Class WorkerSystemBase

An abstract class that creates and runs a system of workers. Use it to refer to worker systems when you don't know the exact derived type (e.g. WorkerSystem. Commonly used members include StartAsync(), Start(), and Config.

This class cannot be inherited directly. To create a custom worker system, derive from WorkerSystemBase<TDerived> and override RunAsync() to provide a custom implementation.

Inheritance

Object

WorkerParent

WorkerSystemBase

WorkerSystemBase<TDerived>

Implements

IDisposeOnFinished

Inherited Members

WorkerParent.AddChildCompletedCallback(Action<WorkerBase>)

WorkerParent.AddStartingChildrenCallback(Func<WorkerParent, Task<ProgressStatus>>)

WorkerParent.Children

WorkerParent.DisposeOnFinished<TDisposable>(TDisposable)

WorkerParent.GetDownstreamFactory<TInput>()

WorkerParent.HasChildren

WorkerParent.IsCanceled

WorkerParent.IsCompleted

WorkerParent.IsCreated

WorkerParent.IsError

WorkerParent.IsFailed

WorkerParent.IsFatal

WorkerParent.IsRunning

WorkerParent.IsSucceeded

WorkerParent.KeepChildrenLevels

WorkerParent.Locator

WorkerParent.LogFactory

WorkerParent.Logger

WorkerParent.MaxRunningChildren

WorkerParent.Name

WorkerParent.RemoveChildren()

WorkerParent.RescheduleChildren()

WorkerParent.RunAsync()

WorkerParent.RunChildrenAsync(Boolean)

WorkerParent.RunChildrenAsync()

WorkerParent.Status

WorkerParent.Item[String]

WorkerParent.ToString()

WorkerParent.WorkerSystem

WorkerParent.DebugCommands

WorkerParent.AggregateErrorOutputRows

WorkerParent.AggregateOutputRows

WorkerParent.AggregateWorkersCompleted

WorkerParent.InstantCompleted

WorkerParent.InstantCreated

WorkerParent.InstantStarted

WorkerParent.RunningDuration

Namespace: actionETL

Assembly: actionETL.dll

Syntax

public abstract class WorkerSystemBase : WorkerParent, IDisposeOnFinished

Properties

Config

Gets the configuration service. If a configuration service is not injected when creating the worker system, one will be automatically created, and populated from a default configuration location, if available.

Note: This property is thread-safe.

Declaration

public AConfig Config { get; }

Property Value

Type	Description
AConfig	The configuration service.

CreationGuid

Gets an identifier that is unique to each created worker system. It is logged to the logging system. It can e.g. be added to user data rows, inserted into databases etc., to simplify linking different sets of user data to each other, and to link user data to logging information.

Note that the logging system uses the default text format: CreationGuid.ToString(); an example of a return value is "382c74c3-721d-4f34-80e5-57657b6cbc27".

Note: This property is thread-safe.

Declaration

public Guid CreationGuid { get; }

Property Value

Type	Description
Guid

IsCancelRequested

Gets a value indicating whether canceling has been requested for the worker system. Long running workers can poll this property periodically, and halt processing on cancel.

Note: This property is thread-safe.

Declaration

public bool IsCancelRequested { get; }

Property Value

Type	Description
Boolean	`true` if canceling has been requested; otherwise, `false`.

LicenseMaxWorkerTypes

Gets the maximum number of distinct worker types allowed for this worker system. null if unlimited.

Declaration

public int? LicenseMaxWorkerTypes { get; }

Property Value

Type	Description
Nullable<Int32>

Methods

AddCompletedCallback(Func<WorkerSystemBase, OutcomeStatus, Task<OutcomeStatus>>)

Adds a callback which will be called as the last step of the worker system Running phase, which is after any children have completed. Multiple callbacks can be added.

These callbacks are useful for performing cleanup tasks. Also see DisposeOnFinished<TDisposable>(TDisposable) and UsingActionWorker<TDisposable> which are specifically for disposing resources.

If the worker system is started, these callbacks will run, even if earlier callbacks, or any children have failures. If multiple callbacks have been added, they will all be called (even if one fails) in the reverse order from they were added, e.g. callbacks from derived classes will be called before callbacks from base classes.

