cancel
Showing results forย 
Search instead forย 
Did you mean:ย 
Data Engineering
Join discussions on data engineering best practices, architectures, and optimization strategies within the Databricks Community. Exchange insights and solutions with fellow data engineers.
cancel
Showing results forย 
Search instead forย 
Did you mean:ย 

Databricks Expectations

youcanlearn
New Contributor III

In the example in https://docs.databricks.com/en/delta-live-tables/expectations.html#fail-on-invalid-records, it wrote that one is able to query the DLT event log for such expectations violation. 

In Databricks, I can use expectation to fail or drop records, but how do I capture the reasons (expectations violated) for each of the record dropped/failed?

Expectation Violated:
{
  "flowName": "a-b",
  "verboseInfo": {
    "expectationsViolated": [
      "x1 is negative"
    ],
    "inputData": {
      "a": {"x1": 1,"y1": "a },
      "b": {
        "x2": 1,
        "y2": "aa"
      }
    },
    "outputRecord": {
      "x1": 1,
      "y1": "a",
      "x2": 1,
      "y2": "aa"
    },
    "missingInputData": false
  }
}

 

2 ACCEPTED SOLUTIONS

Accepted Solutions

brockb
Valued Contributor

Hi @youcanlearn,

This information would be written to `log4j.txt` as part of a stack trace when the expectation is created with one of the `fail` expectation operators (e.g. `expect_or_fail`). When a failure occurs, you would see a `Caused by` log message such as:

Caused by: java.lang.RuntimeException: Expectation violated: {"flowName":"dlt_autoloader_csv_test","verboseInfo":{"expectationsViolated":["valid_max_length"],"inputData":{},"outputRecord":{"col1":"12345678901234567890123456789","col2":"two","_rescued_data":null},"missingInputData":false}}

...which contains a JSON payload such as the one referenced in the docs you linked to.

Additionally, you could find the stack trace with the same messaging in the Event Log within the `error.exceptions` array.

Hope this helps.

View solution in original post

brockb
Valued Contributor

That's right, the "reason" would be "x1 is negative" in your example and "valid_max_length" in the example JSON payload that I shared.

If you are looking for a descriptive reason, you would name the expectation accordingly such as:

@Dlt.expect_or_fail("this expectation will fail because of reason1 and reason2", "count > 0")

 

View solution in original post

3 REPLIES 3

brockb
Valued Contributor

Hi @youcanlearn,

This information would be written to `log4j.txt` as part of a stack trace when the expectation is created with one of the `fail` expectation operators (e.g. `expect_or_fail`). When a failure occurs, you would see a `Caused by` log message such as:

Caused by: java.lang.RuntimeException: Expectation violated: {"flowName":"dlt_autoloader_csv_test","verboseInfo":{"expectationsViolated":["valid_max_length"],"inputData":{},"outputRecord":{"col1":"12345678901234567890123456789","col2":"two","_rescued_data":null},"missingInputData":false}}

...which contains a JSON payload such as the one referenced in the docs you linked to.

Additionally, you could find the stack trace with the same messaging in the Event Log within the `error.exceptions` array.

Hope this helps.

youcanlearn
New Contributor III

Hi @brockb,

I wanted to allow each failed record to have a "reason" for being rejected/failed. Is this the best way for me to capture the "reason"?

brockb
Valued Contributor

That's right, the "reason" would be "x1 is negative" in your example and "valid_max_length" in the example JSON payload that I shared.

If you are looking for a descriptive reason, you would name the expectation accordingly such as:

@Dlt.expect_or_fail("this expectation will fail because of reason1 and reason2", "count > 0")

 

Connect with Databricks Users in Your Area

Join a Regional User Group to connect with local Databricks users. Events will be happening in your city, and you wonโ€™t want to miss the chance to attend and share knowledge.

If there isnโ€™t a group near you, start one and help create a community that brings people together.

Request a New Group