Run Go Functions

Pulsar Functions is a succinct computing abstraction that Apache Pulsar enables users to express simple ETL and streaming tasks. Currently, Function Mesh supports using Java, Python, or Go programming language to define a YAML file of the Functions.

This document describes how to run Go Functions. To run a Go Functions in Function Mesh, you need to package the Functions and then submit it to a Pulsar cluster.

Package Go Functions

After developing and testing your Pulsar Functions, you need to package it so that it can be submitted to a Pulsar cluster. You can package Pulsar Functions to external packages or Docker images.

Go Function packages

This section describes how to package a Go Functions and upload it to the Pulsar package management service.

Build Go Functions packages

This section describes how to build packages for Go Functions.

Prerequisites

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

Steps

To package Go Functions in Go, follow these steps.

1. Write a Go Functions.

   Currently, Go Functions can be only implemented using SDK and the interface of the Functions is exposed in the form of SDK. Before using the Go Functions, you need to import github.com/apache/pulsar/pulsar-function-go/pf.

   import (
       "context"
       "fmt"
   
       "github.com/apache/pulsar/pulsar-function-go/pf"
   )
   
   func HandleRequest(ctx context.Context, input []byte) error {
       fmt.Println(string(input) + "!")
       return nil
   }
   
   func main() {
       pf.Start(HandleRequest)
   }

   When writing a Go Functions, remember that

   • In main(), you only need to register the Functions name to Start(). Only one Functions name is received in Start().

   • Go Functions use Go reflection, which is based on the received Functions name, to verify whether the parameter list and returned value list are correct. The parameter list and returned value list must be one of the following sample Functions:

      func ()
      func () error
      func (input) error
      func () (output, error)
      func (input) (output, error)
      func (context.Context) error
      func (context.Context, input) error
      func (context.Context) (output, error)
      func (context.Context, input) (output, error)

   You can use the context to connect to the Go Functions.

   if fc, ok := pf.FromContext(ctx); ok {
       fmt.Printf("function ID is:%s, ", fc.GetFuncID())
       fmt.Printf("function version is:%s\n", fc.GetFuncVersion())
   }

2. Build the Go Functions.

   go build <your Go Function filename>.go 

Upload Go Function packages

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

This example shows how to upload the package of the my-function@0.1 Functions 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 Function CRDs by specifying the uploaded Go Functions package.

Docker images

This section describes how to package a Pulsar Function to a Docker image.

Prerequisites

• Apache Pulsar 2.7.0 or higher
• Function Mesh v0.1.3 or higher

Build Docker images

To build a Docker image, follow these steps.

1. Package your Go Functions. For details, see package Pulsar functions.

2. Define a Dockerfile.

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

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

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

Submit Go Functions

After packaging your Pulsar Go Functions, you can submit your Go Functions to a Pulsar cluster. This section describes how to submit a Go Functions through a Function CRD. You can use the image field to specify the runner image use for creating the Go Functions. You can also specify the location where the package or the Docker image is stored.

1. Define a Go Functions by using a YAML file and save the YAML file.

   • This example shows how to publish a go-function-sample Functions to a Pulsar cluster by using a JAR package called function://my-tenant/my-ns/my-function@0.1.

     apiVersion: compute.functionmesh.io/v1alpha1
     kind: Function
     metadata:
       name: go-function-sample
       namespace: default
     spec:
       image: streamnative/pulsar-functions-go-runner:2.7.1 # using go function runner
       className: exclamation_function.ExclamationFunction
       forwardSourceMessageProperty: true
       maxPendingAsyncRequests: 1000
       replicas: 1
       maxReplicas: 5
       logTopic: persistent://public/default/logging-function-logs
       input:
         topics:
         - persistent://public/default/go-function-input-topic
         typeClassName: java.lang.String
       output:
         topic: persistent://public/default/go-function-output-topic
         typeClassName: java.lang.String
       pulsar:
         pulsarConfig: "test-pulsar"
       golang:
         go: go_func_all
         goLocation: ""
         # use package name:
         # goLocation: function://public/default/nul-test-go-function@v1
         # to be delete & use admission hook

   • This example shows how to publish a go-function-sample Functions to a Pulsar cluster by using a Docker image.

     apiVersion: compute.functionmesh.io/v1alpha1
     kind: Function
     metadata:
       name: go-function-sample
       namespace: default
     spec:
       image: streamnative/example-function-image:latest # using function image here
       className: exclamation_function.ExclamationFunction
       forwardSourceMessageProperty: true
       maxPendingAsyncRequests: 1000
       replicas: 1
       maxReplicas: 5
       logTopic: persistent://public/default/logging-function-logs
       input:
         topics:
         - persistent://public/default/go-function-input-topic
         typeClassName: java.lang.String
       output:
         topic: persistent://public/default/go-function-output-topic
         typeClassName: java.lang.String
       pulsar:
         pulsarConfig: "test-pulsar"
       golang:
         go: go_func_all
         goLocation: ""
         # use package name:
         # goLocation: function://public/default/nul-test-go-function@v1
         # to be delete & use admission hook

2. Apply the YAML file to create the Go Functions.

   kubectl apply -f /path/to/YAML/file

3. Check whether the Go Functions is created successfully.

   kubectl get all