Google Cloud Functions Sink Connector for Confluent Platform

The Kafka Connect Google Cloud Functions Sink connector integrates Apache Kafka® with Google Cloud Functions. The connector consumes records from Kafka topic(s) and executes a Google Cloud Function. Each request sent to Google Cloud Functions can contain up to max.batch.size records. The connector can also send many requests concurrently, set by max.pending.requests.

The Connector also supports invoking authenticated functions–that is, functions with private access. The user must provide service user credentials using either the gcf.credentials.json or gcf.credentials.path configuration options to use this functionality. The service user, whose credentials are provided, must also have a minimum of cloudfunctions.functions.get and cloudfunctions.functions.invoke IAM roles assigned to it. If the user doesn’t provide the required credentials, it’s assumed that the Google Cloud function can be invoked without any authentication.

The target function must be configured and ready to accept requests with the following JSON format:

    "key": ...,
    "value": ...,
    "topic": string,
    "partition": <number>,
    "offset": <number>,
    "timestamp": <number>


The key and value are encoded as follows:

  • String, int, long, float, double, boolean, null are encoded as-is into JSON.
  • Structs are converted to JSON and exported without the schema.
  • byte[] is encoded as a base64 String and sent as a JSON string.
  • Any other Java objects are converted to String using toString(), and then sent as JSON strings.

The connector receives the responses from the Google Cloud Function and writes it to a result or error topic (set by configurations) depending on the HTTP Response code. Response code 400 and above are considered errors and anything below is a success.

The connector attempts to map each response to a single record before producing it to the corresponding topic. It can receive the responses from the Google Cloud Function in the following three formats.

  1. The first format is JSON:

        "payload": {
          "result": ...,
          "topic": string,
          "partition": <number>,
          "offset": <number>,

    This list can be out of order relative to the order that the records were provided. The connector will correctly match the record to the result based off its Kafka coordinates. However the list must be one-to-one to the list of records that were sent in the request.

  2. The second format is a JSON list:


    As long as the list is one-to-one to the list of records, the list will be assumed to be ordered and matched with the corresponding records.

  3. The third format can be any format that does not satisfy either of the above formats. The connector will report the entire response for each individual record (one-to-many correlation).


At least once delivery

This connector guarantees that records from the Kafka topic are delivered at least once.


The connector does not currently support Google Cloud Functions (2nd gen).

The connector does not currently support Single Message Transformations (SMTs) that modify the topic name. Additionally, the following transformations are not allowed:

  • io.debezium.transforms.ByLogicalTableRouter
  • io.debezium.transforms.outbox.EventRouter
  • org.apache.kafka.connect.transforms.RegexRouter
  • org.apache.kafka.connect.transforms.TimestampRouter
  • io.confluent.connect.transforms.MessageTimestampRouter
  • io.confluent.connect.transforms.ExtractTopic$Key
  • io.confluent.connect.transforms.ExtractTopic$Value

Install the Google Cloud Functions Connector

You can install this connector by using the confluent connect plugin install command, or by manually downloading the ZIP file.


  • You must install the connector on every machine where Connect will run.

  • An installation of the latest (latest) connector version.

    To install the latest connector version, navigate to your Confluent Platform installation directory and run the following command:

    confluent connect plugin install confluentinc/kafka-connect-gcp-functions:latest

    You can install a specific version by replacing latest with a version number as shown in the following example:

    confluent connect plugin install confluentinc/kafka-connect-gcp-functions:1.0.0-preview

Install the connector manually

Download and extract the ZIP file for your connector and then follow the manual connector installation instructions.


You can use this connector for a 30-day trial period without a license key.

After 30 days, you must purchase a connector subscription which includes Confluent enterprise license keys to subscribers, along with enterprise-level support for Confluent Platform and your connectors. If you are a subscriber, you can contact Confluent Support at for more information.

See Confluent Platform license for license properties and Confluent License Properties for information about the license topic.

Configuration Properties

For a complete list of configuration properties for this connector, see Configuration Reference for Google Cloud Functions Sink Connector for Confluent Platform.

For an example of how to get Kafka Connect connected to Confluent Cloud, see Connect Self-Managed Kafka Connect to Confluent Cloud.

Quick Start

This quick start uses the Google Cloud Functions Sink connector to consume records and send them to a Google Cloud Functions function.

  1. Before starting the connector, create and deploy a basic Google Cloud Functions instance.

    • Navigate to the Google Cloud Console.
    • Go to the Cloud Functions tab.
    • Create a new function.
    • For creating an unauthenticated function select Allow unauthenticated invocations and go ahead.
    • For authenticated functions select Require Authentication and then click Variables, Networking and Advanced Settings to display additional settings. Click the Service account drop down and select the desired service account.
    • Note down the project id, the region, and the function name as they will be used later.
    • Further, to add an invoker account for an already deployed function, click Add members in the Permission tab of the functions home page. In the popup, select add member and select Cloud Functions Invoker Role.
  2. Install the connector by running the following command from your Confluent Platform installation directory:

    confluent connect plugin install confluentinc/kafka-connect-gcp-functions:latest
  3. Start Confluent Platform.

    confluent local services start
  4. Produce test data to the functions-messages topic in Kafka using the CLI command below.

    echo key1,value1 | confluent local services kafka produce functions-messages --property parse.key=true --property key.separator=,
    echo key2,value2 | confluent local services kafka produce functions-messages --property parse.key=true --property key.separator=,
    echo key3,value3 | confluent local services kafka produce functions-messages --property parse.key=true --property key.separator=,
  5. Create a gcp-functions.json file with the following contents:

      "name": "gcp-functions",
      "config": {
        "topics": "functions-messages",
        "tasks.max": "1",
        "connector.class": "io.confluent.connect.gcp.functions.GoogleCloudFunctionsSinkConnector",
        "confluent.topic.bootstrap.servers": "localhost:9092",
        "": "<insert function name here>",
        "": "<insert project id here>",
        "region": "<insert region here>",
        "gcf.credentials.path": "<insert path to service credentials JSON here>",
        "reporter.bootstrap.servers": "localhost:9092",
        "": "test-error",
        "reporter.error.topic.replication.factor": 1,
        "reporter.error.topic.key.format": "string",
        "reporter.error.topic.value.format": "string",
        "": "test-result",
        "reporter.result.topic.key.format": "string",
        "reporter.result.topic.value.format": "string",
        "reporter.result.topic.replication.factor": 1


    For details about using this connector with Kafka Connect Reporter, see Connect Reporter.

  6. Load the Google Cloud Functions Sink connector.


    You must include a double dash (--) between the topic name and your flag. For more information, see this post.

    confluent local services connect connector load gcp-functions --config gcp-functions.json


    Don’t use the CLI commands in production environments.

  7. Confirm that the connector is in a RUNNING state.

    confluent local services connect connector status gcp-functions
  8. Confirm that the messages were delivered to the result topic in Kafka

    confluent local services kafka consume test-result --from-beginning
  9. Cleanup resources

    • Delete the connector

      confluent local services connect connector unload gcp-functions
    • Stop Confluent Platform

      confluent local stop
    • Delete the created Google Cloud Function in the Google Cloud Platform portal.