Using Traffic rules to route traffic

Overview

Traffic allows you to define arbitrarily complex rules to route and modify traffic to your Prepress application. This includes:

You set and manage Traffic rules via your Cloud 66 Dashboard. We provide templates to help you write rules, or you can write them from scratch. Traffic is built on top of Google’s Common Expression Language (CEL).

If you need more detailed info on rules we have an in-depth guide to understanding rules as well as a reference to Traffic CEL functions.

How Traffic rules work

Traffic consist of one or more functions that run in a sequence. They run from top to bottom and affect the route that each web request to your application takes. They can also block traffic based on different conditions. If traffic is blocked, it will not run through the rest of the rules that come after the current one.

Each rule is a single function. There are 4 functions in Traffic: Rewrite, Redirect, Header and Block. Each function takes a number of parameters, some required and some optional. The values for each parameter is defined by a type. and you can learn more about these types in CEL documentation.

Now, let’s look at a practical example: we have changed the name of a page and we want the URL to reflect the new name without moving the underlying resource. For this we can use the Rewrite function:

Rewrite {
	from: "/old_page/index.html",
	to: "/new_page/index.html"
}

Let’s break this function down:

Rewrites can also have an optional when parameter - a boolean test that determines whether the rule should be applied to the traffic that it matches. You can use any boolean expression supported by CEL.

Let’s look at a more complex example: you have changed the name of a section of your website from “projects” to “subjects”, which you want to reflect in the public-facing URL, but without changing the underlying location of the files. For this we can use the Rewrite function:

Rewrite {
	from: "^/subjects/(?P<projectname>[?].*)?$",
	to: "/projects/${projectname}"
}

Let’s break this function down:

Let’s look at a final example - this time of a Redirect with a when parameter.

Redirect {
	from: "^/main/(?P<splat>[^?]*)(?P<query>[?].*)?$",
  to: "/es/main/${splat}${query}",
  with: 301
	when: origin.country_code == "ES" || origin.country_code == "MX"
}

As we can see, this function will redirect traffic originating in Spain and Mexico to a Spanish version of the site, and preserve any query strings. This redirect is set to permanent (301) by the with parameter because it should always apply to this traffic. You can also use temporary and permanent here - they are aliases of the underlying HTTP codes.

Creating and managing rules

Rules are managed using your Cloud 66 Dashboard. To create a new rule:

  1. Log into your Cloud 66 Dashboard
  2. Open your Prepress application
  3. Click on WebFlow Rules in the right-hand column
  4. Click the + Add Rule button at the top right of the main rules panel
  5. Choose a template appropriate to your needs
  6. Define your rule using the code editor
  7. Add a description for the rule (rules are version controlled)
  8. Choose a status for the new rule - either Live or Test
  9. Click Save
  10. Click the green Apply button that will appear at the top of the Rules summary page

Rules are applied in the order in which they appear on this page. If rules conflict, we will default to the rule higher up in this list. You can drag rules to reorder them.

References for rule types

Our full reference guide has detailed explanations and examples of syntax for each type of rule. Click the name of a rule below for more details:

Testing Traffic with real payloads

Rules can be challenging to read and debug in the absence of real traffic data. We recommend testing your new rule before setting it live. To do this, choose the Test status when creating a rule and then apply the new rule. This will record the results of the rules in your Live Logs without actually routing the traffic.

To see the logs for your test rule:

  1. Click on Live Logs in the right-hand column
  2. Check the box in the right-hand column next to the rule you wish to test
  3. Visit one of the URLs to which the rule should apply

The output of the logs will record the results of the rule (including any errors). Note that LiveLogs are streamed and are not persisted - they will reset if you close or refresh the page.

Debugging and rule construction

Watching the LiveLogs for your Traffic rules is useful for a number of different reasons:

  1. It allows you to see which traffic is being filtered (and which is being ignored)
  2. It gives you detailed examples of traffic payloads, which you can use to construct new or more specific rules

For example, this is a sample payload from LiveLogs:

{
   "origin":{
      "asn":"AS2089",
      "city_name":"Chiswick",
      "continent_code":"EU",
      "country_code":"GB",
      "ip":"88.11.41.153",
      "latitude":51.2222,
      "longitude":-0.2222,
      "timezone":"Europe/London"
   },
   "request":{
      "host":"help.cloud66.com",
      "method":"GET",
      "path":"/css/legacy.css",
      "url":"/css/legacy.css",
      "user_agent":{
         "client":{
            "family":"Chrome",
            "major":"99",
            "minor":"0",
            "patch":"4844"
         },
         "device":{
            "brand":"Apple",
            "family":"Mac",
            "model":"Mac"
         },
         "os":{
            "family":"Mac OS X",
            "major":"10",
            "minor":"15",
            "patch":"7"
         }
      },
      "user_agent_raw":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.83 Safari/537.36"
   }
}

This gives you practical examples for writing rules for everything from geographical filters to browser versions to device types. You could write a function that targets this traffic like so:

origin.asn == "AS2089" && 
origin.city_name == "Chiswick" && 
device.brand == Apple

Performance

Traffic rules are super fast but inevitably there is a linear performance cost associated with them: the more rules that run, the longer the processing takes. We’re talking milliseconds for hundreds of rules, but in production every millisecond counts.

Note if any rule stops the traffic the rest of the rules won’t evaluated. As such we recommend putting Block rules higher up in the list.

What’s next?