inMemoryEventStore.ts•2.39 kB
import { EventStore } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { JSONRPCMessage } from "@modelcontextprotocol/sdk/types.js";
/**
* A simple in-memory implementation of the EventStore interface for recovery
* Primarily for examples and testing; not suitable for production (use a persistent storage solution)
*/
export class InMemoryEventStore implements EventStore {
private events: Map<string, { streamId: string; message: JSONRPCMessage }> =
new Map();
/**
* Generate a unique event ID for a given stream ID
*/
private generateEventId(streamId: string): string {
return `${streamId}_${Date.now()}_${Math.random()
.toString(36)
.substring(2, 10)}`;
}
/**
* Extract stream ID from event ID
*/
private getStreamIdFromEventId(eventId: string): string {
const parts = eventId.split("_");
return parts.length > 0 ? parts[0] : "";
}
/**
* Store an event with a generated event ID
* Implements EventStore.storeEvent
*/
async storeEvent(streamId: string, message: JSONRPCMessage): Promise<string> {
const eventId = this.generateEventId(streamId);
this.events.set(eventId, { streamId, message });
return eventId;
}
/**
* Replay events occurring after a specific event ID
* Implements EventStore.replayEventsAfter
*/
async replayEventsAfter(
lastEventId: string,
{
send,
}: { send: (eventId: string, message: JSONRPCMessage) => Promise<void> }
): Promise<string> {
if (!lastEventId || !this.events.has(lastEventId)) {
return "";
}
// Extract stream ID from event ID
const streamId = this.getStreamIdFromEventId(lastEventId);
if (!streamId) {
return "";
}
let foundLastEvent = false;
// Sort events by eventId for chronological order
const sortedEvents = [...this.events.entries()].sort((a, b) =>
a[0].localeCompare(b[0])
);
for (const [
eventId,
{ streamId: eventStreamId, message },
] of sortedEvents) {
// Only include events from the same stream
if (eventStreamId !== streamId) {
continue;
}
// Start sending events after lastEventId
if (eventId === lastEventId) {
foundLastEvent = true;
continue;
}
if (foundLastEvent) {
await send(eventId, message);
}
}
return streamId;
}
}