Cloud Spanner to Cloud Storage Text template

The Cloud Spanner to Cloud Storage Text template is a batch pipeline that reads in data from a Cloud Spanner table, and writes it to Cloud Storage as CSV text files.

Pipeline requirements

• The input Spanner table must exist before running the pipeline.

Template parameters

Parameter	Description
spannerProjectId	The Google Cloud Project ID of the Cloud Spanner database that you want to read data from.
spannerDatabaseId	The database ID of the requested table.
spannerInstanceId	The instance ID of the requested table.
spannerTable	The table to read the data from.
textWritePrefix	The directory where output text files are written. Add / at the end. For example, gs://mybucket/somefolder/.
spannerSnapshotTime	(Optional) The timestamp that corresponds to the version of the Cloud Spanner database that you want to read. The timestamp must be specified as per RFC 3339 UTC "Zulu" format. For example, 1990-12-31T23:59:60Z. The timestamp must be in the past and Maximum timestamp staleness applies.

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 regional endpoint 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 Cloud Spanner to Text Files on Cloud Storage 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 classic templates, you must have Google Cloud CLI version 138.0.0 or later.

In your shell or terminal, run the template:

gcloud dataflow jobs run JOB_NAME \
    --gcs-location gs://dataflow-templates/VERSION/Spanner_to_GCS_Text \
    --region REGION_NAME \
    --parameters \
spannerProjectId=SPANNER_PROJECT_ID,\
spannerDatabaseId=DATABASE_ID,\
spannerInstanceId=INSTANCE_ID,\
spannerTable=TABLE_ID,\
textWritePrefix=gs://BUCKET_NAME/output/

Replace the following:

• JOB_NAME: a unique job name of your choice
• 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/latest/
  • the version name, like 2021-09-20-00_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/
  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.
• REGION_NAME: the regional endpoint where you want to deploy your Dataflow job—for example, us-central1
• SPANNER_PROJECT_ID: the Google Cloud project ID of the Spanner database from which you want to read data
• DATABASE_ID: the Spanner database ID
• BUCKET_NAME: the name of your Cloud Storage bucket
• INSTANCE_ID: the Spanner instance ID
• TABLE_ID: the Spanner table ID

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/templates:launch?gcsPath=gs://dataflow-templates/VERSION/Spanner_to_GCS_Text
{
   "jobName": "JOB_NAME",
   "parameters": {
       "spannerProjectId": "SPANNER_PROJECT_ID",
       "spannerDatabaseId": "DATABASE_ID",
       "spannerInstanceId": "INSTANCE_ID",
       "spannerTable": "TABLE_ID",
       "textWritePrefix": "gs://BUCKET_NAME/output/"
   },
   "environment": { "zone": "us-central1-f" }
}

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
• 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/latest/
  • the version name, like 2021-09-20-00_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/
  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.
• LOCATION: the regional endpoint where you want to deploy your Dataflow job—for example, us-central1
• SPANNER_PROJECT_ID: the Google Cloud project ID of the Spanner database from which you want to read data
• DATABASE_ID: the Spanner database ID
• BUCKET_NAME: the name of your Cloud Storage bucket
• INSTANCE_ID: the Spanner instance ID
• TABLE_ID: the Spanner table ID

Template source code

Java

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/*
 * Copyright (C) 2018 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.templates;

import static com.google.cloud.teleport.util.ValueProviderUtils.eitherOrValueProvider;

import com.google.cloud.spanner.Options.RpcPriority;
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.templates.SpannerToText.SpannerToTextOptions;
import com.google.cloud.teleport.templates.common.SpannerConverters;
import com.google.cloud.teleport.templates.common.SpannerConverters.CreateTransactionFnWithTimestamp;
import com.google.cloud.teleport.templates.common.SpannerConverters.SpannerReadOptions;
import com.google.cloud.teleport.templates.common.TextConverters.FilesystemWriteOptions;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.FileSystems;
import org.apache.beam.sdk.io.TextIO;
import org.apache.beam.sdk.io.fs.ResourceId;
import org.apache.beam.sdk.io.gcp.spanner.LocalSpannerIO;
import org.apache.beam.sdk.io.gcp.spanner.ReadOperation;
import org.apache.beam.sdk.io.gcp.spanner.SpannerConfig;
import org.apache.beam.sdk.io.gcp.spanner.Transaction;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.options.ValueProvider;
import org.apache.beam.sdk.transforms.Create;
import org.apache.beam.sdk.transforms.MapElements;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.SerializableFunction;
import org.apache.beam.sdk.transforms.View;
import org.apache.beam.sdk.values.PBegin;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.sdk.values.TypeDescriptors;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Dataflow template which copies a Spanner table to a Text sink. It exports a Spanner table using
 * <a href="https://cloud.google.com/spanner/docs/reads#read_data_in_parallel">Batch API</a>, which
 * creates multiple workers in parallel for better performance. The result is written to a CSV file
 * in Google Cloud Storage. The table schema file is saved in json format along with the exported
 * table.
 *
 * <p>Schema file sample: { "id":"INT64", "name":"STRING(MAX)" }
 *
 * <p>Check out <a
 * href="https://github.com/GoogleCloudPlatform/DataflowTemplates/blob/main/v1/README_Spanner_to_GCS_Text.md">README</a>
 * for instructions on how to use or modify this template.
 */
@Template(
    name = "Spanner_to_GCS_Text",
    category = TemplateCategory.BATCH,
    displayName = "Cloud Spanner to Text Files on Cloud Storage",
    description =
        "A pipeline which reads in Cloud Spanner table and writes it to Cloud Storage as CSV text"
            + " files.",
    optionsClass = SpannerToTextOptions.class,
    documentation =
        "https://cloud.google.com/dataflow/docs/guides/templates/provided/cloud-spanner-to-cloud-storage",
    contactInformation = "https://cloud.google.com/support")
public class SpannerToText {

