B2 MCP Webinar — Event Notification Demo

A B2 event notification fires on upload → an edge function posts to Discord (with an image thumbnail) and triggers a GitHub Actions workflow that opens an Issue. Deployable to Cloudflare Workers or Vercel Edge Functions — same logic.

B2 upload → webhook → edge function ──┬──► Discord (+ thumbnail)
      (relay/relay.js or api/relay.js) └──► repository_dispatch → b2-event.yml → GitHub Issue

Why an edge function at all: GitHub's only external trigger, repository_dispatch, needs a Bearer token header and a fixed {event_type, client_payload} body. B2 sends its own fixed shape and can't do either — something has to translate. The same function posts to Discord directly (no translation needed there).

Secrets

Secret	Value
GITHUB_REPO	backblaze-labs/b2-mcp-webinar (literal string)
GITHUB_TOKEN	Classic PAT, repo scope: github.com/settings/tokens/new. Not fine-grained — org-owned repos can require separate admin approval for those, causing 403 Resource not accessible by personal access token even with correct permissions.
DISCORD_WEBHOOK_URL	Discord channel → Edit Channel → Integrations → Webhooks → New Webhook → Copy URL

Optional, enables the image thumbnail (omit to skip it, everything else still works):

Secret	Value
B2_APPLICATION_KEY_ID / B2_APPLICATION_KEY	A read-only key scoped to the demo bucket (listFiles+readFiles only) — mint via b2_create_key or the B2 console
B2_S3_ENDPOINT	e.g. s3.us-east-005.backblazeb2.com
B2_REGION	e.g. us-east-005

The relay uses the B2 key only to sign a presigned GetObject URL locally (AWS SigV4, no SDK) — Discord fetches the image directly from B2; bytes never pass through the relay.

Setup — Cloudflare Workers (fastest)

npx wrangler login
npx wrangler deploy

Prints your webhook URL (https://<name>.<subdomain>.workers.dev). First-time accounts: if it warns about registering a workers.dev subdomain, do that at the printed link first.

npx wrangler secret put DISCORD_WEBHOOK_URL
npx wrangler secret put GITHUB_TOKEN
npx wrangler secret put GITHUB_REPO
# optional, for the thumbnail:
npx wrangler secret put B2_APPLICATION_KEY_ID
npx wrangler secret put B2_APPLICATION_KEY
npx wrangler secret put B2_S3_ENDPOINT
npx wrangler secret put B2_REGION

Each prompts for the value on stdin (no trailing-argument form). Uses relay/relay.js + wrangler.toml.

Setup — Vercel (alternative)

npx vercel login
npx vercel deploy --prod

Function is reachable at <url>/api/relay. Set the same env vars with npx vercel env add NAME production. Uses api/relay.js.

Finish

1. Point the bucket's event notification (b2_set_bucket_notification_rules, or B2 console) at your deployed URL, event type b2:ObjectCreated:*.
2. Upload a file. Discord message + GitHub Issue both fire within seconds.

Testing without a real upload

# Fire the GitHub side directly, no deploy needed:
gh api repos/backblaze-labs/b2-mcp-webinar/dispatches \
  -f event_type='b2_object_created' \
  -f 'client_payload[objectName]=demo/hello.txt' \
  -f 'client_payload[bucketName]=webinar-demo-media-0928'

# Fire the deployed edge function with B2's real payload shape:
curl -X POST "https://<worker-or-vercel-url>/" \
  -H "Content-Type: application/json" \
  -d '{"events":[{"eventType":"b2:ObjectCreated:Upload","bucketName":"webinar-demo-media-0928","objectName":"test.txt"}]}'

bucketName/objectName/eventType are flat fields on each event object — verified against a live B2 webhook, not a doc guess. A 200 means both downstream actions succeeded; 207 names which one failed and why in the response body.

Troubleshooting

• wrangler secret put NAME value fails with Unknown argument. It reads from stdin, not a trailing arg — omit the value and paste when prompted (or echo value | wrangler secret put NAME).
• Fresh Worker URL won't resolve / TLS errors. workers.dev subdomain not registered yet (wrangler deploy prints the one-time dashboard link) — or, if you just renamed the subdomain, genuine DNS propagation lag (a few minutes; dig @1.1.1.1 <host> shows the real state if your local resolver is stale).
• 403 Resource not accessible by personal access token on the GitHub call → you're using a fine-grained PAT against an org repo; switch to classic (see Secrets above).
• Isolate "workflow broken" vs "relay's token broken": run the manual gh api dispatches test with your own auth. If that opens an Issue but the relay's own calls still fail, only the relay's GITHUB_TOKEN is bad.
• Discord/GitHub Issue says unknown-object. Your test payload doesn't match B2's real flat shape — see the curl example above, not a nested eventData wrapper.

Observability

wrangler.toml enables Cloudflare Workers invocation logging, so console.log output (including the raw incoming payload) is visible under Workers & Pages → Logs in the dashboard without needing a live wrangler tail session.

Files

Path	Purpose
relay/relay.js	Cloudflare Worker — Discord + thumbnail + GitHub trigger.
api/relay.js	Vercel Edge Function port of the same logic.
wrangler.toml	Cloudflare deploy config.
.github/workflows/b2-event.yml	Opens the GitHub Issue on trigger.
package.json	Deploy/secrets/test npm scripts; no runtime deps.
LICENSE	MIT.

Out of scope

Retries, dead-lettering, webhook signature verification (B2 supports an HMAC secret on the rule), and secret rotation — not needed for a 15-minute demo.