Route Firebase Realtime Database events to GKE

Standard

Preview — Eventarc for GKE destinations; Firebase Realtime Database direct events

This feature is subject to the "Pre-GA Offerings Terms" in the General Service Terms section of the Service Specific Terms. Pre-GA features are available "as is" and might have limited support. For more information, see the launch stage descriptions.

An Eventarc trigger declares your interest in a certain event or set of events. You can configure event routing by specifying filters for the trigger, including the event source, and the target Google Kubernetes Engine (GKE) service running in a GKE cluster. Note that targets can only include services running in (public or private) GKE clusters with public endpoints. To target services in GKE clusters with private endpoints, route events to internal HTTP endpoints.

Eventarc delivers events to the event receiver in a CloudEvents format through an HTTP request.

These instructions show you how to configure event routing to your GKE service that is triggered by a direct Firebase Realtime Database event. For more details, see the list of supported direct events.

Note: If both direct and audit log events are supported for a Google provider, we recommend that you create a trigger that filters for the direct event. Direct events offer a number of advantages over audit log events. For more information, see Event routes.

Before you begin

You must enable Workload Identity Federation for GKE on the GKE cluster that the destination service is running on. Workload Identity Federation for GKE is required to properly set up the event forwarder and is the recommended way to access Google Cloud services from applications running within GKE due to its improved security properties and manageability.

Workload Identity Federation for GKE

Applications running on GKE might need access to Google Cloud APIs. Workload Identity Federation for GKE allows a Kubernetes service account in your GKE cluster to act as an IAM service account. Pods that use the configured Kubernetes service account automatically authenticate as the IAM service account when accessing Google Cloud APIs. Using Workload Identity Federation for GKE lets you assign distinct, fine-grained identities and authorization for each application in your cluster. Note that specific permissions must be granted to the Eventarc trigger's service account. In this document, see the steps to Create a service account.

For more information on enabling and configuring Workload Identity Federation for GKE on your GKE clusters, refer to Use Workload Identity Federation for GKE.

Event forwarder

Eventarc's event forwarder pulls new events from Eventarc and forwards them to the GKE destination. This component acts as a mediator between the Pub/Sub transport layer and the GKE service. It works on existing services and also supports signaling services (including those not exposed outside of the fully-managed cluster) while simplifying setup and maintenance. At a networking level, to receive events in a GKE service, you don't need to open the service to external traffic as all events are delivered from an origin that resides within the same GKE cluster.

Note that the event forwarder's lifecycle is managed by Eventarc, and if you accidentally delete the event forwarder, Eventarc will restore this component.

For each trigger pointing to a GKE destination, the event forwarder (a specifically configured gke-forwarder pod) does the following:

1. It uses the Pub/Sub API to open a StreamingPull connection to the trigger transporter (a Pub/Sub topic and subscription) and receives events as they become available.

2. It transforms events to the correct CloudEvents format and encodes and delivers them as an HTTP POST request to the target GKE service.

The Eventarc service agent needs the permission to run and regularly update the gke-forwarder instance. This permission must be granted once-per-project. For details, in this document, see Enable GKE destinations.

Prepare to create a trigger

For each trigger that targets a GKE service, Eventarc creates an event forwarder component. Eventarc requires permissions to install the component and manage resources in the GKE cluster. Before creating an Eventarc trigger for GKE destinations, ensure that you complete the following tasks.

Console

1. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   Go to project selector

2. Enable the Eventarc, Eventarc Publishing, Google Kubernetes Engine, and Resource Manager APIs.

   Enable the APIs

3. If applicable, enable the API related to the direct events. For example, for Firebase Realtime Database events, enable the Firebase Realtime Database API.

4. If you don't already have one, create a user-managed service account, then grant it the roles and permissions necessary so that Eventarc can manage events for your target service.

   1. In the Google Cloud console, go to the Create service account page.

      Go to Create service account

   2. Select your project.

   3. In the Service account name field, enter a name. The Google Cloud console fills in the Service account ID field based on this name.

      In the Service account description field, enter a description. For example, Service account for event trigger.

   4. Click Create and continue.

   5. To provide appropriate access, in the Select a role list, select the required Identity and Access Management (IAM) roles to grant to your service account. For more information, see Roles and permissions for GKE targets.

      For additional roles, click Add another role and add each additional role.

   6. Click Continue.

   7. To finish creating the account, click Done.

gcloud

1. In the Google Cloud console, activate Cloud Shell.

   Activate Cloud Shell

   At the bottom of the Google Cloud console, a Cloud Shell session starts and displays a command-line prompt. Cloud Shell is a shell environment with the Google Cloud CLI already installed and with values already set for your current project. It can take a few seconds for the session to initialize.

