title | linkTitle | description |
---|---|---|
Go |
Go |
Learn how to write a Vela plugin with Go.
|
{{% alert color="warning" %}} We recommend reviewing Docker's best practices before attempting to create a custom plugin.
We recommend that all plugins be placed inside a scratch image. {{% /alert %}}
From Go documentation:
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
To create a plugin using Go, we'll need to first decide what task we want this plugin to accomplish.
For this example, we're going to create a program that makes an HTTP request from the provided input:
package main
import (
"fmt"
"net/http"
"os"
"strings"
)
func main() {
// import method parameter from environment
method := os.Getenv("PARAMETER_METHOD")
// import body parameter from environment
body := os.Getenv("PARAMETER_BODY")
// import url parameter from environment
url := os.Getenv("PARAMETER_URL")
// create payload from body
payload := strings.NewReader(body)
// create new HTTP request from provided input
request, err := http.NewRequest(method, url, payload)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
// send HTTP request and capture response
response, err := http.DefaultClient.Do(request)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
// output the response
fmt.Println(response)
}
{{% alert color="info" %}} An example of this code is provided in the go section of the go-vela/vela-tutorials repository. {{% /alert %}}
Now that we have the program to accomplish our plugin's task, we need to compile the code to produce an executable binary for the target platform:
GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -o vela-sample
{{% alert color="warning" %}} Please ensure the program is compiled for the right target platform.
If it's not, the plugin may fail to properly run and produce unclear error messages. {{% /alert %}}
Once we have the executable needed to accomplish our plugin's task, we need to create a Dockerfile to produce an image.
This image should contain the binary and be setup to run that binary when the plugin is executed:
FROM golang:alpine
RUN apk add --update --no-cache ca-certificates
COPY vela-sample /bin/vela-sample
ENTRYPOINT ["/bin/vela-sample"]
{{% alert color="info" %}} An example of this image is provided in the target/vela-sample Docker repository. {{% /alert %}}
In order to run the plugin in a pipeline, we'll need to make sure we build and publish it to a Docker registry:
# build the image
docker build -t target/vela-sample:go .
# publish the image
docker push target/vela-sample:go
{{% alert color="info" %}} This has the added benefit of enabling others in the community to consume your plugin! {{% /alert %}}
To verify that the plugin performs the desired task, it can be executed locally via the command line:
docker run --rm \
-e PARAMETER_BODY="This is a sample Vela plugin written with Go" \
-e PARAMETER_METHOD="POST" \
-e PARAMETER_URL="http://vela.localhost.com" \
target/vela-sample:go
After publishing the image to a Docker registry, it can be referenced in a pipeline:
version: "1"
steps:
- name: sample go plugin
image: target/vela-sample:go
pull: always
parameters:
url: http://vela.localhost.com
method: POST
body: |
This is a sample Vela plugin written with Go