|
| 1 | +""" |
| 2 | +In-memory event store for demonstrating resumability functionality. |
| 3 | +
|
| 4 | +This is a simple implementation intended for examples and testing, |
| 5 | +not for production use where a persistent storage solution would be more appropriate. |
| 6 | +""" |
| 7 | + |
| 8 | +import logging |
| 9 | +from collections import deque |
| 10 | +from dataclasses import dataclass |
| 11 | +from uuid import uuid4 |
| 12 | + |
| 13 | +from mcp.server.streamable_http import EventCallback, EventId, EventMessage, EventStore, StreamId |
| 14 | +from mcp.types import JSONRPCMessage |
| 15 | + |
| 16 | +logger = logging.getLogger(__name__) |
| 17 | + |
| 18 | + |
| 19 | +@dataclass |
| 20 | +class EventEntry: |
| 21 | + """Represents an event entry in the event store.""" |
| 22 | + |
| 23 | + event_id: EventId |
| 24 | + stream_id: StreamId |
| 25 | + message: JSONRPCMessage | None # None for priming events |
| 26 | + |
| 27 | + |
| 28 | +class InMemoryEventStore(EventStore): |
| 29 | + """ |
| 30 | + Simple in-memory implementation of the EventStore interface for resumability. |
| 31 | + This is primarily intended for examples and testing, not for production use |
| 32 | + where a persistent storage solution would be more appropriate. |
| 33 | +
|
| 34 | + This implementation keeps only the last N events per stream for memory efficiency. |
| 35 | + """ |
| 36 | + |
| 37 | + def __init__(self, max_events_per_stream: int = 100): |
| 38 | + """Initialize the event store. |
| 39 | +
|
| 40 | + Args: |
| 41 | + max_events_per_stream: Maximum number of events to keep per stream |
| 42 | + """ |
| 43 | + self.max_events_per_stream = max_events_per_stream |
| 44 | + # for maintaining last N events per stream |
| 45 | + self.streams: dict[StreamId, deque[EventEntry]] = {} |
| 46 | + # event_id -> EventEntry for quick lookup |
| 47 | + self.event_index: dict[EventId, EventEntry] = {} |
| 48 | + |
| 49 | + async def store_event(self, stream_id: StreamId, message: JSONRPCMessage | None) -> EventId: |
| 50 | + """Stores an event with a generated event ID. |
| 51 | +
|
| 52 | + Args: |
| 53 | + stream_id: ID of the stream the event belongs to |
| 54 | + message: The message to store, or None for priming events |
| 55 | + """ |
| 56 | + event_id = str(uuid4()) |
| 57 | + event_entry = EventEntry(event_id=event_id, stream_id=stream_id, message=message) |
| 58 | + |
| 59 | + # Get or create deque for this stream |
| 60 | + if stream_id not in self.streams: |
| 61 | + self.streams[stream_id] = deque(maxlen=self.max_events_per_stream) |
| 62 | + |
| 63 | + # If deque is full, the oldest event will be automatically removed |
| 64 | + # We need to remove it from the event_index as well |
| 65 | + if len(self.streams[stream_id]) == self.max_events_per_stream: |
| 66 | + oldest_event = self.streams[stream_id][0] |
| 67 | + self.event_index.pop(oldest_event.event_id, None) |
| 68 | + |
| 69 | + # Add new event |
| 70 | + self.streams[stream_id].append(event_entry) |
| 71 | + self.event_index[event_id] = event_entry |
| 72 | + |
| 73 | + return event_id |
| 74 | + |
| 75 | + async def replay_events_after( |
| 76 | + self, |
| 77 | + last_event_id: EventId, |
| 78 | + send_callback: EventCallback, |
| 79 | + ) -> StreamId | None: |
| 80 | + """Replays events that occurred after the specified event ID.""" |
| 81 | + if last_event_id not in self.event_index: |
| 82 | + logger.warning(f"Event ID {last_event_id} not found in store") |
| 83 | + return None |
| 84 | + |
| 85 | + # Get the stream and find events after the last one |
| 86 | + last_event = self.event_index[last_event_id] |
| 87 | + stream_id = last_event.stream_id |
| 88 | + stream_events = self.streams.get(last_event.stream_id, deque()) |
| 89 | + |
| 90 | + # Events in deque are already in chronological order |
| 91 | + found_last = False |
| 92 | + for event in stream_events: |
| 93 | + if found_last: |
| 94 | + # Skip priming events (None messages) during replay |
| 95 | + if event.message is not None: |
| 96 | + await send_callback(EventMessage(event.message, event.event_id)) |
| 97 | + elif event.event_id == last_event_id: |
| 98 | + found_last = True |
| 99 | + |
| 100 | + return stream_id |
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