# Getting Started

Welcome! If you're ready to get started with Meltano and run an EL(T) pipeline with a data source and destination of your choosing, you've come to the right place!

Short on time, or just curious what the fuss is about?

To get a sense of the Meltano experience in just a few minutes, follow the examples on the homepage.

They can be copy-pasted right into your terminal and will take you all the way through installation, data integration (EL), data transformation (T), orchestration, and containerization with the tap-gitlab extractor and the target-jsonl and target-postgres loaders.

# Install Meltano

Before you can get started with Meltano and the meltano CLI, you'll need to install it onto your system.

To learn more about the different installation methods, refer to the Installation guide.

# Local installation

If you're running Linux or macOS and have Python 3.6, 3.7 or 3.8 installed, we recommend installing Meltano into a dedicated Python virtual environment inside the directory that will hold your Meltano projects.

  1. Create and navigate to a directory to hold your Meltano projects:

    mkdir meltano-projects
    cd meltano-projects
    
  2. Create and activate a virtual environment for Meltano inside the .venv directory:

    python3 -m venv .venv
    source .venv/bin/activate
    
  3. Install the meltano package from PyPI:

    pip3 install meltano
    
  4. Optionally, verify that the meltano CLI is now available by viewing the version:

    meltano --version
    

If anything's not behaving as expected, refer to the "Local Installation" section of the Installation guide for more details.

# Docker installation

Alternatively, and assuming you already have Docker installed and running, you can use the meltano/meltano Docker image which exposes the meltano CLI command as its entrypoint.

  1. Pull or update the latest version of the Meltano Docker image:

    docker pull meltano/meltano:latest
    

    By default, this image comes with the oldest version of Python supported by Meltano, currently 3.6. If you'd like to use Python 3.7 or 3.8 instead, add a -python<X.Y> suffix to the image tag, e.g. latest-python3.8.

  2. Optionally, verify that the meltano CLI is now available through the Docker image by viewing the version:

    docker run meltano/meltano --version
    

Now, whenever this guide or the documentation asks you to run the meltano command, you'll need to run it using docker run meltano/meltano <args> as in the example above.

When running a meltano subcommand that requires access to your project (which you'll create in the next step), you'll also need to mount the project directory into the container and set it as the container's working directory:

docker run -v $(pwd):/project -w /project meltano/meltano <args>

If anything's not behaving as expected, refer to the "Installing on Docker" section of the Installation guide for more details.

# Create your Meltano project

Now that you have a way of running the meltano CLI, it's time to create a new Meltano project that (among other things) will hold the plugins that implement the various details of your ELT pipelines.

To learn more about Meltano projects, refer to the Projects concept doc.

  1. Navigate to the directory that you'd like to hold your Meltano projects, if you didn't already do so earlier:

    mkdir meltano-projects
    cd meltano-projects
    
  2. Initialize a new project in a directory of your choosing using meltano init:

    meltano init <project directory name>
    
    # For example:
    meltano init my-meltano-project
    
    # If you're using Docker, don't forget to mount the current working directory:
    docker run -v $(pwd):/projects -w /projects meltano/meltano init my-meltano-project
    
  3. Navigate to the newly created project directory:

    cd <project directory>
    
    # For example:
    cd my-meltano-project
    
  4. Optionally, if you'd like to version control your changes, initialize a Git repository and create an initial commit:

    git init
    git add --all
    git commit -m 'Initial Meltano project'
    

    This will allow you to use git diff to easily check the impact of the meltano commands you'll run below on your project files, most notably your meltano.yml project file.

# Add an extractor to pull data from a source

Now that you have your very own Meltano project, it's time to add some plugins to it!

The first plugin you'll want to add is an extractor, which will be responsible for pulling data out of your data source.

To learn more about adding plugins to your project, refer to the Plugin Management guide.