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

  /** Custom PipelineOptions. */
  public interface SpannerToTextOptions
      extends PipelineOptions, SpannerReadOptions, FilesystemWriteOptions {

    @TemplateParameter.GcsWriteFolder(
        order = 1,
        optional = true,
        description = "Cloud Storage temp directory for storing CSV files",
        helpText = "The Cloud Storage path where the temporary CSV files can be stored.",
        example = "gs://your-bucket/your-path")
    ValueProvider<String> getCsvTempDirectory();

    @SuppressWarnings("unused")
    void setCsvTempDirectory(ValueProvider<String> value);

    @TemplateParameter.Enum(
        order = 2,
        enumOptions = {"LOW", "MEDIUM", "HIGH"},
        optional = true,
        description = "Priority for Spanner RPC invocations",
        helpText =
            "The request priority for Cloud Spanner calls. The value must be one of:"
                + " [HIGH,MEDIUM,LOW].")
    ValueProvider<RpcPriority> getSpannerPriority();

    void setSpannerPriority(ValueProvider<RpcPriority> value);
  }

  /**
   * Runs a pipeline which reads in Records from Spanner, and writes the CSV to TextIO sink.
   *
   * @param args arguments to the pipeline
   */
  public static void main(String[] args) {
    LOG.info("Starting pipeline setup");
    PipelineOptionsFactory.register(SpannerToTextOptions.class);
    SpannerToTextOptions options =
        PipelineOptionsFactory.fromArgs(args).withValidation().as(SpannerToTextOptions.class);

    FileSystems.setDefaultPipelineOptions(options);
    Pipeline pipeline = Pipeline.create(options);

    SpannerConfig spannerConfig =
        SpannerConfig.create()
            .withHost(options.getSpannerHost())
            .withProjectId(options.getSpannerProjectId())
            .withInstanceId(options.getSpannerInstanceId())
            .withDatabaseId(options.getSpannerDatabaseId())
            .withRpcPriority(options.getSpannerPriority())
            .withDataBoostEnabled(options.getDataBoostEnabled());

    PTransform<PBegin, PCollection<ReadOperation>> spannerExport =
        SpannerConverters.ExportTransformFactory.create(
            options.getSpannerTable(),
            spannerConfig,
            options.getTextWritePrefix(),
            options.getSpannerSnapshotTime());

    /* CreateTransaction and CreateTransactionFn classes in LocalSpannerIO
     * only take a timestamp object for exact staleness which works when
     * parameters are provided during template compile time. They do not work with
     * a Timestamp valueProvider which can take parameters at runtime. Hence a new
     * ParDo class CreateTransactionFnWithTimestamp had to be created for this
     * purpose.
     */
    PCollectionView<Transaction> tx =
        pipeline
            .apply("Setup for Transaction", Create.of(1))
            .apply(
                "Create transaction",
                ParDo.of(
                    new CreateTransactionFnWithTimestamp(
                        spannerConfig, options.getSpannerSnapshotTime())))
            .apply("As PCollectionView", View.asSingleton());

    PCollection<String> csv =
        pipeline
            .apply("Create export", spannerExport)
            // We need to use LocalSpannerIO.readAll() instead of LocalSpannerIO.read()
            // because ValueProvider parameters such as table name required for
            // LocalSpannerIO.read() can be read only inside DoFn but LocalSpannerIO.read() is of
            // type PTransform<PBegin, Struct>, which prevents prepending it with DoFn that reads
            // these parameters at the pipeline execution time.
            .apply(
                "Read all records",
                LocalSpannerIO.readAll().withTransaction(tx).withSpannerConfig(spannerConfig))
            .apply(
                "Struct To Csv",
                MapElements.into(TypeDescriptors.strings())
                    .via(struct -> (new SpannerConverters.StructCsvPrinter()).print(struct)));

    ValueProvider<ResourceId> tempDirectoryResource =
        ValueProvider.NestedValueProvider.of(
            eitherOrValueProvider(options.getCsvTempDirectory(), options.getTextWritePrefix()),
            (SerializableFunction<String, ResourceId>) s -> FileSystems.matchNewResource(s, true));

    csv.apply(
        "Write to storage",
        TextIO.write()
            .to(options.getTextWritePrefix())
            .withSuffix(".csv")
            .withTempDirectory(tempDirectoryResource));

    pipeline.run();
    LOG.info("Completed pipeline setup");
  }
}