MongoDB to BigQuery (CDC) template

Beta

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.

This template creates a streaming pipeline that works with MongoDB change streams. To use this template, publish the change stream data to Pub/Sub. The pipeline reads the JSON records from Pub/Sub and writes them to BigQuery. The records written to BigQuery have the same format as the MongoDB to BigQuery batch template.

Pipeline requirements

• The target BigQuery dataset must exist.
• The source MongoDB instance must be accessible from the Dataflow worker machines.
• You must create a Pub/Sub topic to read the change stream. While the pipeline is running, listen for change data capture (CDC) events on the MongoDB change stream and publish them to Pub/Sub as JSON records. For more information about publishing messages to Pub/Sub, see Publish messages to topics.

Template parameters

Parameter	Description
mongoDbUri	MongoDB connection URI in the format mongodb+srv://:@.
database	Database in MongoDB to read the collection from. For example: my-db.
collection	Name of the collection inside MongoDB database. For example: my-collection.
outputTableSpec	BigQuery table to write to. For example, bigquery-project:dataset.output_table.
userOption	FLATTEN or NONE. FLATTEN flattens the documents to the first level. NONE stores the whole document as a JSON string.
inputTopic	The Pub/Sub input topic to read from, in the format of projects/<project>/topics/<topic>.
javascriptDocumentTransformGcsPath	(Optional) The Cloud Storage URI of the .js file that defines the JavaScript user-defined function (UDF) you want to use. For example, gs://my-bucket/my-udfs/my_file.js.
javascriptDocumentTransformFunctionName	(Optional) The name of the JavaScript user-defined function (UDF) that you want to use. For example, if your JavaScript function code is myTransform(inJson) { /*...do stuff...*/ }, then the function name is myTransform. For sample JavaScript UDFs, see UDF Examples.
useStorageWriteApi	(Optional) If true, the pipeline uses the BigQuery Storage Write API. The default value is false. For more information, see Using the Storage Write API.
useStorageWriteApiAtLeastOnce	(Optional) When using the Storage Write API, specifies the write semantics. To use at-least-once semantics, set this parameter to true. To use exactly-once semantics, set the parameter to false. This parameter applies only when useStorageWriteApi is true. The default value is false.
numStorageWriteApiStreams	(Optional) When using the Storage Write API, specifies the number of write streams. If useStorageWriteApi is true and useStorageWriteApiAtLeastOnce is false, then you must set this parameter.
storageWriteApiTriggeringFrequencySec	(Optional) When using the Storage Write API, specifies the triggering frequency, in seconds. If useStorageWriteApi is true and useStorageWriteApiAtLeastOnce is false, then you must set this parameter.

User-defined function

Optionally, you can extend this template by writing a user-defined function (UDF) in JavaScript. The template calls the UDF for each input element. Element payloads are serialized as JSON strings.

To use a UDF, upload the JavaScript file to Cloud Storage and set the following template parameters:

Parameter	Description
javascriptDocumentTransformGcsPath	The Cloud Storage location of the JavaScript file.
javascriptDocumentTransformFunctionName	The name of the JavaScript function.

For more information, see Create user-defined functions for Dataflow templates.

Function specification

The UDF has the following specification:

Input: a MongoDB document.

Output: an object serialized as a JSON string.

Run the template

Console

1. Go to the Dataflow Create job from template page.
Go to Create job from template
2. In the Job name field, enter a unique job name.
3. Optional: For Regional endpoint, select a value from the drop-down menu. The default region is us-central1.

   For a list of regions where you can run a Dataflow job, see Dataflow locations.

4. From the Dataflow template drop-down menu, select the MongoDB to BigQuery (CDC) template.
5. In the provided parameter fields, enter your parameter values.
6. Click Run job.

gcloud

Note: To use the Google Cloud CLI to run flex templates, you must have Google Cloud CLI version 284.0.0 or later.

In your shell or terminal, run the template:

gcloud dataflow flex-template run JOB_NAME \
    --project=PROJECT_ID \
    --region=REGION_NAME \
    --template-file-gcs-location=gs://dataflow-templates-REGION_NAME/VERSION/flex/MongoDB_to_BigQuery_CDC \
    --parameters \
outputTableSpec=OUTPUT_TABLE_SPEC,\
mongoDbUri=MONGO_DB_URI,\
database=DATABASE,\
collection=COLLECTION,\
userOption=USER_OPTION,\
inputTopic=INPUT_TOPIC

Replace the following:

• PROJECT_ID: the Google Cloud project ID where you want to run the Dataflow job
• JOB_NAME: a unique job name of your choice
• REGION_NAME: the region where you want to deploy your Dataflow job—for example, us-central1
• VERSION: the version of the template that you want to use

  You can use the following values:

  • latest to use the latest version of the template, which is available in the non-dated parent folder in the bucket— gs://dataflow-templates-REGION_NAME/latest/
  • the version name, like 2023-09-12-00_RC00, to use a specific version of the template, which can be found nested in the respective dated parent folder in the bucket— gs://dataflow-templates-REGION_NAME/
  Caution: The latest version of templates might update with breaking changes. Your production environments should use templates kept in the most recent dated parent folder to prevent these breaking changes from affecting your production workflows.
• OUTPUT_TABLE_SPEC: your target BigQuery table name.
• MONGO_DB_URI: your MongoDB URI.
• DATABASE: your MongoDB database.
• COLLECTION: your MongoDB collection.
• USER_OPTION: FLATTEN or NONE.
• INPUT_TOPIC: your Pub/Sub input topic.

