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Steps and Pipeline Objects

Pipeline objects are classes that directly translate one-one from the dataduct classes to DP objects. A step is an abstraction layer that can translate into one or more pipeline objects based on the action type. For example a sql-command step translates into a sql-activity or a transform step translates into shell command activity and creates an output s3 node.

Definition of a Step

A step is defined as a series of properties in yaml. For example,

-   step_type: extract-s3
    name: get_file
    file_uri: s3://elasticmapreduce/samples/wordcount/wordSplitter.py

defines an extract-s3 step with properties name and file_uri.

Common

These are the properties that all steps possess.

  • step_type: The step type. Must be either a pre-defined step or a custom step. (Required)
  • name: The user-defined name of the step. Will show up as part of the component name in DataPipeline.
  • input_node: See input and output nodes.
  • depends_on: This step will not run until the step(s) specified have finished.

Extract S3

Extracts the contents from the specified file or directory in S3. May used as input to other steps.

Properties

One of: (Required)

  • file_uri: The location of a single file in S3.
  • directory_uri: The location of a directory in S3.

Example

-   step_type: extract-s3
    file_uri: s3://elasticmapreduce/samples/wordcount/wordSplitter.py

Extract Local

Extracts the contents from the specified file locally. May be used as input to other steps. May only be used with one-time pipelines.

Properties

  • path: The location of a single file. (Required)

Example

-   step_type: extract-local
    path: data/example_file.tsv

Extract RDS

Extracts the contents of a table from an RDS instance. May be used as input to other steps. Data is stored in TSV format.

Properties

  • host_name: The host name to lookup in the mysql section of the configuration file. (Required)
  • database: The database in the RDS instance in which the table resides. (Required)
  • output_path: Output the extracted data to the specified S3 path.

One of: (Required)

  • sql: The SQL query to execute to extract data.
  • table: The table to extract. Equivalent to a sql query of SELECT * FROM table.

Example

-   step_type: extract-rds
    host_name: maestro
    database: maestro
    sql: |
        SELECT *
        FROM example_rds_table;

Extract Redshift

Extracts the contents of a table from a Redshift instance. May be used as input to other steps. Data is stored in TSV format.

Properties

  • schema: The schema of the table. (Required)
  • table: The name of the table. (Required)
  • output_path: Output the extracted data to the specified S3 path. Optional.

Example

-   step_type: extract-redshift
    schema: prod
    table: example_redshift_table

Transform

Runs a specified script on an resource.

Properties

  • output_node: See input and output nodes.
  • script_arguments: Arguments passed to the script.
  • script_name: Required if script_directory is specified. Script to be executed in the directory.
  • additional_s3_files: Additional files to include from S3.
  • output_path: Save the script's output to the specified S3 path.
  • no_output: If true, step will produce no extractable output. Default: false
  • resource_type: If ec2, run step on the EC2 resource. If emr, run step on the EMR resource. Default: ec2

One of: (Required)

  • command: A command to be executed directly.
  • script: Local path to the script that should be executed.
  • script_directory: Local path to a directory of scripts to be uploaded to the resource.

Example

-   step_type: transform
    script: scripts/example_script.py
    script_arguments:
    -   "--foo=bar"

SQL Command

Executes a SQL statement in a Redshift instance.

Properties

  • script_arguments: Arguments passed to the SQL command.
  • queue: Query queue that should be used.
  • wrap_transaction: If true, SQL command will be wrapped inside a transaction. Default: true

One of: (Required)

  • command: Command to be executed directly.
  • script: Local path to the script that should be executed.

Example

-   step_type: sql-command
    command: SELECT * FROM dev.test_table;

EMR Streaming

Executes a map and an optional reduce script using Amazon Elastic MapReduce.

Properties

  • mapper: Local path to the mapper script (Required)
  • reducer: Local path to the reducer script
  • hadoop_params: List of arguments to the hadoop command
  • output_path: Save the script's output to the specified S3 path

Example

-   step_type: emr-streaming
    mapper: scripts/word_mapper.py
    reducer: scripts/word_reducer.py

Load Redshift

Loads the data from its input node into a Redshift instance.

