Node Google Cloud function for setting uploaded files cache-policy

setUploadedObjectMetadata.js

/**
 * Triggered from a change to a Cloud Storage bucket.
 *
 * @param {!Object} event Event payload.
 * @param {!Object} context Metadata for the event.
 */
exports.setUploadedObjectMetadata = (event, context) => {
  // Create a client
  var storage = require('@google-cloud/storage')();
  
  const data = event;
  console.log(`  Object finalized/created`);
  console.log(`  Bucket: ${data.bucket}`);
  console.log(`  Object: ${data.name}`);
  console.log(`  Created: ${data.timeCreated}`);
  console.log(`  Updated: ${data.updated}`);
  
  if(data.name.substr(-1) === '/'){
    console.log(`  Skipping because ${data.name} is a directory`);
    return;
  }
  
  const file = storage
    .bucket(data.bucket)
    .file(data.name);
  
  // Update metadata    
  file.setMetadata({cacheControl: 'public, max-age=31536000'}).then(() => {
    console.log(`  Cache-Control updated successfully for ${data.name}`);
  }).catch((e) => {
    console.log(`  There was an error setting Cache-Control for ${data.name}`);
    console.log(e);
  });
};

Google Storage sets cache expire to 1hr by default, which is not suitable when serving files that are public and not supposed to change (e.g. when using as storage for public CMS uploads). There is no simple way how to change this globally, but you can deploy this short Node function to Cloud Functions to set Cache-Control after upload to one year expire and public.

This function sets the policy for ALL objects - keep this in mind if you store files that are not supposed to be cached!

Use Google Cloud Functions Console to deploy the code with following settings:

Memory allocated: 128MB (can't imagine more could be needed)
Trigger: Cloud Storage
Event type: Finalize/Create
Runtime: Node 10
Function to execute: setUploadedObjectMetadata
Region: Closest possible
Retry on failure: Yes

In case the function fails for any reason, you can run this from the command line to mass set Cache-Control for all objects in the bucket:

gsutil -m setmeta -h "Cache-Control:public, max-age=31536000" gs://<STORAGE-BUCKET-NAME>/**/*.*