Building a Serverless Application Using Azure Functions and Go

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We invite prospective students and everyone interested to participate in the open webinar on the topic "Go-channels outside and inside". During the lesson, participants will receive a simple abstraction in pictures to understand the principles of the channels, learn about the structure of channels at the language level.

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Today we will learn how to integrate a Slack application as a serverless backend.

— FaaS ( ) . , , , ! serverless , , HTTP-. , Slack serverless () Go Azure Functions. Slack , , , Slack.

Giphy Slack. Giphy Slack . -, , () , Giphy Random API. Azure Functions Slack.

:

• (Custom Handlers) Azure Functions;

  
  
  
  
  

• , ;

  
  
  
  
  

• , Azure Functions Slack;

  
  
  
  
  

• , , Slack !

  
  
  
  
  

- Go ( GitHub). , Azure Functions , Go , . (Custom Handlers) !

?

, - -, . , /, HTTP! , HTTP- - / (input/output bindings) .

, ( )

( HTTP, , . .) (Functions host). , : (payload) - () , , . , .

, (, , ) .

, .

.
├── cmd
│   └── main.go
├── funcy
│   └── function.json
├── go.mod
├── host.json
└── pkg
    └── function
        ├── function.go
        ├── giphy.go
        └── slack.go
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

• function.json
  
  
  
  , ( )

  
  
  
  
  

{
    "bindings": [
        {
            "type": "httpTrigger",
            "direction": "in",
            "name": "req",
            "methods": [
                "get",
                "post"
            ]
        },
        {
            "type": "http",
            "direction": "out",
            "name": "res"
        }
    ]
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

• host.json
  
  
  
  , , -, HTTP. customHandler.description.defaultExecutablePath
  
  
  
  , , go_funcy
  
  
  
  — , -. "enableForwardingHttpRequest": true
  
  
  
  , HTTP - :

  
  
  
  
  

{
    "version": "2.0",
    "extensionBundle": {
        "id": "Microsoft.Azure.Functions.ExtensionBundle",
        "version": "[1.*, 2.0.0)"
    },
    "customHandler": {
        "description": {
            "defaultExecutablePath": "go_funcy"
        },
        "enableForwardingHttpRequest": true
    },
    "logging": {
        "logLevel": {
            "default": "Trace"
        }
    }
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

• cmd



pkg
  
  
  
  Go. .

  
  
  
  
  

cmd/main.go



HTTP-. , /api/funcy — , HTTP- .

func main() {
 port, exists := os.LookupEnv("FUNCTIONS_CUSTOMHANDLER_PORT")
 if !exists {
   port = "8080"
 }
 http.HandleFunc("/api/funcy", function.Funcy)
 log.Fatal(http.ListenAndServe(":"+port, nil))
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

function/function.go



.

— ( Slack) , Slack.

signingSecret := os.Getenv("SLACK_SIGNING_SECRET")
	apiKey := os.Getenv("GIPHY_API_KEY")
	if signingSecret == "" || apiKey == "" {
		http.Error(w, "Failed to process request. Please contact the admin", http.StatusUnauthorized)
		return
	}
	slackTimestamp := r.Header.Get("X-Slack-Request-Timestamp")
	b, err := ioutil.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "Failed to process request", http.StatusBadRequest)
		return
	}
	slackSigningBaseString := "v0:" + slackTimestamp + ":" + string(b)
	slackSignature := r.Header.Get("X-Slack-Signature")
	if !matchSignature(slackSignature, signingSecret, slackSigningBaseString) {
		http.Error(w, "Function was not invoked by Slack", http.StatusForbidden)
		return
	}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , Slack, — , (Slack).

vals, err := parse(b)
	if err != nil {
		http.Error(w, "Failed to process request", http.StatusBadRequest)
		return
	}
	giphyTag := vals.Get("text")
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

GIF- , GIPHY REST API

giphyResp, err := http.Get("http://api.giphy.com/v1/gifs/random?tag=" + giphyTag + "&api_key=" + apiKey)
	if err != nil {
		http.Error(w, "Failed to process request", http.StatusFailedDependency)
		return
	}
	resp, err := ioutil.ReadAll(giphyResp.Body)
	if err != nil {
		http.Error(w, "Failed to process request", http.StatusInternalServerError)
		return
	}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, GIPHY API, , Slack . !

var gr GiphyResponse
json.Unmarshal(resp, &gr)
title := gr.Data.Title
url := gr.Data.Images.Downsized.URL
slackResponse := SlackResponse{Text: slackResponseStaticText, Attachments: []Attachment{{Text: title, ImageURL: url}}}
w.Header().Set("Content-Type", "application/json")
json.NewEncoder(w).Encode(slackResponse)
fmt.Println("Sent response to Slack")
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

matchSignature



, , slack.go



giphy.go



( function



), , Go (JSON), . , .

! . ! , , .

• Go, .

  
  
  
  
  

• Azure functions Core Tools — ( ).

  
  
  
  
  

• Slack, .

  
  
  
  
  

• API GIPHY — GIHPY ( !) . API.

  
  
  
  
  

- API GIPHY, .

, Azure Function Slack - (Slash command).

Azure Functions

(Resource Group) .

-

- (Function App) Azure (Add).

: (Custom Handler) (Runtime stack).

(Hosting ) Linux Consumption (Serverless) (Operating system) (Plan type) .

Application Insights ( ).

(Create), .

- :

• App Service plan ( Consumption/Serverless)

  
  
  
  
  

• Azure Storage

  
  
  
  
  

• Azure Application Insights

  
  
  
  
  

GitHub (build



)

git clone https://github.com/abhirockzz/serverless-go-slack-app
cd serverless-go-slack-app
GOOS=linux go build -o go_funcy cmd/main.go
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

GOOS=linux



Linux, Linux -.

Azure Functions core tools CLI

func azure functionapp publish <enter name of the function app>
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

URL- , — .

Slack

, Slack (-) :

• Slack 

  
  
  
  
  

• -

  
  
  
  
  

• 
  
  
  
  

Slack -

Slack Slack.

(Create New Command), - . , URL- (Request URL) - , HTTP , , URL-, . , (Save), .

, -, , (Basic Information) , (Install your app to your workspace) (Install App to Workspace) — Slack, , API Slack. , (App Credentials).

- (Signing Secret) ,

… , - SLACKSIGNINGSECRET GIPHYAPIKEY — .

fun(cy) time!

Slack /funcy <search term>



. , /funcy dog



. !

, : /funcy



Slack, , Giphy API , , GIF ( !).

timeout error



Slack . , cold start



, , . , Slack 3 — .

. , , , !

: , , , , , (-, App Service Plan . .).

Go Azure! , . .

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