Page Rules

For ROSE Online we store our game update archives in Backblaze B2 and serve them directly to our players. When we initially set things up we simply setup a CNAME for our subdomain to our public bucket URL, e.g.

CNAME updates rose-updates.s3.us-west-002.backblazeb2.com

Our intention was that https://updates.roseonlinegame.com would be an alias for the backblaze bucket and files could be retrived directly. Unfortunately this doesn't work as expected due to limitations on the Backblaze side so we had to setup a rewrite rule in Cloudflare using Page Rules to actually make this work.

updates.roseonlinegame.com/*
Forwarding URL (Status Code: 301 - Permanent Redirect, Url: https://rose-updates.s3.us-west-002.backblazeb2.com/$1)

This is actually the guidance recommended by Backblaze in their official documentation: https://www.backblaze.com/docs/cloud-storage-deliver-public-backblaze-b2-content-through-cloudflare-cdn.

In practice this achieved our goal but there were three main downsides:

• Users were exposed to the b2 URL through the redirect
• Backblaze is blocked in some countries so some of our players could not receive updates
• Backblaze is not a CDN so download speeds were slow for some of our players

Transform Rules

We recently have been working on our update process and decided to revist this issue. Since our original implementation Cloudflare has released "Transform Rules" which provide a superior solution.

First, we re-established the CNAME DNS record, (using updates2 to avoid service interruptions) but this time we use the base Backblaze B2 domain for our bucket e.g.

CNAME updates2 f002.backblazeb2.com

and then using a transform rule we can rewrite this URI so that any path components after the domain name only reach our bucket, e.g.

If...
When incoming requests match…

    Custom filter expression
    The rule will only apply to traffic matching the custom expression

        (http.host eq "updates2.roseonlinegame.com")

Then…
Set Rewrite parameters

    Path
    Rewrite to...
    Specify both the input and output pattern within the expression. Cannot be an empty value.

        Dynamic     concat("/file/rose-updates", http.request.uri.path)

    Query

        Preserve

The key line being concat("/file/rose-updates", http.request.uri.path).

With this rule Cloudflare will internally rewrite our URI so that https://updates2.roseonlinegame.com/manifest.json will fetch the files from f002.backblazeb2.com/file/rose-updates/mainfest.json and serve the files for us. Now we get the benefit of using Cloudflare as a CDN, users who can't access backblaze will not have anymore issues and we don't have to expose our ugly backblaze url!