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 an Google Cloud Function. Each request sent to Google Cloud Functions contains 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 i.e. functions with private access. It is required for the user to provide service user credentials either via gcf.credentials.json or gcf.credentials.path configuration option 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 no credentials are provided 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).

Install the Google Cloud Functions Connector

You can install this connector by using the Confluent Hub client (recommended) or you can manually download the ZIP file.

Install the connector using Confluent Hub

Confluent Hub Client must be installed. This is installed by default with Confluent Enterprise.

Navigate to your Confluent Platform installation directory and run the following command to install the latest (latest) connector version. The connector must be installed on every machine where Connect will run.

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

You can install a specific version by replacing latest with a version number. For example:

confluent-hub 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, this connector is available under a Confluent enterprise license. Confluent issues enterprise license keys to subscribers, along with providing enterprise-level support for Confluent Platform and your connectors. If you are a subscriber, please contact Confluent Support at for more information.

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

Configuration Properties

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


For an example of how to get Kafka Connect connected to Confluent Cloud, see Distributed Cluster in Connect 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 connecting, 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 a already deployed function, click Add members in Permission tab of the functions home page. In the popup, select add member and select Cloud Functions Invoker Role.
  2. Install the connector through the Confluent Hub Client.

    # run from your CP installation directory
    confluent-hub install confluentinc/kafka-connect-gcp-functions:latest
  3. Start Confluent Platform.


    The command syntax for the Confluent CLI development commands changed in 5.3.0. These commands have been moved to confluent local. For example, the syntax for confluent start is now confluent local services start. For more information, see confluent local.

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