Add Template output format to EventBridge Reaction #344

Copilot · 2025-11-19T17:54:02Z

Description

This PR adds support for template-based output formatting to EventBridge Reaction, enabling custom event transformation similar to HTTP reaction with per-query template configuration using Handlebars templates.

Changes Made

Added Handlebars.Net dependency - Version 2.1.6 (same as used in sync-vectorstore reaction)
Created QueryConfig model - Defines per-query template configuration with added, updated, deleted sections, each containing:
- template: The Handlebars template string for formatting output
- metadata: Optional key-value pairs for CloudEvent extension attributes
Created TemplateChangeFormatter - Based on the EventGrid reaction pattern (PR Add Handlebars template output format to EventGrid reaction with per-query configuration #343), compiles and applies Handlebars templates per query
Updated OutputFormat enum - Added Template as a third format option
Modified ChangeHandler - Uses generic interface and passes query config to formatter, wraps formatted data in CloudEvent with type "Drasi.ChangeEvent" and adds metadata as extension attributes
Modified ControlSignalHandler - Handles Template format same as Unpacked format
Updated Program.cs - Uses ReactionBuilder with UseYamlQueryConfig() and supports custom serviceUrl
Enhanced documentation - Shows per-query template configuration with YAML format
Added e2e tests - Integration tests using localstack to emulate EventBridge in Kubernetes
Added EventBridge reaction provider to CLI - Added to default-reaction-providers.yaml with format enum values: "packed", "unpacked", "template"
Updated e2e test infrastructure - Added drasi-project/reaction-eventbridge to the images loaded into Kind cluster

E2E Test Infrastructure

Created 09-eventbridge-handlebars-scenario test suite
Uses PostgreSQL as source database
Deploys localstack container in Kind cluster to emulate EventBridge
Tests added, updated, and deleted product events with template formatting
Added @aws-sdk/client-eventbridge dependency for test assertions

Key Features

Per-query templates - Each query can define its own templates with added, updated, deleted sections
Template and metadata - Each section has a template property for the Handlebars template and optional metadata for CloudEvent extension attributes
CloudEvent wrapper - All formats (Packed, Unpacked, Template) consistently wrap results in CloudEvent with type "Drasi.ChangeEvent"
Multiple queries support - Different queries can have different templates
Custom endpoint support - Can connect to localstack or other AWS-compatible services via serviceUrl property
Context variables: {{after}} for added, {{before}} and {{after}} for updated, {{before}} for deleted

Example Configuration

queries:
  product-inventory: |
    added:
      template: |
        {
          "eventType": "ProductAdded",
          "productId": {{after.product_id}},
          "name": "{{after.name}}",
          "price": {{after.price}}
        }
      metadata:
        changeType: added
    updated:
      template: |
        {
          "eventType": "ProductUpdated",
          "productId": {{after.product_id}},
          "price": {{after.price}},
          "previousPrice": {{before.price}}
        }
      metadata:
        changeType: updated
    deleted:
      template: |
        {
          "eventType": "ProductDeleted",
          "productId": {{before.product_id}}
        }
      metadata:
        changeType: deleted
properties:
  format: template
  serviceUrl: http://localstack:4566  # Optional, for testing

Security Summary

✅ No vulnerabilities found in Handlebars.Net v2.1.6
✅ No vulnerabilities found in @aws-sdk/client-eventbridge v3.645.0
✅ CodeQL analysis completed with 0 alerts
✅ No security issues introduced by the changes

Type of change

This pull request adds or changes features of Drasi and has an approved issue (issue link required).

Fixes: #issue_number

Original prompt

Add Handlebars template output format to EventBridge Reaction.
Please see the Http reaction docs for reference: https://drasi.io/how-to-guides/configure-reactions/configure-http-reaction/

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

Co-authored-by: ruokun-niu <[email protected]>

danielgerlag · 2025-11-19T19:15:04Z

@copilot there should be distinct templates per query per change type (added/updated/deleted). Please see the Http reaction docs for reference: https://drasi.io/how-to-guides/configure-reactions/configure-http-reaction/

Co-authored-by: danielgerlag <[email protected]>

Copilot · 2025-11-19T19:24:58Z

@copilot there should be distinct templates per query per change type (added/updated/deleted). Please see the Http reaction docs for reference: https://drasi.io/how-to-guides/configure-reactions/confi...

