聊聊dubbo的TPSLimiter

序

本文主要研究一下dubbo的TPSLimiter

TPSLimiter

dubbo-2.7.2/dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/tps/TPSLimiter.java

public interface TPSLimiter {    /**     * judge if the current invocation is allowed by TPS rule     *     * @param url        url     * @param invocation invocation     * @return true allow the current invocation, otherwise, return false     */    boolean isAllowable(URL url, Invocation invocation);}

• TPSLimiter定义了isAllowable方法

DefaultTPSLimiter

dubbo-2.7.2/dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/tps/DefaultTPSLimiter.java

public class DefaultTPSLimiter implements TPSLimiter {    private final ConcurrentMap<String, StatItem> stats = new ConcurrentHashMap<String, StatItem>();    @Override    public boolean isAllowable(URL url, Invocation invocation) {        int rate = url.getParameter(TPS_LIMIT_RATE_KEY, -1);        long interval = url.getParameter(TPS_LIMIT_INTERVAL_KEY, DEFAULT_TPS_LIMIT_INTERVAL);        String serviceKey = url.getServiceKey();        if (rate > 0) {            StatItem statItem = stats.get(serviceKey);            if (statItem == null) {                stats.putIfAbsent(serviceKey, new StatItem(serviceKey, rate, interval));                statItem = stats.get(serviceKey);            } else {                //rate or interval has changed, rebuild                if (statItem.getRate() != rate || statItem.getInterval() != interval) {                    stats.put(serviceKey, new StatItem(serviceKey, rate, interval));                    statItem = stats.get(serviceKey);                }            }            return statItem.isAllowable();        } else {            StatItem statItem = stats.get(serviceKey);            if (statItem != null) {                stats.remove(serviceKey);            }        }        return true;    }}

• DefaultTPSLimiter实现了TPSLimiter，它使用ConcurrentHashMap来存储StatItem，其key为URL中的serviceKey；isAllowable方法从URL中读取tps参数，默认为-1，小于0则从ConcurrentHashMap中移除，大于0则创建或者获取StatItem，调用StatItem的isAllowable(重置或递减token并返回结果)

StatItem

dubbo-2.7.2/dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/tps/StatItem.java

class StatItem {    private String name;    private long lastResetTime;    private long interval;    private LongAdder token;    private int rate;    StatItem(String name, int rate, long interval) {        this.name = name;        this.rate = rate;        this.interval = interval;        this.lastResetTime = System.currentTimeMillis();        this.token = buildLongAdder(rate);    }    public boolean isAllowable() {        long now = System.currentTimeMillis();        if (now > lastResetTime + interval) {            token = buildLongAdder(rate);            lastResetTime = now;        }        if (token.sum() < 0) {            return false;        }        token.decrement();        return true;    }    public long getInterval() {        return interval;    }    public int getRate() {        return rate;    }    long getLastResetTime() {        return lastResetTime;    }    long getToken() {        return token.sum();    }    @Override    public String toString() {        return new StringBuilder(32).append("StatItem ")                .append("[name=").append(name).append(", ")                .append("rate = ").append(rate).append(", ")                .append("interval = ").append(interval).append("]")                .toString();    }    private LongAdder buildLongAdder(int rate) {        LongAdder adder = new LongAdder();        adder.add(rate);        return adder;    }}

• StatItem定义了LongAdder类型的token，其isAllowable方法会判断是否需要重置token，如果需要则使用buildLongAdder重置token，不需要的话则在token.sum() < 0时返回false，如果大于等于0则递减token

小结

• TPSLimiter定义了isAllowable方法
• DefaultTPSLimiter实现了TPSLimiter，它使用ConcurrentHashMap来存储StatItem，其key为URL中的serviceKey；isAllowable方法从URL中读取tps参数，默认为-1，小于0则从ConcurrentHashMap中移除，大于0则创建或者获取StatItem，调用StatItem的isAllowable(重置或递减token并返回结果)
• StatItem定义了LongAdder类型的token，其isAllowable方法会判断是否需要重置token，如果需要则使用buildLongAdder重置token，不需要的话则在token.sum() < 0时返回false，如果大于等于0则递减token

doc

• TPSLimiter
• DefaultTPSLimiter
• StatItem