Trigger functions with Firestore documents

This guide shows examples of functions that are triggered when you make changes to a document inside of a specified collection.

Before you begin

Before you run the sample code in this guide, you'll need to do the following:

• Enable APIs and grant the required roles for deploying functions
• Set up a Firestore database

Examples

The following examples demonstrate how to write functions that respond to a Firestore trigger.

Example 1: Hello Firestore function

The following sample prints the fields of a triggering Firestore event:

Node.js

/**
 * Cloud Event Function triggered by a change to a Firestore document.
 */
const functions = require('@google-cloud/functions-framework');
const protobuf = require('protobufjs');

functions.cloudEvent('helloFirestore', async cloudEvent => {
  console.log(`Function triggered by event on: ${cloudEvent.source}`);
  console.log(`Event type: ${cloudEvent.type}`);

  console.log('Loading protos...');
  const root = await protobuf.load('data.proto');
  const DocumentEventData = root.lookupType(
    'google.events.cloud.firestore.v1.DocumentEventData'
  );

  console.log('Decoding data...');
  const firestoreReceived = DocumentEventData.decode(cloudEvent.data);

  console.log('\nOld value:');
  console.log(JSON.stringify(firestoreReceived.oldValue, null, 2));

  console.log('\nNew value:');
  console.log(JSON.stringify(firestoreReceived.value, null, 2));
});

Python

from cloudevents.http import CloudEvent
import functions_framework
from google.events.cloud import firestore


@functions_framework.cloud_event
def hello_firestore(cloud_event: CloudEvent) -> None:
    """Triggers by a change to a Firestore document.

    Args:
        cloud_event: cloud event with information on the firestore event trigger
    """
    firestore_payload = firestore.DocumentEventData()
    firestore_payload._pb.ParseFromString(cloud_event.data)

    print(f"Function triggered by change to: {cloud_event['source']}")

    print("\nOld value:")
    print(firestore_payload.old_value)

    print("\nNew value:")
    print(firestore_payload.value)

Go

// Package hellofirestore contains a Cloud Event Function triggered by a Cloud Firestore event.
package hellofirestore

import (
	"context"
	"fmt"

	"github.com/GoogleCloudPlatform/functions-framework-go/functions"
	"github.com/cloudevents/sdk-go/v2/event"
	"github.com/googleapis/google-cloudevents-go/cloud/firestoredata"
	"google.golang.org/protobuf/proto"
)

func init() {
	functions.CloudEvent("helloFirestore", HelloFirestore)
}

// HelloFirestore is triggered by a change to a Firestore document.
func HelloFirestore(ctx context.Context, event event.Event) error {
	var data firestoredata.DocumentEventData

	// If you omit `DiscardUnknown`, protojson.Unmarshal returns an error
	// when encountering a new or unknown field.
	options := proto.UnmarshalOptions{
		DiscardUnknown: true,
	}
	err := options.Unmarshal(event.Data(), &data)

	if err != nil {
		return fmt.Errorf("proto.Unmarshal: %w", err)
	}

	fmt.Printf("Function triggered by change to: %v\n", event.Source())
	fmt.Printf("Old value: %+v\n", data.GetOldValue())
	fmt.Printf("New value: %+v\n", data.GetValue())
	return nil
}

Java

import com.google.cloud.functions.CloudEventsFunction;
import com.google.events.cloud.firestore.v1.DocumentEventData;
import com.google.protobuf.InvalidProtocolBufferException;
import io.cloudevents.CloudEvent;
import java.util.logging.Logger;

public class FirebaseFirestore implements CloudEventsFunction {
  private static final Logger logger = Logger.getLogger(FirebaseFirestore.class.getName());

  @Override
  public void accept(CloudEvent event) throws InvalidProtocolBufferException {
    DocumentEventData firestoreEventData = DocumentEventData
        .parseFrom(event.getData().toBytes());

    logger.info("Function triggered by event on: " + event.getSource());
    logger.info("Event type: " + event.getType());

    logger.info("Old value:");
    logger.info(firestoreEventData.getOldValue().toString());

    logger.info("New value:");
    logger.info(firestoreEventData.getValue().toString());
  }
}

