Configuring Real-Time Event Handlers

This section details the steps required to set up GCP Event Handlers. Alternatively, you can use the gcp_setup baseline which automates this process.

Turbot Guardrails Event Handlers for GCP are responsible for conveying events from GCP Logging back to Guardrails for processing. Event Handlers are required for Guardrails to process and respond in real-time. However, if your organization has more complex requirements that forbid the use of event handlers then Event Pollers can be used. Event Handlers and Event Pollers enable the Guardrails Event-driven model of operation.

The event handlers infrastructure is configured by Guardrails Stacks in each project. These stacks will configure the required infrastructure components:

  • Logging: A logging sink that filters api event messages and publishes them to a topic
  • Pub/Sub Topic: A pub/sub topic where the logging sink publishes events
  • Pub/Sub Subscription: A pub/sub subscription that forwards the events back to Guardrails for processing
  • Pub/Sub Topic IAM Policy: An IAM policy on the pub/sub topic to allow

Guardrails Mods Required for Event Handling

In order to configure real time eventing, the following set of mods must be installed and up to date in the environment:

Email whitelisting and domain verification

GCP no longer requires domain verification for Pub/Sub subscriptions. Existing domain verification DNS records have no effect.

Enabling the Required APIs

Before configuring GCP Event Handlers, you must enable the Pub/Sub and Logging APIs. You can do this by

  • Setting the below policies to Enforce: Enabled so Guardrails will enable the APIs automatically
  • Manually enabling the APIs in the project. If the Guardrails service role doesn't have permissions to enable an API, they will need to be enabled some other way.

These policies can also be set using Terraform:

# Sets the policy Enable for API Enabled in Pub/Sub
# GCP > Pub/Sub > API Enabled
resource "turbot_policy_setting" "pubsubApiEnabled" {
resource = "id of parent folder or smart folder" //highlight-line
type = "tmod:@turbot/gcp-pubsub#/policy/types/pubsubApiEnabled"
value = "Enforce: Enabled"
# Sets the policy Enable for API Enabled in Logging
# GCP > Logging > API Enabled
resource "turbot_policy_setting" "loggingApiEnabled" {
resource = "id of parent folder or smart folder" //highlight-line
type = "tmod:@turbot/gcp-logging#/policy/types/loggingApiEnabled"
value = "Enforce: Enabled"

Configuring the Event Handlers

Workspace Configuration

Here are the Turbot > Workspace policies relevant to event handling for SaaS and Enterprise customers. If desired, these policies should be configured before enabling event handling. Changes to these policies should be done with care as this may force a refresh of all Event Handling infrastructure in the workspace.

Enterprise Specific Policies

Enterprise API GW Configuration

For enterprises with a private Guardrails console, an API gateway must be used. The hostname of the API Gateway must be specified in the Turbot > Workspace > Gateway Domain Name policy. Typically, the domain name will be gateway.{installation_domain_name}. (The installation domain name is taken from the value specified in the Turbot Guardrails Enterprise Foundation (TEF) stack.)

However, some enterprise environments cannot use gateway.{installation_domain_name}, usually because of DNS resolution complexity or enterprise policy. A viable option is to use the AWS API Gateway domain name instead, since it is always publicly resolvable. Follow these steps to retrieve the appropriate hostname then set it in your Guardrails console:

  1. In the Turbot Guardrails Master's account, go to the AWS API Gateway console. Find the Guardrails API Gateway (by default identified as turbot).
  2. Go to APIs. Click into turbot-api or {resource_prefix}-api. Click into Stages then click the turbot stage.
  3. From the top of the turbot stage page, grab the "Invoke URL". It will be in the form of https://{uniqueId}.execute-api.{region} The /turbot path is required. Do not add a / after /turbot. Strip off https://
  4. Copy the stage URL to the Gateway Domain Name policy. It should be in this form: {uniqueId}.execute-api.{region}
  5. If Event Handling has been enabled, let the event handler source policies recalculate then Event Handler control run again. Otherwise, complete the steps outlined in the rest of this document then return to this procedure.
  6. Examine the Pub/Sub Subscription in the GCP Event Handler control logs to make sure it confirmed properly.

Enabling Event Handlers

After the Pub/Sub and Logging APIs have been enabled, event handling infrastructure needs to be deployed. To configure the GCP Event Handlers using the default configuration, set the following policies:

Note: The Logging stack depends on the Pub/Sub Topic and Subscription. It will go into error until the Pub/Subs resources are present.

These policies can also be set using Terraform:

### Setting up the PubSub Event Handlers stacks
# Sets the policy for Pub/Sub
# GCP > Turbot > Event Handlers > Pub/Sub
resource "turbot_policy_setting" "eventHandlersPubSub" {
resource = "id of parent folder or smart folder" //highlight-line
type = "tmod:@turbot/gcp#/policy/types/eventHandlersPubSub"
value = "Enforce: Configured"
# Sets the policy for Logging
# GCP > Turbot > Event Handlers > Logging
resource "turbot_policy_setting" "eventHandlersLogging" {
resource = "id of parent folder or smart folder" //highlight-line
type = "tmod:@turbot/gcp#/policy/types/eventHandlersLogging"
value = "Enforce: Configured"

After setting the policies, the Event Handlers stacks will begin running in all projects defined in the scope. You can verify the state of these controls by browsing by Control Category and filtering by GCP > Turbot > Event Handlers.