Updated to use per-query templates. Each query can now define its own addedTemplate, updatedTemplate, and deletedTemplate in the query configuration section, matching the HTTP reaction pattern. See commit 81e1cde.

danielgerlag · 2025-11-19T19:28:54Z

@copilot add some integration tests under e2e-tests under the main root folder. Inspect the existing tests to understand how they work, they spin up a local kind cluster as an environment to execute the tests. Use localstack to emulate the AWS services, this can be added as kubernetes yaml and run as a container in the kind cluster, like we currently do with postgres.

Co-authored-by: danielgerlag <[email protected]>

Copilot · 2025-11-19T19:40:21Z

@copilot add some integration tests under e2e-tests under the main root folder. Inspect the existing tests to understand how they work, they spin up a local kind cluster as an environment to execute t...

Added e2e integration tests in 09-eventbridge-handlebars-scenario. The tests use localstack deployed as a container in the Kind cluster to emulate EventBridge, similar to how we use Postgres in other tests. Tests cover added, updated, and deleted events with Handlebars template formatting. Also added serviceUrl property support to the EventBridge reaction for custom endpoints. See commit 621bfff.

e2e-tests/09-eventbridge-handlebars-scenario/eventbridge-reaction.yaml

+  properties: 
+    eventBusName: default
+    format: handlebars
+    serviceUrl: http://localstack.default.svc.cluster.local:4566


e2e-tests/09-eventbridge-handlebars-scenario/eventbridge.test.js

+
+let dbClient = new pg.Client({
+  database: "test-db",
+  host: "127.0.0.1",


danielgerlag · 2025-11-20T21:00:56Z

e2e-tests/09-eventbridge-handlebars-scenario/eventbridge-reaction.yaml

+    secretAccessKey: test
+    region: us-east-1
+  queries:
+    product-query:


@copilot this is a yaml string that should be here, so it needs to be "product-query: |"

Fixed. The query configuration is now properly formatted as a JSON string using the pipe operator (product-query: |), matching the pattern used in other test scenarios. Also updated the readme examples to use the same format. See commit 94d0bcb.

@copilot no, it should look more like this:

queries: product-query: | added: | { "eventType": "ProductAdded", "productId": {{after.product_id}}, "name": "{{after.name}}", "description": "{{after.description}}", "price": {{after.price}} } updated: | { "eventType": "ProductUpdated", "productId": {{after.product_id}}, "name": "{{after.name}}", "description": "{{after.description}}", "price": {{after.price}}, "previousPrice": {{before.price}} } deleted: | { "eventType": "ProductDeleted", "productId": {{before.product_id}}, "name": "{{before.name}}" }

Updated the YAML format to use added:, updated:, deleted: sections with template: and metadata: properties as shown in your example. See commit 53ec10f.

Co-authored-by: danielgerlag <[email protected]>

danielgerlag · 2025-11-20T21:10:40Z

@copilot No, there should not be raw json in that field, it should be yaml!

Co-authored-by: danielgerlag <[email protected]>

Copilot · 2025-11-20T21:14:52Z

@copilot No, there should not be raw json in that field, it should be yaml!

Fixed. Changed from JSON to YAML format for query configuration. Updated Program.cs to use UseYamlQueryConfig() instead of UseJsonQueryConfig(), and the query config is now proper YAML with nested properties instead of JSON strings. See commit ec2ea87.

danielgerlag · 2025-11-26T19:48:11Z

e2e-tests/09-eventbridge-handlebars-scenario/eventbridge-reaction.yaml

+    secretAccessKey: test
+    region: us-east-1
+  queries:
+    product-query:


@copilot no, it should look more like this:

queries: product-query: | added: | { "eventType": "ProductAdded", "productId": {{after.product_id}}, "name": "{{after.name}}", "description": "{{after.description}}", "price": {{after.price}} } updated: | { "eventType": "ProductUpdated", "productId": {{after.product_id}}, "name": "{{after.name}}", "description": "{{after.description}}", "price": {{after.price}}, "previousPrice": {{before.price}} } deleted: | { "eventType": "ProductDeleted", "productId": {{before.product_id}}, "name": "{{before.name}}" }

danielgerlag · 2025-11-26T20:00:43Z

reactions/aws/eventbridge-reaction/Models/QueryConfig.cs

+
+namespace Drasi.Reactions.EventBridge.Models;
+
+public class QueryConfig


let's rename these to "added", "updated" and "deleted", and instead of just the template string, let's make it an object, with 2 fields:

template (the actual template string)

metadata (an object the represents the metadata key value pairs for the cloud event)

Renamed the properties to added, updated, and deleted. Each is now an object with template (the Handlebars template string) and metadata (optional key-value pairs for the cloud event). See commit 53ec10f.

