etcd的使用文章。
etcd來zookeeper類似,常用的主要有set,get,getPrefix:獲取指定前綴的所有數據,grant:key的超時設置,watch:監聽回調事件,watchPrefix:監聽某個前綴的事件,keepAlive:爲某個key設置自動續約、自動刷新過期時間。
zk的大部分功能,etcd都有。但有一個,譬如虛擬節點,zk可以做到當客戶端斷開時,立馬監聽到,etcd要靠keepAlive續約機制,超過幾秒不續約了,則認爲掉線了。
還有etcd的超時時間,是需要先新建一個lease,再把這個lease在put時,作爲參數傳過去。
別的不多講,直接上使用指南。
引入pom.xml,https://github.com/IBM/etcd-java 這是一個etcd的java客戶端。
<dependency>
<groupId>com.ibm.etcd</groupId>
<artifactId>etcd-java</artifactId>
<version>0.0.13</version>
</dependency>
自行下載etcd,並啓動它。
定義一個常用的客戶端工具類的接口
import com.ibm.etcd.api.KeyValue;
import com.ibm.etcd.client.kv.KvClient;
import java.util.List;
/**
* @author wuweifeng wrote on 2019-12-09
* @version 1.0
*/
public interface IConfigCenter {
/**
* 存入key,value
*/
void put(String key, String value);
/**
* 存入key、value,和租約id
*/
void put(String key, String value, long leaseId);
/**
* 存入key、value,和過期時間,單位是秒
*/
void putAndGrant(String key, String value, long ttl);
/**
* 根據key,獲取value
*/
String get(String key);
/**
* 獲取指定前綴的所有key-value
*/
List<KeyValue> getPrefix(String key);
/**
* 監聽key
*/
KvClient.WatchIterator watch(String key);
/**
* 監聽前綴爲key的
*/
KvClient.WatchIterator watchPrefix(String key);
/**
* 自動續約
* @param frequencySecs 續約頻率,最小是4秒,默認是5秒
* @param minTtl 最小存活時間,最小是2秒,默認是10秒
* @return 返回leaseId
*/
long keepAlive(String key, String value, int frequencySecs, int minTtl) throws Exception;
/**
* 判斷剩餘的過期時間
*/
long timeToLive(long leaseId);
}
實現這個接口
import com.google.protobuf.ByteString;
import com.ibm.etcd.api.KeyValue;
import com.ibm.etcd.api.LeaseGrantResponse;
import com.ibm.etcd.api.RangeResponse;
import com.ibm.etcd.client.KvStoreClient;
import com.ibm.etcd.client.kv.KvClient;
import com.ibm.etcd.client.lease.LeaseClient;
import com.ibm.etcd.client.lease.PersistentLease;
import com.ibm.etcd.client.lock.LockClient;
import org.springframework.util.CollectionUtils;
import java.util.List;
import java.util.concurrent.ExecutionException;
import static java.util.concurrent.TimeUnit.SECONDS;
/**
* etcd客戶端
*
* @author wuweifeng wrote on 2019-12-06
* @version 1.0
*/
public class JdEtcdClient implements IConfigCenter {
private KvClient kvClient;
private LeaseClient leaseClient;
private LockClient lockClient;
public JdEtcdClient(KvStoreClient kvStoreClient) {
this.kvClient = kvStoreClient.getKvClient();
this.leaseClient = kvStoreClient.getLeaseClient();
this.lockClient = kvStoreClient.getLockClient();
}
@Override
public void put(String key, String value) {
kvClient.put(ByteString.copyFromUtf8(key), ByteString.copyFromUtf8(value)).sync();
}
@Override
public void put(String key, String value, long leaseId) {
kvClient.put(ByteString.copyFromUtf8(key), ByteString.copyFromUtf8(value), leaseId).sync();
}
@Override
public void putAndGrant(String key, String value, long ttl) {
LeaseGrantResponse lease = leaseClient.grant(ttl).sync();
put(key, value, lease.getID());
}
@Override
public String get(String key) {
RangeResponse rangeResponse = kvClient.get(ByteString.copyFromUtf8(key)).sync();
List<KeyValue> keyValues = rangeResponse.getKvsList();
if (CollectionUtils.isEmpty(keyValues)) {
return null;
}
return keyValues.get(0).getValue().toStringUtf8();
}
@Override
public List<KeyValue> getPrefix(String key) {
RangeResponse rangeResponse = kvClient.get(ByteString.copyFromUtf8(key)).asPrefix().sync();
return rangeResponse.getKvsList();
}
@Override
public KvClient.WatchIterator watch(String key) {
return kvClient.watch(ByteString.copyFromUtf8(key)).start();
}
@Override
public KvClient.WatchIterator watchPrefix(String key) {
return kvClient.watch(ByteString.copyFromUtf8(key)).asPrefix().start();
}
@Override
public long keepAlive(String key, String value, int frequencySecs, int minTtl) throws Exception {
//minTtl秒租期,每frequencySecs秒續約一下
PersistentLease lease = leaseClient.maintain().leaseId(SystemClock.now()).keepAliveFreq(frequencySecs).minTtl(minTtl).start();
long newId = lease.get(3L, SECONDS);
put(key, value, newId);
return newId;
}
@Override
public long timeToLive(long leaseId) {
try {
return leaseClient.ttl(leaseId).get().getTTL();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
return 0L;
}
}
}
其中的SystemClock類,就在網上找一下吧,就是一個獲取系統當前時間戳的工具類。
創建這個Client
/**
* @param endPoints 如https://127.0.0.1:2379 有多個時逗號分隔
*/
public static JdEtcdClient build(String endPoints) {
return new JdEtcdClient(EtcdClient.forEndpoints(endPoints).withPlainText().build());
}
之後就可以使用這個etcd客戶端工具類了。