C#

using CloudNative.CloudEvents;
using Google.Cloud.Functions.Framework;
using Google.Events.Protobuf.Cloud.Firestore.V1;
using Microsoft.Extensions.Logging;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace FirebaseFirestore;

public class Function : ICloudEventFunction<DocumentEventData>
{
    private readonly ILogger _logger;

    public Function(ILogger<Function> logger) =>
        _logger = logger;

    public Task HandleAsync(CloudEvent cloudEvent, DocumentEventData data, CancellationToken cancellationToken)
    {
        _logger.LogInformation("Function triggered by event on {subject}", cloudEvent.Subject);
        _logger.LogInformation("Event type: {type}", cloudEvent.Type);
        MaybeLogDocument("Old value", data.OldValue);
        MaybeLogDocument("New value", data.Value);

        // In this example, we don't need to perform any asynchronous operations, so the
        // method doesn't need to be declared async.
        return Task.CompletedTask;
    }

    /// <summary>
    /// Logs the names and values of the fields in a document in a very simplistic way.
    /// </summary>
    private void MaybeLogDocument(string message, Document document)
    {
        if (document is null)
        {
            return;
        }

        // ConvertFields converts the Firestore representation into a .NET-friendly
        // representation.
        IReadOnlyDictionary<string, object> fields = document.ConvertFields();
        var fieldNamesAndTypes = fields
            .OrderBy(pair => pair.Key)
            .Select(pair => $"{pair.Key}: {pair.Value}");
        _logger.LogInformation(message + ": {fields}", string.Join(", ", fieldNamesAndTypes));
    }
}

Deploy the Hello Firestore function

If you haven't already done so, set up your Firestore database.

After deploying a function, you can configure a trigger using the Google Cloud console, Google Cloud CLI, or Terraform.

Console

When you use the Google Cloud console to create a function, you can also add a trigger to your function. Follow these steps to create a trigger for your function:

1. In the Google Cloud console, go to Cloud Run:

   Go to Cloud Run

2. Click Write a function, and enter the function details. For more information about configuring functions during deployment, see Deploy functions.

3. In the Trigger section, click Add trigger.

4. Select Firestore trigger.

5. In the Eventarc trigger pane, modify the trigger details as follows:

   1. Enter a name for the trigger in the Trigger name field, or use the default name.

   2. Select a Trigger type from the list:

      • Google Sources to specify triggers for Pub/Sub, Cloud Storage, Firestore, and other Google event providers.

      • Third-party to integrate with non-Google providers that offer an Eventarc source. For more information, see Third-party events in Eventarc.

   3. Select Cloud Firestore from the Event provider list, to select a product that provides the type of event for triggering your function. For the list of event providers, see Event providers and destinations.

   4. Select type=google.cloud.firestore.document.v1.written from the Event type list. Your trigger configuration varies depending on the supported event type. For more information, see Event types.

   5. Leave the Event data content type field as is.

   6. In the Filters section, select a database, operation and attribute values, or use the default selections.

   7. If the Region field is enabled, select a location for the Eventarc trigger. In general, the location of an Eventarc trigger should match the location of the Google Cloud resource that you want to monitor for events. In most scenarios, you should also deploy your function in the same region. See Understand Eventarc locations for more details about Eventarc trigger locations.

   8. In the Service account field, select a service account. Eventarc triggers are linked to service accounts to use as an identity when invoking your function. Your Eventarc trigger's service account must have the permission to invoke your function. By default, Cloud Run uses the Compute Engine default service account.

   9. Optionally, 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, and route/subroute.

   10. Optionally, to enable retries if the delivery attempt fails, select the Enable retry on failure checkbox; otherwise, the default behavior is a single delivery attempt with no retries. For more information, see Retry events.

6. Once you've completed the required fields, click Save trigger.

7. Click Create.

8. In the Source tab, edit the source code if needed, then select Save and redeploy.

gcloud

When you create a function using the gcloud CLI, you must first deploy your function, and then create a trigger. Follow these steps to create a trigger for your function:

1. Run the following command in the directory that contains the sample code to deploy your function:

   gcloud run deploy FUNCTION \
       --source . \
       --function FUNCTION_ENTRYPOINT \
       --base-image BASE_IMAGE_ID \
       --region REGION
   

   Replace the following:

   • FUNCTION: the name of the function you are deploying. You can omit this parameter entirely, but you will be prompted for the name if you omit it.

