O Tair (Redis OSS-compatible) suporta transações do Redis. Use os comandos MULTI, EXEC, DISCARD, WATCH e UNWATCH para executar operações atômicas.
As transações do Redis diferem das transações de bancos de dados relacionais e de APIs REST. Se uma operação falhar ou você executar o comando DISCARD, o Redis não reverte a transação.
Exemplos de código
Exemplo 1: Dois clientes operam em chaves diferentes
Código de exemplo (defina as credenciais):
package transcation.kvstore.aliyun.com;
import java.util.List;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.Transaction;
public class KVStoreTranscationTest {
static final String host = "xxxxxx.m.cnhza.kvstore.aliyuncs.com";
static final int port = 6379;
static final String password = "password";
// Note: The two keys have different content.
static String client1_key = "KVStore-Transcation-1";
static String client2_key = "KVStore-Transcation-2";
public static void main(String[] args) {
Jedis jedis = new Jedis(host, port);
String authString = jedis.auth(password); // Instance password (password)
if (!authString.equals("OK")) {
System.err.println("Authentication failed: " + authString);
jedis.close();
return;
}
jedis.set(client1_key, "0");
// Start another thread to simulate another client.
new KVStoreTranscationTest().new OtherKVStoreClient().start();
Thread.sleep(500);
Transaction tx = jedis.multi();// Start the transaction.
// The following operations are submitted to the server as an atomic operation.
tx.incr(client1_key);
tx.incr(client1_key);
Thread.sleep(400);// Pausing this thread does not affect consecutive operations in the transaction. Other threads cannot execute operations either.
tx.incr(client1_key);
Thread.sleep(300);// Pausing this thread does not affect consecutive operations in the transaction. Other threads cannot execute operations either.
tx.incr(client1_key);
Thread.sleep(200);// Pausing this thread does not affect consecutive operations in the transaction. Other threads cannot execute operations either.
tx.incr(client1_key);
List<Object> result = tx.exec();// Execute the transaction.
// Parse and print the results.
for(Object rt : result){
System.out.println("Client 1 > In transaction > "+rt.toString());
}
jedis.close();
}
class OtherKVStoreClient extends Thread{
@Override
public void run() {
Jedis jedis = new Jedis(host, port);
String authString = jedis.auth(password);// Instance password (password)
if (!authString.equals("OK")) {
System.err.println("AUTH Failed: " + authString);
jedis.close();
return;
}
jedis.set(client2_key, "100");
for (int i = 0; i < 10; i++) {
try {
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Client 2 > "+jedis.incr(client2_key));
}
jedis.close();
}
}
}Agora, execute o programa com o endpoint e a senha corretos para a sua instância do Tair (Redis OSS-compatible). Na saída, o client1 executa as operações de transação como um bloco atômico. O client2 fica bloqueado até que a transação seja concluída, mesmo que use uma chave diferente.
Saída esperada:
Client 2 > 101
Client 2 > 102
Client 2 > 103
Client 2 > 104
Client 1 > In transaction > 1
Client 1 > In transaction > 2
Client 1 > In transaction > 3
Client 1 > In transaction > 4
Client 1 > In transaction > 5
Client 2 > 105
Client 2 > 106
Client 2 > 107
Client 2 > 108
Client 2 > 109
Client 2 > 110Exemplo 2: Dois clientes operam na mesma chave
Este exemplo modifica o Exemplo 1 para que ambos os clientes operem na mesma chave. O restante do código permanece inalterado.
... ...
// Note: The two keys now have the same content.
static String client1_key = "KVStore-Transcation-1";
static String client2_key = "KVStore-Transcation-1";
... ...Em seguida, execute o programa modificado. Quando o client1 usa uma transação na chave compartilhada, o client2 fica bloqueado até a conclusão da transação.
Client 2 > 101
Client 2 > 102
Client 2 > 103
Client 2 > 104
Client 1 > In transaction > 105
Client 1 > In transaction > 106
Client 1 > In transaction > 107
Client 1 > In transaction > 108
Client 1 > In transaction > 109
Client 2 > 110
Client 2 > 111
Client 2 > 112
Client 2 > 113
Client 2 > 114
Client 2 > 115