• 包含很多static的初始化塊，并通過ServiceLoader的方式加載各種類

一 static初始化塊

static初始化塊.png

二 CtSph

• 提供資源請求entry初始化函數(shù)

2.1 同步context

• 1 超過可限流的context入口類型數(shù)，則不做限流
• 2 未指定則使用默認名稱的context入口節(jié)點
• 3 全局限流開關(guān)Constants.ON，關(guān)閉則不做限流
• 4 獲取當前資源對應(yīng)的處理鏈，每個資源對應(yīng)一個處理鏈，名稱活方法表示資源
• 5 資源對應(yīng)的資源節(jié)點處理鏈數(shù)達到上限，則后續(xù)資源請求不做處理
• 6 實例化資源請求Entry，按資源節(jié)點處理鏈依次處理，進行統(tǒng)計，資源申請等操作
• 7 資源申請失敗，按處理鏈做失敗統(tǒng)計等處理

private Entry entryWithPriority(ResourceWrapper resourceWrapper, int count, boolean prioritized, Object... args)
    throws BlockException {
    Context context = ContextUtil.getContext();
    if (context instanceof NullContext) { //1
        return new CtEntry(resourceWrapper, null, context);
    }

    if (context == null) {//2
        context = MyContextUtil.myEnter(Constants.CONTEXT_DEFAULT_NAME, "", resourceWrapper.getType());
    }

    if (!Constants.ON) {//3
        return new CtEntry(resourceWrapper, null, context);
    }

    ProcessorSlot<Object> chain = lookProcessChain(resourceWrapper);//4

    if (chain == null) {//5
        return new CtEntry(resourceWrapper, null, context);
    }
  
    Entry e = new CtEntry(resourceWrapper, chain, context);
    try {
        chain.entry(context, resourceWrapper, null, count, prioritized, args);//6
    } catch (BlockException e1) {
        e.exit(count, args);//7
        throw e1;
    } catch (Throwable e1) {
        RecordLog.info("Sentinel unexpected exception", e1);
    }
    return e;
}

2.1.1 lookProcessChain

• 根據(jù)context名稱獲取處理鏈
• 使用hashmap存儲
  private static volatile Map<ResourceWrapper, ProcessorSlotChain> chainMap = new HashMap<ResourceWrapper, ProcessorSlotChain>();
• 二次加鎖校驗方式初始化
• 寫拷貝更新的方式更新存儲map

ProcessorSlot<Object> lookProcessChain(ResourceWrapper resourceWrapper) {
    ProcessorSlotChain chain = chainMap.get(resourceWrapper);
    if (chain == null) {
        synchronized (LOCK) {
            chain = chainMap.get(resourceWrapper);
            if (chain == null) {
                // Entry size limit.
                if (chainMap.size() >= Constants.MAX_SLOT_CHAIN_SIZE) {
                    return null;
                }

                chain = SlotChainProvider.newSlotChain();
                Map<ResourceWrapper, ProcessorSlotChain> newMap = new HashMap<ResourceWrapper, ProcessorSlotChain>(
                    chainMap.size() + 1);
                newMap.putAll(chainMap);
                newMap.put(resourceWrapper, chain);
                chainMap = newMap;
            }
        }
    }
    return chain;
}

2.1.2 獲取資源節(jié)點處理鏈

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;
}

2.2 異步context

//todo

三 Entry

3.1 類結(jié)構(gòu)圖

entry類.png

3.2 CtEntry

3.2.1 實例化

• Entry實例化
• 保存資源處理鏈，資源處理上下文context

CtEntry(ResourceWrapper resourceWrapper, ProcessorSlot<Object> chain, Context context) {
    super(resourceWrapper);
    this.chain = chain;
    this.context = context;

    setUpEntryFor(context);
}

• 設(shè)置Entry父子關(guān)系，更新context.curEntry為本次新建的Entry

private void setUpEntryFor(Context context) {
    // The entry should not be associated to NullContext.
    if (context instanceof NullContext) {
        return;
    }
    this.parent = context.getCurEntry();
    if (parent != null) {
        ((CtEntry)parent).child = this;
    }
    context.setCurEntry(this);
}

• 保存對應(yīng)的context名稱
• 保存資源請求時間

public Entry(ResourceWrapper resourceWrapper) {
    this.resourceWrapper = resourceWrapper;
    this.createTime = TimeUtil.currentTimeMillis();
}

3.2.2 資源請求失敗處理

• 1 失敗的entry非context當前entry，則按entry父子關(guān)系依次向上調(diào)用所有entry的失敗處理函數(shù)exit()
• 2 失敗entry是context的當前entry，
  調(diào)用資源處理鏈的exit函數(shù)
  更新context的curEntry為請求失敗Entry的父節(jié)點Entry
  刪除Entry的父子關(guān)系
  如Entry無父節(jié)點，則若是默認context則需要自動清理，手動配置的context則由用戶手動退出。
  清理Entry的context屬性

protected void exitForContext(Context context, int count, Object... args) throws ErrorEntryFreeException {
    if (context != null) {
        // Null context should exit without clean-up.
        if (context instanceof NullContext) {
            return;
        }
        if (context.getCurEntry() != this) {//1
            String curEntryNameInContext = context.getCurEntry() == null ? null : context.getCurEntry().getResourceWrapper().getName();
            // Clean previous call stack.
            CtEntry e = (CtEntry)context.getCurEntry();
            while (e != null) {
                e.exit(count, args);
                e = (CtEntry)e.parent;
            }
            String errorMessage = String.format("The order of entry exit can't be paired with the order of entry"
                + ", current entry in context: <%s>, but expected: <%s>", curEntryNameInContext, resourceWrapper.getName());
            throw new ErrorEntryFreeException(errorMessage);
        } else {//2
            if (chain != null) {
                chain.exit(context, resourceWrapper, count, args);
            }
            context.setCurEntry(parent);
            if (parent != null) {
                ((CtEntry)parent).child = null;
            }
            if (parent == null) {
                if (ContextUtil.isDefaultContext(context)) {
                    ContextUtil.exit();
                }
            }
            clearEntryContext();
        }
    }
}

• 清理線程變量緩存的context

public static void exit() {
    Context context = contextHolder.get();
    if (context != null && context.getCurEntry() == null) {
        contextHolder.set(null);
    }
}

3.3 AsyncEntry

//todo

四 節(jié)點關(guān)系圖

image.png