As promised I released a first implementation of Go support using the technique
I described before.
In short, a library implementing the proxy and serving both /run and /init,
with the ability of replace itself with a new version.
Using the library, implementing a function in Go looks like this:
---
package main
import (
"encoding/json"
"fmt"
"github.com/sciabarracom/openwhisk-runtime-go/openwhisk"
)
func hello(event json.RawMessage) (json.RawMessage, error) {
// input and output
var input struct{ Name string }
var output struct {
Greetings string `json:"greetings"`
}
// read the input event
json.Unmarshal(event, &input)
if input.Name != "" {
// handle the event
output.Greetings = "Hello, " + input.Name
fmt.Println(output.Greetings)
return json.Marshal(output)
}
return nil, fmt.Errorf("no name specified")
}
func main() {
openwhisk.Start(ciao)
}
---
Actually in practice it is better to place the function in a separate package
for implementing some tests, because apparently adding tests in the main
package does not work.
Source code of the library is here:
https://github.com/sciabarracom/openwhisk-runtime-go
Here is a simple transcription of how it works and how I tested it.
First you build a couple of executable, and for simplicity you also prepare
the json payload for the init.
$ cd test
$ go build -o hello ../main/hello.go
$ go build -o ciao ../main/ciao.go
$ echo '{"value":{"binary":true,"code":"'$(base64 hello)'"}}' >hello.json
$ echo '{"value":{"binary":true,"code":"'$(base64 ciao)'"}}' >ciao.json
Now you can start the actual server
$ go run ../main/exec.go
Now the magic happens.
Default behaviour (no executable)
```
$ curl -XPOST http://localhost:8080/run -d '{"value":{"name":"Mike"}}'
{"error":"the action failed to locate a binary"}
```
Now post the `hello` handler and run it:
```
$ curl -XPOST http://localhost:8080/init -d @hello.json
OK
$ curl -XPOST http://localhost:8080/run -d '{"value":{"name":"Mike"}}'
{"greetings":"Hello, Mike"}
```
As you can see, the function changed and now it implements the "hello" handler.
But the replaced server is still able to run init so let's do it again,
replacing with the "ciao" handler.
```
$ curl -XPOST http://localhost:8080/init -d @ciao.json
OK
$ curl -XPOST http://localhost:8080/run -d '{"value":{"name":"Mike"}}'
{"saluti":"Ciao, Mike"}
```
---
I want to say "thank you" to James Thomas, I basically copied his code for
implementing the /run handler since it was ready, then I added my code for the
/init. I also had to dig into the internals of the http Go package more than I
expected.
Work is not yet complete, I have to manage the environment variables (stealing
more code from James Thomas implementation), package in Docker, integrate in
OpenWhisk. But definitely I believe looks like a promising start.
--
Michele Sciabarra
openwh...@sciabarra.com