  1. Find out if an extractor for your data source is supported out of the box by checking the Extractors list or using meltano discover:

    meltano discover extractors
    
  2. Depending on the result, pick your next step:

    • If an extractor is supported out of the box, add it to your project using meltano add:

      meltano add extractor <plugin name>
      
      # For example:
      meltano add extractor tap-gitlab
      
      # If you have a preference for a non-default variant, select it using `--variant`:
      meltano add extractor tap-gitlab --variant=singer-io
      
      # If you're using Docker, don't forget to mount the project directory:
      docker run -v $(pwd):/project -w /project meltano/meltano add extractor tap-gitlab
      

      You can now continue to step 4.

    • If an extractor is not yet discoverable, find out if a Singer tap for your data source already exists by checking Singer's index of taps and/or doing a web search for Singer tap <data source>, e.g. Singer tap COVID-19.

  3. Depending on the result, pick your next step:

    • If a Singer tap for your data source is available, add it to your project as a custom plugin using meltano add --custom:

      meltano add --custom extractor <tap name>
      
      # For example:
      meltano add --custom extractor tap-covid-19
      
      # If you're using Docker, don't forget to mount the project directory,
      # and ensure that interactive mode is enabled so that Meltano can ask you
      # additional questions about the plugin and get your answers over STDIN:
      docker run --interactive -v $(pwd):/project -w /project meltano/meltano add --custom extractor tap-covid-19
      

      Meltano will now ask you some additional questions to learn more about the plugin.

      To learn more about adding custom plugins, refer to the "meltano add: How to use: Custom plugins" section of the CLI Reference.

      TIP

      Once you've got the extractor working in your project, please consider contributing its definition to the index of discoverable plugins so that it can be supported out of the box for new users!

    • If a Singer tap for your data source doesn't exist yet, learn how to build your own tap by following the "Create a Custom Extractor" tutorial or Singer's "Developing a Tap" guide.

      Once you've got your new tap project set up, you can add it to your Meltano project as a custom plugin by following the meltano add --custom instructions above. When asked to provide a pip install argument, you can provide a local directory path or Git repository URL.

  4. Optionally, verify that the extractor was installed successfully and that its executable can be invoked using meltano invoke:

    meltano invoke <plugin> --help
    
    # For example:
    meltano invoke tap-gitlab --help
    

    If you see the extractor's help message printed, the plugin was definitely installed successfully, but an error message related to missing configuration or an unimplemented --help flag would also confirm that Meltano can invoke the plugin's executable.

# Configure the extractor

Chances are that the extractor you just added to your project will require some amount of configuration before it can start extracting data.

To learn more about managing the configuration of your plugins, refer to the Configuration guide.

What if I already have a config file for this extractor?

If you've used this Singer tap before without Meltano, you may have a config file already.

If you'd like to use the same configuration with Meltano, you can skip this section and copy and paste the JSON config object into your meltano.yml project file under the plugin's config key:




 
 
 
 

extractors:
- name: tap-example
  pip_url: tap-example
  config: {
    "setting": "value",
    "another_setting": true
  }

Since YAML is a superset of JSON, the object should be indented correctly, but formatting does not need to be changed.

  1. Find out what settings your extractor supports using meltano config <plugin> list:

    meltano config <plugin> list
    
    # For example:
    meltano config tap-gitlab list
    
  2. Assuming the previous command listed at least one setting, set appropriate values using meltano config <plugin> set:

    meltano config <plugin> set <setting> <value>
    
    # For example:
    meltano config tap-gitlab set projects meltano/meltano
    meltano config tap-gitlab set start_date 2020-05-01T00:00:00Z
    
  3. Optionally, verify that the configuration looks like what the Singer tap expects according to its documentation using meltano config <plugin>:

    meltano config <plugin>
    
    # For example:
    meltano config tap-gitlab
    

# Select entities and attributes to extract

Now that the extractor has been configured, it'll know where and how to find your data, but not yet which specific entities and attributes (tables and columns) you're interested in.

By default, Meltano will instruct extractors to extract all supported entities and attributes, but it's recommended that you specify the specific entities and attributes you'd like to extract, to improve performance and save on bandwidth and storage.

To learn more about selecting entities and attributes for extraction, refer to the Data Integration (EL) guide.

