Service Router

Service Router

v1.8.4+: On Kubernetes, the ServiceRouter custom resource is supported in Consul versions 1.8.4+.
v1.6.0+: On other platforms, this config entry is supported in Consul versions 1.6.0+.

The service-router config entry kind (ServiceRouter on Kubernetes) controls Connect traffic routing and manipulation at networking layer 7 (e.g. HTTP).

If a router is not explicitly configured or is configured with no routes then the system behaves as if a router were configured sending all traffic to a service of the same name.

Interaction with other Config Entries

Service router config entries are a component of L7 Traffic Management.
Service router config entries are restricted to only services that define their protocol as HTTP-based via a corresponding service-defaults config entry or globally via proxy-defaults .
Any route destination that omits the ServiceSubset field is eligible for splitting via a service-splitter should one be configured for that service, otherwise resolution proceeds according to any configured service-resolver.

Sample Config Entries

Path prefix matching

Route HTTP requests with a path starting with /admin to a different service:

HCL

HCL
Kubernetes YAML
JSON

Kind = "service-router"
Name = "web"
Routes = [
  {
    Match {
      HTTP {
        PathPrefix = "/admin"
      }
    }
    Destination {
      Service = "admin"
    }
  },
  # NOTE: a default catch-all will send unmatched traffic to "web"
]

apiVersion: consul.hashicorp.com/v1alpha1
kind: ServiceRouter
metadata:
  name: web
spec:
  routes:
    - match:
        http:
          pathPrefix: /admin
      destination:
        service: admin
  # NOTE: a default catch-all will send unmatched traffic to "web"

{
  "Kind": "service-router",
  "Name": "web",
  "Routes": [
    {
      "Match": {
        "HTTP": {
          "PathPrefix": "/admin"
        }
      },
      "Destination": {
        "Service": "admin"
      }
    }
  ]
}

Header/query parameter matching

Route HTTP requests with a special URL parameter or header to a canary subset:

HCL

HCL
Kubernetes YAML
JSON

Kind = "service-router"
Name = "web"
Routes = [
  {
    Match {
      HTTP {
        Header = [
          {
            Name  = "x-debug"
            Exact = "1"
          },
        ]
      }
    }
    Destination {
      Service       = "web"
      ServiceSubset = "canary"
    }
  },
  {
    Match {
      HTTP {
        QueryParam = [
          {
            Name  = "x-debug"
            Exact = "1"
          },
        ]
      }
    }
    Destination {
      Service       = "web"
      ServiceSubset = "canary"
    }
  },
  # NOTE: a default catch-all will send unmatched traffic to "web"
]

apiVersion: consul.hashicorp.com/v1alpha1
kind: ServiceRouter
metadata:
  name: web
spec:
  routes:
    - match:
        http:
          header:
            - name: x-debug
              exact: '1'
      destination:
        service: web
        serviceSubset: canary
    - match:
        http:
          queryParam:
            - name: x-debug
              exact: '1'
      destination:
        service: web
        serviceSubset: canary
  # NOTE: a default catch-all will send unmatched traffic to "web"

{
  "Kind": "service-router",
  "Name": "web",
  "Routes": [
    {
      "Match": {
        "HTTP": {
          "Header": [
            {
              "Name": "x-debug",
              "Exact": "1"
            }
          ]
        }
      },
      "Destination": {
        "Service": "web",
        "ServiceSubset": "canary"
      }
    },
    {
      "Match": {
        "HTTP": {
          "QueryParam": [
            {
              "Name": "x-debug",
              "Exact": "1"
            }
          ]
        }
      },
      "Destination": {
        "Service": "web",
        "ServiceSubset": "canary"
      }
    }
  ]
}

gRPC routing

Re-route a gRPC method to another service. Since gRPC method calls are HTTP/2, we can use an HTTP path match rule to re-route traffic:

HCL

HCL
Kubernetes YAML
JSON

Kind = "service-router"
Name = "billing"
Routes = [
  {
    Match {
      HTTP {
        PathExact = "/mycompany.BillingService/GenerateInvoice"
      }
    }
    Destination {
      Service = "invoice-generator"
    }
  },
  # NOTE: a default catch-all will send unmatched traffic to "billing"
]

apiVersion: consul.hashicorp.com/v1alpha1
kind: ServiceRouter
metadata:
  name: billing
spec:
  routes:
    - match:
        http:
          pathExact: /mycompany.BillingService/GenerateInvoice
      destination:
        service: invoice-generator
  # NOTE: a default catch-all will send unmatched traffic to "billing"

{
  "Kind": "service-router",
  "Name": "billing",
  "Routes": [
    {
      "Match": {
        "HTTP": {
          "PathExact": "/mycompany.BillingService/GenerateInvoice"
        }
      },
      "Destination": {
        "Service": "invoice-generator"
      }
    }
  ]
}

