/**
 * 單機(jī)限流
 */
@Slf4j
public class FlowLimit {

 //接口限流上限值和限流時(shí)間緩存
    private static Cache<String, AtomicLong> localCache = CacheBuilder.newBuilder().maximumSize(100)
            .expireAfterWrite(1000, TimeUnit.MILLISECONDS).build();

 //每個(gè)接口的上限緩存
    private static Map<String, Long> maxFlowLimitMap = new ConcurrentHashMap<>();

    private static final FlowLimit instance = new FlowLimit();

 //這塊的目的是初始化每個(gè)接口的上限，下面的變量：apiFlowLimitConfigure 
 //實(shí)際使用的時(shí)候應(yīng)該是從db或者其他地方獲取設(shè)置的每個(gè)接口的限流上限值，
 //這樣可以動(dòng)態(tài)的調(diào)整接口上限，比如直接修改db，不用發(fā)布，就可以調(diào)整接口限流值
    static {
        new ScheduledThreadPoolExecutor(1, runnable -> {
            Thread thread = new Thread(runnable, "api-flowLimit-configure");
//            thread.setDaemon(true);
            return thread;
        }).scheduleAtFixedRate(() -> {
            try {
                String apiFlowLimitConfigure = "{\"doAdd\":100}";  //表示/doAdd接口1秒接受100次請(qǐng)求
                Map mapObj = JSONObject.parseObject(apiFlowLimitConfigure, Map.class);
                if(mapObj != null){
                    mapObj.forEach((key, value) -> {
                        if(value != null){
                            instance.setMaxFlowLimit(key.toString(), new Long(value.toString()));
                        }else{
                            log.warn(key + " - 設(shè)置接口限流發(fā)現(xiàn)限流值為空，設(shè)置默認(rèn)值");
                            instance.setMaxFlowLimit(key.toString(), 100L);
                        }
                    });
                }
            } catch (Exception e) {
                log.error("設(shè)置接口限流出現(xiàn)異常{}", e);
            }
        }, 0, 3, TimeUnit.SECONDS);
    }

    public static FlowLimit getInstance() {
        return instance;
    }

    private FlowLimit setMaxFlowLimit(String key, Long maxFlowLimit) {
        maxFlowLimitMap.put(key, maxFlowLimit);
        return this;
    }

    public Boolean isAvailable(String key) {
        return checkAvailable(key, 1L);
    }

    public Boolean isAvailable(String key, Long incrNum) {
        return checkAvailable(key, incrNum);
    }

    private Boolean checkAvailable(String key, Long incrNum){
        Long maxFlowLimit = maxFlowLimitMap.get(key);
        if (null == maxFlowLimit || maxFlowLimit == 0) {
            return true;
        }
        if (incrAndGet(key, incrNum) <= maxFlowLimit.longValue()) {
            return true;
        } else {
            return false;
        }
    }

    private long incrAndGet(String key, final long n) {
        try {
            return localCache.get(key, new Callable<AtomicLong>() {
                @Override
                public AtomicLong call() throws Exception {
                    return new AtomicLong(0);
                }
            }).addAndGet(n);
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
        return 0;
    }

    public long get(String key) {
        return incrAndGet(key, 0);
    }

}

@GetMapping("doAdd")
public Boolean doAdd(){
    FlowLimit instance = FlowLimit.getInstance(); //單例獲取
    //查看當(dāng)前的/doAdd接口是否觸發(fā)了限流
    Boolean flowLimitFlag = instance.isAvailable("doAdd");
    if(!flowLimitFlag){
        log.warn("觸發(fā)限流，拒絕請(qǐng)求");
        return false;
    }
    //doAdd()
    return true;
}