Alternatively, you can query the state via graphQL:

filter: "resource:your-project-name-or-id controlType:tmod:@turbot/gcp#/control/types/eventHandlers"
) {
items {
type {
turbot {
resource {
turbot {

or via the Turbot Guardrails CLI:

items {
type {
turbot {
resource {
turbot {
turbot graphql controls --filter "controlType:tmod:@turbot/gcp#/control/types/eventHandlers" --output "$TURBOT_QUERY_OUTPUT"

After a few minutes, all controls should be in the OK state. If there are any in error, they should be investigated. Any questions can be directed to Turbot Support

Decomissioning Event Handlers

Event handlers can be shut-off by setting:

  • GCP > Turbot > Event Handlers > PubSub to Enforce: Configured
  • GCP > Turbot > Event Handlers > Logging to Enforce: Configured. Turbot will perform the required Terraform runs to destroy the event handler infrastructure. Note: Deleting an GCP project out of a Guardrails workspace will not automatically decommission the event handlers. Event Handlers must be set explicitly destroyed before removing the project from a Guardrails workspace.

When to decommission Event Handlers

Event Handlers should be decommissioned before:

  • Destroying the GCP project itself
  • Removing the account from Guardrails supervision.
  • Switching to GCP Event Pollers. Processing of duplicate events is highly undesirable.
  • Event Handling is no longer desired for this project.

Relationship to AWS Event Pollers

Note that GCP Event Pollers operate based on the value of GCP > Turbot > Event Handler policy setting, not on the state of the Event Handler controls themselves. By default, Event Handling is disabled so the event pollers run automatically. After Event Handling is enabled, the event pollers will stop running.

Event Handlers in Error

It is possible for the event handler controls to be in an error state because of incorrect configuration, permissions issues, etc. With event handling enabled, the event pollers won't run. Until these problems are resolved, events from the environment may be lost. Resolve problems with event handlers as quickly as possible.

Duplicate Events

It is also possible to get duplicate events if Event Pollers are explicitly enabled along with Event Handlers. Event Handlers and Event Pollers should never be enabled at the same time.


The best source of troubleshooting information is in the GCP > Turbot > Event Handlers > Pub/Sub and GCP > Turbot > Event Handlers > Logging control logs for the project.

  • Permissions Issues: If the permissions granted to the Guardrails service account do not allow configuration of Logging and Pub/Sub resources, then the control logs will indicate access denied.
  • Pub/Sub Subscription won't confirm: Check the various Turbot > Workspace policies that they are properly configured. Ensure that resources in the Turbot Guardrails Master VPC can resolve the ALB's hostname.


Congrats! Event handlers are now configured in the target account. To verify that they are working correctly, create a new resource or change an existing resource. Guardrails will receive the event which will trigger relevant controls. If resource creation or modification events do not get picked up by Guardrails, feel free to reach out to Turbot Support

How Event Handlers Work

When troubleshooting events handlers, it helps to know how they work. This section will describe the Guardrails and AWS halves of event handlers.

Guardrails Policies and Stacks

Guardrails uses Terraform to deploy the various pieces of GCP event handling infrastructure. The Terraform source that defines all event handling infrastructure is compiled from several sources. They are:

  • Workspace configuration policies: These policies specify information like the HTTPS endpoint that event handlers should point to, or the webhook secrets that should be sent with each event.
  • Event Handler configuration policies: Enable event handlers. Specify resource prefixes for Pub/Sub topics, and Logging Sink. Any policy in "GCP > Turbot > Event Handler > *"
  • Installed mods: Guardrails will interrogate the list of mods then build a Logging Sink filter to capture the relevant events. See the Mods tab on the Admin page for a full list of installed mods.

All of these input sources are brought together in the read-only GCP > Turbot > Event Handlers > Pub/Sub > Source and GCP > Turbot > Event Handlers > Logging > Source policy values. Looking at the "Depends On" tab of the [Pub/Sub, Logging] > Source policy values shows all the dependent policies and values. Errors in any of these policies may prevent event handlers from deploying or updating properly. The value of GCP > Turbot > Event Handlers > Pub/Sub > Source and GCP > Turbot > Event Handlers > Logging > Source is Terraform.

GCP Resources (Logging through to Guardrails Events Container)

Events in a GCP Project pass through several services on their way to Guardrails. The path is:

  1. Logging service: User events originate here
  2. Logging Sink: Events are directed to the Pub/Sub Topic by the Logging Sink
  3. Pub/Sub Topic: Provides a data path between the Logging Sink and the Subscription
  4. Pub/Sub Subscription: Responsible for making the HTTP call to pass event data back to Guardrails event ingestion endpoint.
  5. (optional) API Gateway and Events Proxy: Some enterprise customers with private ALBs will deploy an API Gateway to make the transition from a public API endpoint to a private ALB. The Events Proxy Lambda function passes an event from the non-VPC API gateway to the VPC bound ALB. Guardrails SaaS customers do not have this step.
  6. Guardrails ALB: The common entry point for events and API calls.
  7. Guardrails Events Container: Events are processed here, triggering CMDB updates, or control runs.