Firestore trigger

Triggers a function in response to a Firestore database update.

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Code sample

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));
        }
    }
}

Go


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

import (
	"context"
	"fmt"
	"log"
	"time"

	"cloud.google.com/go/functions/metadata"
)

// FirestoreEvent is the payload of a Firestore event.
type FirestoreEvent struct {
	OldValue   FirestoreValue `json:"oldValue"`
	Value      FirestoreValue `json:"value"`
	UpdateMask struct {
		FieldPaths []string `json:"fieldPaths"`
	} `json:"updateMask"`
}

// FirestoreValue holds Firestore fields.
type FirestoreValue struct {
	CreateTime time.Time `json:"createTime"`
	// Fields is the data for this value. The type depends on the format of your
	// database. Log the interface{} value and inspect the result to see a JSON
	// representation of your database fields.
	Fields     interface{} `json:"fields"`
	Name       string      `json:"name"`
	UpdateTime time.Time   `json:"updateTime"`
}

// HelloFirestore is triggered by a change to a Firestore document.
func HelloFirestore(ctx context.Context, e FirestoreEvent) error {
	meta, err := metadata.FromContext(ctx)
	if err != nil {
		return fmt.Errorf("metadata.FromContext: %v", err)
	}
	log.Printf("Function triggered by change to: %v", meta.Resource)
	log.Printf("Old value: %+v", e.OldValue)
	log.Printf("New value: %+v", e.Value)
	return nil
}

Java

import com.google.cloud.functions.Context;
import com.google.cloud.functions.RawBackgroundFunction;
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import java.util.logging.Logger;

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

  // Use GSON (https://github.com/google/gson) to parse JSON content.
  private static final Gson gson = new Gson();

  @Override
  public void accept(String json, Context context) {
    JsonObject body = gson.fromJson(json, JsonObject.class);
    logger.info("Function triggered by event on: " + context.resource());
    logger.info("Event type: " + context.eventType());

    if (body != null && body.has("oldValue")) {
      logger.info("Old value:");
      logger.info(body.get("oldValue").getAsString());
    }

    if (body != null && body.has("value")) {
      logger.info("New value:");
      logger.info(body.get("value").getAsString());
    }
  }
}

Node.js

/**
 * Triggered by a change to a Firestore document.
 *
 * @param {!Object} event The Cloud Functions event.
 */
exports.helloFirestore = event => {
  const triggerResource = event.resource;

  console.log(`Function triggered by event on: ${triggerResource}`);
  console.log(`Event type: ${event.eventType}`);

  if (event.oldValue && Object.keys(event.oldValue).length) {
    console.log('\nOld value:');
    console.log(JSON.stringify(event.oldValue, null, 2));
  }

  if (event.value && Object.keys(event.value).length) {
    console.log('\nNew value:');
    console.log(JSON.stringify(event.value, null, 2));
  }
};

PHP


use Google\CloudFunctions\CloudEvent;

function firebaseFirestore(CloudEvent $cloudevent)
{
    $log = fopen(getenv('LOGGER_OUTPUT') ?: 'php://stderr', 'wb');

    fwrite($log, 'Event: ' . $cloudevent->getId() . PHP_EOL);
    fwrite($log, 'Event Type: ' . $cloudevent->getType() . PHP_EOL);

    $data = $cloudevent->getData();

    $resource = $data['resource'];
    fwrite($log, 'Function triggered by event on: ' . $resource . PHP_EOL);

    if (isset($data['oldValue'])) {
        fwrite($log, 'Old value: ' . json_encode($data['oldValue']) . PHP_EOL);
    }

    if (isset($data['value'])) {
        fwrite($log, 'New value: ' . json_encode($data['value']) . PHP_EOL);
    }
}

Python

import json
def hello_firestore(data, context):
    """ Triggered by a change to a Firestore document.
    Args:
        data (dict): The event payload.
        context (google.cloud.functions.Context): Metadata for the event.
    """
    trigger_resource = context.resource

    print('Function triggered by change to: %s' % trigger_resource)

    print('\nOld value:')
    print(json.dumps(data["oldValue"]))

    print('\nNew value:')
    print(json.dumps(data["value"]))

Ruby

require "functions_framework"

# Triggered by a change to a Firestore document.
FunctionsFramework.cloud_event "hello_firestore" do |event|
  # The event parameter is a CloudEvents::Event::V1 object.
  # See https://cloudevents.github.io/sdk-ruby/latest/CloudEvents/Event/V1.html
  payload = event.data

  logger.info "Function triggered by change to: #{event.source}"
  logger.info "Old value: #{payload['oldValue']}"
  logger.info "New value: #{payload['value']}"
end

What's next

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