2. Enable the Eventarc, Eventarc Publishing, Google Kubernetes Engine, and Resource Manager APIs.

   gcloud services enable eventarc.googleapis.com \
       eventarcpublishing.googleapis.com \
       container.googleapis.com \
       cloudresourcemanager.googleapis.com

3. If applicable, enable the API related to the direct events. For example, for Firebase Realtime Database events, enable firebasedatabase.googleapis.com.

4. If you don't already have one, create a user-managed service account, then grant it the roles and permissions necessary so that Eventarc can manage events for your target GKE destination.

   1. Create the service account:

      gcloud iam service-accounts create SERVICE_ACCOUNT_NAME
      

      Replace SERVICE_ACCOUNT_NAME with the name of the service account. It must be between 6 and 30 characters, and can contain lowercase alphanumeric characters and dashes. After you create a service account, you cannot change its name.

   2. Grant the required Identity and Access Management (IAM) roles or permissions. For more information, see Roles and permissions for GKE targets.

Enable GKE destinations

To allow Eventarc to manage resources in the GKE cluster, enable GKE destinations, and bind the Eventarc service agent with the required roles.

1. Enable GKE destinations for Eventarc:

   gcloud eventarc gke-destinations init
   

2. At the prompt to bind the required roles, enter y.

   The following roles are bound:

   • roles/compute.viewer
   • roles/container.developer
   • roles/iam.serviceAccountAdmin

Create a trigger

You can create an Eventarc trigger using the Google Cloud CLI or through the Google Cloud console.

Note: Filtering is done through an exact match and does not support wildcards or regular expressions. However, you can use the --event-filters-path-pattern flag in the following gcloud CLI command, or define a path pattern through the console. For more information, see Understand path patterns.

Console

1. In the Google Cloud console, go to the Eventarc Triggers page.

   Go to Triggers

2. Click Create trigger.
3. Type a Trigger name.

   This is the ID of the trigger and it must start with a letter. It can contain up to 63 lowercase letters, numbers, or hyphens.

4. For the Trigger type, select Google sources.
5. In the Event provider list, select Firebase Realtime Database.

   Note that the event provider name used in the associated Google Cloud documentation might not have a prefix of Cloud or Google Cloud. For example, on the console, Memorystore for Redis is referred to as Google Cloud Memorystore for Redis.

6. In the Event type list, from the Direct events, select an event type.
7. In the Event data content type list, select the encoding of the event payload.

   For direct events from Firebase Realtime Database, this must be application/json.

8. In the Region list, select the same region as the Google Cloud service that is generating events.

   For more information, see Eventarc locations.

9. In the Attribute 1 field, the instance resource ID acts as an event filter. Select an operator for this filter:
   • Equal
   • Path pattern

     For more information, see Understand path patterns.

10. In the Attribute value 1 field, enter the name of the database instance to receive events from. Depending on the operator that you chose in the previous step, the attribute value should be the exact name or a path pattern format.
11. For the ref attribute, select the Path pattern operator.
12. In the Attribute value 2 field, enter the database instance path to receive events from if data is created, updated, or deleted in that path or any child path.
13. Select the Service account that will invoke your service or workflow.

    Or, you can create a new service account.

    This specifies the Identity and Access Management (IAM) service account email associated with the trigger and to which you previously granted specific roles required by Eventarc.

14. In the Event destination list, select Kubernetes Engine.
15. Select a service.
    

    This is the name of the service that receives the events for the trigger. The service must be in the same project as the trigger and will receive events as HTTP POST requests sent to its root URL path (/), whenever the event is generated.

16. Optionally, you can specify the Service URL path to send the incoming request to.

    This is the relative path on the destination service to which the events for the trigger should be sent. For example: /, /route, route, route/subroute.

17. Click Create.

After a trigger is created, the event source filters cannot be modified. Instead, create a new trigger and delete the old one. For more information, see Manage triggers.

gcloud

You can create a trigger by running a gcloud eventarc triggers create command along with required and optional flags.

gcloud eventarc triggers create TRIGGER \
    --location=LOCATION \
    --destination-gke-cluster=DESTINATION_GKE_CLUSTER \
    --destination-gke-location=DESTINATION_GKE_LOCATION \
    --destination-gke-namespace=DESTINATION_GKE_NAMESPACE \
    --destination-gke-service=DESTINATION_GKE_SERVICE \
    --destination-gke-path=DESTINATION_GKE_PATH \
    --event-filters="type=EVENT_FILTER_TYPE" \
    --event-filters="instance=INSTANCE" \
    --event-filters-path-pattern="ref=REF" \
    --service-account=SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com"

Replace the following:

• TRIGGER: the ID of the trigger or a fully qualified identifier

• LOCATION: the location of the Eventarc trigger. Alternatively, you can set the eventarc/location property; for example gcloud config set eventarc/location us-central1.

