알erts 와 워크플로우를 위한 Slack 통합 패턴

[service] -> [alert formatter] -> [slack incoming webhook] -> [channel]

[services] -> [queue topic] -> [slack dispatcher] -> [slack api]
                     |                 |
                     |                 +-> [rate limit handler]
                     +-> [dead letter queue]

[alert] -> [slack message with button] -> [button click]
   -> [action payload] -> [approval handler] -> [internal API] -> [update message]

{
  "text": "checkout error rate elevated",
  "blocks": [
    {
      "type": "header",
      "text": { "type": "plain_text", "text": "checkout error rate elevated" }
    },
    {
      "type": "section",
      "fields": [
        { "type": "mrkdwn", "text": "*severity*\\nwarn" },
        { "type": "mrkdwn", "text": "*context*\\nservice=checkout env=prod region=us-east" }
      ]
    },
    {
      "type": "section",
      "text": { "type": "mrkdwn", "text": "*action_hint*\\nClick Approve to trigger a safe restart." }
    }
  ]
}

package main

import (
  "bytes"
  "crypto/hmac"
  "crypto/sha256"
  "encoding/hex"
  "encoding/json"
  "io"
  "log"
  "net/http"
  "net/url"
  "os"
  "strconv"
  "strings"
  "sync"
  "time"

  "github.com/slack-go/slack"
)

type BlockActionPayload struct {
  Type  string `json:"type"`
  Team  struct{ ID string `json:"id"` } `json:"team"`
  User  struct{ ID string `json:"id"` } `json:"user"`
  Channel struct {
    ID string `json:"id"`
  } `json:"channel"`
  Message struct {
    Ts string `json:"ts"`
  } `json:"message"`
  ResponseURL string `json:"response_url"`
  Actions []struct {
    ActionID string `json:"action_id"`
    Value    string `json:"value"`
    Type     string `json:"type"`
  } `json:"actions"`
}

type InternalAction struct {
  Action     string `json:"action"`
  TeamID     string `json:"team_id"`
  ChannelID  string `json:"channel_id"`
  MessageTS  string `json:"message_ts"`
  UserID     string `json:"user_id"`
  Value      string `json:"value"`
}

var (
  // In production, store this in Redis with TTL
  seenMu sync.Mutex
  seen   = map[string]time.Time{}
  ttl    = 10 * time.Minute
)

func main() {
  botToken := os.Getenv("SLACK_BOT_TOKEN")
  signingSecret := os.Getenv("SLACK_SIGNING_SECRET")
  channelID := os.Getenv("SLACK_CHANNEL_ID")
  internalURL := os.Getenv("INTERNAL_API_URL")
  listenAddr := os.Getenv("LISTEN_ADDR") // e.g. :8080

  if botToken == "" || signingSecret == "" || channelID == "" || internalURL == "" || listenAddr == "" {
    log.Fatal("missing env vars SLACK_BOT_TOKEN SLACK_SIGNING_SECRET SLACK_CHANNEL_ID INTERNAL_API_URL LISTEN_ADDR")
  }

  api := slack.New(botToken)

  // Send an alert message with an approval button.
  // Buttons are interactive Block Kit elements with action_id and value.
  // See Slack Block Kit button element docs.
  blocks := slack.Blocks{
    BlockSet: []slack.Block{
      slack.NewHeaderBlock(slack.NewTextBlockObject("plain_text", "checkout error rate elevated", false, false)),
      slack.NewSectionBlock(
        slack.NewTextBlockObject("mrkdwn", "*severity*\\nwarn\\n*context*\\nservice=checkout env=prod", false, false),
        nil,
        nil,
      ),
      slack.NewActionBlock(
        "actions_1",
        slack.NewButtonBlockElement("approve_restart", "restart", slack.NewTextBlockObject("plain_text", "Approve restart", false, false)),
      ),
    },
  }

  _, ts, err := api.PostMessage(channelID, slack.MsgOptionBlocks(blocks.BlockSet...))
  if err != nil {
    log.Fatalf("PostMessage failed: %v", err)
  }
  log.Printf("posted alert message_ts=%s", ts)

