InMemoryEventStore.tsā¢2.65 kB
/**
* This is a copy of the InMemoryEventStore from the typescript-sdk
* https://github.com/modelcontextprotocol/typescript-sdk/blob/main/src/inMemoryEventStore.ts
*/
import type { EventStore } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import type { JSONRPCMessage } from "@modelcontextprotocol/sdk/types.js";
/**
* Simple in-memory implementation of the EventStore interface for resumability
* This is primarily intended for examples and testing, not for production use
* where a persistent storage solution would be more appropriate.
*/
export class InMemoryEventStore implements EventStore {
private events: Map<string, { message: JSONRPCMessage; streamId: string }> =
new Map();
/**
* Replays events that occurred 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 the stream ID from the event ID
const streamId = this.getStreamIdFromEventId(lastEventId);
if (!streamId) {
return "";
}
let foundLastEvent = false;
// Sort events by eventId for chronological ordering
const sortedEvents = [...this.events.entries()].sort((a, b) =>
a[0].localeCompare(b[0]),
);
for (const [
eventId,
{ message, streamId: eventStreamId },
] of sortedEvents) {
// Only include events from the same stream
if (eventStreamId !== streamId) {
continue;
}
// Start sending events after we find the lastEventId
if (eventId === lastEventId) {
foundLastEvent = true;
continue;
}
if (foundLastEvent) {
await send(eventId, message);
}
}
return streamId;
}
/**
* Stores 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, { message, streamId });
return eventId;
}
/**
* Generates 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)}`;
}
/**
* Extracts the stream ID from an event ID
*/
private getStreamIdFromEventId(eventId: string): string {
const parts = eventId.split("_");
return parts.length > 0 ? parts[0] : "";
}
}