Streaming Data Generator to Pub/Sub, BigQuery, and Cloud Storage template

The Streaming Data Generator template is used to generate either an unlimited or fixed number of synthetic records or messages based on user provided schema at the specified rate. Compatible destinations include Pub/Sub topics, BigQuery tables, and Cloud Storage buckets.

Following are a set of few possible use cases:

  • Simulate large-scale real-time event publishing to a Pub/Sub topic to measure and determine the number and size of consumers required to process published events.
  • Generate synthetic data to a BigQuery table or a Cloud Storage bucket to evaluate performance benchmarks or serve as a proof of concept.

Supported sinks and encoding formats

The following table describes which sinks and encoding formats are supported by this template:
JSON Avro Parquet
Pub/Sub Yes Yes No
BigQuery Yes No No
Cloud Storage Yes Yes Yes

Pipeline requirements

  • The worker service account needs the Dataflow Worker (roles/dataflow.worker) assigned role. For more information, see Introduction to IAM.
  • Create a schema file that contains a JSON template for the generated data. This template uses the JSON Data Generator library, so you can provide various faker functions for each field in the schema. For more information, see the json-data-generator documentation.

    For example:

    {
      "id": {{integer(0,1000)}},
      "name": "{{uuid()}}",
      "isInStock": {{bool()}}
    }
    
  • Upload the schema file to a Cloud Storage bucket.
  • The output target must exist prior to execution. The target must be a Pub/Sub topic, a BigQuery table, or a Cloud Storage bucket depending on sink type.
  • If the output encoding is Avro or Parquet, then create an Avro schema file and store it in a Cloud Storage location.
  • Assign the worker service account an additional IAM role depending on the desired destination.
    Destination Additionally needed IAM role Apply to which resource
    Pub/Sub Pub/Sub Publisher (roles/pubsub.publisher)
    (For more information, see Pub/Sub access control with IAM)
    Pub/Sub topic
    BigQuery BigQuery Data Editor (roles/bigquery.dataEditor)
    (For more information, see BigQuery access control with IAM)
    BigQuery dataset
    Cloud Storage Cloud Storage Object Admin (roles/storage.objectAdmin)
    (For more information, see Cloud Storage access control with IAM)
    Cloud Storage bucket

Template parameters

Parameter Description
schemaLocation Location of the schema file. For example: gs://mybucket/filename.json.
qps Number of messages to be published per second. For example: 100.
sinkType (Optional) Output sink Type. Possible values are PUBSUB, BIGQUERY, GCS. Default is PUBSUB.
outputType (Optional) Output encoding Type. Possible values are JSON, AVRO, PARQUET. Default is JSON.
avroSchemaLocation (Optional) Location of AVRO Schema file. Mandatory when outputType is AVRO or PARQUET. For example: gs://mybucket/filename.avsc.
topic (Optional) Name of the Pub/Sub topic to which the pipeline should publish data. Mandatory when sinkType is Pub/Sub. For example: projects/my-project-id/topics/my-topic-id.
outputTableSpec (Optional) Name of the output BigQuery table. Mandatory when sinkType is BigQuery. For example: my-project-ID:my_dataset_name.my-table-name.
writeDisposition (Optional) BigQuery Write Disposition. Possible values are WRITE_APPEND, WRITE_EMPTY or WRITE_TRUNCATE. Default is WRITE_APPEND.
outputDeadletterTable (Optional) Name of the output BigQuery table to hold failed records. If not provided, pipeline creates table during execution with name {output_table_name}_error_records. For example: my-project-ID:my_dataset_name.my-table-name.
outputDirectory (Optional) Path of the output Cloud Storage location. Mandatory when sinkType is Cloud Storage. For example: gs://mybucket/pathprefix/.
outputFilenamePrefix (Optional) The filename prefix of the output files written to Cloud Storage. Default is output-.
windowDuration (Optional) Window interval at which output is written to Cloud Storage. Default is 1m (in other words, 1 minute).
numShards (Optional) Maximum number of output shards. Mandatory when sinkType is Cloud Storage and should be set to 1 or higher number.
messagesLimit (Optional) Maximum number of output messages. Default is 0 indicating unlimited.
autoscalingAlgorithm (Optional) Algorithm used for autoscaling the workers. Possible values are THROUGHPUT_BASED to enable autoscaling or NONE to disable.
maxNumWorkers (Optional) Maximum number of worker machines. For example: 10.

