要解决Apollo Server中GraphQL订阅WebSocket连接不持久的问题，可以通过以下步骤进行设置和更改：

1. 首先，确保你的Apollo Server是基于最新版本的Apollo Server来构建的。如果不是，请更新到最新版本。

2. 确保你的Apollo Server实例已经启用了WebSocket支持。可以使用subscriptions选项来启动WebSocket支持，例如：

const { ApolloServer, PubSub } = require('apollo-server');
const { RedisPubSub } = require('graphql-redis-subscriptions');
const http = require('http');

const pubsub = new RedisPubSub();

const server = new ApolloServer({
  typeDefs,
  resolvers,
  subscriptions: {
    path: '/subscriptions',
    onConnect: (connectionParams, webSocket) => {
      // 在连接建立时执行的逻辑
    },
    onDisconnect: (webSocket, context) => {
      // 在连接断开时执行的逻辑
    },
  },
  context: ({ req, connection }) => {
    if (connection) {
      // 如果是WebSocket连接，返回相应的上下文
      return {
        ...connection.context,
        pubsub,
      };
    } else {
      // 如果是HTTP连接，返回相应的上下文
      return {
        req,
        pubsub,
      };
    }
  },
});

const httpServer = http.createServer(server);

server.applyMiddleware({ app });
server.installSubscriptionHandlers(httpServer);

httpServer.listen({ port: 4000 }, () => {
  console.log(`Server ready at http://localhost:4000${server.graphqlPath}`);
  console.log(`Subscriptions ready at ws://localhost:4000${server.subscriptionsPath}`);
});

3. 在客户端代码中，确保你的WebSocket连接是持久的。这可以通过设置WebSocket的reconnect选项为true来实现，例如：

import { ApolloClient, InMemoryCache, HttpLink, split } from '@apollo/client';
import { getMainDefinition } from '@apollo/client/utilities';
import { WebSocketLink } from '@apollo/client/link/ws';

const httpLink = new HttpLink({
  uri: 'http://localhost:4000/graphql',
});

const wsLink = new WebSocketLink({
  uri: `ws://localhost:4000/subscriptions`,
  options: {
    reconnect: true,
  },
});

const link = split(
  ({ query }) => {
    const definition = getMainDefinition(query);
    return definition.kind === 'OperationDefinition' && definition.operation === 'subscription';
  },
  wsLink,
  httpLink
);

const client = new ApolloClient({
  cache: new InMemoryCache(),
  link,
});

通过以上步骤，你应该能够解决Apollo Server中GraphQL订阅WebSocket连接不持久的问题，并确保WebSocket连接保持持久性。