What if I already have a catalog file for this extractor?

If you've used this Singer tap before without Meltano, you may have generated a catalog file already.

If you'd like Meltano to use it instead of generating a catalog based on the entity selection rules you'll be asked to specify below, you can skip this section and either set the catalog extractor extra or use meltano elt's --catalog option when running the data integration (EL) pipeline later on in this guide.

  1. Find out whether the extractor supports entity selection, and if so, what entities and attributes are available, using meltano select --list --all:

    meltano select --list --all <plugin>
    
    # For example:
    meltano select --list --all tap-covid-19
    

    If this command fails with an error, this usually means that the Singer tap does not support catalog discovery mode, and will always extract all supported entities and attributes.

  2. Assuming the previous command succeeded, select the desired entities and attributes for extraction using meltano select:

    meltano select <plugin> <entity> <attribute>
    meltano select <plugin> --exclude <entity> <attribute>
    
    # For example:
    meltano select tap-covid-19 eu_daily date
    meltano select tap-covid-19 eu_daily country
    meltano select tap-covid-19 eu_daily cases
    meltano select tap-covid-19 eu_daily deaths
    
    # Include all attributes of an entity
    meltano select tap-covid-19 eu_ecdc_daily "*"
    
    # Exclude matching attributes of all entities
    meltano select tap-covid-19 --exclude "*" "git_*"
    

    As you can see in the example, entity and attribute identifiers can contain wildcards (*) to match multiple entities or attributes at once.

  3. Optionally, verify that only the intended entities and attributes are now selected using meltano select --list:

    meltano select --list <plugin>
    
    # For example:
    meltano select --list tap-covid-19
    

# Choose how to replicate each entity

If the data source you'll be pulling data from is a database, like PostgreSQL or MongoDB, your extractor likely requires one final setup step: setting a replication method for each selected entity (table).

Extractors for SaaS APIs typically hard-code the appropriate replication method for each supported entity, so if you're using one, you can skip this section and move on to setting up a loader.

Most database extractors, on the other hand, support two or more of the following replication methods and require you to choose an appropriate option for each table through the replication-method stream metadata key:

  • LOG_BASED: Log-based Incremental Replication

    The extractor uses the database's binary log files to identify what records were inserted, updated, and deleted from the table since the last run (if any), and extracts only these records.

    This option is not supported by all databases and database extractors.

  • INCREMENTAL: Key-based Incremental Replication

    The extractor uses the value of a specific column on the table (the Replication Key, e.g. an updated_at timestamp or incrementing id integer) to identify what records were inserted or updated (but not deleted) since the last run (if any), and extracts only those records.

  • FULL_TABLE: Full Table Replication

    The extractor extracts all available records in the table on every run.

To learn more about replication methods, refer to the Data Integration (EL) guide.

  1. Find out which replication methods (i.e. options for the replication-method stream metadata key) the extractor supports by checking its documentation or the README in its repository.

  2. Set the desired replication-method metadata for each selected entity using meltano config <plugin> set and the extractor's metadata extra:

    meltano config <plugin> set _metadata <entity> replication-method <LOG_BASED|INCREMENTAL|FULL_TABLE>
    
    # For example:
    meltano config tap-postgres set _metadata some_entity_id replication-method INCREMENTAL
    meltano config tap-postgres set _metadata other_entity replication-method FULL_TABLE
    
    # Set replication-method metadata for all entities
    meltano config tap-postgres set _metadata '*' replication-method INCREMENTAL
    
    # Set replication-method metadata for matching entities
    meltano config tap-postgres set _metadata '*_full' replication-method FULL_TABLE
    

    As you can see in the example, entity identifiers can contain wildcards (*) to match multiple entities at once.