API

To run the template using the REST API, send an HTTP POST request. For more information on the API and its authorization scopes, see projects.templates.launch.

POST https://dataflow.googleapis.com/v1b3/projects/PROJECT_ID/locations/LOCATION/flexTemplates:launch
{
   "launch_parameter": {
      "jobName": "JOB_NAME",
      "parameters": {
          "inputTableSpec": "INPUT_TABLE_SPEC",
          "mongoDbUri": "MONGO_DB_URI",
          "database": "DATABASE",
          "collection": "COLLECTION",
          "userOption": "USER_OPTION",
          "inputTopic": "INPUT_TOPIC"
      },
      "containerSpecGcsPath": "gs://dataflow-templates-LOCATION/VERSION/flex/MongoDB_to_BigQuery_CDC",
   }
}

Replace the following:

• PROJECT_ID: the Google Cloud project ID where you want to run the Dataflow job
• JOB_NAME: a unique job name of your choice
• LOCATION: the region where you want to deploy your Dataflow job—for example, us-central1
• VERSION: the version of the template that you want to use

  You can use the following values:

  • latest to use the latest version of the template, which is available in the non-dated parent folder in the bucket— gs://dataflow-templates-REGION_NAME/latest/
  • the version name, like 2023-09-12-00_RC00, to use a specific version of the template, which can be found nested in the respective dated parent folder in the bucket— gs://dataflow-templates-REGION_NAME/
  Caution: The latest version of templates might update with breaking changes. Your production environments should use templates kept in the most recent dated parent folder to prevent these breaking changes from affecting your production workflows.
• OUTPUT_TABLE_SPEC: your target BigQuery table name.
• MONGO_DB_URI: your MongoDB URI.
• DATABASE: your MongoDB database.
• COLLECTION: your MongoDB collection.
• USER_OPTION: FLATTEN or NONE.
• INPUT_TOPIC: your Pub/Sub input topic.

Template source code

Java

/*
 * Copyright (C) 2019 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.cloud.teleport.v2.mongodb.templates;

import static com.google.cloud.teleport.v2.utils.KMSUtils.maybeDecrypt;

import com.google.api.services.bigquery.model.TableRow;
import com.google.api.services.bigquery.model.TableSchema;
import com.google.cloud.teleport.metadata.Template;
import com.google.cloud.teleport.metadata.TemplateCategory;
import com.google.cloud.teleport.metadata.TemplateParameter;
import com.google.cloud.teleport.v2.common.UncaughtExceptionLogger;
import com.google.cloud.teleport.v2.mongodb.options.MongoDbToBigQueryOptions.BigQueryWriteOptions;
import com.google.cloud.teleport.v2.mongodb.options.MongoDbToBigQueryOptions.JavascriptDocumentTransformerOptions;
import com.google.cloud.teleport.v2.mongodb.options.MongoDbToBigQueryOptions.MongoDbOptions;
import com.google.cloud.teleport.v2.mongodb.options.MongoDbToBigQueryOptions.PubSubOptions;
import com.google.cloud.teleport.v2.mongodb.templates.MongoDbToBigQueryCdc.Options;
import com.google.cloud.teleport.v2.options.BigQueryStorageApiStreamingOptions;
import com.google.cloud.teleport.v2.transforms.JavascriptDocumentTransformer.TransformDocumentViaJavascript;
import com.google.cloud.teleport.v2.utils.BigQueryIOUtils;
import java.io.IOException;
import javax.script.ScriptException;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.gcp.bigquery.BigQueryIO;
import org.apache.beam.sdk.io.gcp.pubsub.PubsubIO;
import org.apache.beam.sdk.options.Default;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.ParDo;
import org.bson.Document;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * The {@link MongoDbToBigQueryCdc} pipeline is a streaming pipeline which reads data pushed to
 * PubSub from MongoDB Changestream and outputs the resulting records to BigQuery.
 *
 * <p>Check out <a
 * href="https://github.com/GoogleCloudPlatform/DataflowTemplates/blob/main/v2/mongodb-to-googlecloud/README_MongoDB_to_BigQuery_CDC.md">README</a>
 * for instructions on how to use or modify this template.
 */
@Template(
    name = "MongoDB_to_BigQuery_CDC",
    category = TemplateCategory.STREAMING,
    displayName = "MongoDB to BigQuery (CDC)",
    description =
        "The MongoDB to BigQuery CDC (Change Data Capture) template is a streaming pipeline that works together with MongoDB change streams. "
            + "The pipeline reads the JSON records pushed to Pub/Sub via a MongoDB change stream and writes them to BigQuery as specified by the <code>userOption</code> parameter.",
    optionsClass = Options.class,
    flexContainerName = "mongodb-to-bigquery-cdc",
    documentation =
        "https://cloud.google.com/dataflow/docs/guides/templates/provided/mongodb-change-stream-to-bigquery",
    contactInformation = "https://cloud.google.com/support",
    preview = true,
    requirements = {
      "The target BigQuery dataset must exist.",
      "The source MongoDB instance must be accessible from the Dataflow worker machines.",
      "The change stream pushing changes from MongoDB to Pub/Sub should be running."
    },
    streaming = true,
    supportsAtLeastOnce = true)
public class MongoDbToBigQueryCdc {

