Gmail Trigger

Gmail Trigger (Push + History)

Overview

• Gmail Trigger is a Dify provider that receives Gmail push notifications via Cloud Pub/Sub and emits concrete events based on Gmail History:
  • gmail_message_added (new messages)
  • gmail_message_deleted (deleted messages)
  • gmail_label_added (labels added to messages)
  • gmail_label_removed (labels removed from messages)
• Dispatch verifies/auths the push, pulls the history delta once, and splits changes for events to consume.
• Note: API Key is NOT supported for Gmail API access. Use OAuth (gmail.readonly) only.

Prerequisites

• A Google account authorized for Gmail API (used during OAuth)
• A Google Cloud project with Pub/Sub API enabled (configured at tenant-level by administrator)

Step-by-step Setup

1. Install the plugin in Dify

• Options:
  • If packaged as .difypkg, import it in Dify’s Plugin Center (Plugins → Import).
  • For local development runs, provision the environment from pyproject.toml / uv.lock first (for example, uv sync --project .) so the runtime uses the locked dependencies.

2. Configure GCP resources (Administrator, one-time setup)

• Create or select the Google Cloud project that will host your Pub/Sub resources. Make sure the following APIs are enabled (APIs & Services → Library):

  • Gmail API: https://console.cloud.google.com/apis/library/gmail.googleapis.com
  • Cloud Pub/Sub API: https://console.cloud.google.com/apis/library/pubsub.googleapis.com

• Create a dedicated service account and grant Pub/Sub permissions:

  1. Go to IAM & Admin → Service Accounts → Create Service Account.
     Console URL: https://console.cloud.google.com/iam-admin/serviceaccounts

     Screenshot:

  2. Assign the roles/pubsub.admin role to this service account or select "Pub/Sub Admin" role which already includes the necessary permissions (required so the plugin can create topics, subscriptions, and update IAM policies automatically).

     • Alternatively, a custom role must include: pubsub.topics.create, pubsub.topics.getIamPolicy, pubsub.topics.setIamPolicy, pubsub.subscriptions.create, pubsub.subscriptions.get, pubsub.subscriptions.delete, pubsub.subscriptions.list.

       Screenshot:

  3. Create a JSON key for this service account and download it securely. Screenshot:

• Note your Google Cloud Project ID (displayed on the project dashboard or IAM page).

3. Configure OAuth client for the plugin (Administrator, one-time setup)

• In Google Cloud Console → APIs & Services → Credentials → Create Credentials → OAuth client ID.
  Console URL: https://console.cloud.google.com/apis/credentials

  Screenshot:

  • Application type: Web application
  • Authorized redirect URIs: copy the redirect URI shown in Dify when you set up the plugin (e.g., https://<your-dify-host>/console/api/plugin/oauth/callback)

• Capture the generated Client ID and Client Secret for later use.

4. Enter OAuth client parameters in Dify

• In the plugin configuration form:
  • client_id: The OAuth client ID created above.
  • client_secret: The corresponding client secret.
  • gcp_project_id: The Google Cloud project ID with Pub/Sub enabled.
  • gcp_service_account_json: Paste the full JSON key created for the service account (keep it private).
• Dify will automatically derive a per-user Pub/Sub topic when the end user authorizes the plugin.

5. User: Authorize and create subscription

• Click "Authorize" to complete OAuth (gmail.readonly scope)
• Create a Gmail subscription with optional parameters:
  • label_ids (optional): Scope to specific labels (INBOX, UNREAD, etc.)
    • Docs: https://developers.google.com/gmail/api/reference/rest/v1/users.labels/list
  • Properties (optional, for enhanced security):
    • require_oidc: Enforce OIDC bearer verification
    • oidc_audience: Webhook endpoint URL (auto-filled)
    • oidc_service_account_email: Service account used for Push subscription

What happens automatically:

• Plugin creates/reuses a Pub/Sub Topic in your GCP project
• Plugin grants Gmail API publisher permission to the topic
• Plugin creates a dedicated Push subscription for this user
• Plugin calls Gmail users.watch API to start monitoring
• On unsubscribe, plugin cleans up the Push subscription (topic is preserved for reuse)

Where To Get OIDC Values

• oidc_audience
  • Use the exact webhook endpoint URL shown in the Dify subscription details (Endpoint). Example:
    • https://<your-dify-host>/triggers/plugin/<subscription-id>
  • The YAML field includes a URL to Google docs for the audience claim: see the OIDC token reference.
• oidc_service_account_email
  • The service account used by the Pub/Sub push subscription (set via --push-auth-service-account).
  • Find it under Google Cloud Console → IAM & Admin → Service Accounts, or via:
    • gcloud iam service-accounts list --format='value(email)'
  • The YAML field links to the Service Accounts console page.

How It Works

• Dispatch (trigger)
  • Optionally verifies OIDC bearer from Pub/Sub push (iss/aud/email)
  • Decodes message.data to get historyId/emailAddress
  • Calls users.history.list(startHistoryId=...) once to gather deltas
  • Splits changes per family and stores pending batches in Dify storage
  • Returns the list of concrete event names for Dify to execute
• Events
  • Read the pending batch for their family
  • gmail_message_added fetches full message metadata (headers, attachments meta)
  • Output matches the event YAML output_schema

Event Outputs (high-level)

• gmail_message_added
  • history_id: string
  • messages[]: id, threadId, internalDate, snippet, sizeEstimate, labelIds, headers{From,To,Subject,Date,Message-Id}, has_attachments, attachments[]
• gmail_message_deleted
  • history_id: string
  • messages[]: id, threadId
• gmail_label_added / gmail_label_removed
  • history_id: string
  • changes[]: id, threadId, labelIds

Attachment Handling

• The trigger attempts to upload at most 20 real attachments (with attachmentId or inline content), skipping individual files larger than 5 MiB.
• attachments[].file_url is the only externally exposed download address; attachments[].file_source identifies its origin (gmail for original links or dify_storage for Dify mirror).
• When attachments are successfully uploaded to Dify, both upload_file_id and original_url (Gmail/Drive original address) are returned; if not mirrored, original_url is omitted.
• Gmail often returns Drive links for oversized attachments, or provides sharing addresses directly in the message body. The event scans text/HTML content to extract these links and returns them as attachment items for unified handling by callers.
• Callers only need to use file_url, determining whether to access Gmail/Drive directly or go through Dify storage based on file_source.

Lifecycle & Refresh

• Create: Plugin auto-provisions Pub/Sub, then calls users.watch with topicName and optional labelIds
• Refresh: users.watch is called again before expiry (Gmail watch is time-limited, ~7 days)
• Delete: Calls users.stop and cleans up the Push subscription

Testing

• Send an email to the watched mailbox (INBOX). You should see gmail_message_added
• Mark read/unread (UNREAD label removed/added) triggers label events
• Delete an email triggers gmail_message_deleted
• Tip: You can view recent deliveries in Pub/Sub subscription details; Dify logs/console will show trigger and event traces.

Troubleshooting

• Plugin fails to create subscription: Check GCP credentials are correctly configured in OAuth client parameters
• Nothing triggers: Verify Gmail API and Pub/Sub API are enabled in your GCP project
• 401/403 at dispatch: OIDC settings mismatch; verify service account and audience
• historyId out of date: Plugin resets checkpoint to the latest notification and skips the batch
• OAuth issues: Re-authorize; ensure gmail.readonly scope is granted

References

• Gmail Push: https://developers.google.com/workspace/gmail/api/guides/push
• History: https://developers.google.com/gmail/api/reference/rest/v1/users.history/list
• Messages: https://developers.google.com/gmail/api/reference/rest/v1/users.messages/get