Run the template

  1. Go to the Dataflow Create job from template page.
  2. Go to Create job from template
  3. In the Job name field, enter a unique job name.
  4. 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.

  5. From the Dataflow template drop-down menu, select the Streaming Data Generator template.
  6. In the provided parameter fields, enter your parameter values.
  7. Click Run job.

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/Streaming_Data_Generator \
    --parameters \
schemaLocation=SCHEMA_LOCATION,\
qps=QPS,\
topic=PUBSUB_TOPIC
  

Replace the following:

  • PROJECT_ID: the Google Cloud project ID where you want to run the Dataflow job
  • REGION_NAME: the region where you want to deploy your Dataflow job—for example, us-central1
  • 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:

  • SCHEMA_LOCATION: the path to schema file in Cloud Storage. For example: gs://mybucket/filename.json.
  • QPS: the number of messages to be published per second
  • PUBSUB_TOPIC: the output Pub/Sub topic. For example: projects/my-project-id/topics/my-topic-id.

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": {
          "schemaLocation": "SCHEMA_LOCATION",
          "qps": "QPS",
          "topic": "PUBSUB_TOPIC"
      },
      "containerSpecGcsPath": "gs://dataflow-templates-LOCATION/VERSION/flex/Streaming_Data_Generator",
   }
}
  

Replace the following:

  • PROJECT_ID: the Google Cloud project ID where you want to run the Dataflow job
  • LOCATION: the region where you want to deploy your Dataflow job—for example, us-central1
  • 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:

  • SCHEMA_LOCATION: the path to schema file in Cloud Storage. For example: gs://mybucket/filename.json.
  • QPS: the number of messages to be published per second
  • PUBSUB_TOPIC: the output Pub/Sub topic. For example: projects/my-project-id/topics/my-topic-id.
Java
/*
 * Copyright (C) 2020 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.templates;

import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkNotNull;

import com.github.vincentrussell.json.datagenerator.JsonDataGenerator;
import com.github.vincentrussell.json.datagenerator.JsonDataGeneratorException;
import com.github.vincentrussell.json.datagenerator.impl.JsonDataGeneratorImpl;
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.metadata.TemplateParameter.TemplateEnumOption;
import com.google.cloud.teleport.v2.common.UncaughtExceptionLogger;
import com.google.cloud.teleport.v2.templates.StreamingDataGenerator.StreamingDataGeneratorOptions;
import com.google.cloud.teleport.v2.transforms.StreamingDataGeneratorWriteToBigQuery;
import com.google.cloud.teleport.v2.transforms.StreamingDataGeneratorWriteToGcs;
import com.google.cloud.teleport.v2.transforms.StreamingDataGeneratorWriteToJdbc;
import com.google.cloud.teleport.v2.transforms.StreamingDataGeneratorWriteToKafka;
import com.google.cloud.teleport.v2.transforms.StreamingDataGeneratorWriteToPubSub;
import com.google.cloud.teleport.v2.transforms.StreamingDataGeneratorWriteToSpanner;
import com.google.cloud.teleport.v2.utils.DurationUtils;
import com.google.cloud.teleport.v2.utils.GCSUtils;
import com.google.cloud.teleport.v2.utils.MetadataValidator;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import javax.annotation.Nonnull;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.PipelineResult;
import org.apache.beam.sdk.io.FileSystems;
import org.apache.beam.sdk.io.GenerateSequence;
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.Validation.Required;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.windowing.FixedWindows;
import org.apache.beam.sdk.transforms.windowing.Window;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PDone;
import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
import org.joda.time.Duration;
import org.joda.time.Instant;