  private static final Logger LOG = LoggerFactory.getLogger(MongoDbToBigQuery.class);

  /** Options interface. */
  public interface Options
      extends PipelineOptions,
          MongoDbOptions,
          PubSubOptions,
          BigQueryWriteOptions,
          JavascriptDocumentTransformerOptions,
          BigQueryStorageApiStreamingOptions {

    // Hide the UseStorageWriteApiAtLeastOnce in the UI, because it will automatically be turned
    // on when pipeline is running on ALO mode and using the Storage Write API
    @TemplateParameter.Boolean(
        order = 1,
        optional = true,
        description = "Use at at-least-once semantics in BigQuery Storage Write API",
        helpText =
            "This parameter takes effect only if \"Use BigQuery Storage Write API\" is enabled. If"
                + " enabled the at-least-once semantics will be used for Storage Write API, otherwise"
                + " exactly-once semantics will be used.",
        hiddenUi = true)
    @Default.Boolean(false)
    @Override
    Boolean getUseStorageWriteApiAtLeastOnce();

    void setUseStorageWriteApiAtLeastOnce(Boolean value);
  }

  /** class ParseAsDocumentsFn. */
  private static class ParseAsDocumentsFn extends DoFn<String, Document> {

    @ProcessElement
    public void processElement(ProcessContext context) {
      context.output(Document.parse(context.element()));
    }
  }

  /**
   * Main entry point for pipeline execution.
   *
   * @param args Command line arguments to the pipeline.
   */
  public static void main(String[] args)
      throws ScriptException, IOException, NoSuchMethodException {
    UncaughtExceptionLogger.register();

    Options options = PipelineOptionsFactory.fromArgs(args).withValidation().as(Options.class);
    BigQueryIOUtils.validateBQStorageApiOptionsStreaming(options);
    run(options);
  }

  /** Pipeline to read data from PubSub and write to MongoDB. */
  public static boolean run(Options options)
      throws ScriptException, IOException, NoSuchMethodException {
    options.setStreaming(true);
    Pipeline pipeline = Pipeline.create(options);
    String userOption = options.getUserOption();
    String inputOption = options.getInputTopic();

    TableSchema bigquerySchema;

    // Get MongoDbUri
    String mongoDbUri = maybeDecrypt(options.getMongoDbUri(), options.getKMSEncryptionKey()).get();

    if (options.getJavascriptDocumentTransformFunctionName() != null
        && options.getJavascriptDocumentTransformGcsPath() != null) {
      bigquerySchema =
          MongoDbUtils.getTableFieldSchemaForUDF(
              mongoDbUri,
              options.getDatabase(),
              options.getCollection(),
              options.getJavascriptDocumentTransformGcsPath(),
              options.getJavascriptDocumentTransformFunctionName(),
              options.getUserOption());
    } else {
      bigquerySchema =
          MongoDbUtils.getTableFieldSchema(
              mongoDbUri, options.getDatabase(), options.getCollection(), options.getUserOption());
    }

    pipeline
        .apply("Read PubSub Messages", PubsubIO.readStrings().fromTopic(inputOption))
        .apply(
            "RTransform string to document",
            ParDo.of(
                new DoFn<String, Document>() {
                  @ProcessElement
                  public void process(ProcessContext c) {
                    Document document = Document.parse(c.element());
                    c.output(document);
                  }
                }))
        .apply(
            "UDF",
            TransformDocumentViaJavascript.newBuilder()
                .setFileSystemPath(options.getJavascriptDocumentTransformGcsPath())
                .setFunctionName(options.getJavascriptDocumentTransformFunctionName())
                .build())
        .apply(
            "Read and transform data",
            ParDo.of(
                new DoFn<Document, TableRow>() {
                  @ProcessElement
                  public void process(ProcessContext c) {
                    Document document = c.element();
                    TableRow row = MongoDbUtils.getTableSchema(document, userOption);
                    c.output(row);
                  }
                }))
        .apply(
            BigQueryIO.writeTableRows()
                .to(options.getOutputTableSpec())
                .withSchema(bigquerySchema)
                .withCreateDisposition(BigQueryIO.Write.CreateDisposition.CREATE_IF_NEEDED)
                .withWriteDisposition(BigQueryIO.Write.WriteDisposition.WRITE_APPEND));
    pipeline.run();
    return true;
  }
}

What's next

• Learn about Dataflow templates.
• See the list of Google-provided templates.