Apache Cassandra to Bigtable template

The Apache Cassandra to Bigtable template copies a table from Apache Cassandra to Bigtable. This template requires minimal configuration and replicates the table structure in Cassandra as closely as possible in Bigtable.

The Apache Cassandra to Bigtable template is useful for the following:

• Migrating Apache Cassandra database when short downtime is acceptable.
• Periodically replicating Cassandra tables to Bigtable for global serving.

Pipeline requirements

• The target Bigtable table must exist before running the pipeline.
• Network connection between Dataflow workers and Apache Cassandra nodes.

Type conversion

The Apache Cassandra to Bigtable template automatically converts Apache Cassandra data types to Bigtable's data types.

Most primitives are represented the same way in Bigtable and Apache Cassandra; however, the following primitives are represented differently:

• Date and Timestamp are converted to DateTime objects
• UUID is converted to String
• Varint is converted to BigDecimal

Apache Cassandra also natively supports more complex types such as Tuple, List, Set and Map. Tuples are not supported by this pipeline as there is no corresponding type in the Apache Beam.

For example, in Apache Cassandra you can have a column of type List called "mylist" and values like those in the following table:

row	mylist
1	(a,b,c)

The pipeline expands the list column into three different columns (known in Bigtable as column qualifiers). The name of the columns is "mylist" but the pipeline appends the index of the item in the list, such as "mylist[0]".

row	mylist[0]	mylist[1]	mylist[2]
1	a	b	c

The pipeline handles sets the same way as lists but adds a suffix to denote if the cell is a key or a value.

row	mymap
1	{"first_key":"first_value","another_key":"different_value"}

After transformation, table appears as follows:

row	mymap[0].key	mymap[0].value	mymap[1].key	mymap[1].value
1	first_key	first_value	another_key	different_value

Primary key conversion

In Apache Cassandra, a primary key is defined using data definition language. The primary key is either simple, composite, or compound with the clustering columns. Bigtable supports manual row-key construction, ordered lexicographically on a byte array. The pipeline automatically collects information about the type of key and constructs a key based on best practices for building row-keys based on multiple values.

Template parameters

Parameter	Description
cassandraHosts	The hosts of the Apache Cassandra nodes in a comma-separated list.
cassandraPort	(Optional) The TCP port to reach Apache Cassandra on the nodes (defaults to 9042).
cassandraKeyspace	The Apache Cassandra keyspace where the table is located.
cassandraTable	The Apache Cassandra table to be copied.
bigtableProjectId	The Google Cloud Project ID of the Bigtable instance where the Apache Cassandra table is copied.
bigtableInstanceId	The Bigtable instance ID in which to copy the Apache Cassandra table.
bigtableTableId	The name of the Bigtable table in which to copy the Apache Cassandra table.
defaultColumnFamily	(Optional) The name of the Bigtable table's column family (defaults to default).
rowKeySeparator	(Optional) The separator used to build row-key (defaults to #).

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 Cassandra to Cloud Bigtable 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-REGION_NAME/VERSION/Cassandra_To_Cloud_Bigtable \
    --region REGION_NAME \
    --parameters \
bigtableProjectId=BIGTABLE_PROJECT_ID,\
bigtableInstanceId=BIGTABLE_INSTANCE_ID,\
bigtableTableId=BIGTABLE_TABLE_ID,\
cassandraHosts=CASSANDRA_HOSTS,\
cassandraKeyspace=CASSANDRA_KEYSPACE,\
cassandraTable=CASSANDRA_TABLE

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-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.
• REGION_NAME: the region where you want to deploy your Dataflow job—for example, us-central1
• BIGTABLE_PROJECT_ID: your project ID where Bigtable is located
• BIGTABLE_INSTANCE_ID: the Bigtable instance id
• BIGTABLE_TABLE_ID: the name of your Bigtable table name
• CASSANDRA_HOSTS: the Apache Cassandra host list; if multiple hosts are provided, follow the instruction on how to escape commas
• CASSANDRA_KEYSPACE: the Apache Cassandra keyspace where table is located
• CASSANDRA_TABLE: the Apache Cassandra table that needs to be migrated