    If you've set a table's replication-method to INCREMENTAL, also choose a Replication Key by setting the replication-key metadata:

    meltano config <plugin> set _metadata <entity> replication-key <column>
    
    # For example:
    meltano config tap-postgres set _metadata some_entity_id replication-key updated_at
    meltano config tap-postgres set _metadata some_entity_id replication-key id
    
  3. Optionally, verify that the stream metadata for each table was set correctly in the extractor's generated catalog file by dumping it using meltano invoke --dump=catalog <plugin>:

    meltano invoke --dump=catalog <plugin>
    
    # For example:
    meltano invoke --dump=catalog tap-postgres
    

# Add a loader to send data to a destination

Now that your Meltano project has everything it needs to pull data from your source, it's time to tell it where that data should go!

This is where the loader comes in, which will be responsible for loading extracted data into an arbitrary data destination.

To learn more about adding plugins to your project, refer to the Plugin Management guide.

  1. Find out if a loader for your data destination is supported out of the box by checking the Loaders list or using meltano discover:

    meltano discover loaders
    
  2. Depending on the result, pick your next step:

    • If a loader is supported out of the box, add it to your project using meltano add:

      meltano add loader <plugin name>
      
      # For example:
      meltano add loader target-postgres
      
      # If you have a preference for a non-default variant, select it using `--variant`:
      meltano add loader target-postgres --variant=transferwise
      

      You can now continue to step 4.

    • If a loader is not yet discoverable, find out if a Singer target for your data source already exists by checking Singer's index of targets and/or doing a web search for Singer target <data destination>, e.g. Singer target BigQuery.

  3. Depending on the result, pick your next step:

    • If a Singer target for your data destination is available, add it to your project as a custom plugin using meltano add --custom:

      meltano add --custom loader <target name>
      
      # For example:
      meltano add --custom loader target-bigquery
      
      # If you're using Docker, don't forget to mount the project directory,
      # and ensure that interactive mode is enabled so that Meltano can ask you
      # additional questions about the plugin and get your answers over STDIN:
      docker run --interactive -v $(pwd):/project -w /project meltano/meltano add --custom loader target-bigquery
      

      Meltano will now ask you some additional questions to learn more about the plugin.

      To learn more about adding custom plugins, refer to the "meltano add: How to use: Custom plugins" section of the CLI Reference.

      TIP

      Once you've got the loader working in your project, please consider contributing its definition to the index of discoverable plugins so that it can be supported out of the box for new users!

    • If a Singer target for your data source doesn't exist yet, learn how to build your own target by following Singer's "Developing a Target" guide.

      Once you've got your new target project set up, you can add it to your Meltano project as a custom plugin by following the meltano add --custom instructions above. When asked to provide a pip install argument, you can provide a local directory path or Git repository URL.

  4. Optionally, verify that the loader was installed successfully and that its executable can be invoked using meltano invoke:

    meltano invoke <plugin> --help
    
    # For example:
    meltano invoke target-postgres --help
    

    If you see the loader's help message printed, the plugin was definitely installed successfully, but an error message related to missing configuration or an unimplemented --help flag would also confirm that Meltano can invoke the plugin's executable.

# Configure the loader

Chances are that the loader you just added to your project will require some amount of configuration before it can start loading data.

To learn more about managing the configuration of your plugins, refer to the Configuration guide.

What if I already have a config file for this loader?

If you've used this Singer target before without Meltano, you may have a config file already.

If you'd like to use the same configuration with Meltano, you can skip this section and copy and paste the JSON config object into your meltano.yml project file under the plugin's config key:




 
 
 
 

loaders:
- name: target-example
  pip_url: target-example
  config: {
    "setting": "value",
    "another_setting": true
  }

Since YAML is a superset of JSON, the object should be indented correctly, but formatting does not need to be changed.

  1. Find out what settings your loader supports using meltano config <plugin> list:

    meltano config <plugin> list
    
    # For example:
    meltano config target-postgres list
    
  2. Assuming the previous command listed at least one setting, set appropriate values using meltano config <plugin> set:

    meltano config <plugin> set <setting> <value>
    
    # For example:
    meltano config target-postgres set postgres_host localhost
    meltano config target-postgres set postgres_port 5432
    meltano config target-postgres set postgres_username meltano
    meltano config target-postgres set postgres_password meltano
    meltano config target-postgres set postgres_database warehouse
    meltano config target-postgres set postgres_schema public
    
  3. Optionally, verify that the configuration looks like what the Singer target expects according to its documentation using meltano config <plugin>:

    meltano config <plugin>
    
    # For example:
    meltano config target-postgres
    

# Run a data integration (EL) pipeline

Now that your Meltano project, extractor, and loader are all set up, we've reached the final chapter of this adventure, and it's time to run your first data integration (EL) pipeline!