Properties

  • schema: The schema of the table. (Required)
  • table: The name of the table. (Required)
  • insert_mode: See Amazon's RedshiftCopyActivity documentation. Default: TRUNCATE
  • max_errors: The maximum number of errors to be ignored during the load
  • replace_invalid_char: Character to replace non-utf8 characters with

Example

-   step_type: load-redshift
    schema: dev
    table: example_table

Pipeline Dependencies

Keeps running until another pipeline has finished. Use with depends_on properties to stall the pipeline.

Properties

  • dependent_pipelines: List of pipelines to wait for. (Required)
  • refresh_rate: Time, in seconds, to wait between polls. Default: 300
  • start_date: Date on which the pipelines started at. Default: Current day

Example

-   step_type: pipeline-dependencies
    refresh_rate: 60
    dependent_pipelines:
    -   example_transform

Create Load Redshift

Special transform step that loads the data from its input node into a Redshift instance. If the table it's loading into does not exist, the table will be created.

Properties

  • table_definition: Schema file for the table to be loaded. (Required)
  • script_arguments: Arguments for the runner.
    • --max_error: The maximum number of errors to be ignored during the load. Usage: --max_error=5
    • --replace_invalid_char: Character the replace non-utf8 characters with. Usage: --replace_invalid_char='?'
    • --no_escape: If passed, does not escape special characters. Usage: --no_escape
    • --gzip: If passed, compresses the output with gzip. Usage: --gzip
    • --command_options: A custom SQL string as the options for the copy command. Usage: --command_options="DELIMITER '\t'"
      • Note: If --command_options is passed, script arguments --max_error, --replace_invalid_char, --no_escape, and --gzip have no effect.

Example

-   step_type: create-load-redshift
    table_definition: tables/dev.example_table.sql

Load, Reload, Primary Key Check

Combine create-load-redshift, reload and primary-key-check into one single step.

Properties

  • staging_table_definition: Intermidiate staging schema file for the table to be loaded into. (Required)
  • production_table_definition: Production schema file for the table to be reloaded into. (Required)
  • script_arguments: Arguments for the runner.
    • --max_error: The maximum number of errors to be ignored during the load. Usage: --max_error=5
    • --replace_invalid_char: Character the replace non-utf8 characters with. Usage: --replace_invalid_char='?'
    • --no_escape: If passed, does not escape special characters. Usage: --no_escape
    • --gzip: If passed, compresses the output with gzip. Usage: --gzip
    • --command_options: A custom SQL string as the options for the copy command. Usage: --command_options="DELIMITER '\t'"
      • Note: If --command_options is passed, script arguments --max_error, --replace_invalid_char, --no_escape, and --gzip have no effect.

Example

-   step_type: load-reload-pk
    staging_table_definition: tables/staging.example_table.sql
    production_table_definition: tables/dev.example_table.sql
    script_arguments:
    -   "--foo=bar"

Upsert

Extracts data from a Redshift instance and upserts the data into a table. Upsert = Update + Insert. If a row already exists (by matching primary keys), the row will be updated. If the row does not already exist, insert the row. If the table it's upserting into does not exist, the table will be created.

Properties

  • destination: Schema file for the table to upsert into. (Required)
  • enforce_primary_key: If true, de-duplicates data by matching primary keys. Default: true
  • history: Schema file for the history table to record the changes in the destination table.
  • analyze_table: If true, runs ANALYZE on the table afterwards. Default: true

One of: (Required)

  • sql: The SQL query to run to extract data.
  • script: Local path to a SQL query to run.
  • source: The table to extract. Equivalent to a sql query of SELECT * FROM source.

Example

-   step_type: upsert
    source: tables/dev.example_table.sql
    destination: tables/dev.example_table_2.sql

Reload

Extracts data from a Redshift instance and reloads a table with the data. If the table it's reloading does not exist, the table will be created.

