7.1.5 Configuring HTTP clients

Global Configuration for All Clients

The default HTTP client configuration is a Configuration Properties called DefaultHttpClientConfiguration that allows configuring the default behaviour for all HTTP clients. For example, in application.yml:

Altering default HTTP client configuration

micronaut:
    http:
        client:
            read-timeout: 5s

The above example sets of readTimeout property of the HttpClientConfiguration class.

Client Specific Configuration

If you wish to have a separate configuration per client then there a couple of options. You can configure Service Discovery manually in application.yml and apply per-client configuration:

Manually configuring HTTP services

micronaut:
    http:
        services:
            foo:
                urls:
                    - http://foo1
                    - http://foo2
                read-timeout: 5s (1)

WARN: This client configuration can be used in conjunction with the @Client annotation, either by injecting an HttpClient directly or use on a client interface. In any case, all other attributes on the annotation will be ignored other than the service id.

Then simply inject the named client configuration:

Injecting an HTTP client

@Client("foo") @Inject RxHttpClient httpClient;

You can also simply define a bean that extends from HttpClientConfiguration and ensuring that the javax.inject.Named annotation is used to name it appropriately:

Defining an HTTP client configuration bean

@Named("twitter")
@Singleton
class TwitterHttpClientConfiguration extends HttpClientConfiguration {
   public TwitterHttpClientConfiguration(ApplicationConfiguration applicationConfiguration) {
        super(applicationConfiguration);
    }
}

This configuration will then be picked up if you inject a service called twitter using @Client using Service Discovery:

Injecting an HTTP client

@Client("twitter") @Inject RxHttpClient httpClient;

Alternatively if you are not using service discovery then you can use the configuration member of @Client to refer to a specific type:

Injecting an HTTP client

@Client(value="https://api.twitter.com/1.1",
        configuration=TwitterHttpClientConfiguration.class)
@Inject
RxHttpClient httpClient;

Using HTTP Client Connection Pooling

If you have a client that needs to handle a significant number of requests then you can benefit from enabling HTTP client connection pooling. The following configuration will enable pooling for the foo client:

Manually configuring HTTP services

micronaut:
    http:
        services:
            foo:
                urls:
                    - http://foo1
                    - http://foo2
                pool:
                    enabled: true (1)
                    max-connections: 50 (2)

See the API for ConnectionPoolConfiguration for details on available options to configure the pool.

Configuring Event Loop Groups

By default Micronaut will share a common Netty EventLoopGroup for worker threads and all HTTP clients threads.

This common EventLoopGroup can be configured via the micronaut.netty.event-loops.default property:

Configuring The Default Event Loop

micronaut:
    netty:
        event-loops:
            default:
                num-threads: 10
                prefer-native-transport: true

You can also use the micronaut.netty.event-loops setting to configure one or more additional event loops. The following table summarizes the properties:

🔗

For example, if your interactions with an HTTP client involve CPU intensive work it may be worthwhile configuring a separate EventLoopGroup for one or all clients.

The following example configures an additional event loop group called “other” that uses 10 threads:

Configuring Additional Event Loops

micronaut:
    netty:
        event-loops:
            other:
                num-threads: 10
                prefer-native-transport: true

Once an additional event loop has been configured you can alter the HTTP client configuration to use the newly defined event loop group:

Altering the Event Loop Group used by Clients

micronaut:
    http:
        client:
            event-loop-group: other