Application Boot-up Process

Concepts

The startup process of a service provider includes initializing Log4j, loading bean(including its parameters), and registering service.

• Initialize Log4j:

  By default, Log4jUtils merges the log4j configurations from classpath\*:config/base/log4j.properties and classpath\*:config/log4j.properties, then transfer them to log4j's PropertyConfigurator method to initialize it. If the configuration file with the highest priority is stored on the disk directory with write permission, the combined configuration will be saved to this location to view which parameters take effect during maintenance.

• Load the bean.

  By default BeanUtils loads the configuration file from the classpath\*:META-INF/spring/\*.bean.xml and transfer the configuration to ClassPathXmlApplicationContext of the Spring framework to load the application context. The bean of foundation-config module will be loaded during the process.

• Register the service.

  When Spring context is loaded, org.apache.servicecomb.core.CseApplicationListener will load the handlers configurations and providers' schema info, then register the microservice in the Service Center.

NOTE:

ServiceComb has 3 configuration sources: configuration center, environment variables and local files, with priorities from high to low. If there are configuration items with the same name in different sources, then items with lower priority will be overwritten. Configuration items stored in the configuration center can be modified at runtime.