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A simple failover library for Java
package com.github.phantomthief.failover.impl;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.concurrent.TimeUnit.SECONDS;
import static java.util.function.Function.identity;
import static java.util.stream.Collectors.toMap;
import static org.slf4j.LoggerFactory.getLogger;
import java.util.Collection;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;
import java.util.function.IntUnaryOperator;
import java.util.function.Predicate;
import java.util.function.ToDoubleFunction;
import javax.annotation.CheckReturnValue;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import org.slf4j.Logger;
import com.github.phantomthief.util.ThrowableFunction;
import com.github.phantomthief.util.ThrowablePredicate;
/**
* WeightFailover的builder。
*
* @param 要构建的资源的类型
* @see WeightFailover#newGenericBuilder()
*/
@SuppressWarnings({"checkstyle:VisibilityModifier", "checkstyle:HiddenField"})
public class WeightFailoverBuilder {
private static final Logger logger = getLogger(WeightFailoverBuilder.class);
private static final int DEFAULT_INIT_WEIGHT = 100;
private static final int DEFAULT_FAIL_REDUCE_WEIGHT = 5;
private static final int DEFAULT_SUCCESS_INCREASE_WEIGHT = 1;
private static final long DEFAULT_CHECK_DURATION = SECONDS.toMillis(1);
IntUnaryOperator failReduceWeight;
IntUnaryOperator successIncreaseWeight;
Map initWeightMap;
ToDoubleFunction checker;
long checkDuration;
Consumer onMinWeight;
Consumer onRecovered;
int minWeight = 0;
Integer weightOnMissingNode;
String name;
Predicate filter;
/**
* 设定failover的name。
* @param value 名称
* @param 要构建的failover中的资源类型
* @return this
*/
@CheckReturnValue
@SuppressWarnings("unchecked")
@Nonnull
public WeightFailoverBuilder name(String value) {
this.name = value;
return (WeightFailoverBuilder) this;
}
/**
* 设定自动添加的资源的权重，自动添加指的是调用
* {@link com.github.phantomthief.failover.SimpleFailover#success(Object)}、
* {@link com.github.phantomthief.failover.SimpleFailover#fail(Object)}、
* {@link com.github.phantomthief.failover.SimpleFailover#down(Object)}
* 这三个方法时，如果传入的参数不在原本的资源列表中，WeightFailover将自动添加该资源。
*
* 如果本方法没有被调用，那么构建出来的{@link WeightFailover}将不支持自动添加资源。可以看出
* {@link WeightFailover}内部的资源列表是可变的，
* 作为对比{@link PriorityFailover}的资源列表是不可变的，它使用{@link PriorityFailoverManager}来
* 协助资源列表的变更。
*
* @param weight 权重
* @param 要构建的failover中的资源类型
* @return this
*/
@CheckReturnValue
@SuppressWarnings("unchecked")
@Nonnull
public WeightFailoverBuilder autoAddOnMissing(int weight) {
checkArgument(weight >= 0);
WeightFailoverBuilder thisBuilder = (WeightFailoverBuilder) this;
this.weightOnMissingNode = weight;
return thisBuilder;
}
/**
* 设置一个回调器，当资源的当前权重从非最小权重减少到最小权重时，触发一次回调。
* 也就是说，一直连续失败不会导致这个回调多次被调用，除非中间夹杂了成功导致权重上升到非最小权重。
* @param listener 回调器
* @param 要构建的failover中的资源类型
* @return this
*/
@CheckReturnValue
@SuppressWarnings("unchecked")
@Nonnull
public WeightFailoverBuilder onMinWeight(Consumer listener) {
checkNotNull(listener);
WeightFailoverBuilder thisBuilder = (WeightFailoverBuilder) this;
thisBuilder.onMinWeight = listener;
return thisBuilder;
}
/**
* 设置一个回调器，当后台检查检查任务恢复某个资源的权重以后，触发一次回调。
* @param listener 回调器
* @param 要构建的failover中的资源类型
* @return this
*/
@CheckReturnValue
@SuppressWarnings("unchecked")
@Nonnull
public WeightFailoverBuilder onRecovered(Consumer listener) {
checkNotNull(listener);
WeightFailoverBuilder thisBuilder = (WeightFailoverBuilder) this;
thisBuilder.onRecovered = listener;
return thisBuilder;
}
/**
* 设置权重最小值
* @param value 最小权重
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder minWeight(int value) {
checkArgument(value >= 0);
this.minWeight = value;
return this;
}
/**
* 指定失败时要扣减的最大权重比例，应该在0到1之间，例如最大权重100，rate=0.05，那么失败以后当前权重扣5。
* @param rate 扣减最大权重的比例
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder failReduceRate(double rate) {
checkArgument(rate > 0 && rate <= 1);
failReduceWeight = i -> Math.max(1, (int) (rate * i));