  // Interactivity endpoint
  http.HandleFunc("/slack/actions", func(w http.ResponseWriter, r *http.Request) {
    rawBody, err := io.ReadAll(r.Body)
    if err != nil {
      http.Error(w, "read body failed", http.StatusBadRequest)
      return
    }
    r.Body.Close()

    // Verify Slack request signature on the raw body and timestamp.
    // See Slack verifying requests docs.
    if !verifySlackRequest(r.Header, rawBody, signingSecret) {
      http.Error(w, "invalid signature", http.StatusUnauthorized)
      return
    }

    // Slack sends application/x-www-form-urlencoded with payload=JSON
    vals, err := url.ParseQuery(string(rawBody))
    if err != nil {
      http.Error(w, "bad form body", http.StatusBadRequest)
      return
    }
    payloadStr := vals.Get("payload")
    if payloadStr == "" {
      http.Error(w, "missing payload", http.StatusBadRequest)
      return
    }

    var p BlockActionPayload
    if err := json.Unmarshal([]byte(payloadStr), &p); err != nil {
      http.Error(w, "bad payload json", http.StatusBadRequest)
      return
    }

    // Ack within 3 seconds. Do real work async and use response_url for updates.
    // See Slack interactivity docs on acknowledgment timing.
    w.WriteHeader(http.StatusOK)
    _, _ = w.Write([]byte(""))

    go func() {
      if p.Type != "block_actions" || len(p.Actions) == 0 {
        return
      }
      a := p.Actions[0]
      if a.ActionID != "approve_restart" {
        return
      }

      // Dedupe approvals
      key := strings.Join([]string{p.Team.ID, p.Channel.ID, p.Message.Ts, p.User.ID, a.ActionID, a.Value}, "|")
      if !tryOnce(key) {
        return
      }

      req := InternalAction{
        Action:    "approve_restart",
        TeamID:    p.Team.ID,
        ChannelID: p.Channel.ID,
        MessageTS: p.Message.Ts,
        UserID:    p.User.ID,
        Value:     a.Value,
      }

      if err := postJSON(internalURL, req); err != nil {
        log.Printf("internal action failed: %v", err)
        _ = replyViaResponseURL(p.ResponseURL, "action failed, check logs")
        return
      }

      _ = replyViaResponseURL(p.ResponseURL, "approval received, internal action triggered")
    }()
  })

  log.Printf("listening on %s", listenAddr)
  log.Fatal(http.ListenAndServe(listenAddr, nil))
}

func tryOnce(key string) bool {
  now := time.Now()

  seenMu.Lock()
  defer seenMu.Unlock()

  for k, t := range seen {
    if now.Sub(t) > ttl {
      delete(seen, k)
    }
  }
  if _, ok := seen[key]; ok {
    return false
  }
  seen[key] = now
  return true
}

func verifySlackRequest(h http.Header, body []byte, signingSecret string) bool {
  ts := h.Get("X-Slack-Request-Timestamp")
  sig := h.Get("X-Slack-Signature")
  if ts == "" || sig == "" {
    return false
  }

  tsInt, err := strconv.ParseInt(ts, 10, 64)
  if err != nil {
    return false
  }

  // Reject requests older than 5 minutes to reduce replay risk.
  if time.Since(time.Unix(tsInt, 0)) > 5*time.Minute {
    return false
  }

  base := "v0:" + ts + ":" + string(body)
  mac := hmac.New(sha256.New, []byte(signingSecret))
  mac.Write([]byte(base))
  sum := hex.EncodeToString(mac.Sum(nil))
  expected := "v0=" + sum

  return hmac.Equal([]byte(expected), []byte(sig))
}

func postJSON(url string, body any) error {
  b, err := json.Marshal(body)
  if err != nil {
    return err
  }
  req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(b))
  if err != nil {
    return err
  }
  req.Header.Set("Content-Type", "application/json")
  c := &http.Client{Timeout: 5 * time.Second}
  res, err := c.Do(req)
  if err != nil {
    return err
  }
  defer res.Body.Close()
  if res.StatusCode < 200 || res.StatusCode >= 300 {
    return io.ErrUnexpectedEOF
  }
  return nil
}

func replyViaResponseURL(responseURL string, text string) error {
  if responseURL == "" {
    return nil
  }
  // response_url accepts JSON payloads and can post ephemeral by default.
  b, _ := json.Marshal(map[string]string{
    "text": text,
  })
  req, _ := http.NewRequest(http.MethodPost, responseURL, bytes.NewReader(b))
  req.Header.Set("Content-Type", "application/json")
  c := &http.Client{Timeout: 5 * time.Second}
  res, err := c.Do(req)
  if err != nil {
    return err
  }
  defer res.Body.Close()
  return nil
}

import os
import json
import time
import threading
import requests
from flask import Flask, request, make_response
from slack_sdk import WebClient
from slack_sdk.signature import SignatureVerifier

