使用lua+redis解决发多张券的并发问题

public boolean sendCoupons(Long userId, Long couponId) {
// 一堆校验
// …
// 查出券码
List<CouponCode> couponCodes = couponCodeService.findByCouponId(couponId, num);
// batchUpdateStatus是一个被@Transactional(propagation = Propagation.REQUIRES_NEW)修饰的方法
// 批量更新为已被领取状态
couponCodeService.batchUpdateStatus(couponCods);
// 发券
// 发权益
// 新增用户券码领取记录
}

local result = {}
for i=1,ARGV[1],1 do
result[i] = redis.call(“lpop”, KEYS[1])
end
return table.contact(result , “|”)

@Slf4j
@Component
public class CouponCodeRedisQueueClient implements InitializingBean {

/**
* redis lua脚本文件路径
*/
public static final String POP_COUPON_CODE_LUA_PATH = “lua/pop-coupon-code.lua”;
public static final String SEPARATOR = “|”;

private static final String COUPON_CODE_KEY_PATTERN = “PROMOTION:COUPON_CODE_{0}”;
private String LUA_COUPON_CODE_SCRIPT;

private String LUA_COUPON_CODE_SCRIPT_SHA;

@Autowired
private JedisTemplate jedisTemplate;

@Override
public void afterPropertiesSet() throws Exception {

LUA_COUPON_CODE_SCRIPT = Resources.toString(Resources.getResource(POP_COUPON_CODE_LUA_PATH), Charsets.UTF_8);
if (StringUtils.isNotBlank(LUA_COUPON_CODE_SCRIPT)) {

LUA_COUPON_CODE_SCRIPT_SHA = jedisTemplate.execute(jedis -> {
return jedis.scriptLoad(LUA_COUPON_CODE_SCRIPT);
});
log.info(“redis lock script sha:{}”, LUA_COUPON_CODE_SCRIPT_SHA);
}

}

/**
* 获取Code
*
* @param activityId
* @param num
* @return
*/
public List<String> popCouponCode(Long activityId, String num , int retryNum) {
if(retryNum == 0){
log.error(“reload lua script error , try limit times ,activityId:{}”, activityId);
return Collections.emptyList();
}
List<String> keys = Lists.newArrayList();
String key = buildKey(String.valueOf(activityId));
keys.add(key);
List<String> args = Lists.newArrayList();
args.add(num);

try {
Object result = jedisTemplate.execute(jedis -> {
if (StringUtils.isNotBlank(LUA_COUPON_CODE_SCRIPT_SHA)) {
return jedis.evalsha(LUA_COUPON_CODE_SCRIPT_SHA, keys, args);
} else {
return jedis.eval(LUA_COUPON_CODE_SCRIPT, keys, args);
}
});
log.info(“pop coupon code by lua script.result:{}”, result);
if (Objects.isNull(result)) {
return Collections.emptyList();
}
return Splitter.on(SEPARATOR).splitToList(result.toString());
} catch (JedisNoScriptException jnse) {
log.error(“no lua lock script found.try to reload it”, jnse);
reloadLuaScript();
//加载后重新执行
popCouponCode(activityId, num, –retryNum);
} catch (Exception e) {
log.error(“failed to get a redis lock.key:{}”, key, e);
}
return Collections.emptyList();
}

/**
* 重新加载LUA脚本
*
* @throws Exception
*/
public void reloadLuaScript() {
synchronized (CouponCodeRedisQueueClient.class) {
try {
afterPropertiesSet();
} catch (Exception e) {
log.error(“failed to reload redis lock lua script.retry load it.”);
reloadLuaScript();
}
}
}

/**
* 构建Key
*
* @param activityId
* @return
*/
public String buildKey(String activityId) {
return MessageFormat.format(COUPON_CODE_KEY_PATTERN, activityId);
}

}