return this;
}
/**
* 指定失败时要扣减的权重数值。
* @param weight 要扣减的权重
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder failReduce(int weight) {
checkArgument(weight > 0);
failReduceWeight = i -> weight;
return this;
}
/**
* 指定成功后要增加的最大权重比例，应该在0到1之间，例如最大权重100，rate=0.05，那么成功以后当前权重加5。
* @param rate 最大权重比例
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder successIncreaseRate(double rate) {
checkArgument(rate > 0 && rate <= 1);
successIncreaseWeight = i -> Math.max(1, (int) (rate * i));
return this;
}
/**
* 指定成功以后要增加的权重数值。
* @param weight 权重数值
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder successIncrease(int weight) {
checkArgument(weight > 0);
successIncreaseWeight = i -> weight;
return this;
}
/**
* 指定健康检查时间间隔。
* @param time 时间数值
* @param unit 时间单位
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder checkDuration(long time, TimeUnit unit) {
checkNotNull(unit);
checkArgument(time > 0);
checkDuration = unit.toMillis(time);
return this;
}
/**
* 指定一个过滤器，从failover获取资源的时候会过滤掉部分资源。
* @param filter 用户定义的过滤器
* @param 资源类型
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder filter(@Nonnull Predicate filter) {
checkNotNull(filter);
@SuppressWarnings("unchecked")
WeightFailoverBuilder thisBuilder = (WeightFailoverBuilder) this;
thisBuilder.filter = filter;
return thisBuilder;
}
/**
* 指定健康检查器，健康检查器将在资源达到最小权重后开始针对该资源调度。
* @param failChecker 健康检查器，输入是资源，输出是健康检查成功后，需要恢复的最大权重比例
* @param 资源类型
* @return this
*/
@SuppressWarnings("unchecked")
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder
checker(@Nonnull ThrowableFunction failChecker) {
checkNotNull(failChecker);
WeightFailoverBuilder thisBuilder = (WeightFailoverBuilder) this;
thisBuilder.checker = t -> {
try {
return failChecker.apply(t);
} catch (Throwable e) {
logger.error("", e);
return 0;
}
};
return thisBuilder;
}
/**
* 指定健康检查器，健康检查器将在资源达到最小权重后开始针对该资源调度。
* @param failChecker 健康检查器，输入是资源，输出是资源是否健康
* @param recoveredInitRate 健康检查成功后，需要恢复的最大权重的比例
* @param 资源类型
* @return this
*/
@CheckReturnValue
@Nonnull
public WeightFailoverBuilder checker(
@Nonnull ThrowablePredicate failChecker,
@Nonnegative double recoveredInitRate) {
checkArgument(recoveredInitRate >= 0 && recoveredInitRate <= 1);
checkNotNull(failChecker);
return checker(it -> failChecker.test(it) ? recoveredInitRate : 0);
}
/**
* 构造一个WeightFailover实例，使用100作为默认的初始/最大权重。WeightFailover没有区分初始权重和最大权重，初始权重和最大权重是相等的。
* @param original 资源列表
* @param 资源类型
* @return 构造出来的WeightFailover实例
*/
@Nonnull
public WeightFailover build(Collection original) {
return build(original, DEFAULT_INIT_WEIGHT);
}
/**
* 构造一个WeightFailover实例。注意WeightFailover没有区分初始权重和最大权重，初始权重和最大权重是相等的。
* @param original 资源列表
* @param initWeight 初始权重
* @param 资源类型
* @return 构造出来的WeightFailover实例
*/
@Nonnull
public WeightFailover build(Collection original, int initWeight) {
checkNotNull(original);
checkArgument(initWeight > 0);
return build(original.stream().collect(toMap(identity(), i -> initWeight, (u, v) -> u)));
}
/**
* 构造一个WeightFailover实例。注意WeightFailover没有区分初始权重和最大权重，初始权重和最大权重是相等的。
* @param original 资源列表，map里面的key是资源，value是初始权重。
* @param 资源类型
* @return 构造出来的WeightFailover实例
*/
@SuppressWarnings("unchecked")
@Nonnull
public WeightFailover build(Map original) {
checkNotNull(original);
WeightFailoverBuilder thisBuilder = (WeightFailoverBuilder) this;
thisBuilder.initWeightMap = (Map) original;
return thisBuilder.build();
}
private WeightFailover build() {
ensure();
return new WeightFailover<>(this);
}
private void ensure() {
if (minWeight <= 0) { // if min weight>0, there is no checker need.
checkNotNull(checker);
} else {
if (checker != null) {
logger.warn(
"a failover checker found but minWeight>0. the checker would never reached.");
}
}
if (failReduceWeight == null) {
failReduceWeight = i -> DEFAULT_FAIL_REDUCE_WEIGHT;
}
if (successIncreaseWeight == null) {
successIncreaseWeight = i -> DEFAULT_SUCCESS_INCREASE_WEIGHT;
}
if (checkDuration == 0) {
checkDuration = DEFAULT_CHECK_DURATION;
}
}
}