  Firebase Realtime Database triggers for Eventarc are only available in certain locations and the trigger must be in the same location as the Firebase Realtime Database instance. For more information, see Eventarc locations and Realtime Database locations.

• DESTINATION_GKE_CLUSTER: the name of the GKE cluster in which the target GKE service that receives events is running.
• DESTINATION_GKE_LOCATION: (optional) the Compute Engine region of the GKE cluster in which the destination GKE service is running in. If not specified, it is assumed that the cluster is a regional cluster and is in the same region as the trigger.
• DESTINATION_GKE_NAMESPACE: (optional) the namespace in which the destination GKE service is running. If not specified, the default namespace is used.
• DESTINATION_GKE_SERVICE: the name of the GKE service that receives the events for the trigger. The service can be in any of the GKE supported locations and does not need to be in the same location as the trigger. However, the service must be in the same project as the trigger and will receive events as HTTP POST requests sent to its root URL path (/), whenever the event is generated.
• DESTINATION_GKE_PATH: (optional) the relative path you specify on the destination GKE service to which the events for the trigger should be sent. For example: /, /route, route, route/subroute.

• EVENT_FILTER_TYPE: the identifier of the Firebase Realtime Database event and can be one of the following:

  • google.firebase.database.ref.v1.created: event is sent when data is created in the database
  • google.firebase.database.ref.v1.updated: event is sent when data is updated in the database
  • google.firebase.database.ref.v1.deleted: event is sent when data is deleted in the database
  • google.firebase.database.ref.v1.written: event is sent when data is created, updated, or deleted in the database

• INSTANCE: a single database instance and the operator can be one of the following:

  • Equal; for example, --event-filters="instance=INSTANCE"
  • Path pattern; for example, --event-filters-path-pattern="instance=INSTANCE". For more information, see Understand path patterns.

• REF: the path within the database instance for which you want to receive events from when data is created, updated, or deleted in that path, or any of its children.

• SERVICE_ACCOUNT_NAME: the name of your user-managed service account.
• PROJECT_ID: your Google Cloud project ID.

Notes:

• For direct events from Firebase Realtime Database, the encoding of the event payload is application/json.
• These flags are required:
  • --event-filters="type=EVENT_FILTER_TYPE"
  • --event-filters="instance=INSTANCE" or --event-filters-path-pattern="instance=INSTANCE"
  • --event-filters-path-pattern="ref=REF"
  • After a trigger is created, the event filter type can't be changed. For a different event type, you must create a new trigger and delete the old one.
  • The --service-account flag is used to specify the Identity and Access Management (IAM) service account email associated with the trigger.

Example:

gcloud eventarc triggers create helloworld-trigger \
    --location=us-central1 \
    --destination-gke-cluster=gke-events-cluster \
    --destination-gke-location=us-central1-a \
    --destination-gke-namespace=default \
    --destination-gke-service=helloworld-events \
    --destination-gke-path=/ \
    --event-filters="type=google.firebase.database.ref.v1.created" \
    --event-filters="instance=test-instance" \
    --event-filters-path-pattern="ref=users/*" \
    --service-account=${SERVICE_ACCOUNT_NAME}@${PROJECT_ID}.iam.gserviceaccount.com

This command creates a trigger called helloworld-trigger for the event identified as google.firebase.database.ref.v1.created and for the users/* path within the database instance identified as test-instance.

Terraform

You can create a trigger for a GKE destination using Terraform. For details, see Create a trigger using Terraform.

Note: Although your trigger is created immediately, it can take up to two minutes for a trigger to propagate and filter events.

List a trigger

You can confirm the creation of a trigger by listing Eventarc triggers using the Google Cloud CLI or through the Google Cloud console.

Console

1. In the Google Cloud console, go to the Eventarc Triggers page.

   Go to Triggers

   This page lists your triggers in all locations, and includes details such as names, regions, event providers, destinations, and more.

2. To filter your triggers:

   1. Click Filter or the Filter triggers field.
   2. In the Properties list, select an option to filter the triggers by.

   You can select a single property or use the logical operator OR to add more properties.

3. To sort your triggers, beside any supported column heading, click Sort.

gcloud

Run the following command to list your triggers:

gcloud eventarc triggers list --location=-

This command lists your triggers in all locations, and includes details such as names, types, destinations, and statuses.

What's next

• Learn more about Eventarc.
• Learn how to manage triggers.