Read from databases to Dataflow

To read from relational databases to Dataflow, use the managed I/O connector.

Dependencies

Add the following dependencies to your project:

Java 

<dependency>
  <groupId>org.apache.beam</groupId>
  <artifactId>beam-sdks-java-managed</artifactId>
  <version>${beam.version}</version>
</dependency>

<dependency>
  <groupId>org.apache.beam</groupId>
  <artifactId>beam-sdks-java-io-jdbc</artifactId>
  <version>${beam.version}</version>
</dependency>

Example

The following example reads from a PostgreSQL database and writes the data to text files. While this example uses PostgreSQL, configuring other supported databases is similar.

Java

To authenticate to Dataflow, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

import com.google.common.collect.ImmutableMap;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.PipelineResult;
import org.apache.beam.sdk.io.TextIO;
import org.apache.beam.sdk.managed.Managed;
import org.apache.beam.sdk.options.Description;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.transforms.MapElements;
import org.apache.beam.sdk.values.TypeDescriptors;

public class PostgresRead {

  public interface Options extends PipelineOptions {
    @Description("The JDBC URL of the PostgreSQL database to read from.")
    String getJdbcUrl();

    void setJdbcUrl(String value);

    @Description("The PostgresSQL table to read from.")
    String getTable();

    void setTable(String value);

    @Description("The username for the PostgreSQL database.")
    String getUsername();

    void setUsername(String value);

    @Description("The password for the PostgreSQL database.")
    String getPassword();

    void setPassword(String value);

    @Description(
        "The path to write the output file. Can be a local file path, "
            + "a GCS path, or a path to any other supported file systems.")
    String getOutputPath();

    void setOutputPath(String value);
  }

  public static PipelineResult.State main(String[] args) {
    // Parse the pipeline options passed into the application. Example:
    //   --runner=DirectRunner --jdbcUrl=$JDBC_URL --table=$TABLE
    //   --username=$USERNAME --password=$PASSWORD --outputPath=$OUTPUT_FILE
    // For more information, see
    // https://beam.apache.org/documentation/programming-guide/#configuring-pipeline-options
    var options = PipelineOptionsFactory.fromArgs(args).withValidation().as(Options.class);
    Pipeline pipeline = createPipeline(options);
    return pipeline.run().waitUntilFinish();
  }

  public static Pipeline createPipeline(Options options) {

    // Create configuration parameters for the Managed I/O transform.
    ImmutableMap<String, Object> config =
        ImmutableMap.<String, Object>builder()
            .put("jdbc_url", options.getJdbcUrl())
            .put("location", options.getTable())
            .put("username", options.getUsername())
            .put("password", options.getPassword())
            .build();

    // Build the pipeline.
    var pipeline = Pipeline.create(options);
    pipeline
        // Read data from a Postgres database using Managed I/O.
        .apply(Managed.read(Managed.POSTGRES).withConfig(config))
        .getSinglePCollection()
        // Convert each row to a string.
        .apply(
            MapElements.into(TypeDescriptors.strings())
                .via((row -> String.format("%d,%s", row.getInt32("id"), row.getString("name")))))
        // Write strings to a text file.
        .apply(TextIO.write().to(options.getOutputPath()).withSuffix(".txt").withNumShards(1));
    return pipeline;
  }
}

What's next