feat(core): Implement inter-main communication for test webhooks in multi-main setup

[ivov]

Summary

In single-main setup, the main process keeps the frontend informed of the real-time state of the execution via hooks that push events using websockets or server-sent events. At the end of a test webhook execution, the main process also cleans up test webhooks, i.e. clears the 2-minute timeout, deregisters all test webhooks from the cache hash, and deletes them from the third-party service.

In multi-main setup, it may happen that the user's browser is connected to the main process that created the webhook, but the webhook call then arrives at a different main process. In this case events are not being informed to the frontend that the creator process is connected to, and cleanup is not happening in the creator process either.

To address this, we implement inter-main communication. The webhook-handling process does not push to its frontend - rather, the webhook-handling process sends a series of events into the command channel that all main instances are listening to. On receiving an event via this channel, the main process, if it has the relevant session ID, reacts by pushing the event to the FE.

Additionally, we set up a new event for a successful test webhook execution, and following the same procedure we instruct the original process to clear the webhooks after execution. And as a safeguard if the creator process crashes, we set a TTL on the test webhook registration hash in the cache - this TTL is extended on each new registration.

Diagram

How to test

1. Run Postgres and Redis containers and set up config file:

docker network create n8n

docker run --name n8n-postgres --network n8n -p 5433:5432 -d postgres

docker exec n8n-postgres psql -U postgres -c "CREATE DATABASE n8n;"

docker run --name n8n-redis --network n8n -p 6379:6379 -d redis

2. Start ngrok:

ngrok http --domain=<subdomain>.ngrok-free.app 5678

3. Start first main:

EXECUTIONS_MODE=queue N8N_CONFIG_FILES=<path> N8N_MULTI_MAIN_SETUP_ENABLED=true N8N_LICENSE_TENANT_ID=<id> N8N_LICENSE_ACTIVATION_KEY=<key> N8N_LOG_LEVEL=debug WEBHOOK_URL=https://<subdomain>.ngrok-free.app pnpm start

4. Start second main:

EXECUTIONS_MODE=queue N8N_MULTI_MAIN_SETUP_ENABLED=true N8N_LICENSE_TENANT_ID=<id> N8N_LICENSE_ACTIVATION_KEY=<key> N8N_LOG_LEVEL=debug N8N_PORT=5679 WEBHOOK_URL=https://<subdomain>.hooks.n8n.cloud/ pnpm start

5. Start worker:

EXECUTIONS_MODE=queue N8N_CONFIG_FILES=<path> N8N_LICENSE_TENANT_ID=<id> N8N_LICENSE_ACTIVATION_KEY=<key> N8N_ENCRYPTION_KEY=<key> N8N_LOG_LEVEL=debug pnpm worker

Expectations:

• Log into the second main at http://localhost:5679, set up a test webhook, run it, and call it at http://localhost:5679/webhook-test/<path>. The webhook call should land via ngrok on the first main, which should handle it successfully, relaying execution lifecycle events to the second main, and clearing test webhooks on success.
• Log into the first main at http://localhost:5678, set up a test webhook, run it, and call it at http://localhost:5678/webhook-test/<path>. The webhook call should land on the first main, which should handle it successfully and clear test webhooks, without going through inter-main communication.
• Test webhook cancellation and expiration should continue to work as before, without going through inter-main communication.

Story

https://linear.app/n8n/issue/PAY-1189

[ivov]

Generally this file needs refactoring and cleanup, hopefully soon. Only added to it to avoid increasing the scope.

[krynble]

LGTM

[cypress]

2 flaky tests on run #3734 ↗︎

0

330

5

0

2

Details:

🌳 🖥️ browsers:node18.12.0-chrome107 🤖 ivov 🗃️ e2e/*
Project: n8n	Commit: 302103eeb2
Status: Passed	Duration: 04:01 💡
Started: Jan 12, 2024 10:43 AM	Ended: Jan 12, 2024 10:47 AM

  24-ndv-paired-item.cy.ts • 1 flaky test

View Output Video

Test		Artifacts
NDV > resolves expression with default item when input node is not parent, while still pairing items		Screenshots Video

  29-templates.cy.ts • 1 flaky test

View Output Video

Test		Artifacts
Templates > should save template id with the workflow		Screenshots Video

Review all test suite changes for PR #8267 ↗︎

[github-actions]

✅ All Cypress E2E specs passed

[janober]

Got released with n8n@1.25.0