   • FUNCTION_ENTRYPOINT: the entry point to your function in your source code. This is the code Cloud Run executes when your function runs. The value of this flag must be a function name or fully-qualified class name that exists in your source code.

   • BASE_IMAGE_ID: the base image environment for your function. For more details about base images and the packages included in each image, see Runtimes base images.

   • REGION: the Google Cloud region where you want to deploy your function. For example, europe-west1.

2. Run the following command to create a trigger that filters and routes events:

   gcloud eventarc triggers create TRIGGER_NAME  \
       --location=LOCATION \
       --destination-run-service=FUNCTION  \
       --destination-run-region=DESTINATION_RUN_REGION \
       --event-filters="type=EVENT_FILTER_TYPE" \
       --event-filters=database='(default)' \
       --event-data-content-type=application/protobuf \
       --event-filters-path-pattern=document='users/{username}' \
       --service-account=SERVICE_ACCOUNT_NAME@PROJECT_ID.
   

   Replace the following:

   • TRIGGER_NAME: 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.

     To avoid any performance and data residency issues, the location must match the location of the Google Cloud service that is generating events. For more information, see Eventarc locations.

   • FUNCTION: the name of the deployed Cloud Run function that receives the events for the trigger.
   • DESTINATION_RUN_REGION: (optional) the Cloud Run location in which the destination Cloud Run function can be found. If not specified, it is assumed that the function is in the same region as the trigger.
   • EVENT_FILTER_TYPE: the identifier of the event. An event is generated when an API call for the method succeeds. For long-running operations, the event is only generated at the end of the operation, and only if the action is performed successfully. For a list of supported event types, see Google event types supported by Eventarc.
   • SERVICE_ACCOUNT_NAME: the name of your user-managed service account.
   • PROJECT_ID: your Google Cloud project ID.

   Notes:

   • After a trigger is created, the event filter type can't be changed. For a different event type, you must create a new trigger.
   • --event-filters=type=google.cloud.firestore.document.v1.written specifies that the function is triggered when a document is created, updated or deleted, per the event type.
   • --event-filters=database='(default)' specifies the Firebase database. For the default database name, use (default).
   • --event-filters-path-pattern=document='users/{username}' provides the path pattern of the documents that should be monitored for relevant changes. This path pattern states that all documents in the users collection should be monitored. For more information, see Understand path patterns.
   • Optionally, to specify a single event delivery attempt with no retries, use the --max-retry-attempts flag. The only valid value is 1. If you omit the flag, the standard retry behavior applies. For more information, see Retry events.
   • Other flags are available. For more information, see gcloud eventarc triggers create.

Terraform

To create an Eventarc trigger for a Cloud Run function, see Create a trigger using Terraform.

Test the Hello Firestore function

To test the Hello Firestore function, set up a collection called users in your Firestore database:

1. In the Google Cloud console, go to the Firestore databases page:

   Go to Firestore

2. Click Start a collection.

3. Specify users as the collection ID.

4. To start adding the collection's first document, under Add its first document accept the auto-generated Document ID.

5. Add at least one field for the document, specifying a name and value. For example, in Field name, enter username, and in Field value, enter rowan.

6. When you're done, click Save.

   This action creates a new document, thereby triggering your function.

7. To confirm that your function was triggered, click the linked name of the function in the Google Cloud console Cloud Run Overview page to open the Service details page.

8. In the Observability tab, select the Logs tab and look for the following string:

   Function triggered by change to: //firestore.googleapis.com/projects/your-project-id/databases/(default)'

Example 2: Convert to Uppercase function

The following example retrieves the value added by the user, converts the string at that location to uppercase, and replaces the value with the uppercase string:

Node.js

Use protobufjs to decode the event data. Include the google.events.cloud.firestore.v1 data.proto in your source.

const functions = require('@google-cloud/functions-framework');
const Firestore = require('@google-cloud/firestore');
const protobuf = require('protobufjs');

const firestore = new Firestore({
  projectId: process.env.GOOGLE_CLOUD_PROJECT,
});

