Traefik – Dynamic Config not working: ERR error=”field not found, node: middleware”

Are you tired of staring at the frustrating error message “ERR error=“field not found, node: middleware”” in your Traefik dynamic configuration? You’re not alone! This pesky issue has been plaguing developers for far too long. But fear not, dear reader, for we’re about to embark on a journey to conquer this error and get your dynamic config up and running smoothly.

The Problem: A Quick Recap

Before we dive into the solution, let’s take a step back and understand the problem at hand. Traefik’s dynamic configuration is a powerful feature that allows you to define your routing, services, and middleware using a YAML or TOML file. However, when you try to use middleware in your dynamic config, things can quickly go awry.

The error message “ERR error=“field not found, node: middleware”” typically occurs when Traefik is unable to find the middleware you’ve specified in your configuration file. This can happen for a variety of reasons, which we’ll explore in the following sections.

Cause 1: Incorrect Middleware Naming

One of the most common causes of the “field not found” error is incorrect middleware naming. In Traefik, middleware names must follow a specific format: ` Traefik middleware names must start with “middleware-” followed by the name of the middleware. For example, `middleware- stripprefix` or `middleware- headers`.

Here’s an example of an incorrect middleware name:

http:
  routers:
    router1:
      service: service1
      middleware:
        - mymiddleware

The above configuration will result in the “field not found” error because the middleware name “mymiddleware” does not start with “middleware-“. To fix this, simply rename the middleware to follow the correct format:

http:
  routers:
    router1:
      service: service1
      middleware:
        - middleware-mymiddleware

Cause 2: Middleware Not Defined

Another common cause of the “field not found” error is that the middleware is not defined in the Traefik configuration file. In Traefik, middleware must be defined in the `http.middlewares` section of the configuration file.

Here’s an example of an incorrect middleware definition:

http:
  routers:
    router1:
      service: service1
      middleware:
        - middleware-mymiddleware

In the above example, the middleware “middleware-mymiddleware” is not defined anywhere in the configuration file. To fix this, you need to define the middleware in the `http.middlewares` section:

http:
  middlewares:
    mymiddleware:
      stripPrefix:
        prefixes:
          - "/api"
  routers:
    router1:
      service: service1
      middleware:
        - middleware-mymiddleware

Cause 3: Middleware Not Enabled

In Traefik, middleware can be enabled or disabled using the `enabled` field. If the `enabled` field is set to `false`, the middleware will not be applied, resulting in the “field not found” error.

Here’s an example of a disabled middleware:

http:
  middlewares:
    mymiddleware:
      stripPrefix:
        prefixes:
          - "/api"
      enabled: false
  routers:
    router1:
      service: service1
      middleware:
        - middleware-mymiddleware

In the above example, the middleware “mymiddleware” is defined but disabled. To fix this, simply set the `enabled` field to `true`:

http:
  middlewares:
    mymiddleware:
      stripPrefix:
        prefixes:
          - "/api"
      enabled: true
  routers:
    router1:
      service: service1
      middleware:
        - middleware-mymiddleware

Solution: A Step-by-Step Guide

Now that we’ve explored the common causes of the “field not found” error, let’s put it all together with a step-by-step guide to configuring middleware in Traefik:

1. Define your middleware in the `http.middlewares` section of your Traefik configuration file:

   
   http:
     middlewares:
       mymiddleware:
         stripPrefix:
           prefixes:
             - "/api"
         enabled: true
   
   

2. Ensure the middleware name starts with “middleware-” :

   
   http:
     middlewares:
       middleware-mymiddleware:
         stripPrefix:
           prefixes:
             - "/api"
         enabled: true
   
   

3. Reference the middleware in your router configuration:

   
   http:
     routers:
       router1:
         service: service1
         middleware:
           - middleware-mymiddleware
   
   

4. Double-check that the middleware is enabled:

   
   http:
     middlewares:
       middleware-mymiddleware:
         stripPrefix:
           prefixes:
             - "/api"
         enabled: true
   
   

5. Save your Traefik configuration file and restart the Traefik service:

   
   sudo systemctl restart traefik
   
   

Conclusion

Traefik’s dynamic configuration is a powerful tool that can simplify your routing and service management. However, when middleware is involved, things can quickly get complicated. By following the steps outlined in this article, you should be able to diagnose and fix the “ERR error=“field not found, node: middleware”” error in no time.

Remember to double-check your middleware naming, definition, and enablement to ensure that Traefik can find and apply your middleware correctly.

Cause	Solution
Incorrect Middleware Naming	Rename middleware to start with “middleware-“
Middleware Not Defined	Define middleware in `http.middlewares` section
Middleware Not Enabled	Set `enabled` field to `true`

With these tips and tricks, you’ll be well on your way to mastering Traefik’s dynamic configuration and middleware management. Happy coding!

Frequently Asked Question

Traefik dynamic config not working, and you’re stuck with the error “ERR error=“field not found, node: middelwares””? Don’t worry, we’ve got you covered! Check out these frequently asked questions to get your Traefik up and running smoothly.