Parsing Methods#

Cosmos offers several options to parse your dbt project:

  • automatic. Tries to find a user-supplied manifest.json file. If it can’t find one, it will run dbt ls to generate one. If that fails, it will use Cosmos’ dbt parser.

  • dbt_manifest. Parses a user-supplied manifest.json file. This can be generated manually with dbt commands or via a CI/CD process.

  • dbt_ls. Parses a dbt project directory using the dbt ls command.

  • dbt_ls_file. Parses a dbt project directory using the output of dbt ls command from a file.

  • custom. Uses Cosmos’ custom dbt parser, which extracts dependencies from your dbt’s model code.

There are benefits and drawbacks to each method:

  • dbt_manifest: You have to generate the manifest file on your own. When using the manifest, Cosmos gets a complete set of metadata about your models. However, Cosmos uses its own selecting & excluding logic to determine which models to run, which may not be as robust as dbt’s.

  • dbt_ls: Cosmos will generate the manifest file for you. This method uses dbt’s metadata AND dbt’s selecting/excluding logic. This is the most robust method. However, this requires the dbt executable to be installed on your machine (either on the host directly or in a virtual environment).

  • dbt_ls_file (new in 1.3): Path to a file containing the dbt ls output. To use this method, run dbt ls using --output json and store the output in a file. RenderConfig.select and RenderConfig.exclude will not work using this method.

  • custom: Cosmos will parse your project and model files. This means that Cosmos will not have access to dbt’s metadata. However, this method does not require the dbt executable to be installed on your machine, and does not require the user to provide any dbt artifacts.

If you’re using the local mode, you should use the dbt_ls method.

If you’re using the docker or kubernetes modes, you should use either dbt_manifest or custom modes.

automatic#

When you don’t supply an argument to the load_mode parameter (or you supply the value "automatic"), Cosmos will attempt the other methods in order:

  1. Use a pre-existing manifest.json file (dbt_manifest)

  2. Try to generate a manifest.json file from your dbt project (dbt_ls)

  3. Use Cosmos’ dbt parser (custom)

To use this method, you don’t need to supply any additional config. This is the default.

dbt_manifest#

If you already have a manifest.json file created by dbt, Cosmos will parse the manifest to generate your DAG.

You can supply a manifest_path parameter on the DbtDag / DbtTaskGroup with a path to a manifest.json file.

Before Cosmos 1.6.0, the path to manifest.json supplied via the DbtDag / DbtTaskGroup manifest_path argument accepted only local paths. However, starting with Cosmos 1.6.0, if you’ve Airflow >= 2.8.0, you can supply a a remote path (e.g., an S3 URL) too. For supporting remote paths, Cosmos leverages the Airflow Object Storage feature released in Airflow 2.8.0. For remote paths, you can specify a manifest_conn_id, which is an Airflow connection ID containing the credentials to access the remote path. If you do not specify a manifest_conn_id, Cosmos will use the default connection ID specific to the scheme, identified using the Airflow hook’s default_conn_id corresponding to the URL’s scheme.

Examples of how to supply manifest.json using manifest_path argument:

  • Local path:

    local_example = DbtTaskGroup(
        group_id="local_example",
        project_config=ProjectConfig(
            manifest_path=DBT_ROOT_PATH / "jaffle_shop" / "target" / "manifest.json",
            project_name="jaffle_shop",
        ),
        profile_config=profile_config,
        render_config=render_config,
        execution_config=execution_config,
        operator_args={"install_deps": True},
    )

  • AWS S3 URL (available since Cosmos 1.6):

Ensure that you have the required dependencies installed to use the S3 URL. You can install the required dependencies using the following command: pip install "astronomer-cosmos[amazon]"

    aws_s3_example = DbtTaskGroup(
        group_id="aws_s3_example",
        project_config=ProjectConfig(
            manifest_path="s3://cosmos-manifest-test/manifest.json",
            manifest_conn_id="aws_s3_conn",
            # `manifest_conn_id` is optional. If not provided, the default connection ID `aws_default` is used.
            project_name="jaffle_shop",
        ),
        profile_config=profile_config,
        render_config=render_config,
        execution_config=execution_config,
        operator_args={"install_deps": True},
    )

  • GCP GCS URL (available since Cosmos 1.6):

Ensure that you have the required dependencies installed to use the GCS URL. You can install the required dependencies using the following command: pip install "astronomer-cosmos[google]"

    gcp_gs_example = DbtTaskGroup(
        group_id="gcp_gs_example",
        project_config=ProjectConfig(
            manifest_path="gs://cosmos-manifest-test/manifest.json",
            manifest_conn_id="gcp_gs_conn",
            # `manifest_conn_id` is optional. If not provided, the default connection ID `google_cloud_default` is used.
            project_name="jaffle_shop",
        ),
        profile_config=profile_config,
        render_config=render_config,
        execution_config=execution_config,
        operator_args={"install_deps": True},
    )

  • Azure Blob Storage URL (available since Cosmos 1.6):

Ensure that you have the required dependencies installed to use the Azure blob URL. You can install the required dependencies using the following command: pip install "astronomer-cosmos[microsoft]"

    azure_abfs_example = DbtTaskGroup(
        group_id="azure_abfs_example",
        project_config=ProjectConfig(
            manifest_path="abfs://cosmos-manifest-test/manifest.json",
            manifest_conn_id="azure_abfs_conn",
            # `manifest_conn_id` is optional. If not provided, the default connection ID `wasb_default` is used.
            project_name="jaffle_shop",
        ),
        profile_config=profile_config,
        render_config=render_config,
        execution_config=execution_config,
        operator_args={"install_deps": True},
    )

dbt_ls#

Note

This only works if a dbt command / executable is available to the scheduler.

If you don’t have a manifest.json file, Cosmos will attempt to generate one from your dbt project. It does this by running dbt ls and parsing the output.

When Cosmos runs dbt ls, it also passes your select and exclude arguments to the command. This means that Cosmos will only generate a manifest for the models you want to run.

Starting in Cosmos 1.5, Cosmos will cache the output of the dbt ls command, to improve the performance of this parsing method. Learn more here.

To use this:

DbtDag(
    render_config=RenderConfig(
        load_method=LoadMode.DBT_LS,
    )
    # ...,
)

dbt_ls_file#

Note

New in Cosmos 1.3.

If you provide the output of dbt ls --output json as a file, you can use this to parse similar to dbt_ls. You can supply a dbt_ls_path parameter on the DbtDag / DbtTaskGroup with a path to a dbt_ls_output.txt file. Check this Dag for an example.

To use this:

DbtDag(
    render_config=RenderConfig(
        load_method=LoadMode.DBT_LS_FILE, dbt_ls_path="/path/to/dbt_ls_file.txt"
    )
    # ...,
)

custom#

If the above methods fail, Cosmos will default to using its own dbt parser. This parser is not as robust as dbt’s, so it’s recommended that you use one of the above methods if possible.

The following are known limitations of the custom parser:

  • it does not read from the dbt_project.yml file

  • it does not parse Python files or models

To use this:

DbtDag(
    render_config=RenderConfig(
        load_method=LoadMode.CUSTOM,
    )
    # ...,
)
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