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-LOCATION/VERSION/Cassandra_To_Cloud_Bigtable
{
   "jobName": "JOB_NAME",
   "parameters": {
       "bigtableProjectId": "BIGTABLE_PROJECT_ID",
       "bigtableInstanceId": "BIGTABLE_INSTANCE_ID",
       "bigtableTableId": "BIGTABLE_TABLE_ID",
       "cassandraHosts": "CASSANDRA_HOSTS",
       "cassandraKeyspace": "CASSANDRA_KEYSPACE",
       "cassandraTable": "CASSANDRA_TABLE"
   },
   "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-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.
• LOCATION: the region where you want to deploy your Dataflow job—for example, us-central1
• BIGTABLE_PROJECT_ID: your project ID where Bigtable is located
• BIGTABLE_INSTANCE_ID: the Bigtable instance id
• BIGTABLE_TABLE_ID: the name of your Bigtable table name
• CASSANDRA_HOSTS: the Apache Cassandra host list; if multiple hosts are provided, follow the instruction on how to escape commas
• CASSANDRA_KEYSPACE: the Apache Cassandra keyspace where table is located
• CASSANDRA_TABLE: the Apache Cassandra table that needs to be migrated

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.bigtable;

import com.datastax.driver.core.Session;
import com.google.cloud.teleport.bigtable.CassandraToBigtable.Options;
import com.google.cloud.teleport.metadata.Template;
import com.google.cloud.teleport.metadata.TemplateCategory;
import com.google.cloud.teleport.metadata.TemplateParameter;
import java.util.Arrays;
import java.util.List;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.coders.SerializableCoder;
import org.apache.beam.sdk.io.cassandra.CassandraIO;
import org.apache.beam.sdk.io.cassandra.Mapper;
import org.apache.beam.sdk.io.gcp.bigtable.BigtableIO;
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.options.ValueProvider;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.SerializableFunction;
import org.apache.beam.sdk.values.Row;

/**
 * This Dataflow Template performs a one off copy of one table from Apache Cassandra to Cloud
 * Bigtable. It is designed to require minimal configuration and aims to replicate the table
 * structure in Cassandra as closely as possible in Cloud Bigtable.
 *
 * <p>Check out <a
 * href="https://github.com/GoogleCloudPlatform/DataflowTemplates/blob/main/v1/README_Cassandra_To_Cloud_Bigtable.md">README</a>
 * for instructions on how to use or modify this template.
 */
@Template(
    name = "Cassandra_To_Cloud_Bigtable",
    category = TemplateCategory.BATCH,
    displayName = "Cassandra to Cloud Bigtable",
    description = {
      "The Apache Cassandra to Cloud Bigtable template copies a table from Apache Cassandra to Cloud Bigtable. "
          + "This template requires minimal configuration and replicates the table structure in Cassandra as closely as possible in Cloud Bigtable.",
      "The Apache Cassandra to Cloud Bigtable template is useful for the following:\n"
          + "- Migrating Apache Cassandra database when short downtime is acceptable.\n"
          + "- Periodically replicating Cassandra tables to Cloud Bigtable for global serving."
    },
    optionsClass = Options.class,
    documentation =
        "https://cloud.google.com/dataflow/docs/guides/templates/provided/cassandra-to-bigtable",
    contactInformation = "https://cloud.google.com/support",
    requirements = {
      "The target Bigtable table must exist before running the pipeline.",
      "Network connection between Dataflow workers and Apache Cassandra nodes."
    })
final class CassandraToBigtable {

  /** TODO - refactor to extend BigtableCommonOptions.WriteOptions. */
  public interface Options extends PipelineOptions {

    @TemplateParameter.Text(
        order = 1,
        regexes = {"^[a-zA-Z0-9\\.\\-,]*$"},
        description = "Cassandra Hosts",
        helpText = "Comma separated value list of hostnames or ips of the Cassandra nodes.")
    ValueProvider<String> getCassandraHosts();

    @SuppressWarnings("unused")
    void setCassandraHosts(ValueProvider<String> hosts);

    @TemplateParameter.Text(
        order = 2,
        optional = true,
        regexes = {
          "^([0-9]{1,4}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$"
        },
        description = "Cassandra Port",
        helpText = "The port where cassandra can be reached. Defaults to 9042.")
    @Default.Integer(9042)
    ValueProvider<Integer> getCassandraPort();

    @SuppressWarnings("unused")
    void setCassandraPort(ValueProvider<Integer> port);

    @TemplateParameter.Text(
        order = 3,
        regexes = {"^[a-zA-Z0-9][a-zA-Z0-9_]{0,47}$"},
        description = "Cassandra Keyspace",
        helpText = "Cassandra Keyspace where the table to be migrated can be located.")
    ValueProvider<String> getCassandraKeyspace();

    @SuppressWarnings("unused")
    void setCassandraKeyspace(ValueProvider<String> keyspace);

    @TemplateParameter.Text(
        order = 4,
        regexes = {"^[a-zA-Z][a-zA-Z0-9_]*$"},
        description = "Cassandra Table",
        helpText = "The name of the Cassandra table to Migrate")
    ValueProvider<String> getCassandraTable();

    @SuppressWarnings("unused")
    void setCassandraTable(ValueProvider<String> cassandraTable);

