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Object Storage XCom Backend

The default XCom backend is the :class:~airflow.models.xcom.BaseXCom class, which stores XComs in the Airflow database. This is fine for small values, but can be problematic for large values, or for large numbers of XComs.

To enable storing XComs in an object store, you can set the xcom_backend configuration option to airflow.providers.common.io.xcom.backend.XComObjectStorageBackend. You will also need to set xcom_objectstorage_path to the desired location. The connection id is obtained from the user part of the url the you will provide, e.g. xcom_objectstorage_path = s3://conn_id@mybucket/key. Furthermore, xcom_objectstorage_threshold is required to be something larger than -1. Any object smaller than the threshold in bytes will be stored in the database and anything larger will be be put in object storage. This will allow a hybrid setup. If an xcom is stored on object storage a reference will be saved in the database. Finally, you can set xcom_objectstorage_compression to fsspec supported compression methods like zip or snappy to compress the data before storing it in object storage.

So for example the following configuration will store anything above 1MB in S3 and will compress it using gzip::

  [core]
  xcom_backend = airflow.providers.common.io.xcom.backend.XComObjectStorageBackend

  [common.io]
  xcom_objectstorage_path = s3://conn_id@mybucket/key
  xcom_objectstorage_threshold = 1048576
  xcom_objectstorage_compression = gzip

Another example using the local filesystem::

  [core]
  xcom_backend = airflow.providers.common.io.xcom.backend.XComObjectStorageBackend

  [common.io]
  xcom_objectstorage_path = file://airflow/xcoms

The local filesystem scheme can also be used as it's the same as file show above, see the fsspec <https://github.com/fsspec/filesystem_spec/blob/f30bc759f30327dfb499f37e967648f175750fac/fsspec/implementations/local.py#L30>_::

  [core]
  xcom_backend = airflow.providers.common.io.xcom.backend.XComObjectStorageBackend

  [common.io]
  xcom_objectstorage_path = local://airflow/xcoms

.. note::

Compression requires the support for it is installed in your python environment. For example, to use snappy compression, you need to install python-snappy. Zip, gzip and bz2 work out of the box.