/**
 * The {@link StreamingDataGenerator} is a streaming pipeline which generates messages at a
 * specified rate to either Pub/Sub, BigQuery, GCS, JDBC, or Spanner. The messages are generated
 * according to a schema template which instructs the pipeline how to populate the messages with
 * fake data compliant to constraints.
 *
 * <p>The number of workers executing the pipeline must be large enough to support the supplied QPS.
 * Use a general rule of 2,500 QPS per core in the worker pool.
 *
 * <p>See <a href="https://github.com/vincentrussell/json-data-generator">json-data-generator</a>
 * for instructions on how to construct the schema file.
 *
 * <p>Check out <a
 * href="https://github.com/GoogleCloudPlatform/DataflowTemplates/blob/main/v2/streaming-data-generator/README_Streaming_Data_Generator.md">README</a>
 * for instructions on how to use or modify this template.
 */
@Template(
    name = "Streaming_Data_Generator",
    category = TemplateCategory.UTILITIES,
    displayName = "Streaming Data Generator",
    description =
        "A pipeline to publish messages at specified QPS.This template can be used to benchmark"
            + " performance of streaming pipelines.",
    optionsClass = StreamingDataGeneratorOptions.class,
    flexContainerName = "streaming-data-generator",
    documentation =
        "https://cloud.google.com/dataflow/docs/guides/templates/provided/streaming-data-generator",
    contactInformation = "https://cloud.google.com/support",
    streaming = true,
    supportsAtLeastOnce = true)
public class StreamingDataGenerator {

  /**
   * The {@link StreamingDataGeneratorOptions} class provides the custom execution options passed by
   * the executor at the command-line.
   */
  public interface StreamingDataGeneratorOptions extends PipelineOptions {
    @TemplateParameter.Long(
        order = 1,
        description = "Required output rate",
        helpText = "Indicates rate of messages per second to be published to Pub/Sub")
    @Required
    Long getQps();

    void setQps(Long value);

    @TemplateParameter.Enum(
        order = 2,
        enumOptions = {@TemplateEnumOption("GAME_EVENT")},
        optional = true,
        description = "Schema template to generate fake data",
        helpText = "Pre-existing schema template to use. The value must be one of: [GAME_EVENT]")
    SchemaTemplate getSchemaTemplate();

    void setSchemaTemplate(SchemaTemplate value);

    @TemplateParameter.GcsReadFile(
        order = 3,
        optional = true,
        description = "Location of Schema file to generate fake data",
        helpText = "Cloud Storage path of schema location.",
        example = "gs://<bucket-name>/prefix")
    String getSchemaLocation();

    void setSchemaLocation(String value);

    @TemplateParameter.PubsubTopic(
        order = 4,
        optional = true,
        description = "Output Pub/Sub topic",
        helpText = "The name of the topic to which the pipeline should publish data.",
        example = "projects/<project-id>/topics/<topic-name>")
    String getTopic();

    void setTopic(String value);

    @TemplateParameter.Long(
        order = 5,
        optional = true,
        description = "Maximum number of output Messages",
        helpText =
            "Indicates maximum number of output messages to be generated. 0 means unlimited.")
    @Default.Long(0L)
    Long getMessagesLimit();

    void setMessagesLimit(Long value);

    @TemplateParameter.Enum(
        order = 6,
        enumOptions = {
          @TemplateEnumOption("AVRO"),
          @TemplateEnumOption("JSON"),
          @TemplateEnumOption("PARQUET")
        },
        optional = true,
        description = "Output Encoding Type",
        helpText = "The message Output type. Default is JSON.")
    @Default.Enum("JSON")
    OutputType getOutputType();

    void setOutputType(OutputType value);

    @TemplateParameter.GcsReadFile(
        order = 7,
        optional = true,
        parentName = "outputType",
        parentTriggerValues = {"AVRO", "PARQUET"},
        description = "Location of Avro Schema file",
        helpText =
            "Cloud Storage path of Avro schema location. Mandatory when output type is AVRO or"
                + " PARQUET.",
        example = "gs://your-bucket/your-path/schema.avsc")
    String getAvroSchemaLocation();

    void setAvroSchemaLocation(String value);

