public AgentConfigurations getAgentConfigurations(String service) {
        AgentConfigurations agentConfigurations = agentConfigurationsTable.getAgentConfigurationsCache().get(service);
        if (null == agentConfigurations) {
            return emptyAgentConfigurations;
        } else {
            return agentConfigurations;
        }
    }
Get service dynamic configuration information, if there is no dynamic configuration information, return to empty
dynamic configuration to prevent the server from deleted the dynamic configuration, but it does not take effect
on the agent side.

@param service Service name to be queried
@return Service dynamic configuration information
oap-server/server-receiver-plugin/configuration-discovery-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/receiver/configuration/discovery/AgentConfigurationsWatcher.java