Parameter Effect

The parameter effect serializes train inputs and outputs to JSON and stores them on the Metadata record. Without this provider, the Metadata.Input and Metadata.Output columns are null — you'll know a train ran and whether it succeeded, but not what data it processed.

Registration

dotnet add package Trax.Effect.Provider.Parameter

services.AddTrax(trax => trax
    .AddEffects(effects => effects
        .UsePostgres(connectionString)
        .SaveTrainParameters()
    )
);

You can pass custom serialization options:

.SaveTrainParameters(new JsonSerializerOptions
{
    PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
    WriteIndented = false
})

Configuration

By default, both inputs and outputs are serialized. You can control this with the configure parameter:

// Save only inputs (skip output serialization)
.SaveTrainParameters(configure: cfg =>
{
    cfg.SaveInputs = true;
    cfg.SaveOutputs = false;
})
 
// Save only outputs
.SaveTrainParameters(configure: cfg =>
{
    cfg.SaveInputs = false;
    cfg.SaveOutputs = true;
})

The configuration is registered as a singleton and can be modified at runtime via the Dashboard Effects page. Changes take effect on the next train execution scope.

How It Works

The parameter effect only cares about Metadata objects — it ignores other tracked models. When SaveChanges runs:

1. It iterates through every tracked Metadata instance.
2. If SaveInputs is enabled, it calls metadata.GetInputObject(), serializes it to JSON, and assigns it to metadata.Input.
3. If SaveOutputs is enabled, it calls metadata.GetOutputObject(), serializes it to JSON, and assigns it to metadata.Output.

These fields are then persisted by whatever data provider you have registered (Postgres or InMemory). When you later inspect train executions — through the Dashboard, direct database queries, or the metadata API — you can see exactly what went in and what came out.

On disposal, the provider clears the input/output object references from metadata to release memory.

Requires a Data Provider

This effect populates fields on Metadata, but it doesn't persist the metadata itself. You need either UsePostgres or UseInMemory registered alongside it. Without a data provider, the serialized parameters are written to a Metadata object that's never saved anywhere.

When to Use It

• Production — When you need to query or debug train executions after the fact. "What input caused this failure?"
• Audit trails — The serialized input/output gives you a record of what data each train processed.
• Dashboard — The Dashboard displays Input and Output in its metadata detail view. Without this provider, those fields show as empty.

SDK Reference

> SaveTrainParameters