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Delegate requests to sub-tables

Delegate requests through one root route table to other sub-tables.

As your Gloo Mesh environment grows in size and complexity, the number of routes configured might increase considerably. Or, you might have multiple ways of routing to a particular path for an app that are difficult to consistently switch between. To organize multiple routes, you can create sub-tables for individual route setups. Then, you create a root route table that delegates requests to those sub-tables based on a specified sorting method.

For more information, see the Gloo Mesh API docs for route table delegation.

Delegate to sub-tables based on weight

Delegate routing to sub-tables based on an assigned order. Individual routes are kept in the order that they appear relative to their tables, but tables are sorted by the weight that you assign to them. When a service in your mesh sends a request to another service, the request is matched against the routes in the highest-weighted route table first. If the request doesn't match a route in the first sub-table, it is matched against the routes in the second-highest-weighted table, and so on.

Follow the guides in Forward requests to a destination to set up each route table that you want to include in this sub-table set. For each route table, include the following additional settings for delegation:

In the spec section, do not include the hosts or workloadSelectors fields. The root route table dictates these fields instead.
In the spec section, add the weight field to indicate route table priority. Higher integer values indicate a higher priority in the list of sub-tables. Note that tables of the same weight stay in the same order that you list them in the root route table, which is the list order when you specify sub-tables by name, or the creation timestamp when you select sub-tables by label.
Optional: If you want to refer to the sub-tables by label rather than by table name, add a label in the metadata section. Be sure to use the same label for each sub-table.

Example: Say that you are testing multiple types of request matching for myapp. You define two different route tables, one for each type of matching, and label them as table: myapp. You assign a higher weight to the table that uses prefix matching to test that matching method now, and a lower weight to the table that uses query parameters to focus on that later. Your sub-tables might look like the following configurations:

apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: prefix-match
  namespace: global
  # Label for the sub-table set
  labels:
    table: myapp
spec:
  # Higher weight means first priority in the sub-table order
  weight: 100
  hosts:
    - 'one.solo.io'
  virtualGateways:
    - name: istio-ingressgateway
      namespace: bookinfo
      cluster: ${CLUSTER_NAME}
  http:
  # Table routes any requests to 'one.solo.io/myapp/.*'
  - matchers:
    - uri:
        prefix: /myapp
        ignoreCase: true
    forwardTo:
      destinations:
      - ref:
          name: myapp
          namespace: global
          cluster: ${CLUSTER_NAME}
        port:
          number: 8090
        kind: SERVICE
---
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: query-parameters-match
  namespace: global
  # Label for the sub-table set
  labels:
    table: myapp
spec:
  # Lower weight means second priority in the sub-table order
  weight: 90
  hosts:
    - 'one.solo.io'
  virtualGateways:
    - name: istio-ingressgateway
      namespace: bookinfo
      cluster: ${CLUSTER_NAME}
  http:
  # Table routes any requests to 'one.solo.io/myapp/.*?version=stage'
  - matchers:
    - uri:
        prefix: /myapp
    - queryParameters:
      - name: version
        value: stage
    forwardTo:
      destinations:
      - ref:
          name: myapp
          namespace: global
          cluster: ${CLUSTER_NAME}
        port:
          number: 8090
        kind: SERVICE

Create the root route table to delegate requests based on sub-table weight. In this example root table, requests to the myapp.global.svc.cluster.local host are delegated to sub-tables with the table: myapp label, based on the order created by table weights. Note that you can also specify the sub-table names instead of the label by using the routeTables.name field.

kubectl apply --context $REMOTE_CONTEXT1 -n global -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: delegate-weight
  namespace: global
spec:
  hosts:
    - 'myapp.global.svc.cluster.local'
  http:
  - delegate:
      # Selects tables based on label
      routeTables:
        - labels:
            table: myapp
      # Delegates based on order of weights
      sortMethod: TABLE_WEIGHT
EOF

Test route table delegation by accessing the host and any necessary request-matching criteria.
- For example, log in to an app in your mesh and send a request to http://myapp:9080/myapp/foo to verify that the request is routed to the prefix-matching route in the prefix-match sub-table.
- You might also change the weights for the sub-tables to test that order instead, such as putting the query-parameters-match sub-table higher in the order. Then, you can log in to an app in your service mesh and send a request to http://myapp:9080/myapp/foo?version=stage to verify that the request is routed to the query parameter-matching route in the query-parameters-match sub-table.

