server.js

const next = require("next");
const Koa = require("koa");
const router = require("koa-route");
const LRUCache = require("lru-cache");
const c2k = require("koa2-connect");
const proxyMiddleware = require("http-proxy-middleware");

const port = parseInt(process.env.PORT, 10) || 9527;
const dev = process.env.NODE_ENV !== "production";
const test = process.env.NODE_TEST === "test";
const app = next({ dev });
const handle = app.getRequestHandler();

// This is where we cache our rendered HTML pages
const ssrCache = new LRUCache({
  max: 100,
  maxAge: 1000 * 60 * 60 // 1hour
});

/*
 * NB: make sure to modify this to take into account anything that should trigger
 * an immediate page change (e.g a locale stored in req.session)
 */
function getCacheKey(ctx) {
  return ctx.url;
}

function renderAndCache(ctx, pagePath, noCache, queryParams = null) {
  if (dev || test) ssrCache.reset();
  if (noCache === "noCache") {
    return app
      .renderToHTML(ctx.req, ctx.res, pagePath, queryParams)
      .then(html => {
        // Let's cache this page
        console.info("no cache");
        ctx.body = html;
      })
      .catch(err => {
        console.info("ERRR", err);
        return app.renderError(err, ctx.req, ctx.res, pagePath, queryParams);
      });
  }

  const key = getCacheKey(ctx.req);

  // If we have a page in the cache, let's serve it
  if (ssrCache.has(key)) {
    console.info(`CACHE HIT: ${key}`);
    ctx.body = ssrCache.get(key);
    return Promise.resolve();
  }

  // If not let's render the page into HTML
  return app
    .renderToHTML(ctx.req, ctx.res, pagePath, queryParams)
    .then(html => {
      // Let's cache this page
      console.info(`CACHE MISS: ${key}`);
      ssrCache.set(key, html);
      ctx.body = html;
    })
    .catch(err => {
      console.info("ERRR", err);
      return app.renderError(err, ctx.req, ctx.res, pagePath, queryParams);
    });
}
app.prepare().then(() => {
  const server = new Koa();

  server.use(router.get("/", ctx => renderAndCache(ctx, "/index")));

  if (dev) {
    // Set up the proxy.
    server.use(async (ctx, next) => {
      router.get(
        "*",
        c2k(
          proxyMiddleware("/api", {
            target: "https://api.github.com",
            pathRewrite: { "^/api": "/" },
            changeOrigin: true
          })
        )(ctx, next)
      );
    });
  }

  server.use(async ctx => {
    await handle(ctx.req, ctx.res);
    ctx.respond = false;
  });

  server.use(async (ctx, next) => {
    ctx.res.statusCode = 200;
    await next();
  });
  server.listen(port, err => {
    if (err) throw err;
    console.info(`> Ready on http://localhost:${port}`);
  });
});