    @TemplateParameter.Enum(
        order = 8,
        enumOptions = {
          @TemplateEnumOption("BIGQUERY"),
          @TemplateEnumOption("GCS"),
          @TemplateEnumOption("PUBSUB"),
          @TemplateEnumOption("JDBC"),
          @TemplateEnumOption("SPANNER"),
          @TemplateEnumOption("KAFKA")
        },
        optional = true,
        description = "Output Sink Type",
        helpText = "The message Sink type. Default is PUBSUB")
    @Default.Enum("PUBSUB")
    SinkType getSinkType();

    void setSinkType(SinkType value);

    @TemplateParameter.BigQueryTable(
        order = 9,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"BIGQUERY"},
        description = "Output BigQuery table",
        helpText = "Output BigQuery table. Mandatory when sinkType is BIGQUERY",
        example = "<project>:<dataset>.<table_name>")
    String getOutputTableSpec();

    void setOutputTableSpec(String value);

    @TemplateParameter.Enum(
        order = 10,
        enumOptions = {
          @TemplateEnumOption("WRITE_APPEND"),
          @TemplateEnumOption("WRITE_EMPTY"),
          @TemplateEnumOption("WRITE_TRUNCATE")
        },
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"BIGQUERY"},
        description = "Write Disposition to use for BigQuery",
        helpText =
            "BigQuery WriteDisposition. For example, WRITE_APPEND, WRITE_EMPTY or WRITE_TRUNCATE.")
    @Default.String("WRITE_APPEND")
    String getWriteDisposition();

    void setWriteDisposition(String writeDisposition);

    @TemplateParameter.BigQueryTable(
        order = 11,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"BIGQUERY"},
        description = "The dead-letter table name to output failed messages to BigQuery",
        helpText =
            "Messages failed to reach the output table for all kind of reasons (e.g., mismatched"
                + " schema, malformed json) are written to this table. If it doesn't exist, it will"
                + " be created during pipeline execution.",
        example = "your-project-id:your-dataset.your-table-name")
    String getOutputDeadletterTable();

    void setOutputDeadletterTable(String outputDeadletterTable);

    @TemplateParameter.Duration(
        order = 12,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"GCS"},
        description = "Window duration",
        helpText =
            "The window duration/size in which data will be written to Cloud Storage. Allowed"
                + " formats are: Ns (for seconds, example: 5s), Nm (for minutes, example: 12m), Nh"
                + " (for hours, example: 2h).",
        example = "1m")
    @Default.String("1m")
    String getWindowDuration();

    void setWindowDuration(String windowDuration);

    @TemplateParameter.GcsWriteFolder(
        order = 13,
        optional = true,
        description = "Output file directory in Cloud Storage",
        helpText =
            "The path and filename prefix for writing output files. Must end with a slash. DateTime"
                + " formatting is used to parse directory path for date & time formatters.",
        example = "gs://your-bucket/your-path/")
    String getOutputDirectory();

    void setOutputDirectory(String outputDirectory);

    @TemplateParameter.Text(
        order = 14,
        optional = true,
        description = "Output filename prefix of the files to write",
        helpText = "The prefix to place on each windowed file.",
        example = "output-")
    @Default.String("output-")
    String getOutputFilenamePrefix();

    void setOutputFilenamePrefix(String outputFilenamePrefix);

    @TemplateParameter.Integer(
        order = 15,
        optional = true,
        description = "Maximum output shards",
        helpText =
            "The maximum number of output shards produced when writing. A higher number of shards"
                + " means higher throughput for writing to Cloud Storage, but potentially higher"
                + " data aggregation cost across shards when processing output Cloud Storage files."
                + " Default value is decided by Dataflow.")
    @Default.Integer(0)
    Integer getNumShards();

    void setNumShards(Integer numShards);

    @TemplateParameter.Text(
        order = 16,
        optional = true,
        regexes = {"^.+$"},
        description = "JDBC driver class name.",
        helpText = "JDBC driver class name to use.",
        example = "com.mysql.jdbc.Driver")
    String getDriverClassName();

    void setDriverClassName(String driverClassName);