SLACK_BOT_TOKEN = os.environ["SLACK_BOT_TOKEN"]
SLACK_SIGNING_SECRET = os.environ["SLACK_SIGNING_SECRET"]
SLACK_CHANNEL_ID = os.environ["SLACK_CHANNEL_ID"]
INTERNAL_API_URL = os.environ["INTERNAL_API_URL"]

client = WebClient(token=SLACK_BOT_TOKEN)
verifier = SignatureVerifier(signing_secret=SLACK_SIGNING_SECRET)

app = Flask(__name__)

# In production, store these in Redis
_seen = {}
_TTL_SECONDS = 600

def try_once(key: str) -> bool:
    now = int(time.time())
    expired = [k for k, t in _seen.items() if now - t > _TTL_SECONDS]
    for k in expired:
        _seen.pop(k, None)
    if key in _seen:
        return False
    _seen[key] = now
    return True

def post_internal_action(payload: dict) -> None:
    requests.post(INTERNAL_API_URL, json=payload, timeout=5)

def reply_via_response_url(response_url: str, text: str) -> None:
    if not response_url:
        return
    requests.post(response_url, json={"text": text}, timeout=5)

def send_alert_with_button() -> None:
    blocks = [
        {"type": "header", "text": {"type": "plain_text", "text": "checkout error rate elevated"}},
        {"type": "section", "text": {"type": "mrkdwn", "text": "*severity*\\nwarn\\n*context*\\nservice=checkout env=prod"}},
        {
            "type": "actions",
            "block_id": "actions_1",
            "elements": [
                {
                    "type": "button",
                    "text": {"type": "plain_text", "text": "Approve restart"},
                    "action_id": "approve_restart",
                    "value": "restart"
                }
            ]
        }
    ]
    # chat.postMessage requires chat:write scope.
    client.chat_postMessage(channel=SLACK_CHANNEL_ID, text="checkout error rate elevated", blocks=blocks)

@app.post("/slack/actions")
def slack_actions():
    raw_body = request.get_data()  # Slack recommends verifying raw body before parsing
    if not verifier.is_valid_request(raw_body, request.headers):
        return make_response("invalid signature", 401)

    # Slack sends application/x-www-form-urlencoded with a payload field containing JSON.
    payload_str = request.form.get("payload", "")
    if not payload_str:
        return make_response("missing payload", 400)
    payload = json.loads(payload_str)

    # Ack within 3 seconds. Slack user sees errors if you do not.
    # See Slack interactivity docs on acknowledgment.
    resp = make_response("", 200)

    def work():
        if payload.get("type") != "block_actions":
            return
        actions = payload.get("actions", [])
        if not actions:
            return

        a = actions[0]
        if a.get("action_id") != "approve_restart":
            return

        team_id = payload.get("team", {}).get("id", "")
        channel_id = payload.get("channel", {}).get("id", "")
        user_id = payload.get("user", {}).get("id", "")
        message_ts = payload.get("message", {}).get("ts", "")
        value = a.get("value", "")

        key = "|".join([team_id, channel_id, message_ts, user_id, "approve_restart", value])
        if not try_once(key):
            return

        internal_payload = {
            "action": "approve_restart",
            "team_id": team_id,
            "channel_id": channel_id,
            "message_ts": message_ts,
            "user_id": user_id,
            "value": value,
        }

        try:
            post_internal_action(internal_payload)
            reply_via_response_url(payload.get("response_url", ""), "approval received, internal action triggered")
        except Exception:
            reply_via_response_url(payload.get("response_url", ""), "action failed, check logs")

    threading.Thread(target=work, daemon=True).start()
    return resp

if __name__ == "__main__":
    send_alert_with_button()
    app.run(host="0.0.0.0", port=int(os.getenv("PORT", "8080")))