Routing

apm-hub can possibly serve hundreds of backends, but you might not want all of them to serve a request. Routing helps you to control which backends should serve a given request based on the parameters shown below.

Route

Field	Description	Scheme	Required
type	Serve queries if the type matches this value.	string	optional
idPrefix	Serve queries if the id has this prefix.	string	optional
labels	Serve queries matching these labels.	map[string]string	true
additive	Specifies whether this backend should return results exclusively. (Defaults to false)	bool	optional

Every backend should have at least one route defined. If multiple routes are defined, then the backend will be used if any of the routes match the query.

Wildcard

If you need a backend to serve all the requests, you have the option to specify a wildcard route. A route with an empty value for idPrefix indicates a wildcard route.

backends:
  - kubernetes:
      routes:
        - idPrefix: ''

Labels matching

Labels are a set of key value pairs that are compared against the labels in the search request. If the labels in the route match the labels in the search request, then the backend will be used.

backends:
  - kubernetes:
      routes:
        - labels:
            app: my-app
            env: prod

For the configuration above, the kubernetes backend will be used if the search request contained those labels.

Wildcard labels

If you don't really care the value of the label but need the label to be there, you can use a wildcard label.

backends:
  - kubernetes:
      routes:
        - labels:
            app: *
            env: prod

Blacklisting labels

You can also blacklist labels by using a ! prefix.

backends:
  - kubernetes:
      routes:
        - labels:
            app: !frontend
            env: prod

Set of values

You can provide a set of values for a label by using a comma separated list.

backends:
  - kubernetes:
      routes:
        - labels:
            app: !frontend
            env: dev,stage

Additive routes

As you can imagine, a single search query can possibly be served by numerous backends. A non-additive route enables a backend to return the results exclusively. This means that if a backend is configured with a non-additive route, then it will discard all the results from other backends collected so far and return only its results. Once a non-additive route is matched, the search will stop and the results will be returned.

Info

All routes are non-additive by default.

```yaml
backends:
  - kubernetes:
      routes:
        - additive: true
          labels:
            app: !frontend
            env: dev,stage