    @TemplateParameter.Text(
        order = 17,
        optional = true,
        regexes = {
          "(^jdbc:[a-zA-Z0-9/:@.?_+!*=&-;]+$)|(^([A-Za-z0-9+/]{4}){1,}([A-Za-z0-9+/]{0,3})={0,3})"
        },
        description = "JDBC connection URL string.",
        helpText = "Url connection string to connect to the JDBC source.",
        example = "jdbc:mysql://some-host:3306/sampledb")
    String getConnectionUrl();

    void setConnectionUrl(String connectionUrl);

    @TemplateParameter.Text(
        order = 18,
        optional = true,
        regexes = {"^.+$"},
        description = "JDBC connection username.",
        helpText = "User name to be used for the JDBC connection.")
    String getUsername();

    void setUsername(String username);

    @TemplateParameter.Password(
        order = 19,
        optional = true,
        description = "JDBC connection password.",
        helpText = "Password to be used for the JDBC connection.")
    String getPassword();

    void setPassword(String password);

    @TemplateParameter.Text(
        order = 20,
        optional = true,
        regexes = {"^[a-zA-Z0-9_;!*&=@#-:\\/]+$"},
        description = "JDBC connection property string.",
        helpText =
            "Properties string to use for the JDBC connection. Format of the string must be"
                + " [propertyName=property;]*.",
        example = "unicode=true;characterEncoding=UTF-8")
    String getConnectionProperties();

    void setConnectionProperties(String connectionProperties);

    @TemplateParameter.Text(
        order = 21,
        optional = true,
        regexes = {"^.+$"},
        description = "Statement which will be executed against the database.",
        helpText =
            "SQL statement which will be executed to write to the database. The statement must"
                + " specify the column names of the table in any order. Only the values of the"
                + " specified column names will be read from the json and added to the statement.",
        example = "INSERT INTO tableName (column1, column2) VALUES (?,?)")
    String getStatement();

    void setStatement(String statement);

    @TemplateParameter.ProjectId(
        order = 22,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        description = "GCP Project Id of where the Spanner table lives.",
        helpText = "GCP Project Id of where the Spanner table lives.")
    String getProjectId();

    void setProjectId(String projectId);

    @TemplateParameter.Text(
        order = 23,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        regexes = {"^.+$"},
        description = "Cloud Spanner instance name.",
        helpText = "Cloud Spanner instance name.")
    String getSpannerInstanceName();

    void setSpannerInstanceName(String spannerInstanceName);

    @TemplateParameter.Text(
        order = 24,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        regexes = {"^.+$"},
        description = "Cloud Spanner database name.",
        helpText = "Cloud Spanner database name.")
    String getSpannerDatabaseName();

    void setSpannerDatabaseName(String spannerDBName);

    @TemplateParameter.Text(
        order = 25,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        regexes = {"^.+$"},
        description = "Cloud Spanner table name.",
        helpText = "Cloud Spanner table name.")
    String getSpannerTableName();

    void setSpannerTableName(String spannerTableName);

    @TemplateParameter.Long(
        order = 26,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        description = "Max mutatated cells per batch.",
        helpText =
            "Specifies the cell mutation limit (maximum number of mutated cells per batch). Default value is 5000")
    Long getMaxNumMutations();

    void setMaxNumMutations(Long value);

    @TemplateParameter.Long(
        order = 27,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        description = "Max rows per batch.",
        helpText =
            "Specifies the row mutation limit (maximum number of mutated rows per batch). Default value is 1000")
    Long getMaxNumRows();

    void setMaxNumRows(Long value);

    @TemplateParameter.Long(
        order = 28,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        description = "Max batch size in bytes.",
        helpText =
            "Specifies the batch size limit (max number of bytes mutated per batch). Default value is 1MB")
    Long getBatchSizeBytes();

    void setBatchSizeBytes(Long value);

    @TemplateParameter.Long(
        order = 29,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"SPANNER"},
        description = "Commit deadline in seconds for write requests.",
        helpText = "Specifies the deadline in seconds for the Commit API call.")
    Long getCommitDeadlineSeconds();

    void setCommitDeadlineSeconds(Long value);

