java - 用于 Java/Spring 配置的 ZooKeeper？

Question

是否有任何使用 Apache ZooKeeper 用于分发 Java 应用程序配置(尤其是 Spring 服务)的有据可查的用例？

像许多云服务用户一样，我需要更改大量 Java 服务的配置，最好在运行时更改，而无需重新启动服务。

更新

最终我写了一些东西，将 ZooKeeper 节点加载为属性文件，并创建一个 ResourcePropertySource 并将其插入到 Spring 上下文中。请注意，这不会反射(reflect)上下文启动后 ZooKeeper 节点中的更改。

public class ZooKeeperPropertiesApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
    private static final Logger logger = LoggerFactory.getLogger(ZooKeeperPropertiesApplicationContextInitializer.class);

    private final CuratorFramework curator;
    private String projectName;
    private String projectVersion;

    public ZooKeeperPropertiesApplicationContextInitializer() throws IOException {
        logger.trace("Attempting to construct CuratorFramework instance");

        RetryPolicy retryPolicy = new ExponentialBackoffRetry(10, 100);
        curator = CuratorFrameworkFactory.newClient("zookeeper", retryPolicy);
        curator.start();
    }

    /**
     * Add a primary property source to the application context, populated from
     * a pre-existing ZooKeeper node.
     */
    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        logger.trace("Attempting to add ZooKeeper-derived properties to ApplicationContext PropertySources");

        try {
            populateProjectProperties();
            Properties properties = populatePropertiesFromZooKeeper();
            PropertiesPropertySource propertySource = new PropertiesPropertySource("zookeeper", properties);
            applicationContext.getEnvironment().getPropertySources().addFirst(propertySource);

            logger.debug("Added ZooKeeper-derived properties to ApplicationContext PropertySources");
            curator.close();
        } catch (IOException e) {
            logger.error("IO error attempting to load properties from ZooKeeper", e);
            throw new IllegalStateException("Could not load ZooKeeper configuration");
        } catch (Exception e) {
            logger.error("IO error attempting to load properties from ZooKeeper", e);
            throw new IllegalStateException("Could not load ZooKeeper configuration");
        } finally {
            if (curator != null && curator.isStarted()) {
                curator.close();
            }
        }
    }

    /**
     * Populate the Maven artifact name and version from a property file that
     * should be on the classpath, with values entered via Maven filtering.
     * 
     * There is a way of doing these with manifests, but it's a right faff when
     * creating shaded uber-jars.
     * 
     * @throws IOException
     */
    private void populateProjectProperties() throws IOException {
        logger.trace("Attempting to get project name and version from properties file");

        try {
            ResourcePropertySource projectProps = new ResourcePropertySource("project.properties");
            this.projectName = (String) projectProps.getProperty("project.name");
            this.projectVersion = (String) projectProps.getProperty("project.version");
        } catch (IOException e) {
            logger.error("IO error trying to find project name and version, in order to get properties from ZooKeeper");
        }
    }

    /**
     * Do the actual loading of properties.
     * 
     * @return
     * @throws Exception
     * @throws IOException
     */
    private Properties populatePropertiesFromZooKeeper() throws Exception, IOException {
        logger.debug("Attempting to get properties from ZooKeeper");

        try {
            byte[] bytes = curator.getData().forPath("/distributed-config/" + projectName + "/" + projectVersion);
            InputStream in = new ByteArrayInputStream(bytes);
            Properties properties = new Properties();
            properties.load(in);
            return properties;
        } catch (NoNodeException e) {
            logger.error("Could not load application configuration from ZooKeeper as no node existed for project [{}]:[{}]", projectName, projectVersion);
            throw e;
        }

    }

}

Answer 1

你应该考虑 Spring Cloud Config:

http://projects.spring.io/spring-cloud/

Spring Cloud Config Centralized external configuration management backed by a git repository. The configuration resources map directly to Spring Environment but could be used by non-Spring applications if desired.

这里有源代码:

https://github.com/spring-cloud/spring-cloud-config

此处的示例应用程序:

https://github.com/spring-cloud/spring-cloud-config/blob/master/spring-cloud-config-sample/src/main/java/sample/Application.java