Properties

  • destination: Schema file for the table to reload. (Required)
  • enforce_primary_key: If true, de-duplicates data by matching primary keys. Default: true
  • history: Schema file for the history table to record the changes in the destination table.
  • analyze_table: If true, runs ANALYZE on the table afterwards. Default: true

One of: (Required)

  • sql: The SQL query to run to extract data.
  • script: Local path to a SQL query to run.
  • source: The table to extract. Equivalent to a sql query of SELECT * FROM source.

Example

-   step_type: reload
    source: tables/dev.example_table.sql
    destination: tables/dev.example_table_2.sql

Create Update SQL

Creates a table if it exists and then runs a SQL command.

Properties

  • table_definition: Schema file for the table to create. (Required)
  • script_arguments: Arguments for the SQL script.
  • non_transactional: If true, does not wrap the command in a transaction. Default: false
  • analyze_table: If true, runs ANALYZE on the table afterwards. Default: true

One of: (Required)

  • command: SQL command to execute directly.
  • script: Local path to a SQL command to run.

Example

-   step_type: create-update-sql
    command: |
        DELETE FROM dev.test_table WHERE id < 0;
        INSERT INTO dev.test_table
        SELECT * FROM dev.test_table_2
        WHERE id < %s;
    table_definition: tables/dev.test_table.sql
    script_arguments:
    -   4

Primary Key Check

Checks for primary key violations on a specific table.

Properties

  • table_definition: Schema file for the table to check. (Required)
  • script_arguments: Arguments for the runner script.
  • log_to_s3: If true, logs the output to a file in S3. Default: false

Example

-   step_type: primary-key-check
    table_definition: tables/dev.test_table.sql

Count Check

Compares the number of rows in the source and destination tables/SQL scripts.

Properties

  • source_host: The source host name to lookup in the mysql section of the configuration file. (Required)
  • tolerance: Tolerance threshold, in %, for the difference in count between source and destination. Default: 1
  • log_to_s3: If true, logs the output to a file in S3. Default: false
  • script: Replace the default count script.
  • script_arguments: Arguments for the script.

One of: (Required)

  • source_sql: SQL query to select rows to count for the source.
  • source_count_sql: SQL query that returns a count for the source.
  • source_table_name: Name of source table to count. Equivalent to a source_count_sql of SELECT COUNT(1) from source_table_name.

One of: (Required)

  • destination_sql: SQL query to select rows to count for the destination.
  • destination_table_name: Name of the destination table to count.
  • destination_table_definition: Schema file for the destination table to count.

Example

-   step_type: count-check
    source_sql: "SELECT id, name FROM networks_network;"
    source_host: maestro
    destination_sql: "SELECT network_id, network_name FROM prod.networks"
    tolerance: 2.0
    log_to_s3: true

Column Check

Compares a sample of rows from the source and destination tables/SQL scripts to see if they match

Properties

  • source_host: The source host name to lookup in the mysql section of the configuration file. (Required)
  • source_sql: SQL query to select rows to check for the source. (Required)
  • sql_tail_for_source: Statement to append at the end of the SQL query for the source
  • sample_size: Number of samples to check. Default: 100
  • tolerance: Tolerance threshold, in %, for mismatched rows. Default: 1
  • log_to_s3: If true, logs the output to a file in S3. Default: false
  • script: Replace the default column check script.
  • script_arguments: Arguments for the script.

One of: (Required)

  • destination_sql: SQL query to select rows to check for the destination.
  • destination_table_definition: Schema file for the destination table to check.

Example

-   step_type: column-check
    source_sql: "SELECT id, name FROM networks_network;"
    source_host: maestro
    destination_sql: "SELECT network_id, network_name FROM prod.networks"
    sql_tail_for_source: "ORDER BY RAND() LIMIT LIMIT_PLACEHOLDER"
    sample_size: 10
    log_to_s3: true