    @TemplateParameter.Text(
        order = 30,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"KAFKA"},
        regexes = {"[,:a-zA-Z0-9._-]+"},
        description = "Output Kafka Bootstrap Server",
        helpText = "Kafka Bootstrap Server ",
        example = "localhost:9092")
    String getBootstrapServer();

    void setBootstrapServer(String bootstrapServer);

    @TemplateParameter.Text(
        order = 31,
        optional = true,
        parentName = "sinkType",
        parentTriggerValues = {"KAFKA"},
        regexes = {"[a-zA-Z0-9._-]+"},
        description = "Kafka topic to write to",
        helpText = "Kafka topic to write to.",
        example = "topic")
    String getKafkaTopic();

    void setKafkaTopic(String outputTopic);
  }

  /** Allowed list of existing schema templates. */
  public enum SchemaTemplate {
    GAME_EVENT(
        "{\n"
            + "  \"eventId\": \"{{uuid()}}\",\n"
            + "  \"eventTimestamp\": {{timestamp()}},\n"
            + "  \"ipv4\": \"{{ipv4()}}\",\n"
            + "  \"ipv6\": \"{{ipv6()}}\",\n"
            + "  \"country\": \"{{country()}}\",\n"
            + "  \"username\": \"{{username()}}\",\n"
            + "  \"quest\": \"{{random(\"A Break In the Ice\", \"Ghosts of Perdition\", \"Survive"
            + " the Low Road\")}}\",\n"
            + "  \"score\": {{integer(100, 10000)}},\n"
            + "  \"completed\": {{bool()}}\n"
            + "}"),
    LOG_ENTRY(
        "{\n"
            + "  \"logName\": \"{{alpha(10,20)}}\",\n"
            + "  \"resource\": {\n"
            + "    \"type\": \"{{alpha(5,10)}}\"\n"
            + "  },\n"
            + "  \"timestamp\": {{timestamp()}},\n"
            + "  \"receiveTimestamp\": {{timestamp()}},\n"
            + "  \"severity\": \"{{random(\"DEFAULT\", \"DEBUG\", \"INFO\", \"NOTICE\","
            + " \"WARNING\", \"ERROR\", \"CRITICAL\", \"ERROR\")}}\",\n"
            + "  \"insertId\": \"{{uuid()}}\",\n"
            + "  \"trace\": \"{{uuid()}}\",\n"
            + "  \"spanId\": \"{{uuid()}}\",\n"
            + "  \"jsonPayload\": {\n"
            + "    \"bytes_sent\": {{integer(1000,20000)}},\n"
            + "    \"connection\": {\n"
            + "      \"dest_ip\": \"{{ipv4()}}\",\n"
            + "      \"dest_port\": {{integer(0,65000)}},\n"
            + "      \"protocol\": {{integer(0,6)}},\n"
            + "      \"src_ip\": \"{{ipv4()}}\",\n"
            + "      \"src_port\": {{integer(0,65000)}}\n"
            + "    },\n"
            + "    \"dest_instance\": {\n"
            + "      \"project_id\": \"{{concat(\"PROJECT\", integer(0,3))}}\",\n"
            + "      \"region\": \"{{country()}}\",\n"
            + "      \"vm_name\": \"{{username()}}\",\n"
            + "      \"zone\": \"{{state()}}\"\n"
            + "    },\n"
            + "    \"end_time\": {{timestamp()}},\n"
            + "    \"packets_sent\": {{integer(100,400)}},\n"
            + "    \"reporter\": \"{{random(\"SRC\", \"DEST\")}}\",\n"
            + "    \"rtt_msec\": {{integer(0,20)}},\n"
            + "    \"start_time\": {{timestamp()}}\n"
            + "  }\n"
            + "}");

    private final String schema;

    SchemaTemplate(String schema) {
      this.schema = schema;
    }

    public String getSchema() {
      return schema;
    }
  }

  /** Allowed list of message encoding types. */
  public enum OutputType {
    JSON(".json"),
    AVRO(".avro"),
    PARQUET(".parquet");

    private final String fileExtension;

