Resource Publishing

Aspire provides a flexible mechanism for publishing resource manifests, enabling seamless integration with various deployment environments. Resources are serialized into JSON format, which can be consumed by deployment tools.

Custom resources that publish JSON manifest entries must:

1. Register a callback using ManifestPublishingCallbackAnnotation in the constructor.
2. Implement the callback to write JSON via ManifestPublishingContext.Writer.
3. Use value objects (IManifestExpressionProvider) for structured fields.

Resources can opt-out of being included in the publishing manifest entirely by calling the ExcludeFromManifest() extension method on the IResourceBuilder<T>. Resources marked this way will be omitted when generating publishing assets like Docker Compose files or Kubernetes manifests.

Registering the Callback

Consider the following example of a custom Azure Bicep resource that publishes its parameters to a manifest:

C# — AzureBicepResource.cs

public class AzureBicepResource : Resource, IAzureResource
{
    public AzureBicepResource(string name, ...) : base(name)
    {
        Annotations.Add(new ManifestPublishingCallbackAnnotation(WriteToManifest));
    }
}

Writing to the Manifest

As an example, the WriteToManifest method serializes the resource’s parameters into a JSON object. This method is invoked during the manifest publishing phase:

public virtual void WriteToManifest(ManifestPublishingContext context)
{
    context.Writer.WriteString("type", "azure.bicep.v0");
    context.Writer.WriteString("path", context.GetManifestRelativePath(path));

    context.Writer.WriteStartObject("params");
    foreach (var kv in Parameters)
    {
        context.Writer.WritePropertyName(kv.Key);
        var v = kv.Value is IManifestExpressionProvider p ? p.ValueExpression : kv.Value?.ToString();
        context.Writer.WriteString(kv.Key, v ?? "");
        context.TryAddDependentResources(kv.Value);
    }
    context.Writer.WriteEndObject();
}

Summary Table

The following table summarizes the key steps and conventions for publishing resources:

Step	API / Call	Purpose
Register callback	Annotations.Add(new ManifestPublishingCallbackAnnotation(WriteToManifest))	Hook custom JSON writer
Implement WriteToManifest	Use context.Writer to emit JSON properties	Define resource manifest representation
Structured fields	IManifestExpressionProvider.ValueExpression	Ensure publish-time placeholders are preserved

Key Conventions

Convention	Rationale
Data-only resource classes	Separates data model from behavior
*BuilderExtensions classes	Groups all API methods per integration
Public annotations	Allow dynamic runtime addition/removal
[ResourceName] attribute	Enforces valid resource naming at compile time
Preserve parameter/value objects	Ensures deferred evaluation of secrets/outputs