Make DirectoryResolver Response Cacheable

[tjwiebell]

Description

Outlined in issue #52, resolvers were lacking caching headers, which was in turn causing some down stream issues in Fastly around text encoding/compression; which was dinging us on Lighthouse. I do think we should leave the issue open and have a general conversation about caching, because this issue is cross platform and also affects upward-js, but this resolve some Magento Cloud specific issues in the meantime.

As a starting point for, we're going to make the assumption that all static assets should be cached, and just hard-code this header into the Directory resolver.

Related Issue

• [https://jira.corp.magento.com/browse/PWA-215] Enable Text Compression (Lighthouse)

Acceptance

Verification Stakeholders

Specification

Verification Steps

1. Deploy to Magento Cloud (will require feature/upward-dependency-testing for magento/module-upward-connector dependency)
2. With Developer Console open, clear cache and open the app
3. Filter for a static asset like client-<hash>.js or vendor-<hash>.js
4. Verify Cache-Control header has a max-age value > 0
5. Verify Content-Encoding header value is gzip

Screenshots / Screen Captures (if appropriate)

Checklist

• I have updated the documentation accordingly, if necessary.
• I have added tests to cover my changes, if necessary.

[sirugh]

LGTM!

[opepin]

hello,
After upgrading to 1.1.2, I'm getting the new cache header from the directory
cache-control: max-age=31557600

but also some conflicting cache headers that may mess up some web browsers/proxy
expires: Thu, 19 Nov 1981 08:52:00 GMT
pragma: no-cache

This headers are coming from PHP session cache limiter. There is no need for a session to serve static resources in Upward .
Is there a way to disable Magento session creation in that scope ?

this is related to some issues with web api magento/magento2#26032

A workaround could be to force the session cache limiter to public for Directory Resolver to override those headers