Today, I hit an exception when I tried to code my Redis logic to be transactional.
io.lettuce.core.RedisCommandExecutionException: ERR EXEC without MULTI
Below is my code implementation.
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redisTemplate.opsForHash().put("customer001", "salary", "5000");
redisTemplate.watch("customer001");
redisTemplate.multi();
redisTemplate.opsForHash().put("customer001", "age", "20");
redisTemplate.exec();
From the code you will notice that I actually used multi() but somehow the framework not able to detect. I read from few blog stated transactional support is disabled by default in Spring Redis (see the source code below) and setEnableTransactionSupport(true) will solve the issue.
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public class RedisTemplate<K, V> extends RedisAccessor implements RedisOperations<K, V>, BeanClassLoaderAware {
private boolean enableTransactionSupport = false;
....
However, I still get the same exception after I set setEnableTransactionSupport(true)
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redisTemplate.opsForHash().put("customer001", "salary", "5000");
redisTemplate.setEnableTransactionSupport(true);
redisTemplate.watch("customer001");
redisTemplate.multi();
redisTemplate.opsForHash().put("customer001", "age", "20");
redisTemplate.exec();
Solution
I managed to fix the issue by using SessionCallback provided by Spring Data Redis. It is an interface for use when multiple operations need to be performed with the same connection.
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redisTemplate.execute(new SessionCallback<List<Object>>() {
@Override
public <K, V> List<Object> execute(RedisOperations<K, V> operations) throws DataAccessException {
redisTemplate.opsForHash().put("customer001", "salary", "5000");
redisTemplate.watch("customer001");
redisTemplate.multi();
redisTemplate.opsForHash().put("customer001", "age", "20");
return redisTemplate.exec();
}
});
Note: This solution only work for Redis standalone mode as cluster mode does not support command like watch. Execute the logic using Lua script could be the solution for cluster mode.
Reference