Version: 0.8.0

Package Python Functions

After developing and testing your Pulsar function, you need to package it so that the function can be submitted to a Pulsar cluster. This document describes how to package a Python function to an external package (one Python file or ZIP file) or an image.

Function packages

This section describes how to package a Python function and upload it to the Pulsar package management service.

Prerequisites

Apache Pulsar 2.8.0 or higher
Function Mesh v0.1.3 or higher

Steps

You can package a Python function into the One Python file or ZIP file.

One Python file
This example shows how to package a Python function with the One Python file.
```
from pulsar import Function //  import the Function module from Pulsar

# The classic ExclamationFunction that appends an exclamation at the end
# of the input
class ExclamationFunction(Function):
  def __init__(self):
    pass

  def process(self, input, context):
    return input + '!'
```
In this example, when you write a Python function, you need to inherit the Function class and implement the process() method.
The process() method mainly has two parameters:
- input: represents your input.
- context: represents an interface exposed by the Pulsar function. You can get the attributes in the Python function based on the provided context object.
ZIP file
To package a Python function with the ZIP file in Python, you need to prepare a ZIP file. The following is required when packaging the ZIP file of the Python function.
```
Assuming the zip file is named as `func.zip`, unzip the `func.zip` folder:
  "func/src"
  "func/requirements.txt"
  "func/deps"
```
Take exclamation.zip as an example. The internal structure of the example is as follows.
```
.
├── deps
│   └── sh-1.12.14-py2.py3-none-any.whl
└── src
    └── exclamation.py
```

Upload a Python function package

Use the pulsar-admin CLI tool to upload the package to the Pulsar package management service.

Note
Before uploading the package to the Pulsar package management service, you need to enable the package management service in the broker.config file.

This example shows how to upload the package of the my-function@0.1 function to the Pulsar package management service.

bin/pulsar-admin packages upload function://my-tenant/my-ns/my-function@0.1 --path "/path/to/package-file" --description PACKAGE_DESCRIPTION

Then, you can define a function CRD by specifying the uploaded Python function package.

Docker images

This section describes how to package a Python function to a Docker image.

Prerequisites

Apache Pulsar 2.7.0 or higher
Function Mesh v0.1.3 or higher
Install Docker. Download the Community edition and follow the instructions for your OS.
Install kubectl.

Build a Docker image

To build a Docker image, follow these steps.

Package your Python function. For details, see function packages.

Define a Dockerfile.

This example shows how to define a Dockerfile with a JAR package (example-function.jar) of the Python function.

# Use pulsar-functions-python-runner since we pack python function
FROM streamnative/pulsar-functions-python-runner:2.7.1
# Copy function JAR package into /pulsar directory  
COPY example-function.jar /pulsar/

Then, you can push the Docker image to an image registry (such as Docker Hub, or any private registry) and use the Docker image to configure and submit the function to a Pulsar cluster.

Self-built images

This section describes how to create a Python function image by using Buildpacks.

User flow

To create a Python function image, you need to go through the following steps:

Create a Build image.
Create a Run image.
Create a buildpack.
Create a Builder.

Prerequisites

Apache Pulsar 2.7.0 or higher
Function Mesh v0.1.3 or higher
Install the Pack CLI tools.
Install Docker. Download the Community edition and follow the instructions for your OS.
Install kubectl.

Create a Build image

This example shows how to create a Build image.

Define a Dockerfile.

This example defines a Dockerfile with the Stack ID (io.functionmesh.stack).

FROM ubuntu:20.04

ARG pulsar_uid=10000
ARG pulsar_gid=10001
ARG stack_id="io.functionmesh.stack"

RUN apt-get update && \
  apt-get install -y xz-utils ca-certificates git wget jq gcc && \
  rm -rf /var/lib/apt/lists/* && \
  wget -O /usr/local/bin/yj https://github.com/bruceadams/yj/releases/download/v1.2.2/yj.linux.x86_64 && \
  chmod +x /usr/local/bin/yj

LABEL io.buildpacks.stack.id=${stack_id}

RUN groupadd pulsar --gid ${pulsar_gid} && \
  useradd --uid ${pulsar_uid} --gid ${pulsar_gid} -m -s /bin/bash pulsar

ENV CNB_USER_ID=${pulsar_uid}
ENV CNB_GROUP_ID=${pulsar_gid}
ENV CNB_STACK_ID=${stack_id}

USER ${CNB_USER_ID}:${CNB_GROUP_ID}

Run the following command to create the Build image.

docker build -t fm-stack-build:v1 -f ./stack.build.Dockerfile .

Create a Run image

This example shows how to create a Run image.

Define a Dockerfile.

This example uses the streamnative/pulsar-functions-python-runner:2.9.2.23 runner image as the base image. You can specify a specific base image based on your requirements.