// Converts strings added to /messages/{pushId}/original to uppercase
functions.cloudEvent('makeUpperCase', async cloudEvent => {
  console.log('Loading protos...');
  const root = await protobuf.load('data.proto');
  const DocumentEventData = root.lookupType(
    'google.events.cloud.firestore.v1.DocumentEventData'
  );

  console.log('Decoding data...');
  const firestoreReceived = DocumentEventData.decode(cloudEvent.data);

  const resource = firestoreReceived.value.name;
  const affectedDoc = firestore.doc(resource.split('/documents/')[1]);

  const curValue = firestoreReceived.value.fields.original.stringValue;
  const newValue = curValue.toUpperCase();

  if (curValue === newValue) {
    // Value is already upper-case
    // Don't perform a(nother) write to avoid infinite loops
    console.log('Value is already upper-case.');
    return;
  }

  console.log(`Replacing value: ${curValue} --> ${newValue}`);
  affectedDoc.set({
    original: newValue,
  });
});

Python

from cloudevents.http import CloudEvent
import functions_framework
from google.cloud import firestore
from google.events.cloud import firestore as firestoredata

client = firestore.Client()


# Converts strings added to /messages/{pushId}/original to uppercase
@functions_framework.cloud_event
def make_upper_case(cloud_event: CloudEvent) -> None:
    firestore_payload = firestoredata.DocumentEventData()
    firestore_payload._pb.ParseFromString(cloud_event.data)

    path_parts = firestore_payload.value.name.split("/")
    separator_idx = path_parts.index("documents")
    collection_path = path_parts[separator_idx + 1]
    document_path = "/".join(path_parts[(separator_idx + 2) :])

    print(f"Collection path: {collection_path}")
    print(f"Document path: {document_path}")

    affected_doc = client.collection(collection_path).document(document_path)

    cur_value = firestore_payload.value.fields["original"].string_value
    new_value = cur_value.upper()

    if cur_value != new_value:
        print(f"Replacing value: {cur_value} --> {new_value}")
        affected_doc.set({"original": new_value})
    else:
        # Value is already upper-case
        # Don't perform a second write (which can trigger an infinite loop)
        print("Value is already upper-case.")

Go

// Package upper contains a Firestore Cloud Function.
package upper

import (
	"context"
	"errors"
	"fmt"
	"log"
	"os"
	"strings"

	"cloud.google.com/go/firestore"
	firebase "firebase.google.com/go/v4"
	"github.com/GoogleCloudPlatform/functions-framework-go/functions"
	"github.com/cloudevents/sdk-go/v2/event"
	"github.com/googleapis/google-cloudevents-go/cloud/firestoredata"
	"google.golang.org/protobuf/proto"
)

// set the GOOGLE_CLOUD_PROJECT environment variable when deploying.
var projectID = os.Getenv("GOOGLE_CLOUD_PROJECT")

// client is a Firestore client, reused between function invocations.
var client *firestore.Client

func init() {
	// Use the application default credentials.
	conf := &firebase.Config{ProjectID: projectID}

	// Use context.Background() because the app/client should persist across
	// invocations.
	ctx := context.Background()

	app, err := firebase.NewApp(ctx, conf)
	if err != nil {
		log.Fatalf("firebase.NewApp: %v", err)
	}

	client, err = app.Firestore(ctx)
	if err != nil {
		log.Fatalf("app.Firestore: %v", err)
	}

	// Register cloud event function
	functions.CloudEvent("MakeUpperCase", MakeUpperCase)
}

// MakeUpperCase is triggered by a change to a Firestore document. It updates
// the `original` value of the document to upper case.
func MakeUpperCase(ctx context.Context, e event.Event) error {
	var data firestoredata.DocumentEventData

	// If you omit `DiscardUnknown`, protojson.Unmarshal returns an error
	// when encountering a new or unknown field.
	options := proto.UnmarshalOptions{
		DiscardUnknown: true,
	}
	err := options.Unmarshal(e.Data(), &data)

	if err != nil {
		return fmt.Errorf("proto.Unmarshal: %w", err)
	}

	if data.GetValue() == nil {
		return errors.New("Invalid message: 'Value' not present")
	}

	fullPath := strings.Split(data.GetValue().GetName(), "/documents/")[1]
	pathParts := strings.Split(fullPath, "/")
	collection := pathParts[0]
	doc := strings.Join(pathParts[1:], "/")

	var originalStringValue string
	if v, ok := data.GetValue().GetFields()["original"]; ok {
		originalStringValue = v.GetStringValue()
	} else {
		return errors.New("Document did not contain field \"original\"")
	}

	newValue := strings.ToUpper(originalStringValue)
	if originalStringValue == newValue {
		log.Printf("%q is already upper case: skipping", originalStringValue)
		return nil
	}
	log.Printf("Replacing value: %q -> %q", originalStringValue, newValue)

	newDocumentEntry := map[string]string{"original": newValue}
	_, err = client.Collection(collection).Doc(doc).Set(ctx, newDocumentEntry)
	if err != nil {
		return fmt.Errorf("Set: %w", err)
	}
	return nil
}