Each callback takes the worker system itself (typed as WorkerSystemBase) and the OutcomeStatus from previous steps (including any children) as parameters.

Note: Adding the callback is thread-safe.

Declaration

public WorkerSystemBase AddCompletedCallback(Func<WorkerSystemBase, OutcomeStatus, Task<OutcomeStatus>> completedFuncAsync)

Parameters

Type	Name	Description
Func<WorkerSystemBase, OutcomeStatus, Task<OutcomeStatus>>	completedFuncAsync	The asynchronous callback that will be called when the worker system has completed. See "Remarks" below for details.

Returns

Type	Description
WorkerSystemBase	The instance itself, so you can chain multiple calls.

Remarks

The callback takes two parameters:

`WorkerSystemBase`	The worker system itself
`OutcomeStatus`	From previous execution steps (including any children)

The callback implementation is either synchronous and returns a Task<OutcomeStatus> explicitly, or is async and returns an OutcomeStatus.

To leave the OutcomeStatus unchanged, return the OutcomeStatus that was passed in as a parameter (and use ToTask() in synchronous callbacks).
To change the OutcomeStatus (e.g. changing Error to Succeeded), return a new OutcomeStatus instance. If appropriate, use Combine(Boolean, OutcomeStatus) to also retain the previous information, both of which the system will log.

If you need to access members of the derived worker system type, there are three options:

Use AddCompletedCallback(Func<TDerived, OutcomeStatus, Task<OutcomeStatus>>) instead if you know the derived worker system type.
If you have access to the source of the worker system type, implement the callback as a (non-static) method in that type. This allows accessing members without casting the worker system parameter to the derived worker system type.
If you don't have access to the source of the worker system type, or you want to implement the callback using a lambda, cast the worker system parameter to the actual derived type of the worker system.

Examples

In this example we roll back a transaction on failure:

workerSystem.AddCompletedCallback((ws, outcomeStatus) =>
{
    if (!outcomeStatus.IsSucceeded)
        transaction?.Rollback();
    return outcomeStatus.ToTask();
});

Exceptions

Type	Condition
ArgumentNullException	`completedFuncAsync`
InvalidOperationException	Cannot add 'Starting' callback after the worker system has completed.

AddStartingCallback(Func<WorkerSystemBase, Task<ProgressStatus>>)

Adds a callback which will be called as the first step of the worker system Running phase, which is before Root(Action<WorkerSystem>) overloads and RunAsync() is called or worker children are started. Multiple callbacks can be added.

These callbacks are often used for initialization, or for adding child workers, e.g. from outside the worker system.

If the worker system is started, these callbacks will all run, even if some fail, in the order they were added, e.g. callbacks added in base classes will be called before callbacks added in derived classes.

The callback takes the worker system itself as a parameter, typed as WorkerSystemBase.

Note: Adding the callback is thread-safe.

Declaration

public WorkerSystemBase AddStartingCallback(Func<WorkerSystemBase, Task<ProgressStatus>> startingFuncAsync)

Parameters

Type	Name	Description
Func<WorkerSystemBase, Task<ProgressStatus>>	startingFuncAsync	The asynchronous callback that will be called when the worker system has started. See "Remarks" below for details.

Returns

Type	Description
WorkerSystemBase	The instance itself, so you can chain multiple calls.

Remarks

The callback takes the worker system itself as a parameter, typed as WorkerSystemBase.

If you need to access members of a derived worker system type, there are three options:

Use AddStartingCallback(Func<TDerived, Task<ProgressStatus>>) instead if you know the derived worker system type.
If you have access to the source of the worker system type, implement the callback as a (non-static) method in that worker. This allows accessing worker system members without casting the worker parameter to the derived worker system type.
If you don't have access to the source of the worker system type, or you want to implement the callback using a lambda, cast the worker system parameter to the actual derived type of the worker system.

The callback implementation is either synchronous and returns a Task<ProgressStatus> explicitly, or is async and returns a ProgressStatus.

