Router

A handler that performs the following tasks:

  • Defines the routes directory and loads routes into the configuration.

  • Depending on the scanning interval, periodically scans the routes directory and updates the IG configuration when routes are added, removed, or changed. The router updates the IG configuration without needing to restart IG or access the route.

  • Manages an internal list of routes, where routes are ordered lexicographically by route name. If a route is not named, then the route ID is used instead. For more information, see Route.

  • Routes requests to the first route in the internal list of routes, whose condition is satisfied.

    Because the list of routes is ordered lexicographically by route name, name your routes with this in mind:

    • If a request satisfies the condition of more than one route, it is routed to the first route in the list whose condition is met.

    • Even if the request matches a later route in the list, it might never reach that route.

    If a request does not satisfy the condition of any route, it is routed to the default handler if one is configured.

The router does not have to know about specific routes in advance - you can configure the router first and then add routes while IG is running.

Studio deploys and undeploys routes through a main router named _router, which is the name of the main router in the default configuration. If you use a custom config.json, make sure that it contains a main router named _router.

Usage

{
    "name": string,
    "type": "Router",
    "config": {
        "defaultHandler": Handler reference,
        "directory": expression,
        "scanInterval": duration string or integer
    }
}

An alternative value for type is RouterHandler.

Properties

"defaultHandler": Handler reference, optional

Handler to use when a request does not satisfy the condition of any route.

Provide either the name of a handler object defined in the heap, or an inline handler configuration object.

Default: If no default route is set either here or in the route configurations, IG aborts the request with an internal error.

See also Handlers.

"directory": expression, optional

Directory from which to load route configuration files.

Default: The default directory for route configuration files, at $HOME/.openig(on Windows, appdata\OpenIG).

With the following example, route configuration files are loaded from /path/to/safe/routes instead of from the default directory:

{
  "type": "Router",
  "config": {
    "directory": "/path/to/safe/routes"
  }
}
If you define multiple routers, configure directory so that the routers load route configuration files from different directories.

An infinite route-loading sequence is triggered when a router starts a route that, directly or indirectly, starts another router, which then loads route configuration files from the same directory.

See also Expressions.

"scanInterval": duration string or integer, optional

Time interval at which IG scans the specified directory for changes to routes. When a route is added, removed, or changed, the router updates the IG configuration without needing to restart IG or access the route.

When an integer is used for the scanInterval, the time unit is seconds.

To load routes at startup only, and prevent changes to the configuration if the routes are changed, set the scan interval to disabled.

Default: 10 seconds

Router Metrics at the Prometheus Scrape Endpoint

Router metrics at the Prometheus Scrape Endpoint have the following labels:

  • fully_qualified_name: Fully qualified name of the router, for example, gateway.main-router.

  • heap: Name of the heap in which this router is declared, for example, gateway.

  • name: Simple name declared in router configuration, for example, main-router.

The following table summarizes the recorded metrics:

Name Monitoring Type Description

ig_router_deployed_routes

Gauge

Number of routes deployed in the configuration.

For more information about the the Prometheus Scrape Endpoint, see Prometheus Scrape Endpoint.

Router Metrics at the Common REST Monitoring Endpoint

Router metrics at the Common REST Monitoring Endpoint are JSON objects, with the following form:

  • [heap name].[router name].deployed-routes

The following table summarizes the recorded metrics:

Name Monitoring Type Description

deployed-routes

Gauge

Number of routes deployed in the configuration.

For more information about the the Common REST Monitoring Endpoint, see Common REST Monitoring Endpoint.