⚙️ FEATURE-#115: Add StorageGCS provider for Google Cloud Storage persistence

docs/nav/reference/storage-gcs.md

@@ -0,0 +1,3 @@
+# StorageGCS
+
+::: dotflow.providers.storage_gcs.StorageGCS

docs/nav/tutorial/storage-gcs.md

@@ -0,0 +1,25 @@
+# Storage GCS
+
+Persists task output to Google Cloud Storage. Good for serverless and cloud-native workflows on GCP.
+
+/// note
+Requires `pip install dotflow[gcp]`
+///
+
+## Example
+
+{* ./docs_src/storage/storage_gcs.py ln[1:34] hl[2,16:22] *}
+
+## Authentication
+
+`StorageGCS` uses Application Default Credentials (ADC):
+
+1. Environment variable: `GOOGLE_APPLICATION_CREDENTIALS` pointing to a service account JSON
+2. `gcloud auth application-default login` for local development
+3. Service account: automatic on Cloud Run, Cloud Functions, GKE
+
+No credentials are needed in code — the GCP client handles it transparently.
+
+## References
+
+- [StorageGCS](https://dotflow-io.github.io/dotflow/nav/reference/storage-gcs/)

docs_src/storage/storage_gcs.py

@@ -0,0 +1,36 @@
+from dotflow import Config, DotFlow, action
+from dotflow.providers import StorageGCS
+
+
+@action
+def step_one():
+    return {"message": "hello from GCS"}
+
+
+@action
+def step_two(previous_context):
+    print(previous_context.storage)
+    return "ok"
+
+
+config = Config(
+    storage=StorageGCS(
+        bucket="dotflow-io-bucket",
+        prefix="workflows/",
+        project="etl-test",
+    )
+)
+
+
+def main():
+    workflow = DotFlow(config=config)
+
+    workflow.task.add(step=step_one)
+    workflow.task.add(step=step_two)
+    workflow.start()
+
+    return workflow
+
+
+if __name__ == "__main__":
+    main()

dotflow/providers/__init__.py

@@ -13,6 +13,7 @@
     "StorageDefault",
     "StorageFile",
     "StorageS3",
+    "StorageGCS",
 ]
 
 
@@ -21,4 +22,10 @@ def __getattr__(name):
         from dotflow.providers.storage_s3 import StorageS3
 
         return StorageS3
+
+    if name == "StorageGCS":
+        from dotflow.providers.storage_gcs import StorageGCS
+
+        return StorageGCS
+
     raise AttributeError(f"module {__name__!r} has no attribute {name!r}")

dotflow/providers/storage_gcs.py

@@ -0,0 +1,119 @@
+"""Storage GCS"""
+
+from collections.abc import Callable
+from json import dumps, loads
+from typing import Any
+
+from dotflow.abc.storage import Storage
+from dotflow.core.context import Context
+from dotflow.core.exception import ModuleNotFound
+
+
+class StorageGCS(Storage):
+    """
+    Import:
+        You can import the **StorageGCS** class directly from dotflow providers:
+
+            from dotflow.providers import StorageGCS
+
+    Example:
+        `class` dotflow.providers.storage_gcs.StorageGCS
+
+            from dotflow import Config
+            from dotflow.providers import StorageGCS
+
+            config = Config(
+                storage=StorageGCS(
+                    bucket="my-dotflow-bucket",
+                    prefix="workflows/",
+                    project="my-gcp-project"
+                )
+            )
+
+    Args:
+        bucket (str): GCS bucket name.
+
+        prefix (str): Key prefix for all stored objects.
+
+        project (str): GCP project ID. Defaults to ADC project.
+    """
+
+    def __init__(
+        self,
+        *args,
+        bucket: str,
+        prefix: str = "dotflow/",
+        project: str = None,
+        **kwargs,
+    ):
+        try:
+            from google.api_core.exceptions import NotFound
+            from google.cloud import storage as gcs
+        except ImportError:
+            raise ModuleNotFound(
+                module="google-cloud-storage",
+                library="dotflow[gcp]",
+            ) from None
+
+        self._not_found = NotFound
+        self.client = gcs.Client(project=project)
+        self.bucket_obj = self.client.bucket(bucket)
+        self.bucket_obj.reload()
+        self.prefix = prefix
+
+    def post(self, key: str, context: Context) -> None:
+        task_context = []
+
+        if isinstance(context.storage, list):
+            for item in context.storage:
+                if isinstance(item, Context):
+                    task_context.append(self._dumps(storage=item.storage))
+        else:
+            task_context.append(self._dumps(storage=context.storage))
+
+        self._write(key=key, data=task_context)
+
+    def get(self, key: str) -> Context:
+        task_context = self._read(key)
+
+        if len(task_context) == 0:
+            return Context()
+
+        if len(task_context) == 1:
+            return self._loads(storage=task_context[0])
+
+        contexts = Context(storage=[])
+        for context in task_context:
+            contexts.storage.append(self._loads(storage=context))
+
+        return contexts
+
+    def key(self, task: Callable):
+        return f"{task.workflow_id}-{task.task_id}"
+
+    def _read(self, key: str) -> list:
+        blob = self.bucket_obj.blob(f"{self.prefix}{key}")
+        try:
+            data = blob.download_as_text()
+            return loads(data)
+        except self._not_found:
+            return []
+
+    def _write(self, key: str, data: list) -> None:
+        blob = self.bucket_obj.blob(f"{self.prefix}{key}")
+        blob.upload_from_string(
+            dumps(data),
+            content_type="application/json",
+        )
+
+    def _loads(self, storage: Any) -> Context:
+        try:
+            return Context(storage=loads(storage))
+        except Exception:
+            return Context(storage=storage)
+
+    def _dumps(self, storage: Any) -> str:
+        try:
+            return dumps(storage)
+        except TypeError:
+            return str(storage)

mkdocs.yml

@@ -130,6 +130,7 @@ nav:
           - nav/tutorial/storage-default.md
           - nav/tutorial/storage-file.md
           - nav/tutorial/storage-s3.md
+          - nav/tutorial/storage-gcs.md
         - nav/tutorial/provider-notify.md
         - nav/tutorial/provider-log.md
       - Tutorial - User Guide:
@@ -187,6 +188,7 @@ nav:
         - nav/reference/storage-init.md
         - nav/reference/storage-file.md
         - nav/reference/storage-s3.md
+        - nav/reference/storage-gcs.md
       - Instance:
         - nav/reference/task-instance.md
         - nav/reference/context-instance.md