    /** Sets file extension associated with output type. */
    OutputType(String fileExtension) {
      this.fileExtension = fileExtension;
    }

    /** Returns file extension associated with output type. */
    public String getFileExtension() {
      return fileExtension;
    }
  }

  /** Allowed list of sink types. */
  public enum SinkType {
    PUBSUB,
    BIGQUERY,
    GCS,
    JDBC,
    SPANNER,
    KAFKA
  }

  /**
   * The main entry-point for pipeline execution. This method will start the pipeline but will not
   * wait for it's execution to finish. If blocking execution is required, use the {@link
   * StreamingDataGenerator#run(StreamingDataGeneratorOptions)} method to start the pipeline and
   * invoke {@code result.waitUntilFinish()} on the {@link PipelineResult}.
   *
   * @param args command-line args passed by the executor.
   */
  public static void main(String[] args) {
    UncaughtExceptionLogger.register();

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

    run(options);
  }

  /**
   * Runs the pipeline to completion with the specified options. This method does not wait until the
   * pipeline is finished before returning. Invoke {@code result.waitUntilFinish()} on the result
   * object to block until the pipeline is finished running if blocking programmatic execution is
   * required.
   *
   * @param options the execution options.
   * @return the pipeline result.
   */
  public static PipelineResult run(@Nonnull StreamingDataGeneratorOptions options) {
    checkNotNull(options, "options argument to run method cannot be null.");
    MetadataValidator.validate(options);

    // FileSystems does not set the default configuration in workers till Pipeline.run
    // Explicitly registering standard file systems.
    FileSystems.setDefaultPipelineOptions(options);
    String schema = getSchema(options.getSchemaTemplate(), options.getSchemaLocation());

    // Create the pipeline
    Pipeline pipeline = Pipeline.create(options);

    /*
     * Steps:
     *  1) Trigger at the supplied QPS
     *  2) Generate messages containing fake data
     *  3) Write messages to appropriate Sink
     */
    PCollection<byte[]> generatedMessages =
        pipeline
            .apply("Trigger", createTrigger(options))
            .apply("Generate Fake Messages", ParDo.of(new MessageGeneratorFn(schema)));

    if (options.getSinkType().equals(SinkType.GCS)) {
      generatedMessages =
          generatedMessages.apply(
              options.getWindowDuration() + " Window",
              Window.into(
                  FixedWindows.of(DurationUtils.parseDuration(options.getWindowDuration()))));
    }

    generatedMessages.apply(
        "Write To " + options.getSinkType().name(), createSink(options, schema));

    return pipeline.run();
  }

  /**
   * Creates either Bounded or UnBounded Source based on messageLimit pipeline option.
   *
   * @param options the pipeline options.
   */
  private static GenerateSequence createTrigger(@Nonnull StreamingDataGeneratorOptions options) {
    checkNotNull(options, "options argument to createTrigger method cannot be null.");
    GenerateSequence generateSequence =
        GenerateSequence.from(0L)
            .withRate(options.getQps(), /* periodLength= */ Duration.standardSeconds(1L));

    return options.getMessagesLimit() > 0
        ? generateSequence.to(options.getMessagesLimit())
        : generateSequence;
  }

  /**
   * The {@link MessageGeneratorFn} class generates fake messages based on supplied schema
   *
   * <p>See <a href="https://github.com/vincentrussell/json-data-generator">json-data-generator</a>
   * for instructions on how to construct the schema file.
   */
  @VisibleForTesting
  static class MessageGeneratorFn extends DoFn<Long, byte[]> {

    // Not initialized inline or constructor because {@link JsonDataGenerator} is not serializable.
    private transient JsonDataGenerator dataGenerator;
    private final String schema;

    MessageGeneratorFn(String schema) {
      this.schema = schema;
    }

    @Setup
    public void setup() {
      dataGenerator = new JsonDataGeneratorImpl();
    }