    @TemplateParameter.ProjectId(
        order = 5,
        description = "Bigtable Project ID",
        helpText = "The Project ID where the target Bigtable Instance is running.")
    ValueProvider<String> getBigtableProjectId();

    @SuppressWarnings("unused")
    void setBigtableProjectId(ValueProvider<String> projectId);

    @TemplateParameter.Text(
        order = 6,
        regexes = {"[a-z][a-z0-9\\-]+[a-z0-9]"},
        description = "Target Bigtable Instance",
        helpText = "The target Bigtable Instance where you want to write the data.")
    ValueProvider<String> getBigtableInstanceId();

    @SuppressWarnings("unused")
    void setBigtableInstanceId(ValueProvider<String> bigtableInstanceId);

    @TemplateParameter.Text(
        order = 7,
        regexes = {"[_a-zA-Z0-9][-_.a-zA-Z0-9]*"},
        description = "Target Bigtable Table",
        helpText = "The target Bigtable table where you want to write the data.")
    ValueProvider<String> getBigtableTableId();

    @SuppressWarnings("unused")
    void setBigtableTableId(ValueProvider<String> bigtableTableId);

    @TemplateParameter.Text(
        order = 8,
        optional = true,
        regexes = {"[-_.a-zA-Z0-9]+"},
        description = "The Default Bigtable Column Family",
        helpText =
            "This specifies the default column family to write data into. If no columnFamilyMapping is specified all Columns will be written into this column family. Default value is \"default\"")
    @Default.String("default")
    ValueProvider<String> getDefaultColumnFamily();

    @SuppressWarnings("unused")
    void setDefaultColumnFamily(ValueProvider<String> defaultColumnFamily);

    @TemplateParameter.Text(
        order = 9,
        optional = true,
        description = "The Row Key Separator",
        helpText =
            "All primary key fields will be appended to form your Bigtable Row Key. The rowKeySeparator allows you to specify a character separator. Default separator is '#'.")
    @Default.String("#")
    ValueProvider<String> getRowKeySeparator();

    @SuppressWarnings("unused")
    void setRowKeySeparator(ValueProvider<String> rowKeySeparator);

    @TemplateParameter.Boolean(
        order = 10,
        optional = true,
        description = "If true, large rows will be split into multiple MutateRows requests",
        helpText =
            "The flag for enabling splitting of large rows into multiple MutateRows requests. Note that when a large row is split between multiple API calls, the updates to the row are not atomic. ")
    ValueProvider<Boolean> getSplitLargeRows();

    void setSplitLargeRows(ValueProvider<Boolean> splitLargeRows);
  }

  /**
   * Runs a pipeline to copy one Cassandra table to Cloud Bigtable.
   *
   * @param args arguments to the pipeline
   */
  public static void main(String[] args) {

    Options options = PipelineOptionsFactory.fromArgs(args).withValidation().as(Options.class);

    // Split the Cassandra Hosts value provider into a list value provider.
    ValueProvider.NestedValueProvider<List<String>, String> hosts =
        ValueProvider.NestedValueProvider.of(
            options.getCassandraHosts(),
            (SerializableFunction<String, List<String>>) value -> Arrays.asList(value.split(",")));

    Pipeline p = Pipeline.create(PipelineUtils.tweakPipelineOptions(options));

    // Create a factory method to inject the CassandraRowMapperFn to allow custom type mapping.
    SerializableFunction<Session, Mapper> cassandraObjectMapperFactory =
        new CassandraRowMapperFactory(options.getCassandraTable(), options.getCassandraKeyspace());

    CassandraIO.Read<Row> source =
        CassandraIO.<Row>read()
            .withHosts(hosts)
            .withPort(options.getCassandraPort())
            .withKeyspace(options.getCassandraKeyspace())
            .withTable(options.getCassandraTable())
            .withMapperFactoryFn(cassandraObjectMapperFactory)
            .withEntity(Row.class)
            .withCoder(SerializableCoder.of(Row.class));

    BigtableIO.Write sink =
        BigtableIO.write()
            .withProjectId(options.getBigtableProjectId())
            .withInstanceId(options.getBigtableInstanceId())
            .withTableId(options.getBigtableTableId());

    p.apply("Read from Cassandra", source)
        .apply(
            "Convert Row",
            ParDo.of(
                BeamRowToBigtableFn.createWithSplitLargeRows(
                    options.getRowKeySeparator(),
                    options.getDefaultColumnFamily(),
                    options.getSplitLargeRows(),
                    BeamRowToBigtableFn.MAX_MUTATION_PER_REQUEST)))
        .apply("Write to Bigtable", sink);
    p.run();
  }
}

What's next

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