Refresh the AMP cache with the invalidation API

refresh-amp-cache-with-node.md

Bust AMP cache

Demo on how to force cache refresh with AMP

NB : all the follwing instructions are on node.js

Demo

https://glitch.com/edit/#!/bust-amp-cache

Generate the keys

openssl genrsa 2048 > private-key.pem 

openssl rsa -in private-key.pem -pubout >public-key.pem

Expose your public-key.pem

The public-key.pem should be accesible to the public on this URL :

https://myAwesomeSite.com/.well-known/amphtml/apikey.pub

NB : Do not convert your public key to .pub

NB : You should send you keys in the text/plain content-type

Example :

router.get("/.well-known/amphtml/apikey.pub", (request, response) => {
  
  try{
    
    // we get the key 
    const key = fs.readFileSync('/app/public-key.pem').toString();
    
    // we set the content-type to text/plain 
    response.type('text/plain');
    
    // let's send the key !
    response.send(key);
    
  }catch(e){
  
      response.send(e.toString());
  }
  
});

Request a cache refresh

Let's create a file ( bustCache.js ) and add this code :

//  Install ( amp-toolbox-update-cache ) with npm install amp-toolbox-update-cache 
const UpdateCacheUrlProvider = require('amp-toolbox-update-cache');

// we use fs to get our key 
const fs = require('fs');

// We wil have to make HTTP requests to the cache. here I use node-fetch ( npm install node-fetch )
const fetch = require('node-fetch');

// we get our key
const privateKey = fs.readFileSync('/app/private-key.pem').toString();


/**
 * @description Clear the cache for a given URL
 * @param {string} url the URL you want to invalid 
 * @returns {promise} 
 */
const bustThatUrl = async (url) => {
  
  // we init UpdateCacheUrlProvider with our private key
  const updateCacheUrlProvider = UpdateCacheUrlProvider.create(privateKey);
  
  // we get all the URLs from the cache
  let cacheUpdateUrls = await updateCacheUrlProvider.calculateFromOriginUrl(url); 
  
  // We only want Google ( remove this line if you want to refresh the cache not only on Google )
  cacheUpdateUrls = cacheUpdateUrls.filter( c => c.cacheId === "google");
  
  const requestsToCaches = cacheUpdateUrls.map( c => fetch(c.updateCacheUrl) );
  
  const responsesFromCaches = await Promise.all(requestsToCaches);
  
  
  for ( const responsesFromCache of responsesFromCaches){
    
      const textResponse = await responsesFromCache.text();
  
      if( textResponse !== "OK") throw new Error(textResponse); 
      
  }
  
  return true;


};


// we list the urls we want to refresh
const URLS_TO_CLEAR = ["https://bust-amp-cache.glitch.me/","https://bust-amp-cache.glitch.me/amp-list"];


(async () => {

  
  for( const URL of URLS_TO_CLEAR){
    
    try {
      
        // we refresh the cache 
        const bustingResult = await bustThatUrl(URL);
    
        console.log(`✅ ${URL} has been busted with the following response : ${bustingResult}`);
    
    }catch(e) {
      
        console.log(`${URL} didn't get busted with the following response : ${e}`);
        
    }



  }
  


})()
.catch(console.log)

Execute this script

node bustCache.js