Microservices Engine:Conditional registration for graceful start (public preview)

When to use conditional registration

Use conditional registration instead of fixed-delay registration when your application:

• Loads caches, precomputes indexes, or performs other asynchronous initialization with unpredictable duration.

• Depends on local resource readiness that cannot be expressed as a simple time delay.

• Requires precise control over when the service starts accepting microservice traffic.

If your initialization timing is predictable, fixed-delay registration is simpler and sufficient. If you are new to the graceful start and shutdown features of MSE, use the fixed-delay registration solution first. It covers most typical application scenarios. Conditional registration requires a code change in your application -- evaluate this trade-off before proceeding.

How it works

The MSE agent polls a Java system property that you define in the startup parameters or environment variables. Your application sets this property to true after it completes its custom initialization logic. When the agent detects the property value, it triggers microservice registration.

Before the condition is met, the service is not registered and receives no traffic.

Prerequisites

Before you begin, make sure that you have:

• MSE agent version 4.6.0 or later. See Specify an MSE agent version

Declare the condition key

Add the following configuration to your application's startup parameters or environment variables to declare the system property key used as the registration condition.

Format:

mse_lossless_register_condition_on_system_property_true="<your-condition-key>"

Example:

# Use PRODUCT_PRELOAD_COMPLETED as the registration condition key
mse_lossless_register_condition_on_system_property_true="PRODUCT_PRELOAD_COMPLETED"

Replace <your-condition-key> with a descriptive name that reflects your initialization logic.

Set the condition in your application code

After all initialization tasks are complete, call System.setProperty to set the condition key to true. The MSE agent detects this change and registers the service.

In the following example, a product cache loads asynchronously. After the cache is ready, the code sets the system property to signal readiness:

@Component
public class HotProductInitComponent {
    public ScheduledExecutorService executor = Executors.newScheduledThreadPool(
            1,
            new NameThreadFactory("product-preload-pool"));

    @Value("${demo.product.init.delay.seconds:3}")
    public long initDelaySeconds;

    public void asyncLoadPoductDataIntoCache() {
        executor.schedule(() -> {
            // ... load product data into cache ...

            // Signal that initialization is complete.
            // The MSE agent detects this and registers the service.
            System.setProperty("PRODUCT_PRELOAD_COMPLETED", "true");

        }, initDelaySeconds, TimeUnit.SECONDS);
    }
}

Interaction with other MSE features