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Define errors and warnings

In the previous lesson, you learnt about error and warning operations. In this tutorial, you will use errors and warnings to perform validations in a live solution. You will:

  • define error, warning and log operations in a pipeline, and
  • launch a solution and observe the results.

This lesson will assume that you have an empty project and asset which you can to deploy to a workspace named 03_04_02_define_errors_and_warnings with the following command:

edk template deploy -ycw 03_04_02_define_errors_and_warnings

Define and deploy a template

To use the error() method you will first perform the following steps:

  1. define a datasource using a similar pattern as your previous My Source definition.
  2. add the datasource to a template

In an asset, perform the above steps to create the resulting Typescript code:

import { SourceBuilder, PipelineBuilder, Template, Add, Const } from "@elaraai/core";

const my_source = new SourceBuilder("My Source")
    .value({ value: 2n });

export default Template(my_source);

Define an error

To define an error on a datastream value, you use the error() method of PipelineBuilder(). As arguments, you provide a Typescript object with the properties

  • if where you define the BooleanType expression to be evaluated as the error logic, and
  • message where you define a custom message (as a StringType expression) to return should the if expression evaluate to False.

Both properties have the same in-scope variables available to be used in the expressions. The first variable that is available is the datastream value itself, and the second variable is a TypeScript object with properties for any and all additional input datastreams to the pipeline.

  1. add a new pipeline "My Pipeline"
  2. add an error() operation
  3. define the if condition, to create an error if the value is greater than 50
  4. define the message based on the value
  5. add the new pipeline to the template

In the definition My Pipeline add the above changes:

import { SourceBuilder, PipelineBuilder, Template, Add, Const, StringJoin, Greater } from "@elaraai/core";

const my_source = new SourceBuilder("My Source")
    .value({ value: 2n });

const my_pipeline = new PipelineBuilder("My Pipeline")
    .from(my_source.outputStream())
    .error({
        if: (stream) => Greater(stream, Const(50n)),
        message: (stream) => StringJoin`Require value less than 50, got ${stream}`,
    });

export default Template(my_source, my_pipeline);

Observe errors

Once deployed, you can test your error() by observing the task using the edk task logs command:

edk task logs "Pipeline.My Pipeline" -w 03_04_02_define_errors_and_warnings

Which will result in the logs below:

Listing task logs for Pipeline.My Pipeline available in tenant with identifier: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX and workspace 03_04_02_define_errors_and_warnings.


UUID                                 REASON              STATUS LEVEL MESSAGE                                                                                                           LOGGEDATE               
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition error  info  Worker XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX starting task instance XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX attempt 1 YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition error  info  Loading inputs ["input"]                                                                                          YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition error  info  Executing pipeline with 1 operations                                                                              YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition error  info  Performing assert operation                                                                                       YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition error  error Require value less than 50, got 55                                                                                YYYY-MM-DDTHH:MM:SS.MSZ

You can see from the output of edk task logs that the pipeline stopped running once it encountered the error.

Define a warning and log

To define a warning or log on a datastream value, you use the warn() and log() methods of PipelineBuilder(). Just like the error() method, you provide a Typescript object with the properties.

  • if where you define the BooleanType expression to be evaluated as the error logic for each entry of the collection, and
  • message where you define a custom message (as a StringType expression) to return should the if expression evaluate to False.

You can use warn() and log() by taking the following steps:

  1. add another pipeline "My Other Pipeline"
  2. add warn(), and log() operations
  3. for each define the if condition
  4. for each define the message based on the value
  5. add the new pipeline to the template

In the definition in a new pipeline My Other Pipeline add the above changes:

import { SourceBuilder, PipelineBuilder, Template, Add, Const, StringJoin, Greater } from "@elaraai/core";

const my_source = new SourceBuilder("My Source")
    .value({ value: 2n });

const my_pipeline = new PipelineBuilder("My Pipeline")
    .from(my_source.outputStream())
    .error({
        if: (stream) => Greater(stream, Const(50n)),
        message: (stream) => StringJoin`Require value less than 50, got ${stream}`,
    })

const my_other_pipeline = new PipelineBuilder("My Other Pipeline")
    .from(my_source.outputStream())
    .warn({
        if: (stream) => Greater(stream, Const(20n)),
        message: (stream) => StringJoin`Prefer value less than 20, got ${stream}`,
    })
    .log({
        if: (stream) => Greater(stream, Const(10n)),
        message: (stream) => StringJoin`Noticed value greater than 10, got ${stream}`,
    });

export default Template(my_source, my_pipeline, my_other_pipeline);

Observe warnings and logs

Once deployed, you can test your warning() and log() by observing the task using the edk task logs command:

edk task logs "Pipeline.My Other Pipeline" -w 03_04_02_define_errors_and_warnings

Which will result in the logs below:

Listing task logs for Pipeline.My Other Pipeline available in tenant with identifier: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX and workspace 03_04_02_define_errors_and_warnings.


UUID                                 REASON              STATUS LEVEL MESSAGE                                                                                                           LOGGEDAT                
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Worker XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX starting task instance XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX attempt 1 YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Loading inputs ["input"]                                                                                          YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Executing pipeline with 2 operations                                                                              YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Performing assert operation                                                                                       YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   warn  Prefer value less than 20, got 55                                                                                 YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Performing assert operation                                                                                       YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Noticed value greater than 10, got 55                                                                                   YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Saving outputs ["output"]                                                                                         YYYY-MM-DDTHH:MM:SS.MSZ
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX new_task_definition warn   info  Task XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX complete                                                                YYYY-MM-DDTHH:MM:SS.MSZ

You can see from the output of edk task logs that the pipeline generated logs and warnings based on the value.

Example solution

The code for this tutorial is available below:

Next steps

You have now defined error, warning and log operations in a pipeline. You interacted with a solution to understand how Assertions and warnings perform and observed states and messages from executed Task instances using the edk task logs command.

In the next module, you will move away from using the simple primitive IntegerType and begin using collection data types.

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