node. JS architecture optimization: reverse proxy and cache service

// The following notes are all notes from the learning video , Make it easy to remember

// Video address ：https://time.geekbang.org/course/intro/232　

 

app.js file

const app = new (require('koa'))

const cacheRedis = require('redis')('cache')

const backupRedis = require('redis')('backup')

//koa The middle bond of the onion conforms to an onion model

app.use(async(ctx,next) => {

      const result  = await cacheRedis(ctx.url);  // RPC Asynchronous invocation of , from redis Extract a cached file from the

　　// The request url As key, from redis Take out a copy of the results , Assign a value to result

      if(result){ // If there is a result , Directly return the result ; Hit cache

              ctx.body = result;

              return;

      }

      await next()　　// If you miss the cache , Then execute the following middle key

      if(ctx.status == 200){  // Judge whether the request result is normal

　　　　cacheRedis.set(ctx.url,ctx.body, {expire: 200}); // Write request results to cache , Set expiration time

              backupRedis.set(ctx.url,ctx.body, {expire: 200}); // Write the request results to the backup cache , Set expiration time

      }

      if(ctx.status != 200){

           const result = await backupRedis(ctx.url); // From backup redis Take out the results

           ctx.status = 200;

           ctx.body = result;

      }

})