Java

import com.google.cloud.firestore.Firestore;
import com.google.cloud.firestore.FirestoreOptions;
import com.google.cloud.firestore.SetOptions;
import com.google.cloud.functions.CloudEventsFunction;
import com.google.events.cloud.firestore.v1.DocumentEventData;
import com.google.events.cloud.firestore.v1.Value;
import com.google.protobuf.InvalidProtocolBufferException;
import io.cloudevents.CloudEvent;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.logging.Logger;

public class FirebaseFirestoreReactive implements CloudEventsFunction {
  private static final Logger logger = Logger.getLogger(FirebaseFirestoreReactive.class.getName());
  private final Firestore firestore;

  private static final String FIELD_KEY = "original";
  private static final String APPLICATION_PROTOBUF = "application/protobuf";

  public FirebaseFirestoreReactive() {
    this(FirestoreOptions.getDefaultInstance().getService());
  }

  public FirebaseFirestoreReactive(Firestore firestore) {
    this.firestore = firestore;
  }

  @Override
  public void accept(CloudEvent event)
      throws InvalidProtocolBufferException, InterruptedException, ExecutionException {
    if (event.getData() == null) {
      logger.warning("No data found in event!");
      return;
    }

    if (!event.getDataContentType().equals(APPLICATION_PROTOBUF)) {
      logger.warning(String.format("Found unexpected content type %s, expected %s",
          event.getDataContentType(),
          APPLICATION_PROTOBUF));
      return;
    }

    DocumentEventData firestoreEventData = DocumentEventData
        .parseFrom(event.getData().toBytes());

    // Get the fields from the post-operation document snapshot
    // https://firebase.google.com/docs/firestore/reference/rest/v1/projects.databases.documents#Document
    Map<String, Value> fields = firestoreEventData.getValue().getFieldsMap();
    if (!fields.containsKey(FIELD_KEY)) {
      logger.warning("Document does not contain original field");
      return;
    }
    String currValue = fields.get(FIELD_KEY).getStringValue();
    String newValue = currValue.toUpperCase();

    if (currValue.equals(newValue)) {
      logger.info("Value is already upper-case");
      return;
    }

    // Retrieve the document name from the resource path:
    // projects/{project_id}/databases/{database_id}/documents/{document_path}
    String affectedDoc = firestoreEventData.getValue()
        .getName()
        .split("/documents/")[1]
        .replace("\"", "");

    logger.info(String.format("Replacing values: %s --> %s", currValue, newValue));

    // Wait for the async call to complete
    this.firestore
        .document(affectedDoc)
        .set(Map.of(FIELD_KEY, newValue), SetOptions.merge())
        .get();
  }
}

C#

using CloudNative.CloudEvents;
using Google.Cloud.Firestore;
using Google.Cloud.Functions.Framework;
using Google.Cloud.Functions.Hosting;
using Google.Events.Protobuf.Cloud.Firestore.V1;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace FirestoreReactive;

public class Startup : FunctionsStartup
{
    public override void ConfigureServices(WebHostBuilderContext context, IServiceCollection services) =>
        services.AddSingleton(FirestoreDb.Create());
}

// Register the startup class to provide the Firestore dependency.
[FunctionsStartup(typeof(Startup))]
public class Function : ICloudEventFunction<DocumentEventData>
{
    private readonly ILogger _logger;
    private readonly FirestoreDb _firestoreDb;

    public Function(ILogger<Function> logger, FirestoreDb firestoreDb) =>
        (_logger, _firestoreDb) = (logger, firestoreDb);

    public async Task HandleAsync(CloudEvent cloudEvent, DocumentEventData data, CancellationToken cancellationToken)
    {
        // Get the recently-written value. This expression will result in a null value
        // if any of the following is true:
        // - The event doesn't contain a "new" document
        // - The value doesn't contain a field called "original"
        // - The "original" field isn't a string
        string currentValue = data.Value?.ConvertFields().GetValueOrDefault("original") as string;
        if (currentValue is null)
        {
            _logger.LogWarning($"Event did not contain a suitable document");
            return;
        }

        string newValue = currentValue.ToUpperInvariant();
        if (newValue == currentValue)
        {
            _logger.LogInformation("Value is already upper-cased; no replacement necessary");
            return;
        }

