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本文主要研究一下sentinel的DefaultSlotsChainBuilder
DefaultSlotsChainBuilder
com/alibaba/csp/sentinel/slots/DefaultSlotsChainBuilder.java
public class DefaultSlotsChainBuilder implements SlotsChainBuilder {
@Override
public ProcessorSlotChain build() {
ProcessorSlotChain chain = new DefaultProcessorSlotChain();
chain.addLast(new NodeSelectorSlot());
chain.addLast(new ClusterBuilderSlot());
chain.addLast(new LogSlot());
chain.addLast(new StatisticSlot());
chain.addLast(new SystemSlot());
chain.addLast(new AuthoritySlot());
chain.addLast(new FlowSlot());
chain.addLast(new DegradeSlot());
return chain;
}
}
- 实现build方法,返回DefaultProcessorSlotChain,通过它addLast方法构造链式调用
DefaultProcessorSlotChain
com/alibaba/csp/sentinel/slotchain/DefaultProcessorSlotChain.java
public class DefaultProcessorSlotChain extends ProcessorSlotChain {
AbstractLinkedProcessorSlot<?> first = new AbstractLinkedProcessorSlot<Object>() {
@Override
public void entry(Context context, ResourceWrapper resourceWrapper, Object t, int count, Object... args)
throws Throwable {
super.fireEntry(context, resourceWrapper, t, count, args);
}
@Override
public void exit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) {
super.fireExit(context, resourceWrapper, count, args);
}
};
AbstractLinkedProcessorSlot<?> end = first;
@Override
public void addFirst(AbstractLinkedProcessorSlot<?> protocolProcessor) {
protocolProcessor.setNext(first.getNext());
first.setNext(protocolProcessor);
if (end == first) {
end = protocolProcessor;
}
}
@Override
public void addLast(AbstractLinkedProcessorSlot<?> protocolProcessor) {
end.setNext(protocolProcessor);
end = protocolProcessor;
}
/**
* Same as {@link #addLast(AbstractLinkedProcessorSlot)}.
*
* @param next processor to be added.
*/
@Override
public void setNext(AbstractLinkedProcessorSlot<?> next) {
addLast(next);
}
@Override
public AbstractLinkedProcessorSlot<?> getNext() {
return first.getNext();
}
@Override
public void entry(Context context, ResourceWrapper resourceWrapper, Object t, int count, Object... args)
throws Throwable {
first.transformEntry(context, resourceWrapper, t, count, args);
}
@Override
public void exit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) {
first.exit(context, resourceWrapper, count, args);
}
}
- 主要有两个属性,一个是first,一个是end,它们是AbstractLinkedProcessorSlot类型
- 方法主要有addFirst,addLast,setNext
- 这里默认设置了first,之后主要是通过getNext方法来开启链式调用,getNext方法返回的是first的next
AbstractLinkedProcessorSlot
com/alibaba/csp/sentinel/slotchain/AbstractLinkedProcessorSlot.java
public abstract class AbstractLinkedProcessorSlot<T> implements ProcessorSlot<T> {
private AbstractLinkedProcessorSlot<?> next = null;
@Override
public void fireEntry(Context context, ResourceWrapper resourceWrapper, Object obj, int count, Object... args)
throws Throwable {
if (next != null) {
next.transformEntry(context, resourceWrapper, obj, count, args);
}
}
@SuppressWarnings("unchecked")
void transformEntry(Context context, ResourceWrapper resourceWrapper, Object o, int count, Object... args)
throws Throwable {
T t = (T)o;
entry(context, resourceWrapper, t, count, args);
}
@Override
public void fireExit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) {
if (next != null) {
next.exit(context, resourceWrapper, count, args);
}
}
public AbstractLinkedProcessorSlot<?> getNext() {
return next;
}
public void setNext(AbstractLinkedProcessorSlot<?> next) {
this.next = next;
}
}
- AbstractLinkedProcessorSlot是所有slot的基类,有个next属性,用来标识下一个slot
- entry是整个链式调用的入口,默认是会触发fireEntry,通过判断next不为null,则调用next的transformEntry,进而调用next的entry方法
- 子类的entry方法会做一些前置校验工作,通过之后调用fireEntry方法,进而完成整个链式调用
小结
sentinel使用了责任链模式来进行各种slot逻辑的执行,其构建是通过DefaultSlotsChainBuilder来进行build。
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