Traefik Docker provider and File provider routing priority synchronization

Question

A repeatable development environment in Traefik is commonly built by decoupling static infrastructure with the file-provider and dynamic services with the Docker provider. The Docker provider discovers containers via labels and hot-reloads routing rules without restarting the proxy.

Routing selection is documented to use the longest path prefix unless an explicit priority is set. When a file-provider rule defines a global fallback that overlaps a Docker-provider label rule, the internal routing table state during rapid start-stop sequences is unclear.

What guarantees deterministic priority resolution between file-provider and Docker-provider rules when both match the same request during container churn? Is there a defined synchronization order for configuration updates from multiple dynamic providers?

Tasadduq Burney · Answer

Answer

Deterministic priority is guaranteed when you assign an explicit numeric priority to each router. If priorities differ, the router with the highest value wins. If priorities are equal, Traefik breaks the tie by load‑order: the router that was loaded (or last updated) last wins. This load‑order is deterministic as long as the static provider list and the sequence of updates do not change.

Likely explanation

Traefik merges configurations from all enabled providers into a single routing table. Each router receives a priority value (default 0). When multiple routers match a request, Traefik selects the one with the highest priority; equal priorities are resolved by the router that was processed most recently.

Confirmed facts

In Traefik v2 and v3, Docker‑provider routers set priority via the label traefik.http.routers..priority.
File‑provider routers set priority directly in the static YAML/TOML under routers..priority.
The numeric values are comparable across providers.

Steps to synchronize priority

Decide the priority you want for the overlapping route (e.g., 10).

In the file‑provider configuration (e.g., traefik.yml), set:

http:
  routers:
    web:
      rule: Host(`example.com`) && PathPrefix(`/`)  
      priority: 10

Apply the same numeric value to the matching Docker container via a label:
```
traefik.http.routers.web.priority=10
```
Ensure both providers are listed in the same static providers section (or load a dynamic file that overrides Docker labels) so the load‑order is fixed.
Reload Traefik (or let it hot‑reload) and verify.

Verification

Access the Traefik dashboard (http://<traefik>:8080/dashboard/) and check the Routers list; each router should display the priority number you set. Perform a curl request to the target host/path and confirm the expected service responds. Changing a priority label and observing the response switch confirms the synchronization works.

Missing diagnostic detail

If the observed behavior does not match the expected priority, please provide the current priority values seen for the conflicting routers from both the Docker container (docker inspect <container> --format '{{ index .Config.Labels "traefik.http.routers.web.priority" }}') and the file‑based router (from the dashboard or static config). This detail determines whether the tie‑break rule is being applied.