//DegradeSlot.entry
@Override
public void entry(Context context, ResourceWrapper resourceWrapper, DefaultNode node, int count,
                  boolean prioritized, Object... args) throws Throwable {
    // 熔断降级检测
    performChecking(context, resourceWrapper);
    // 触发下一个节点
    fireEntry(context, resourceWrapper, node, count, prioritized, args);
}

// 获取到指定资源的所有流控规则
Collection<FlowRule> rules = ruleProvider.apply(resource.getName());
// 逐个应用流控规则。若无法通过则抛出异常，后续规则不再应用
if (rules != null) {
    for (FlowRule rule : rules) {
        if (!canPassCheck(rule, context, node, count, prioritized)) {
            // FlowException继承BlockException
            throw new FlowException(rule.getLimitApp(), rule);
        }
    }
}
-------------------------------------------------------------------------------------------
// 这里调用的apply方法就是FlowSlot中的对应方法
private final Function<String, Collection<FlowRule>> ruleProvider = new Function<String, Collection<FlowRule>>() {
    @Override
    public Collection<FlowRule> apply(String resource) {
        // Flow rule map should not be null.
        // 获取所有资源和对应的流控规则 key为资源名称，value为该资源对应的所有流控规则
        Map<String, List<FlowRule>> flowRules = FlowRuleManager.getFlowRuleMap();
        // 获取指定资源的流控规则
        return flowRules.get(resource);
    }
};

//CtSph中
try {
    // 针对资源操作
    chain.entry(context, resourceWrapper, null, count, prioritized, args);
} catch (BlockException e1) {
    e.exit(count, args);
    throw e1;
} catch (Throwable e1) {
    // This should not happen, unless there are errors existing in Sentinel internal.
    RecordLog.info("Sentinel unexpected exception", e1);
}

//NodeSelectorSlot.entry()
@Override
public void entry(Context context, ResourceWrapper resourceWrapper, Object obj, int count, boolean prioritized, Object... args)
    throws Throwable {
    // 从缓存中获取，创建DefaultNode
    DefaultNode node = map.get(context.getName());
    // 双重判断，如果判断为空
    if (node == null) {
        synchronized (this) {
            node = map.get(context.getName());
            if (node == null) {
                // 创建一个DefaultNode并且放入到缓存中
                node = new DefaultNode(resourceWrapper, null);
                HashMap<String, DefaultNode> cacheMap = new HashMap<String, DefaultNode>(map.size());
                cacheMap.putAll(map);
                cacheMap.put(context.getName(), node);
                map = cacheMap;
                // Build invocation tree
                // 将新建的Node添加到调用树中
                ((DefaultNode) context.getLastNode()).addChild(node);
            }

        }
    }

    context.setCurNode(node);
    // 触发下一个节点
    fireEntry(context, resourceWrapper, node, count, prioritized, args);
}

/**
* This class is used for skip context name checking.
此类型是用于跳过Context名称的检测
*/
private final static class InternalContextUtil extends ContextUtil {
    static Context internalEnter(String name) {
        // 从这里继续跟踪
        return trueEnter(name, "");
    }

    static Context internalEnter(String name, String origin) {
        return trueEnter(name, origin);
    }
}