FROM streamnative/pulsar-functions-python-runner:2.9.2.23

ARG pulsar_uid=10000
ARG pulsar_gid=10001
ARG stack_id="io.functionmesh.stack"
LABEL io.buildpacks.stack.id=${stack_id}

ENV CNB_USER_ID=${pulsar_uid}
ENV CNB_GROUP_ID=${pulsar_gid}
ENV CNB_STACK_ID=${stack_id}

Run the following command to create the Run image.

docker build -t fm-stack-python-runner-run:v1 -f ./stack.python-runner.run.Dockerfile .

Create a buildpack

This example shows how to create a buildpack with the buildpack ID functionmesh/python-py.

pack buildpack new functionmesh/python-py \
  --api 0.7 \
  --path python-py \
  --version 0.0.1 \
  --stacks io.functionmesh.stack

Then, a buildpack directory named python-py is created.

`-- python-py
    |-- bin
    |   |-- build
    |   `-- detect
    `-- buildpack.toml

Update the content of the three files with the following content.

buildpack.toml

api = "0.7"

[buildpack]
  id = "functionmesh/java-maven"
  version = "0.0.1"

[[stacks]]
  id = "io.functionmesh.stack"

bin/detect

#!/usr/bin/env bash

set -eo pipefail

# Skip this buildpack if there are no Python files in the current directory
py_num=$(find . -maxdepth 1 -name "*.py" | wc -l)
if [[ ${py_num} -eq 0 ]]; then
  exit 100
fi

exit 0

bin/build

#!/usr/bin/env bash

set -euo pipefail

layers_dir="$1"
env_dir="$2/env"
plan_path="$3"

echo "Do nothing is the build logic of this Buildpack!"

exit 0

Create a Builder image

This section describes how to create a Builder image.

Define a Builder configuration file (builder.toml) with the following content.

# Buildpacks to include in builder
[[buildpacks]]
uri = "../../buildpacks/python-py"

# Order used for detection
[[order]]
  # This buildpack will display build-time information (as a dependency)
  [[order.group]]
  id = "functionmesh/python-py"
  version = "0.0.1"

# Stack that will be used by the builder
[stack]
id = "io.functionmesh.stack"
# This image is used at runtime
run-image = "fm-stack-python-runner-run:v1"
# This image is used at build-time
build-image = "fm-stack-build:v1"

Run the following command to create the Builder image.

pack builder create fm-python-py-builder:v1 \
  --config ./builder.toml \
  --pull-policy if-not-present

Create a Python function image

After creating the Build image (fm-stack-build:v1), the Run image (fm-stack-python-runner-run:v1), and the Builder image (fm-python-py-builder:v1), you can build a Python function image and then use the Python function image to run a Python function.

The package directory structure is similar to:

.
|-- pom.xml
`-- src/
    `-- main/
        `-- java/
            `-- org.example/
                `-- ExclamationFunction.java

Prepare a Python function file.

This example writes a Python function named exclamation_example.py.

from pulsar import Function

class ExclamationFunction(Function):
  def __init__(self):
      pass

  def process(self, input, context):
      return input + '!'

Run the following command to build the Python function image in the current directory.

pack build python-exclamation-function:v1 \
    --builder fm-python-py-builder:v1 \
    --workspace /pulsar \
    --pull-policy if-not-present

The output is similar to:

===> ANALYZING
[analyzer] Previous image with name "python-exclamation-function:v1" not found
===> DETECTING
[detector] functionmesh/python-py 0.0.1
===> RESTORING
===> BUILDING
[builder] Do nothing is the build logic of this Buildpack!
===> EXPORTING
[exporter] Adding layer 'launch.sbom'
[exporter] Adding 1/1 app layer(s)
[exporter] Adding layer 'launcher'
[exporter] Adding layer 'config'
[exporter] Adding label 'io.buildpacks.lifecycle.metadata'
[exporter] Adding label 'io.buildpacks.build.metadata'
[exporter] Adding label 'io.buildpacks.project.metadata'
[exporter] no default process type
[exporter] Saving python-exclamation-function:v1...
[exporter] *** Images (274630b94169):
[exporter]       python-exclamation-function:v1
Successfully built image python-exclamation-function:v1

Next step

Run Python Functions

Function packages​

Prerequisites​

Steps​

Upload a Python function package​

Docker images​

Prerequisites​

Build a Docker image​

Self-built images​

User flow​

Prerequisites​

Create a Build image​

Create a Run image​

Create a buildpack​

Create a Builder image​

Create a Python function image​

Next step​

Function packages

Prerequisites

Steps

Upload a Python function package

Docker images

Prerequisites

Build a Docker image

Self-built images

User flow

Prerequisites

Create a Build image

Create a Run image

Create a buildpack

Create a Builder image

Create a Python function image

Next step