the "how". | ||
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Note that to create or delete Assertions and Monitors for a specific entity on DataHub, you'll need the | ||
`Edit Assertions` and `Edit Monitors` privileges for it. | ||
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#### GraphQL | ||
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In order to create a Volume Assertion that is being monitored on a specific **Evaluation Schedule**, you'll need to use 2 | ||
GraphQL mutation queries to create a Volume Assertion entity and create an Assertion Monitor entity responsible for evaluating it. | ||
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Start by creating the Volume Assertion entity using the `createVolumeAssertion` query and hang on to the 'urn' field of the Assertion entity | ||
you get back. Then continue by creating a Monitor entity using the `createAssertionMonitor`. | ||
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##### Examples | ||
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To create a Volume Assertion Entity that checks whether a table has been updated in the past 8 hours: | ||
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```json | ||
mutation createVolumeAssertion { | ||
createVolumeAssertion( | ||
input: { | ||
entityUrn: "<urn of the table to be monitored>" | ||
type: DATASET_CHANGE | ||
schedule: { | ||
type: FIXED_INTERVAL | ||
fixedInterval: { unit: HOUR, multiple: 8 } | ||
} | ||
} | ||
) { | ||
urn | ||
} | ||
} | ||
``` | ||
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To create an Assertion Monitor Entity that evaluates the volume assertion every 8 hours using the Information Schema: | ||
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```json | ||
mutation createAssertionMonitor { | ||
createAssertionMonitor( | ||
input: { | ||
entityUrn: "<urn of entity being monitored>", | ||
assertionUrn: "<urn of assertion created in first query>", | ||
schedule: { | ||
cron: "0 */8 * * *", | ||
timezone: "America/Los_Angeles" | ||
}, | ||
parameters: { | ||
type: DATASET_VOLUME, | ||
datasetVolumeParameters: { | ||
sourceType: INFORMATION_SCHEMA, | ||
} | ||
} | ||
} | ||
) { | ||
urn | ||
} | ||
} | ||
``` | ||
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This entity defines _when_ to run the check (Using CRON format - every 8th hour) and _how_ to run the check (using the Information Schema). | ||
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After creating the monitor, the new assertion will start to be evaluated every 8 hours in your selected timezone. | ||
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You can delete assertions along with their monitors using GraphQL mutations: `deleteAssertion` and `deleteMonitor`. | ||
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### Tips | ||
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:::info | ||
**Authorization** | ||
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Remember to always provide a DataHub Personal Access Token when calling the GraphQL API. To do so, just add the 'Authorization' header as follows: | ||
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``` | ||
Authorization: Bearer <personal-access-token> | ||
``` | ||
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**Exploring GraphQL API** | ||
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Also, remember that you can play with an interactive version of the Acryl GraphQL API at `https://your-account-id.acryl.io/api/graphiql` | ||
::: |