Load Balancer Routing
If you have an API that is hosted at two or more endpoints, you can use the load balancing option to distribute requests among the endpoints. Requests are distributed across multiple endpoints. The requests are routed based on the round-robin strategy. The load for a service is balanced by directing requests to two or more services in a pool, until the optimum level is achieved. The application routes requests to services in the pool sequentially, starting from the first to the last service without considering the individual performance of the services. After the requests have been forwarded to all the services in the pool, the first service is chosen for the next loop of forwarding.
If the entry protocol is HTTP or HTTPS, you can select the Load Balancer routing.
| Property | Description |
|---|---|
| Route To. Specifies the URLs of two or more native services in a pool to which the requests are routed. | |
| Endpoint URI | Specifies the URI of the native API
endpoint to route the request to in case all routing rules evaluate to False.
Service registries that have been added to the API Gateway instance are also
included in the list.
If you choose a service registry, API Gateway sends a request to the service registry to discover the IP address and port at which the native service is running. API Gateway replaces the service registry alias in the Endpoint URI with the IP address and port returned by the service registry. For example, if your service is hosted at the URL:
As this property supports variable framework, you can make
use of the available variables. For example, you can configure the endpoint URI
using hard coded URL, simple alias, endpoint alias, and variable syntax or any
of these combination. If you define the endpoint URI as
For details about the variables available in API Gateway, see Variables Available in API Gateway. Note: If you use endpoint alias, make sure the endpoint alias
is created before you define it in the policy. For example, if you define
${alias} syntax in the policy before creating the
alias as endpoint alias,
API Gateway
considers ${alias} as custom variable or simple alias and tries to resolve
against those. So in that case, after creating endpoint alias you have to edit
and save the API or policy to associate ${alias} syntax with the endpoint
alias.
|
| HTTP Method | This is applicable to REST APIs.
Specifies the available routing methods: GET, POST, PUT, DELETE, and CUSTOM (default). When CUSTOM is selected, the HTTP method in the incoming request is sent to the native service. When other methods are selected, the selected method is used in the request sent to the native service. |
| SOAP Optimization Method | This is applicable for SOAP-based APIs.
Specifies the optimization methods that API Gateway can use to parse SOAP requests to the native API. Select one of the following options:
|
| HTTP Connection Timeout (seconds) | Specifies the time interval (in seconds)
after which a connection attempt times out.
The precedence of the Connection Timeout configuration is as follows:
|
| Read Timeout (seconds) | Specifies the time interval (in seconds)
after which a socket read attempt times out.
The precedence of the Read Timeout configuration is as follows:
|
| Native Service Timeout (seconds) | Specifies the time interval (in seconds) after which an HTTP
connection attempt when calling the Integration Server HTTP backend service
pub.client:http for REST APIs times out. The precedence of the Native Service Timeout configuration is as follows.
When a native service timeout is defined for an API, both the connection timeout and the read timeout values are set to the value of the native service timeout during the connection process to the native service. |
| Suspend duration (seconds) | A numeric timeout value (in seconds). The
default value is 30.
This property specifies the time, in seconds, for which API Gateway temporarily suspends an endpoint, whenever Read time-out or Connection time-out occurs for the endpoint, and routes the request to the next configured endpoint in this time interval. For example: If you have 3 endpoints configured endpoint #1, endpoint #2, and endpoint #3, the suspend duration is configured as 60 seconds for endpoint #2, and there is a Read Timeout or Connection Timeout for endpoint #2, then API Gateway temporarily suspends endpoint #2 for 60 seconds. In this time interval API Gateway skips endpoint #2 while routing the requests to the configured endpoints. Request 1 -> endpoint #1 Request 2 -> endpoint #3 (endpoint #2 is suspended for 60 seconds and hence the request is sent to endpoint #3 Request 3 -> endpoint #1 |
| Pass WS-Security Headers | This is applicable for SOAP-based APIs.
Selecting this indicates that API Gateway should pass the WS-Security headers of the incoming requests to the native API. |
| SSL Configuration. Configures keystore, key alias, and truststore for securing connections to native APIs. | |
| Keystore Alias | Specifies the keystore alias configured
in
API Gateway.
This value (along with the value of Client Certificate Alias) is used for
performing SSL client authentication.
Lists all available keystores. If you have not configured any keystore, the list is empty. |
| Key Alias | Specifies the alias for the private key, which must be stored in the keystore specified by the above keystore alias. |
| Truststore Alias | Specifies the alias for the truststore
that contains the list of CA certificates that API Gateway uses to validate the
trust relationship with the native API.
If you do not configure any truststore alias, it implies that API Gateway does not validate the certificates provided by native APIs. |
| Service Registry Configuration | |
| Service Discovery Endpoint Parameter | Values required for constructing the
discovery service URI.
For example: if the service registry configuration of the service registry that you have selected in Endpoint URI has Service discovery path set to /catalog/service/{serviceName} (and the {serviceName} alias is intended for passing the service name), you must enter {serviceName} as Parameter and the name of the service as Value. As the Value field supports variable framework, you can make use of the available variables as path parameters. For example, if you provide a parameter as
{serviceName}( in
Service discovery path while you
define a service register) and the corresponding values for the path parameter
as
For details about the variables available in API Gateway, see Variables Available in API Gateway. |
Failover behavior during load balancing
When an endpoint that is configured in Load balancer routing returns any of these exceptions - ConnectException, MalformedURLException, NoRouteToHostException, ProtocolException, SocketTimeoutException, UnknownHostException, UnknownServiceException - then API Gateway treats the endpoint to be inactive and routes to the next endpoint as per the round-robin strategy. In this case, the endpoint is suspended for the duration mentioned in the suspendDuration parameter (default is 30s), which indicates the duration to suspend the endpoint without repeatedly trying to reach it.
In this way API Gateway tries to invoke all the endpoints configured in the load balance routing. If all endpoints return downtime error, API Gateway returns a Service is down error.
If an endpoint returns an exception other than the Downtime exception then that exception is sent to the client and the remaining endpoints are not invoked.
You can control the behavior of considering Downtime exceptions only for load balancing through the extended property pg.lb.failoverOnDowntimeErrorOnly, which you can set through Administration > General > Extended settings page. The default value of this property is true. If you set the value to false all failures from the endpoint are treated as downtime and load balancing takes place.