如何在客户端 NextJS 中使用 Apollo GraphQL 订阅？

Question

我是 NextJS 的新手。 我有一个页面需要显示从 Hasura GraphQL 后端提取的实时数据。

在其他非 NextJS 应用程序中，我将 GraphQL 订阅与 Apollo 客户端库一起使用。 在引擎盖下，这使用了 websockets。

当不使用订阅时，我可以让 GraphQL 在 NextJS 中工作。 我很确定这是在服务器端运行的：

import React from "react";
import { AppProps } from "next/app";
import withApollo from 'next-with-apollo';
import { ApolloProvider } from '@apollo/react-hooks';
import ApolloClient, { InMemoryCache } from 'apollo-boost';
import { getToken } from "../util/auth";

interface Props extends AppProps {
    apollo: any
}

const App: React.FC<Props> = ({ Component, pageProps, apollo }) => (
    <ApolloProvider client={apollo}>
        <Component {...pageProps}/>
    </ApolloProvider>
);

export default withApollo(({ initialState }) => new ApolloClient({
    uri: "https://my_hasura_instance.com/v1/graphql",
    cache: new InMemoryCache().restore(initialState || {}),
    request: (operation: any) => {
        const token = getToken();
        operation.setContext({
            headers: {
                authorization: token ? `Bearer ${token}` : ''
            }
        });
    }
}))(App);

我这样使用它：

import { useQuery } from '@apollo/react-hooks';
import { gql } from 'apollo-boost';

const myQuery = gql`
    query {
        ...
    }
`;

const MyComponent: React.FC = () => {
    const { data } = useQuery(myQuery);
    return <p>{JSON.stringify(data)}</p>
}

但是，我想这样做：

import { useSubscription } from '@apollo/react-hooks';
import { gql } from 'apollo-boost';


const myQuery = gql`
    subscription {
        ...
    }
`;

const MyComponent: React.FC = () => {
    const { data } = useSubscription(myQuery);
    return <p>{JSON.stringify(data)}</p>
}

我试过的

我尝试在 ApolloClient 中拆分 HttpLink 和 WebsocketLink 元素，如下所示：

import React from "react";
import { AppProps } from "next/app";

import { ApolloProvider } from '@apollo/react-hooks';
import withApollo from 'next-with-apollo';
import { InMemoryCache } from "apollo-cache-inmemory";
import ApolloClient from "apollo-client";
import { split } from 'apollo-link';
import { HttpLink } from 'apollo-link-http';
import { WebSocketLink } from 'apollo-link-ws';
import { getMainDefinition } from 'apollo-utilities';

import { getToken } from "../util/auth";

interface Props extends AppProps {
    apollo: any
}

const App: React.FC<Props> = ({ Component, pageProps, apollo }) => (
    <ApolloProvider client={apollo}>
        <Component {...pageProps}/>
    </ApolloProvider>
);

const wsLink = new WebSocketLink({
    uri: "wss://my_hasura_instance.com/v1/graphql",
    options: {
        reconnect: true,
        timeout: 10000,
        connectionParams: () => ({
            headers: {
                authorization: getToken() ? `Bearer ${getToken()}` : ""
            }
        })
    },
});

const httpLink = new HttpLink({
    uri: "https://hasura-g3uc.onrender.com/v1/graphql",
});

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

export default withApollo(({ initialState }) => new ApolloClient({
    link: link,
    cache: new InMemoryCache().restore(initialState || {}),
}))(App);

但是当我加载页面时，我得到一个Internal Server Error ，并且在终端中出现这个错误：

Error: Unable to find native implementation, or alternative implementation for WebSocket!

在我看来， ApolloClient是在服务器端生成的，没有 WebSocket 实现。 我怎样才能在客户端发生这种情况？

Answer 1

找到解决方法使其工作，看看这个答案https://github.com/apollographql/subscriptions-transport-ws/issues/333#issuecomment-359261024

原因是服务器端渲染； 这些语句必须在浏览器中运行，所以我们测试我们是否有process.browser ！

随附 github 链接中的相关部分：

const wsLink = process.browser ? new WebSocketLink({ // if you instantiate in the server, the error will be thrown
  uri: `ws://localhost:4000/subscriptions`,
  options: {
    reconnect: true
  }
}) : null;

const httplink = new HttpLink({
    uri: 'http://localhost:3000/graphql',
    credentials: 'same-origin'
});

const link = process.browser ? split( //only create the split in the browser
  // split based on operation type
  ({ query }) => {
    const { kind, operation } = getMainDefinition(query);
    return kind === 'OperationDefinition' && operation === 'subscription';
  },
  wsLink,
  httplink,
) : httplink;

Answer 2

这个答案似乎更实际

https://github.com/apollographql/subscriptions-transport-ws/issues/333#issuecomment-775578327

您应该通过npm i ws安装ws并将webSocketImpl: ws添加到 WebSocketLink 参数。

import ws from 'ws';

const wsLink = new WebSocketLink({
    uri: endpoints.ws,
    options: {
        reconnect: true,
        connectionParams: () => ({
            ...getToken() && {Authorization: getToken()}
        })
    },
    webSocketImpl: ws
});

Answer 3

解决方案：将 wsLink 设为 function 变量，如下面的代码。

// src/apollo.ts

import { ApolloClient, HttpLink, InMemoryCache } from "@apollo/client";
import { GraphQLWsLink } from "@apollo/client/link/subscriptions";
import { createClient } from "graphql-ws";


const httpLink = new HttpLink({
  uri: 'http://localhost:3000/graphql'
});

const wsLink = () => {
  return new GraphQLWsLink(createClient({
    url: 'ws://localhost:3000/graphql'
  }));
}

export const apolloClient = new ApolloClient({
    link: typeof window === 'undefined' ? httpLink : wsLink(),
    cache: new InMemoryCache(),
  });

// pages/_app.tsx

import { ApolloProvider } from "@apollo/client";
import { apolloClient } from "./apollo";

function MyApp({ Component, pageProps }) {
  return (
    <ApolloProvider client={apolloClient}>
      <Component {...pageProps} />
    </ApolloProvider>
  );
}