Google Cloud Functions
Create a Cloud Function with Python.
Pants can create a Google Cloud Function-compatible zip file from your Python code, allowing you to develop your functions in your repository.
Step 1: Activate the Python Google Cloud Function backend
Add this to your pants.toml
:
[GLOBAL]
backend_packages.add = [
"pants.backend.google_cloud_function.python",
"pants.backend.python",
]
This adds the new python_google_cloud_function
target, which you can confirm by running pants help python_google_cloud_function
Step 2: Define a python_google_cloud_function
target
First, add your Cloud function in a Python file like you would normally do with Google Cloud Functions, such as creating a function def my_handler_name(event, context)
for event-based functions.
Then, in your BUILD file, make sure that you have a python_source
or python_sources
target with the handler file included in the sources
field. You can use pants tailor ::
to automate this.
Add a python_google_cloud_function
target and define the runtime
, handler
, and type
fields. The type
should be either "event"
or "http"
. The runtime
should be one of the values from https://cloud.google.com/functions/docs/concepts/python-runtime. The handler
has the form handler_file.py:handler_func
, which Pants will convert into a well-formed entry point. Alternatively, you can set handler
to the format path.to.module:handler_func
.
For example:
- project/BUILD
- project/google_cloud_function_example.py
# The default `sources` field will include our handler file.
python_sources(name="lib")
python_google_cloud_function(
name="cloud_function",
runtime="python38",
# Pants will convert this to `project.lambda_example:example_handler`.
handler="google_cloud_function_example.py:example_handler",
type="event",
)
def example_handler(event, context):
print("Hello Google Cloud Function!")
Pants will use dependency inference based on the handler
field, which you can confirm by running pants dependencies path/to:cloud_function
. You can also manually add to the dependencies
field.
You can optionally set the output_path
field to change the generated zip file's path.
resource
instead of file
file
/ files
targets will not be included in the built Cloud Function because filesystem APIs like open()
would not load them as expected. Instead, use the resource
/ resources
target. See Assets and archives for further explanation.
Step 3: Run package
Now run pants package
on your python_google_cloud_function
target to create a zipped file.
For example:
$ pants package project/google_cloud_function_example.py
Wrote code bundle to dist/project.zip
Runtime: python3.8
Handler: handler
Cloud Functions must run on Linux, so Pants tells PEX and Pip to build for Linux when resolving your third party dependencies. This means that you can only use pre-built wheels (bdists). If your project requires any source distributions (sdists) that must be built locally, PEX and pip will fail to run.
If this happens, you must either change your dependencies to only use dependencies with pre-built wheels or find a Linux environment to run pants package
.
Step 4: Upload to Google Cloud
You can use any of the various Google Cloud methods to upload your zip file, such as the Google Cloud console or the Google Cloud CLI.
You must specify the handler as handler
.