Develop a Custom Artifact Store

How to develop a custom artifact store

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ZenML comes equipped with Artifact Store implementations that you can use to store artifacts on a local filesystem or in the managed AWS, GCP or Azure cloud object storage services. However, if you need to use a different type of object storage service as a backend for your ZenML Artifact Store, you can extend ZenML to provide your own custom Artifact Store implementation.

Base Abstraction

The Artifact Store establishes one of the main components in every ZenML stack. Now, let us take a deeper dive into the fundamentals behind its abstraction, namely the BaseArtifactStore class:

  1. As it is the base class for a specific type of StackComponent, it inherits from the StackComponent class. This sets the TYPE variable to a StackComponentType. The FLAVOR class variable needs to be set in the specific subclass.

  2. As ZenML only supports filesystem-based artifact stores, it features an instance configuration parameter called path, which will indicate the root path of the artifact store. When creating an instance of any flavor of an ArtifactStore, users will have to define this parameter.

  3. Moreover, there is an empty class variable called SUPPORTED_SCHEMES that needs to be defined in every flavor implementation. It indicates the supported filepath schemes for the corresponding implementation. For instance, for the Azure artifact store, this set will be defined as {"abfs://", "az://"}.

  4. Lastly, the base class features a set of abstractmethods: open, copyfile,exists,glob,isdir,listdir,makedirs,mkdir,remove, rename,rmtree,stat,walk. In the implementation of every ArtifactStore flavor, it is required to define these methods with respect to the flavor at hand.

Putting all these considerations together, we end up with the following implementation:

from zenml.enums import StackComponentType
from zenml.stack import StackComponent

PathType = Union[bytes, str]

class BaseArtifactStore(StackComponent):
    """Base class for all ZenML artifact stores."""

    # --- Instance configuration ---
    path: str  # The root path of the artifact store.

    # --- Class variables ---
    TYPE: ClassVar[StackComponentType] = StackComponentType.ARTIFACT_STORE
    SUPPORTED_SCHEMES: ClassVar[Set[str]]

    # --- User interface ---
    def open(self, name: PathType, mode: str = "r") -> Any:
        """Open a file at the given path."""

    def copyfile(
        self, src: PathType, dst: PathType, overwrite: bool = False
    ) -> None:
        """Copy a file from the source to the destination."""

    def exists(self, path: PathType) -> bool:
        """Returns `True` if the given path exists."""

    def glob(self, pattern: PathType) -> List[PathType]:
        """Return the paths that match a glob pattern."""

    def isdir(self, path: PathType) -> bool:
        """Returns whether the given path points to a directory."""

    def listdir(self, path: PathType) -> List[PathType]:
        """Returns a list of files under a given directory in the filesystem."""

    def makedirs(self, path: PathType) -> None:
        """Make a directory at the given path, recursively creating parents."""

    def mkdir(self, path: PathType) -> None:
        """Make a directory at the given path; parent directory must exist."""

    def remove(self, path: PathType) -> None:
        """Remove the file at the given path. Dangerous operation."""

    def rename(
        self, src: PathType, dst: PathType, overwrite: bool = False
    ) -> None:
        """Rename source file to destination file."""

    def rmtree(self, path: PathType) -> None:
        """Deletes dir recursively. Dangerous operation."""

    def stat(self, path: PathType) -> Any:
        """Return the stat descriptor for a given file path."""

    def walk(
        top: PathType,
        topdown: bool = True,
        onerror: Optional[Callable[..., None]] = None,
    ) -> Iterable[Tuple[PathType, List[PathType], List[PathType]]]:
        """Return an iterator that walks the contents of the given directory."""

This is a slimmed-down version of the base implementation which aims to highlight the abstraction layer. In order to see the full implementation and get the complete docstrings, please check the API docs.

The effect on the

If you created an instance of an artifact store, added it to your stack and activated the stack, it will create a filesystem each time you run a ZenML pipeline and make it available to the module.

This means that when you utilize a method such as with a filepath which starts with one of the SUPPORTED_SCHEMES within your steps or materializers, it will be able to use the open(...) method that you defined within your artifact store.

Build your own custom artifact store

If you want to implement your own custom Artifact Store, you can follow the following steps:

  1. Create a class which inherits from the BaseArtifactStore base class.

  2. Define the FLAVOR and SUPPORTED_SCHEMES class variables.

  3. Implement the abstractmethods based on your desired filesystem.

Once you are done with the implementation, you can register it through the CLI as:

zenml artifact-store flavor register <THE-SOURCE-PATH-OF-YOUR-ARTIFACT-STORE>

ZenML includes a range of Artifact Store implementations, some built-in and other provided by specific integration modules. You can use them as examples of how you can extend the base Artifact Store abstraction to implement your own custom Artifact Store:

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