To learn more about data integration, refer to the Data Integration (EL) guide.

There's just one step here: run your newly added extractor and loader in a pipeline using meltano elt:

meltano elt <extractor> <loader> --job_id=<pipeline name>

# For example:
meltano elt tap-gitlab target-postgres --job_id=gitlab-to-postgres

If everything was configured correctly, you should now see your data flow from your source into your destination!

If the command failed, but it's not obvious how to resolve the issue, consider enabling debug mode to get some more insight into what's going on behind the scenes. If that doesn't get you closer to a solution, learn how to get help with your issue.

If you run meltano elt another time with the same Job ID, you'll see it automatically pick up where the previous run left off, assuming the extractor supports incremental replication.

What if I already have a state file for this extractor?

If you've used this Singer tap before without Meltano, you may have a state file already.

If you'd like Meltano to use it instead of looking up state based on the Job ID, you can either use meltano elt's --state option or set the state extractor extra.

If you'd like to dump the state generated by the most recent run into a file, so that you can explicitly pass it along to the next invocation, you can use meltano elt's --dump=state option:

meltano elt <extractor> <loader> --job_id=<pipeline name> --dump=state > state.json

# For example:
meltano elt tap-gitlab target-postgres --job_id=gitlab-to-postgres --dump=state > state.json

# Next steps

Now that you've successfully run your first data integration (EL) pipeline using Meltano, you have a few possible next steps:

# Schedule pipelines to run regularly

Most pipelines aren't run just once, but over and over again, to make sure additions and changes in the source eventually make their way to the destination.

To help you realize this, Meltano supports scheduled pipelines that can be orchestrated using Apache Airflow.

To learn more about orchestration, refer to the Orchestration guide.

  1. Schedule a new meltano elt pipeline to be invoked on an interval using meltano schedule:

    meltano schedule <pipeline name> <extractor> <loader> <interval>
    
    # For example:
    meltano schedule gitlab-to-postgres tap-gitlab target-postgres @daily
    

    The pipeline name argument corresponds to the --job_id flag on meltano elt, which identifies related EL(T) runs when storing and looking up incremental replication state. To have scheduled runs pick up where your earlier manual run left off, ensure you use the same pipeline name.

  2. Optionally, verify that the schedule was created successfully using meltano schedule list:

    meltano schedule list
    
  3. Add the Apache Airflow orchestrator to your project using meltano add, which will be responsible for managing the schedule and executing the appropriate meltano elt commands:

    meltano add orchestrator airflow
    

    This will automatically add a meltano elt DAG generator to your project's orchestrate/dags directory, where Airflow will be configured to look for DAGs by default.

  4. Start the Airflow scheduler using meltano invoke:

    meltano invoke airflow scheduler
    
    # Add `-D` to run the scheduler in the background:
    meltano invoke airflow scheduler -D
    
  5. Optionally, verify that a DAG was automatically created for each scheduled pipeline by starting the Airflow web interface:

    meltano invoke airflow webserver
    
    # Add `-D` to run the scheduler in the background:
    meltano invoke airflow webserver -D
    

    The web interface and DAG overview will be available at http://localhost:8080.

# Transform loaded data for analysis

Once your raw data has arrived in your data warehouse, its schema will likely need to be transformed to be more appropriate for analysis.

To help you realize this, Meltano supports transformation using dbt.

To learn about data transformation, refer to the Data Transformation (T) guide.

# Containerize your project

To learn how to containerize your project, refer to the Containerization guide.

# Deploy your pipelines in production

To learn how to deploy your pipelines in production, refer to the Deployment in Production guide.