Sentinel源码解析之限流

请求进入CommonFilter的doFilter方法调用SphU.entry(target, EntryType.IN);经过层层调用最终调用了CtSph的entryWithPriority(ResourceWrapper resourceWrapper, int count, boolean prioritized, Object… args)方法。lookProcessChain(resourceWrapper);方法会通过SlotChainBuilder.build方法生成slot链并且获取slot链，这其中就包括了FlowSlot，DegradeSlot

private Entry entryWithPriority(ResourceWrapper resourceWrapper, int count, boolean prioritized, Object... args)
    throws BlockException {
    Context context = ContextUtil.getContext();
    if (context instanceof NullContext) {
        // The {@link NullContext} indicates that the amount of context has exceeded the threshold,
        // so here init the entry only. No rule checking will be done.
        return new CtEntry(resourceWrapper, null, context);
    }

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

    // Global switch is close, no rule checking will do.
    if (!Constants.ON) {
        return new CtEntry(resourceWrapper, null, context);
    }
    // 通过SlotChainBuilder.build方法生成slot链并且获取slot链
    ProcessorSlot