        // The CloudEvent subject is "documents/x/y/...".
        // The Firestore SDK FirestoreDb.Document method expects a reference relative to
        // "documents" (so just the "x/y/..." part). This may be simplified over time.
        if (cloudEvent.Subject is null || !cloudEvent.Subject.StartsWith("documents/"))
        {
            _logger.LogWarning("CloudEvent subject is not a document reference.");
            return;
        }
        string documentPath = cloudEvent.Subject.Substring("documents/".Length);

        _logger.LogInformation("Replacing '{current}' with '{new}' in '{path}'", currentValue, newValue, documentPath);
        await _firestoreDb.Document(documentPath).UpdateAsync("original", newValue, cancellationToken: cancellationToken);
    }
}

Note: Updating the function-triggering Firestore document might create subsequent updated events, which might cascade into an infinite loop within your function. To solve this problem, use trigger types that ignore updates (such as created), or configure your function to only write to Firestore if the underlying value has changed.

Deploy the Convert to Uppercase function

If you haven't already done so, set up your Firestore database.

After deploying a function, you can configure a trigger using the Google Cloud console, Google Cloud CLI, or Terraform.

Console

When you use the Google Cloud console to create a function, you can also add a trigger to your function. Follow these steps to create a trigger for your function:

1. In the Google Cloud console, go to Cloud Run:

   Go to Cloud Run

2. Click Write a function, and enter the function details. For more information about configuring functions during deployment, see Deploy functions.

3. In the Trigger section, click Add trigger.

4. Select Firestore trigger.

5. In the Eventarc trigger pane, modify the trigger details as follows:

   1. Enter a name for the trigger in the Trigger name field, or use the default name.

   2. Select a Trigger type from the list:

      • Google Sources to specify triggers for Pub/Sub, Cloud Storage, Firestore, and other Google event providers.

      • Third-party to integrate with non-Google providers that offer an Eventarc source. For more information, see Third-party events in Eventarc.

   3. Select Firestore from the Event provider list, to select a product that provides the type of event for triggering your function. For the list of event providers, see Event providers and destinations.

   4. Select type=google.cloud.firestore.document.v1.written from the Event type list. Your trigger configuration varies depending on the supported event type. For more information, see Event types.

   5. Leave the Event data content type field as is.

   6. In the Filters section, select a database, operation and attribute values, or use the default selections. If you named your database, enter the name in the Attribute value 1 field.

   7. If the Region field is enabled, select a location for the Eventarc trigger. In general, the location of an Eventarc trigger should match the location of the Google Cloud resource that you want to monitor for events. In most scenarios, you should also deploy your function in the same region. See Understand Eventarc locations for more details about Eventarc trigger locations.

   8. In the Service account field, select a service account. Eventarc triggers are linked to service accounts to use as an identity when invoking your function. Your Eventarc trigger's service account must have the permission to invoke your function. By default, Cloud Run uses the Compute Engine default service account.

   9. Optionally, 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, and route/subroute.

   10. Optionally, to enable retries if the delivery attempt fails, select the Enable retry on failure checkbox; otherwise, the default behavior is a single delivery attempt with no retries. For more information, see Retry events.

6. Once you've completed the required fields, click Save trigger.

7. Click Create.

8. In the Source tab, edit the source code if needed, then select Save and redeploy.

gcloud

When you create a function using the gcloud CLI, you must first deploy your function, and then create a trigger. Follow these steps to create a trigger for your function:

1. Run the following command in the directory that contains the sample code to deploy your function:

   gcloud run deploy FUNCTION \
       --source . \
       --function FUNCTION_ENTRYPOINT \
       --base-image BASE_IMAGE_ID \
       --region REGION
   

   Replace the following:

   • FUNCTION: the name of the function you are deploying. You can omit this parameter entirely, but you will be prompted for the name if you omit it.