Available Fields

Kind - Must be set to service-router
Name (string: <required>) - Set to the name of the service being configured.
Namespace (string: "default")

Enterprise

- Specifies the namespace the config entry will apply to.
Meta (map<string|string>: nil) - Specifies arbitrary KV metadata pairs. Added in Consul 1.8.4.
Routes (array<ServiceRoute>) - The list of routes to consider when processing L7 requests. The first route to match in the list is terminal and stops further evaluation. Traffic that fails to match any of the provided routes will be routed to the default service.
- Match (ServiceRouteMatch: <optional>) - A set of criteria that can match incoming L7 requests. If empty or omitted it acts as a catch-all.
  - HTTP (ServiceRouteHTTPMatch: <optional>) - A set of HTTP-specific match criteria.
- Destination (ServiceRouteDestination: <optional>) - Controls how to proxy the matching request(s) to a service.

`ServiceRouteHTTPMatch`

PathExact (string: "") - Exact path to match on the HTTP request path.

At most only one of PathExact, PathPrefix, or PathRegex may be configured.
PathPrefix (string: "") - Path prefix to match on the HTTP request path.

At most only one of PathExact, PathPrefix, or PathRegex may be configured.
PathRegex (string: "") - Regular expression to match on the HTTP request path.

The syntax is described below.

At most only one of PathExact, PathPrefix, or PathRegex may be configured.
Methods (array<string>) - A list of HTTP methods for which this match applies. If unspecified all HTTP methods are matched. If provided the names must be a valid method.
Header (array<ServiceRouteHTTPMatchHeader>)) - A set of criteria that can match on HTTP request headers. If more than one is configured all must match for the overall match to apply.
- Name (string: <required>) - Name of the header to match.
- Present (bool: false) - Match if the header with the given name is present with any value.
  
  At most only one of Exact, Prefix, Suffix, Regex, or Present may be configured.
- Exact (string: "") - Match if the header with the given name is this value.
  
  At most only one of Exact, Prefix, Suffix, Regex, or Present may be configured.
- Prefix (string: "") - Match if the header with the given name has this prefix.
  
  At most only one of Exact, Prefix, Suffix, Regex, or Present may be configured.
- Suffix (string: "") - Match if the header with the given name has this suffix.
  
  At most only one of Exact, Prefix, Suffix, Regex, or Present may be configured.
- Regex (string: "") - Match if the header with the given name matches this pattern.
  
  The syntax is described below.
  
  At most only one of Exact, Prefix, Suffix, Regex, or Present may be configured.
- Invert (bool: false) - Inverts the logic of the match
QueryParam (array<ServiceRouteHTTPMatchQueryParam>)) - A set of criteria that can match on HTTP query parameters. If more than one is configured all must match for the overall match to apply.
- Name (string: <required>) - The name of the query parameter to match on.
- Present (bool: false) - Match if the query parameter with the given name is present with any value.
  
  At most only one of Exact, Regex, or Present may be configured.
- Exact (string: "") - Match if the query parameter with the given name is this value.
  
  At most only one of Exact, Regex, or Present may be configured.
- Regex (string: "") - Match if the query parameter with the given name matches this pattern.
  
  The syntax is described below.
  
  At most only one of Exact, Regex, or Present may be configured.

`ServiceRouteDestination`

Service (string: "") - The service to resolve instead of the default service. If empty then the default service name is used.
ServiceSubset (string: "") - A named subset of the given service to resolve instead of the one defined as that service’s DefaultSubset. If empty, the default subset is used.
Namespace (string: "")

Enterprise

- The Consul namespace to resolve the service from instead of the current namespace. If empty the current namespace is assumed.
PrefixRewrite (string: "") - Defines how to rewrite the HTTP request path before proxying it to its final destination.

This requires that either Match.HTTP.PathPrefix or Match.HTTP.PathExact be configured on this route.
RequestTimeout (duration: 0) - The total amount of time permitted for the entire downstream request (and retries) to be processed.
NumRetries (int: 0) - The number of times to retry the request when a retryable result occurs.
RetryOnConnectFailure (bool: false) - Allows for connection failure errors to trigger a retry.
RetryOnStatusCodes (array<int>) - A list of HTTP response status codes that are eligible for retry.

ACLs

Configuration entries may be protected by ACLs.

Reading a service-router config entry requires service:read on the resource.

Creating, updating, or deleting a service-router config entry requires service:write on the resource and service:read on any other service referenced by name in these fields:

Routes[].Destination.Service

Regular Expression Syntax

The actual syntax of the regular expression fields described here is entirely proxy-specific.

When using Envoy as a proxy (the only supported proxy in Kubernetes), the syntax for these fields is version specific:

Envoy Version	Syntax
1.11.2 or newer	documentation
1.11.1 or older	documentation