第七章 初始化配置

SkyWalking 初始化配置项

做了部分注释，源码如下：

public static void initialize(String agentOptions) throws ConfigNotFoundException, AgentPackageNotFoundException {
    InputStreamReader configFileStream;

    try {
        // 通过agent.config 配置文件 对应的属性值
        configFileStream = loadConfig();
        Properties properties = new Properties();
        properties.load(configFileStream);
        for (String key : properties.stringPropertyNames()) {
            String value = (String)properties.get(key);
            //replace the key's value. properties.replace(key,value) in jdk8+
            properties.put(key, PropertyPlaceholderHelper.INSTANCE.replacePlaceholders(value, properties));
        }
        // 获取到的配置值，组装 config对象
        ConfigInitializer.initialize(properties, Config.class);
    } catch (Exception e) {
        logger.error(e, "Failed to read the config file, skywalking is going to run in default config.");
    }

    try {
        // 通过系统环境变量、覆盖相应变量
        overrideConfigBySystemProp();
    } catch (Exception e) {
        logger.error(e, "Failed to read the system properties.");
    }

    if (!StringUtil.isEmpty(agentOptions)) {
        try {
            agentOptions = agentOptions.trim();
            logger.info("Agent options is {}.", agentOptions);
            // 解析agent 参数 覆盖相应参数
            overrideConfigByAgentOptions(agentOptions);
        } catch (Exception e) {
            logger.error(e, "Failed to parse the agent options, val is {}.", agentOptions);
        }
    }

    if (StringUtil.isEmpty(Config.Agent.SERVICE_NAME)) {
        throw new ExceptionInInitializerError("`agent.service_name` is missing.");
    }
    if (StringUtil.isEmpty(Config.Collector.BACKEND_SERVICE)) {
        throw new ExceptionInInitializerError("`collector.backend_service` is missing.");
    }

    IS_INIT_COMPLETED = true;
}

图解

相对SkyWalking 配置加载相对比较简单。这个优先级规则还是需要在使用过程中记住的原则。