Delegate to sub-tables based on route specificity

Delegate routing to sub-tables based on individual route specificity. When a service in your mesh sends a request to another service, the request is matched against all routes in each sub-table, sorted by specificity, to reduce the chance that a general route short-circuits a more specific route.

The following specificity rules apply:

Exact path matchers are considered more specific than regex path matchers, which are more specific than prefix path matchers.
Matchers of the same type are sorted by length of the path in descending order.
Only the most specific matcher on each route is used.
In the event of a sort tie, table weights are used across sub-tables, and route order is used within sub-tables.

For example, consider the following two sub-tables that are sorted by specificity and the resulting route list.

Sub-table A, with a table weight of 1 in case of sort ties:
- prefix: /foo
- prefix: /foo/more/specific
- prefix: /foo/even/more/specific
- exact: /foo/exact
- exact: /foo/another/exact
- regex: /foo/*
- regex: /fooo/*
Sub-table B, with a table weight of 2:
- prefix: /bar
- prefix: /bar/more/specific
- prefix: /bar/even/more/specific
- exact: /bar/exact
- regex: /bar/*

The resulting routes are sorted in this order:

exact: /foo/another/exact
exact: /bar/exact
exact: /foo/exact
regex: /bar/*
regex: /foo/*
regex: /fooo/*
prefix: /bar/even/more/specific
prefix: /foo/even/more/specific
prefix: /bar/more/specific
prefix: /foo/more/specific
prefix: /bar
prefix: /foo

In the spec section, do not include the hosts or workloadSelectors fields. The root route table dictates these fields instead.
Optional: If you want to refer to the sub-tables by label rather than by table name, add a label in the metadata section. Be sure to use the same label for each sub-table.

Example: Say that you are testing multiple types of request matching for myapp. You define two different route tables, one for exact and one for prefix matching, and label them as table: myapp. Your route tables might look like the following:

apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: exact-match
  namespace: global
  # Label for the sub-table set
  labels:
    table: myapp
spec:
  hosts:
    - 'one.solo.io'
  virtualGateways:
    - name: istio-ingressgateway
      namespace: bookinfo
      cluster: ${CLUSTER_NAME}
  http:
  # Match only requests to exactly 'one.solo.io/myapp/foo'
  - matchers:
    - uri:
        exact: /myapp/foo
    forwardTo:
      destinations:
      - ref:
          name: myapp
          namespace: global
          cluster: ${CLUSTER_NAME}
        port:
          number: 8090
        kind: SERVICE
---
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: prefix-match
  namespace: global
  # Label for the sub-table set
  labels:
    table: myapp
spec:
  hosts:
    - 'one.solo.io'
  virtualGateways:
    - name: istio-ingressgateway
      namespace: bookinfo
      cluster: ${CLUSTER_NAME}
  http:
  # Match any requests to 'one.solo.io/myapp/.*'
  - matchers:
    - uri:
        prefix: /myapp
        ignoreCase: true
    forwardTo:
      destinations:
      - ref:
          name: myapp
          namespace: global
          cluster: ${CLUSTER_NAME}
        port:
          number: 8090
        kind: SERVICE

Create the root route table to delegate requests based on individual route specificity. In this example root table, requests to the myapp.global.svc.cluster.local host are matched against the list of all routes in sub-tables with the table: myapp label, sorted by specificity. The request is matched to the most specific route. Note that you can also specify the sub-table names instead of the label by using the routeTables.name field.

kubectl apply --context $REMOTE_CONTEXT1 -n global -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: delegate-specificity
  namespace: global
spec:
  hosts:
    - 'myapp.global.svc.cluster.local'
  http:
  - delegate:
      # Selects tables based on label
      routeTables:
        - labels:
            table: myapp
      # Delegates based on route specificity
      sortMethod: ROUTE_SPECIFICITY
EOF