   • FUNCTION_ENTRYPOINT: the entry point to your function in your source code. This is the code Cloud Run executes when your function runs. The value of this flag must be a function name or fully-qualified class name that exists in your source code.

   • BASE_IMAGE_ID: the base image environment for your function. For more details about base images and the packages included in each image, see Runtimes base images.

   • REGION: the Google Cloud region where you want to deploy your function. For example, europe-west1.

2. Run the following command to create a trigger that filters and routes events:

   gcloud eventarc triggers create TRIGGER_NAME  \
       --location=LOCATION \
       --destination-run-service=FUNCTION  \
       --destination-run-region=DESTINATION_RUN_REGION \
       --event-filters=type=google.cloud.firestore.document.v1.written \
       --event-filters=database='(default)' \
       --event-data-content-type=application/protobuf \
       --event-filters-path-pattern=document='messages/{pushId}' \
       --service-account=SERVICE_ACCOUNT_NAME@PROJECT_ID.
   

   Replace the following:

   • TRIGGER_NAME: 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.

     To avoid any performance and data residency issues, the location must match the location of the Google Cloud service that is generating events. For more information, see Eventarc locations.

   • FUNCTION: the name of the deployed Cloud Run function that receives the events for the trigger.
   • DESTINATION_RUN_REGION: (optional) the Cloud Run location in which the destination Cloud Run function can be found. If not specified, it is assumed that the function is in the same region as the trigger.
   • EVENT_FILTER_TYPE: the identifier of the event. An event is generated when an API call for the method succeeds. For long-running operations, the event is only generated at the end of the operation, and only if the action is performed successfully. For a list of supported event types, see Google event types supported by Eventarc.
   • SERVICE_ACCOUNT_NAME: the name of your user-managed service account.
   • PROJECT_ID: your Google Cloud project ID.

   Notes:

   • After a trigger is created, the event filter type can't be changed. For a different event type, you must create a new trigger.
   • --event-filters=type=google.cloud.firestore.document.v1.written specifies that the function is triggered when a document is created, updated or deleted, per the event type.
   • --event-filters=database='(default)' specifies the Firebase database. For the default database name, use (default).
   • --event-filters-path-pattern=document='users/{username}' provides the path pattern of the documents that should be monitored for relevant changes. This path pattern states that all documents in the users collection should be monitored. For more information, see Understand path patterns.
   • Optionally, to specify a single event delivery attempt with no retries, use the --max-retry-attempts flag. The only valid value is 1. If you omit the flag, the standard retry behavior applies. For more information, see Retry events.
   • Other flags are available. For more information, see gcloud eventarc triggers create.

Terraform

To create an Eventarc trigger for a Cloud Run function, see Create a trigger using Terraform.

Use the other fields as is:

• --event-filters=type=google.cloud.firestore.document.v1.written specifies that the function is triggered when a document is created, updated or deleted, per the google.cloud.firestore.document.v1.written event type.
• --event-filters=database='(default)' specifies the Firestore database. For the default database name, use (default).
• --event-filters-path-pattern=document='messages/{pushId}' provides the path pattern of the documents that should be monitored for relevant changes. This path pattern states that all documents in the messages collection should be monitored. For more information, see Understand path patterns.

Test the Convert to Uppercase function

To test the Convert to Uppercase function you just deployed, set up a collection called messages in your Firestore database:

1. In the Google Cloud console, go to the Firestore databases page:

   Go to Firestore

2. Select the Database ID for your Firestore database.

3. Click Start a collection.

4. Specify messages as the collection ID.

5. To start adding the collection's first document, under Add its first document accept the auto-generated Document ID.

6. To trigger your deployed function, add a document where the Field name is original and the Field value is minka.

7. When you save the document, you can see the lowercase word in the value field convert to uppercase.

   If you subsequently edit the field value to contain lowercase letters, that triggers the function again, converting all lowercase letters to uppercase.

Limitations for functions

• Ordering is not guaranteed. Rapid changes can trigger function invocations in an unexpected order.
• Events are delivered at least once, but a single event may result in multiple function invocations. Avoid depending on exactly-once mechanics, and write idempotent functions.
• A trigger is associated with a single database. You cannot create a trigger that matches multiple databases.
• Deleting a database does not automatically delete any triggers for that database. The trigger stops delivering events but continues to exist until you delete the trigger.