feat(nbstore): init (#7639)

TODO

- [x] basic
- [x] storages
- [x] producer/consumer
- [x] operation pattern
- [x] events
- [x] worker
- [x] readme
- [x] peer dependencies

packages/common/nbstore/src/connection/connection.ts

@@ -0,0 +1,132 @@
+import EventEmitter2 from 'eventemitter2';
+
+export type ConnectionStatus =
+  | 'idle'
+  | 'connecting'
+  | 'connected'
+  | 'error'
+  | 'closed';
+
+export abstract class Connection<T = any> {
+  private readonly event = new EventEmitter2();
+  private _inner: T | null = null;
+  private _status: ConnectionStatus = 'idle';
+  protected error?: Error;
+  private refCount = 0;
+
+  constructor() {
+    this.autoReconnect();
+  }
+
+  get shareId(): string | undefined {
+    return undefined;
+  }
+
+  get maybeConnection() {
+    return this._inner;
+  }
+
+  get inner(): T {
+    if (!this._inner) {
+      throw new Error(
+        `Connection ${this.constructor.name} has not been established.`
+      );
+    }
+
+    return this._inner;
+  }
+
+  protected set inner(inner: T | null) {
+    this._inner = inner;
+  }
+
+  get status() {
+    return this._status;
+  }
+
+  protected setStatus(status: ConnectionStatus, error?: Error) {
+    const shouldEmit = status !== this._status && error !== this.error;
+    this._status = status;
+    this.error = error;
+    if (shouldEmit) {
+      this.emitStatusChanged(status, error);
+    }
+  }
+
+  abstract doConnect(): Promise<T>;
+  abstract doDisconnect(conn: T): Promise<void>;
+
+  ref() {
+    this.refCount++;
+  }
+
+  deref() {
+    this.refCount = Math.max(0, this.refCount - 1);
+  }
+
+  async connect() {
+    if (this.status === 'idle' || this.status === 'error') {
+      this.setStatus('connecting');
+      try {
+        this._inner = await this.doConnect();
+        this.setStatus('connected');
+      } catch (error) {
+        this.setStatus('error', error as any);
+      }
+    }
+  }
+
+  async disconnect() {
+    this.deref();
+    if (this.refCount > 0) {
+      return;
+    }
+
+    if (this.status === 'connected') {
+      try {
+        if (this._inner) {
+          await this.doDisconnect(this._inner);
+          this._inner = null;
+        }
+        this.setStatus('closed');
+      } catch (error) {
+        this.setStatus('error', error as any);
+      }
+    }
+  }
+
+  private autoReconnect() {
+    // TODO:
+    //   - maximum retry count
+    //   - dynamic sleep time (attempt < 3 ? 1s : 1min)?
+    this.onStatusChanged(() => {
+      this.connect().catch(() => {});
+    });
+  }
+
+  onStatusChanged(
+    cb: (status: ConnectionStatus, error?: Error) => void
+  ): () => void {
+    this.event.on('statusChanged', cb);
+    return () => {
+      this.event.off('statusChanged', cb);
+    };
+  }
+
+  private readonly emitStatusChanged = (
+    status: ConnectionStatus,
+    error?: Error
+  ) => {
+    this.event.emit('statusChanged', status, error);
+  };
+}
+
+export class DummyConnection extends Connection<undefined> {
+  doConnect() {
+    return Promise.resolve(undefined);
+  }
+
+  doDisconnect() {
+    return Promise.resolve(undefined);
+  }
+}

packages/common/nbstore/src/connection/index.ts

@@ -0,0 +1,2 @@
+export * from './connection';
+export * from './shared-connection';

packages/common/nbstore/src/connection/shared-connection.ts

@@ -0,0 +1,22 @@
+import type { Connection } from './connection';
+
+const CONNECTIONS: Map<string, Connection<any>> = new Map();
+export function share<T extends Connection<any>>(conn: T): T {
+  if (!conn.shareId) {
+    throw new Error(
+      `Connection ${conn.constructor.name} is not shareable.\nIf you want to make it shareable, please override [shareId].`
+    );
+  }
+
+  const existing = CONNECTIONS.get(conn.shareId);
+
+  if (existing) {
+    existing.ref();
+    return existing as T;
+  }
+
+  CONNECTIONS.set(conn.shareId, conn);
+  conn.ref();
+
+  return conn;
+}