Slack notify — templates/slack-notify

state_stores:
  local:
    namespace: hookway
    memory: {} # Per process; select Redis or PostgreSQL for shared protection.

# TEMPLATE: post an event summary to a Slack incoming webhook.
#
# This file has two jobs. It is a complete, runnable config so that
# `make validate-examples` proves the template still compiles against the
# current node schema. It is also the source of a builder palette template:
# the config UI extracts only the `fmt` and `post` nodes (see the TEMPLATES
# manifest in web/src/graph/templates.ts) and drops them onto the canvas.
# The trigger/gates/auth/envelope prefix exists to make the file valid and
# to show a complete flow; it is not part of the inserted template.
#
# Requires SLACK_WEBHOOK_URL (the incoming-webhook URL, which is itself the
# credential — never commit it), SLACK_SOURCE_SECRET (the HMAC secret of
# whatever system posts TO Hookway), and HOOKWAY_API_KEY to keep /metrics
# off an open port.
#
# The inbound prefix is GitHub-style HMAC (no signed timestamp), so
# replay_guard is what stops a captured body from being replayed. Do not
# swap that auth node for no_auth. The outbound URL is an env reference, not
# a value from the request, so a caller cannot redirect the POST.
#
# Slack incoming webhooks accept roughly one message per second and answer a
# malformed payload with 400 invalid_payload. A 4xx is therefore terminal: fix
# the script, do not retry. 429/5xx still retry. Inbound Authorization and
# Cookie are not forwarded to Slack.
server:
  addr: ":8080"
  read_timeout: "5s"
  write_timeout: "10s"
  idle_timeout: "60s"
  shutdown_timeout: "10s"
  publish_timeout: "10s"
  max_body_bytes: 1048576
  max_inflight_requests: 256
  fanout_concurrency: 8

metrics:
  enabled: true
  path: /metrics
  addr: ":9090"

security:
  api_key: "${HOOKWAY_API_KEY}"
  forwarded_header_allowlist:
    - Content-Type

flows:
  slack_notify:
    nodes:
      - {id: in, type: http_trigger, description: "Where the source system delivers its webhook.", path: /webhooks/slack-notify, methods: [POST]}
      - {id: hops, type: loop_guard, description: "Rejects a request that already looped through Hookway.", max_hops: 3}
      - {id: rl, type: rate_limit, store: local, description: "Caps inbound callers per source IP in this process.", rpm: 60, burst: 20, key_by: source_ip}
      - {id: body, type: read_body, description: "Buffers the raw body so the signature can be verified.", max_bytes: 1048576}
      - id: auth
        type: auth
        description: "Verifies the sending system's HMAC signature."
        scheme: hmac_sha256_hex
        secret_ref: {provider: env, name: SLACK_SOURCE_SECRET, refresh: 15m, overlap: 5m}
        signature_header: X-Hub-Signature-256
      - {id: replay, type: replay_guard, store: local, description: "Drops a body already accepted within the TTL. Hex HMAC has no signed timestamp.", ttl: 24h, max_entries: 100000}
      - {id: env, type: envelope, description: "Decodes the JSON event.", body_format: json}
      - id: fmt
        type: code
        description: "Builds the Slack message payload. Edit the text to suit your event."
        timeout: 50ms
        script: |
          const summary = input.body && input.body.summary ? String(input.body.summary) : 'event received';
          return { body: { text: 'Hookway: ' + summary }, vars: input.vars };
      - id: post
        type: http_request
        description: "Posts the message to the Slack incoming webhook. 4xx is terminal; 429/5xx retry."
        url: "${SLACK_WEBHOOK_URL}"
        body: transformed
        timeout: 5s
        error_on_status: [4xx, 5xx]
        retry: {max_attempts: 4, initial_backoff: 1s, max_backoff: 10s}
      - {id: ack, type: respond, description: "Acknowledges the source system once the Slack post succeeded. Not part of the inserted template.", status: 202, body: "notified"}
    edges: [in>hops, hops>rl, rl>body, body>auth, auth>replay, replay>env, env>fmt, fmt>post, post>ack]