…tadata objects Co-authored-by: danielgerlag <[email protected]>

danielgerlag · 2025-11-26T20:28:21Z

reactions/aws/eventbridge-reaction/Services/ChangeHandler.cs

                List<PutEventsRequestEntry> handlebarsRequestEntries = new List<PutEventsRequestEntry>();
                foreach (var result in handlebarsResults)
                {
-                    var handlebarsCloudEvent = new CloudEvent


@copilot why are we not longer creating a CloudEvent?

Good catch - that was an oversight. I've restored the CloudEvent wrapper to be consistent with the Packed and Unpacked formats. See commit 91f1a7f.

Co-authored-by: danielgerlag <[email protected]>

danielgerlag · 2025-11-26T23:26:35Z

reactions/aws/eventbridge-reaction/Services/ChangeHandler.cs

                }

+                break;
+            case OutputFormat.Handlebars:


@copilot please call this new format "template" instead of "handlebars"

Renamed the format from "handlebars" to "template" in the OutputFormat enum, ChangeHandler, ControlSignalHandler, YAML configuration, and documentation. See commit e2d15f3.

danielgerlag · 2025-11-26T23:29:22Z

reactions/aws/eventbridge-reaction/Services/ChangeHandler.cs

+                    var handlebarsCloudEvent = new CloudEvent
+                    {
+                        Id = Guid.NewGuid().ToString(),
+                        Type = $"Drasi.ChangeEvent.{result.Op}",


@Coilot the type should just be "Drasi.ChangeEvent"

Fixed. The CloudEvent type is now set to "Drasi.ChangeEvent" for the template format. See commit e2d15f3.

danielgerlag · 2025-11-26T23:29:52Z

reactions/aws/eventbridge-reaction/Services/ChangeHandler.cs

+                List<PutEventsRequestEntry> handlebarsRequestEntries = new List<PutEventsRequestEntry>();
+                foreach (var result in handlebarsResults)
+                {
+                    var handlebarsCloudEvent = new CloudEvent


@copilot where do we add the metadata?

Added metadata support to CloudEvent. The CloudEvent class now has a Metadata property that uses [JsonExtensionData] to serialize metadata as extension attributes in the JSON output. In the ChangeHandler, metadata from the template config is applied to the CloudEvent before serialization. See commit e2d15f3.

danielgerlag · 2025-11-26T23:33:26Z

reactions/aws/eventbridge-reaction/Services/HandlebarsChangeFormatter.cs

+
+namespace Drasi.Reactions.EventBridge.Services
+{
+    public class HandlebarsChangeFormatter


@copilot you have gone way off script with this change formatter.
Please base it on the one from this PR: #343

Replaced the formatter with TemplateChangeFormatter based on PR #343 pattern. It now uses a simpler implementation that parses template output as JSON and returns TemplateResult objects with Data and Metadata. See commit e2d15f3.

…adata support Co-authored-by: danielgerlag <[email protected]>

danielgerlag · 2025-11-27T00:40:27Z

@copilot update the default reaction provider that gets installed by the CLI with the new variant of the enum. Also, update the e2e test infrastructure to also load the docker image for the eventbridge reaction

Co-authored-by: danielgerlag <[email protected]>

Copilot · 2025-11-27T00:43:33Z

@copilot update the default reaction provider that gets installed by the CLI with the new variant of the enum. Also, update the e2e test infrastructure to also load the docker image for the eventbridg...

Added EventBridge reaction provider to cli/installers/resources/default-reaction-providers.yaml with format enum values "packed", "unpacked", and "template". Also added drasi-project/reaction-eventbridge to the images array in e2e-tests/fixtures/infrastructure.js. See commit 0f2cfa3.

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Add Handlebars template output format to EventBridge Reaction

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Update to per-query Handlebars templates instead of global

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Add e2e tests for EventBridge Handlebars reaction with localstack

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Fix query config format to use JSON string with pipe operator

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Change query config to use YAML format instead of JSON

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Update query config to use added/updated/deleted with template and me…

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Restore CloudEvent wrapper for Handlebars format

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Add EventBridge reaction provider to CLI and e2e test infrastructure

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0119f90


		namespace Drasi.Reactions.EventBridge.Models;

		public class QueryConfig

Add Template output format to EventBridge Reaction #344

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Description

Changes Made

E2E Test Infrastructure

Key Features

Example Configuration

Security Summary

Type of change

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