Class RowsTransformBase<TDerived, TInput, TOutput>

An abstract dataflow worker which repeatedly executes the OnRowsAndDemandAsync() method when there is both data to consume from the upstream worker and RowsPerBuffer demand available from the downstream worker. The library user must inherit this class and override OnRowsAndDemandAsync to provide custom functionality.

This class allows the developer to write synchronous or asynchronous code as needed, without having to check for output demand (which simplifies the implementation), as long as no more than RowsPerBuffer rows are sent on each invocation (without checking row demand explicitly).

The derived class can additionally override RunAsync() to add logic that runs before and after all processing of rows, in which case the base class base.RunAsync() must be called. The derived class (or its user) can also use worker callbacks to add logic.

The input port uses the Default policy. Consider whether this is appropriate, or should be overridden, see BufferingMode for further details.

Use RowsTransformBase<TDerived, TInput, TOutput, TError> instead if an ErrorOutput port is needed. Also see the RowsTransformBase example.

Inheritance
Object
WorkerParent
WorkerBase
WorkerBase<TDerived>
RowsTransformBase<TDerived, TInput, TOutput>
RowsTransformBase<TDerived, TInput, TOutput, TError>
RowTransformBase<TDerived, TInputError, TOutput>
Implements
Inherited Members
Namespace: actionETL
Assembly: actionETL.dll
Syntax
public abstract class RowsTransformBase<TDerived, TInput, TOutput> : WorkerBase<TDerived>, IDisposeOnFinished where TDerived : RowsTransformBase<TDerived, TInput, TOutput> where TInput : class where TOutput : class
Type Parameters
Name Description
TDerived

The type of the derived worker. Class definition example:

public class MyTransform<TInput,TOutput>
    : RowsTransformBase<MyTransform<TInput,TOutput>,TInput,TOutput>
    where TInput : class
    where TOutput : class
{ 
    // ...
}
TInput

The type of each Input row.
TOutput

The type of each Output row.

Constructors

RowsTransformBase(in DownstreamFactory<TInput>, String, Boolean)

Initializes a new instance of the RowsTransformBase<TDerived, TInput, TOutput> abstract dataflow worker, which repeatedly executes a synchronous action when there is both data to consume from the upstream worker and RowsPerBuffer demand available from the downstream worker. The Output will be automatically completed, if needed.

Declaration
protected RowsTransformBase(in DownstreamFactory<TInput> downstreamFactory, string workerName, bool autoCompleteOutput)
Parameters
Type Name Description
DownstreamFactory<TInput> downstreamFactory

The downstream factory, which specifies the parent worker and (optionally) the upstream port to link the "first" input port of this dataflow worker to.

Get it from Link when the upstream port is known ahead of time (which is usually the case). Otherwise get it from GetDownstreamFactory<TInput>(), and link the transform or target explicitly using LinkTo(InputPort<TOutput>) or LinkFrom(OutputPortBase<TInput>).

String workerName

Name of the worker.

Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1.

While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1.

The name cannot otherwise contain "/", and cannot start with double underscore "__".

Boolean autoCompleteOutput
Exceptions
Type Condition
ArgumentException

workerName:

  • Workers with the same parent must have unique names.
  • Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException

workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException
  • Cannot add child worker to parent which has completed. Are you adding it to the correct parent?
  • Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

Properties

Input

Gets the input port for receiving rows from an upstream worker.

Declaration
public InputPort<TInput> Input { get; }
Property Value
Type Description
InputPort<TInput>

Output

Gets the output port for sending rows to the downstream worker.

Declaration
public OutputPort<TOutput> Output { get; }
Property Value
Type Description
OutputPort<TOutput>

Methods

OnRowsAndDemandAsync()

An abstract method that gets called repeatedly when there is both data to consume from the upstream worker and RowsPerBuffer demand available from the downstream worker.

Override it and call methods on the ports to input and output rows. Note that taking more rows than is available, or sending more rows than there is row demand will throw an exception.

Declaration
protected abstract Task<ProgressStatus> OnRowsAndDemandAsync()
Returns
Type Description
Task<ProgressStatus>
  • NotCompleted to continue to be called when there are input rows available
  • Succeeded to discard all additional incoming rows, and successfully finish row processing and the worker.
  • Error or Fatal to fail the worker

RunAsync()

This method can be overridden to add custom functionality to the derived worker that runs before and after the row processing. In this case, the base class base.RunAsync() must be called for the worker to function correctly.

Typically, only OnRowsAndDemandAsync() is overridden to add required custom logic.

Declaration
protected override async Task<OutcomeStatus> RunAsync()
Returns
Type Description
Task<OutcomeStatus>

A Task describing the success or failure of the worker. An asynchronous async implementation would e.g. return OutcomeStatus.Succeeded on success, while a synchronous implementation would return OutcomeStatus.SucceededTask.
Overrides

Implements