    @ProcessElement
    public void processElement(
        @Element Long element,
        @Timestamp Instant timestamp,
        OutputReceiver<byte[]> receiver,
        ProcessContext context)
        throws IOException, JsonDataGeneratorException {

      byte[] payload;

      // Generate the fake JSON according to the schema.
      try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
        dataGenerator.generateTestDataJson(schema, byteArrayOutputStream);
        payload = byteArrayOutputStream.toByteArray();
      }

      receiver.output(payload);
    }
  }

  /**
   * Creates appropriate sink based on sinkType pipeline option.
   *
   * @param options the pipeline options.
   */
  @VisibleForTesting
  static PTransform<PCollection<byte[]>, PDone> createSink(
      @Nonnull StreamingDataGeneratorOptions options, @Nonnull String schema) {
    checkNotNull(options, "options argument to createSink method cannot be null.");
    checkNotNull(schema, "schema argument to createSink method cannot be null.");

    switch (options.getSinkType()) {
      case PUBSUB:
        checkArgument(
            options.getTopic() != null,
            String.format(
                "Missing required value --topic for %s sink type", options.getSinkType().name()));
        return StreamingDataGeneratorWriteToPubSub.Writer.builder(options, schema).build();
      case BIGQUERY:
        checkArgument(
            options.getOutputTableSpec() != null,
            String.format(
                "Missing required value --outputTableSpec in format"
                    + " <project>:<dataset>.<table_name> for %s sink type",
                options.getSinkType().name()));
        return StreamingDataGeneratorWriteToBigQuery.builder(options).build();
      case GCS:
        checkArgument(
            options.getOutputDirectory() != null,
            String.format(
                "Missing required value --outputDirectory in format gs:// for %s sink type",
                options.getSinkType().name()));
        return StreamingDataGeneratorWriteToGcs.builder(options).build();
      case JDBC:
        checkArgument(
            options.getDriverClassName() != null,
            String.format(
                "Missing required value --driverClassName for %s sink type",
                options.getSinkType().name()));
        checkArgument(
            options.getConnectionUrl() != null,
            String.format(
                "Missing required value --connectionUrl for %s sink type",
                options.getSinkType().name()));
        checkArgument(
            options.getStatement() != null,
            String.format(
                "Missing required value --statement for %s sink type",
                options.getSinkType().name()));
        return StreamingDataGeneratorWriteToJdbc.builder(options).build();
      case SPANNER:
        checkArgument(
            options.getProjectId() != null,
            String.format(
                "Missing required value --projectId for %s sink type",
                options.getSinkType().name()));
        checkArgument(
            options.getSpannerInstanceName() != null,
            String.format(
                "Missing required value --spannerInstanceName for %s sink type",
                options.getSinkType().name()));
        checkArgument(
            options.getSpannerDatabaseName() != null,
            String.format(
                "Missing required value --spannerDatabaseName for %s sink type",
                options.getSinkType().name()));
        checkArgument(
            options.getSpannerTableName() != null,
            String.format(
                "Missing required value --spannerTableName for %s sink type",
                options.getSinkType().name()));
        return StreamingDataGeneratorWriteToSpanner.builder(options).build();
      case KAFKA:
        checkArgument(
            options.getBootstrapServer() != null,
            String.format(
                "Missing required value --bootstrapServer for %s sink type",
                options.getSinkType().name()));
        checkArgument(
            options.getKafkaTopic() != null,
            String.format(
                "Missing required value --kafkaTopic for %s sink type",
                options.getSinkType().name()));
        return StreamingDataGeneratorWriteToKafka.Writer.builder(options).build();
      default:
        throw new IllegalArgumentException("Unsupported Sink.");
    }
  }

  private static String getSchema(SchemaTemplate schemaTemplate, String schemaLocation) {
    checkArgument(
        schemaTemplate != null || schemaLocation != null,
        "Either schemaTemplate or schemaLocation argument of MessageGeneratorFn class must be"
            + " provided.");
    if (schemaLocation != null) {
      return GCSUtils.getGcsFileAsString(schemaLocation);
    } else {
      return schemaTemplate.getSchema();
    }
  }
}

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