> ## Documentation Index > Fetch the complete documentation index at: https://gofastmcp.com/llms.txt > Use this file to discover all available pages before exploring further. # notifications # `fastmcp.server.tasks.notifications` Distributed notification queue for background task events (SEP-1686). Enables distributed Docket workers to send MCP notifications to clients without holding session references. Workers push to a Redis queue, the MCP server process subscribes and forwards to the client's session. Pattern: Fire-and-forward with retry * One queue per session\_id * LPUSH/BRPOP for reliable ordered delivery * Retry up to 3 times on delivery failure, then discard * TTL-based expiration for stale messages Note: Docket's execution.subscribe() handles task state/progress events via Redis Pub/Sub. This module handles elicitation-specific notifications that require reliable delivery (input\_required prompts, cancel signals). ## Functions ### `push_notification` ```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} push_notification(session_id: str, notification: dict[str, Any], docket: Docket) -> None ``` Push notification to session's queue (called from Docket worker). Used for elicitation-specific notifications (input\_required, cancel) that need reliable delivery across distributed processes. **Args:** * `session_id`: Target session's identifier * `notification`: MCP notification dict (method, params, \_meta) * `docket`: Docket instance for Redis access ### `notification_subscriber_loop` ```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} notification_subscriber_loop(session_id: str, session: ServerSession, docket: Docket, fastmcp: FastMCP) -> None ``` Subscribe to notification queue and forward to session. Runs in the MCP server process. Bridges distributed workers to clients. This loop: 1. Maintains a heartbeat (active subscriber marker for debugging) 2. Blocks on BRPOP waiting for notifications 3. Forwards notifications to the client's session 4. Retries failed deliveries, then discards (no dead-letter queue) **Args:** * `session_id`: Session identifier to subscribe to * `session`: MCP ServerSession for sending notifications * `docket`: Docket instance for Redis access * `fastmcp`: FastMCP server instance (for elicitation relay) ### `ensure_subscriber_running` ```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} ensure_subscriber_running(session_id: str, session: ServerSession, docket: Docket, fastmcp: FastMCP) -> None ``` Start notification subscriber if not already running (idempotent). Subscriber is created on first task submission and cleaned up on disconnect. Safe to call multiple times for the same session. **Args:** * `session_id`: Session identifier * `session`: MCP ServerSession * `docket`: Docket instance * `fastmcp`: FastMCP server instance (for elicitation relay) ### `stop_subscriber` ```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} stop_subscriber(session_id: str) -> None ``` Stop notification subscriber for a session. Called when session disconnects. Pending messages remain in queue for delivery if client reconnects (with TTL expiration). **Args:** * `session_id`: Session identifier ### `get_subscriber_count` ```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} get_subscriber_count() -> int ``` Get number of active subscribers (for monitoring).