在众多的zookeeper客户端工具中，elastic-job拥抱了Curator，而不是ZKClient，或者原生的zookeeper原生的客户端 。
先看一下Elastic-Job引入的依赖：
curator.png
从图中看，引入了curator-client, curator-framework,curator-recipes。他们各自是做了哪些事情？(答案来自搜索引擎)
- curator-framework：对zookeeper的底层api的一些封装
- curator-client：提供一些客户端的操作，例如重试策略等
- curator-recipes：封装了一些高级特性，如：Cache事件监听、选举、分布式锁、分布式计数器、分布式Barrier等
注册中心的设计.png
看类图，在elasticJob中，所有的关于zk的操作都会交给ZookeeperRegistryCenter该对象去协调，在这里去初始化zookeeper，操作节点，使用缓存等。
elastic-Job创建zk的Client方法：
public void init() {
CuratorFrameworkFactory.Builder builder = CuratorFrameworkFactory
.builder()
.connectString(zkConfig.getServerLists())
.retryPolicy(new ExponentialBackoffRetry( //重试策略
zkConfig.getBaseSleepTimeMilliseconds()
, zkConfig.getMaxRetries(), zkConfig.getMaxSleepTimeMilliseconds()))
.namespace(zkConfig.getNamespace());//设置namespace
builder.sessionTimeoutMs(zkConfig.getSessionTimeoutMilliseconds());//session超时时间 if条件忽略
builder.connectionTimeoutMs(zkConfig.getConnectionTimeoutMilliseconds());//连接超时时间 if条件忽略
builder.authorization("digest", zkConfig.getDigest().getBytes(Charsets.UTF_8))
//令牌验证 if条件忽略
.aclProvider(new ACLProvider() {
@Override
public List getDefaultAcl() {
return ZooDefs.Ids.CREATOR_ALL_ACL;
}
@Override
public List getAclForPath(final String path) {
return ZooDefs.Ids.CREATOR_ALL_ACL;
}
});
}
client = builder.build(); //创建了client
client.start();
try {
//阻塞，等到连接成功，或者连接重试超时
if (!client.blockUntilConnected(
zkConfig.getMaxSleepTimeMilliseconds() *
zkConfig.getMaxRetries(), TimeUnit.MILLISECONDS)) {
client.close();
throw new KeeperException.OperationTimeoutException();
}
} catch (final Exception ex) {
RegExceptionHandler.handleException(ex);
}
｝
关闭zookeeper：
@Override
public void close() {
for (Entry each : caches.entrySet()) {
each.getValue().close(); //先关缓存
}
//等到缓存关闭 这里是用线程等待 因为关闭缓存和client都是异步，关闭client之前需要关闭缓存
waitForCacheClose(); // Thread.sleep(500L);
CloseableUtils.closeQuietly(client); //关闭zkClient
}
获取节点：
@Override
public String get(final String key) {
TreeCache cache = findTreeCache(key); //从caches 中获取treeCache
if (null == cache) {
return getDirectly(key); //获取不到，直接从注册中心获取
}
ChildData resultInCache = cache.getCurrentData(key);
//缓存中获取不到，再从注册中心获取
if (null != resultInCache) {
return null == resultInCache.getData() ? null : new String(resultInCache.getData(), Charsets.UTF_8);
}
return getDirectly(key);
}
直接从注册中心获取，使用api:client.getData().forPath(key)：
@Override
public String getDirectly(final String key) {
try {
return new String(client.getData().forPath(key), Charsets.UTF_8);
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
return null;
}
}
获取注册中心子节点集合：client.getChildren().forPath(key)
@Override
public List getChildrenKeys(final String key) {
try {
List result = client.getChildren().forPath(key);
Collections.sort(result, new Comparator() {
@Override
public int compare(final String o1, final String o2) {
return o2.compareTo(o1);
}
});
return result;
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
return Collections.emptyList();
}
}
获取子节点数量：client.checkExists().forPath(key).getNumChildren();
@Override
public int getNumChildren(final String key) {
try {
Stat stat = client.checkExists().forPath(key);
if (null != stat) {
return stat.getNumChildren();
}
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
return 0;
}
判断节点是否存在：null!=client.checkExists().forPath(key)
@Override
public boolean isExisted(final String key) {
try {
return null != client.checkExists().forPath(key);
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
return false;
}
}
创建节点：client.create().creatingParentsIfNeeded().withMode(CreateMode.PERSISTENT).forPath(key,value);
//判断节点是否存在，存在更新，不存在创建
@Override
public void persist(final String key, final String value) {
try {
if (!isExisted(key)) {
client.create().creatingParentsIfNeeded()
.withMode(CreateMode.PERSISTENT)
.forPath(key, value.getBytes(Charsets.UTF_8));
} else {
update(key, value);
}
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
}
更新节点：client.inTransaction().check().forPath(key).and().setData().forPath(key,value).and().commit();
@Override
public void update(final String key, final String value) {
try {
client.inTransaction().check()
.forPath(key)
.and()
.setData()
.forPath(key, value.getBytes(Charsets.UTF_8)).and().commit();
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
}
插入临时节点client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(key,value);
//如果节点存在，先删除，然后再创建临时节点
@Override
public void persistEphemeral(final String key, final String value) {
try {
if (isExisted(key)) {
client.delete().deletingChildrenIfNeeded().forPath(key);
}
client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(key, value.getBytes(Charsets.UTF_8));
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
}
持久化顺序注册数据client.create().creatingParentsIfNeeded().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath(key,value);
@Override
public String persistSequential(final String key, final String value) {
try {
return client
.create()
.creatingParentsIfNeeded()
.withMode(CreateMode.PERSISTENT_SEQUENTIAL)
.forPath(key, value.getBytes(Charsets.UTF_8));
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
return null;
}
持久化顺序临时注册数据client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath(key,value);
@Override
public String persistEphemeralSequential(final String key, final String value) {
try {
return client
.create()
.creatingParentsIfNeeded()
.withMode(CreateMode.EPHEMERAL_SEQUENTIAL)
.forPath(key, value.getBytes(Charsets.UTF_8));
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
return null;
}
删除节点：client.delete().deletingChildrenIfNeeded().forPath(key);
@Override
public void remove(final String key) {
try {
client.delete().deletingChildrenIfNeeded().forPath(key);
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
}
获取节点注册时间：client.checkExists().forPath(key).getMtime();，
注册中心时间为创建一个临时节点，然后获取该节点时间。
@Override
public long getRegistryCenterTime(final String key) {
long result = 0L;
try {
persist(key, "");
result = client.checkExists().forPath(key).getMtime();
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
Preconditions.checkState(0L != result, "Cannot get registry center time.");
return result;
}
添加缓存数据： new TreeCache(client, cachePath).start();
@Override
public void addCacheData(final String cachePath) {
TreeCache cache = new TreeCache(client, cachePath);
try {
cache.start();
//CHECKSTYLE:OFF
} catch (final Exception ex) {
//CHECKSTYLE:ON
RegExceptionHandler.handleException(ex);
}
caches.put(cachePath + "/", cache);
}
删除缓存：将缓存从map中删除，关闭treeCache
@Override
public void evictCacheData(final String cachePath) {
TreeCache cache = caches.remove(cachePath + "/");
if (null != cache) {
cache.close();
}
}