The callback should return:

ProgressStatus.NotCompletedTask (or ProgressStatus.NotCompleted) to continue normal processing.
ProgressStatus.SucceededTask (or ProgressStatus.Succeeded) to skip calling the Root() and AddStartingChildrenCallback(Func<WorkerParent, Task<ProgressStatus>>) callbacks, and child workers will not be started. All other AddStartingCallback(), AddCompletedCallback(Func<WorkerSystemBase, OutcomeStatus, Task<OutcomeStatus>>), and parent AddChildCompletedCallback(Action<WorkerBase>) callbacks will be called.
A failure ProgressStatus on failure, which will give the worker system that failure status. The Root() and AddStartingChildrenCallback() callbacks won't be called, and child workers will not be started. All other AddStartingCallback(), AddCompletedCallback(), and parent AddChildCompletedCallbacks() callbacks will be called.

Examples

In this example we allocate a buffer:

workerSystem.AddStartingCallback(ws =>
{
    _buffer = new int[BufferSize];
    return ProgressStatus.NotCompletedTask;
});

Exceptions

Type	Condition
ArgumentNullException	`startingFuncAsync`
InvalidOperationException	Cannot add 'Starting' callback after the worker system has started running.

Start()

Starts the worker system synchronously. This will run any user added callbacks, the RunAsync() method, and any workers they add. With the out-of-box WorkerSystem, this includes any Root(Action<WorkerSystem>) overload callback.

Note: Only call this method from the default SynchronizationContext, i.e. from console programs. The recommended way to start the worker system is via StartAsync(), which also works with all types of programs, including GUI, etc.

Declaration

public virtual SystemOutcomeStatus Start()

Returns

Type Description

SystemOutcomeStatus

A SystemOutcomeStatus that represents the completion of the worker system, i.e. when both RunAsync() and user callbacks have completed, and no more workers are running or can be started.

await this task and check the result for success or failure (a corresponding result is then also available in the Status property):

`Fatal`	A worker or user code has thrown an unhandled exception, or `Fatal` has been explicitly returned from a worker. Note that a `Fatal` status from any worker will stop the whole worker system.
`Error`	A worker is `Error`, and it and its ancestors have `EscalateError` set to `true`
`Canceled`	The worker system is canceled
`Succeeded`	All other cases

Exceptions

Type	Condition
InvalidOperationException	Can only be used with the default (null) SynchronizationContext, e.g. from console programs, but not from frameworks that set a SynchronizationContext, e.g. WinForms, WPF, UWP, ASP.NET programs, and some testing frameworks. The worker system can only be started once.

StartAsync()

Starts the worker system asynchronously, which is the recommended way. This will run any user added callbacks, the RunAsync() method, and any workers they add. With the out-of-box WorkerSystem, this includes any Root(Action<WorkerSystem>) overload callback.

Also see Start().

Declaration

public virtual Task<SystemOutcomeStatus> StartAsync()

Returns

Type Description

Task<SystemOutcomeStatus>

A SystemOutcomeStatus that represents the completion of the worker system, i.e. when both RunAsync() and user callbacks have completed, and no more workers are running or can be started.

await this task and check the result for success or failure (a corresponding result is then also available in the Status property):

`Fatal`	A worker or user code has thrown an unhandled exception, or `Fatal` has been explicitly returned from a worker. Note that a `Fatal` status from any worker will stop the whole worker system.
`Error`	A worker is `Error`, and it and its ancestors have `EscalateError` set to `true`
`Canceled`	The worker system is canceled
`Succeeded`	All other cases

Exceptions

Type	Condition
InvalidOperationException	The worker system can only be started once.

TryCancel(String)

Cancel the worker system (unless already completed or no more workers to run), which stops dispatching workers by setting their OutcomeStatus to Canceled, without executing the worker itself. Any workers that are already running will complete as per normal.

By default (i.e. with EscalateError set to true), failed workers will escalate any error to their parents, recursively, including to the WorkerSystem.

Note: This method is thread-safe.

Declaration

public bool TryCancel(string message)

Parameters

Type	Name	Description
String	message	The message. Can be empty or `null`.

Returns

Type	Description
Boolean	`true` if canceling the worker system; `false` if already canceled or completed, or no more workers to run.

Implements

IDisposeOnFinished