public ServerGroupList build() {
        if (!agentSet.isEmpty()) {
            // if agent name exists (physical server exists)
            if (logger.isDebugEnabled()) {
                List<String> agents = agentSet.stream()
                        .map(AgentAndStatus::getAgentInfo)
                        .map(AgentInfo::getAgentId)
                        .toList();
                this.logger.debug("buildPhysicalServer: {}", agents);
            }
            return buildPhysicalServer(agentSet);
        } else {
            // otherwise, create logical name
            this.logger.debug("buildLogicalServer");
            AgentHistogramList agentHistogramList = agentHistogramBuilder.build();
            return buildLogicalServer(agentHistogramList);
        }
    }
filled with application information of physical server and service instance

@param hostHistogram
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/nodes/ServerBuilder.java