private HealthCheckedEndpointGroup build(HealthCheckedEndpointGroupBuilder builder) {
        // Specify backoff explicitly to disable jitter.
        builder.retryBackoff(Backoff.fixed(RETRY_INTERVAL.toMillis()));
        builder.withClientOptions(b -> {
            b.decorator(LoggingClient.newDecorator());
            b.decorator((delegate, ctx, req) -> {
                // Record when health check requests were sent.
                final Queue<RequestLog> healthCheckRequestLogs = this.healthCheckRequestLogs;
                if (healthCheckRequestLogs != null) {
                    ctx.log().whenComplete().thenAccept(healthCheckRequestLogs::add);
                }
                return delegate.execute(ctx, req);
            });
            return b;
        });
        return builder.build();
    }
Makes sure the notification occurs as soon as possible thanks to long polling.
core/src/test/java/com/linecorp/armeria/client/endpoint/healthcheck/HealthCheckedEndpointGroupLongPollingTest.java