com.alibaba.csp.sentinel.slots.nodeselector

Class NodeSelectorSlot

java.lang.Object

com.alibaba.csp.sentinel.slotchain.AbstractLinkedProcessorSlot<Object>

com.alibaba.csp.sentinel.slots.nodeselector.NodeSelectorSlot

All Implemented Interfaces:

ProcessorSlot<Object>

@Spi(isSingleton=false,
     order=-10000)
public class NodeSelectorSlot
extends AbstractLinkedProcessorSlot<Object>

This class will try to build the calling traces via

1. adding a new DefaultNode if needed as the last child in the context. The context's last node is the current node or the parent node of the context.
2. setting itself to the context current node.

It works as follow:

 ContextUtil.enter("entrance1", "appA");
 Entry nodeA = SphU.entry("nodeA");
 if (nodeA != null) {
     nodeA.exit();
 }
 ContextUtil.exit();
 

Above code will generate the following invocation structure in memory:

              machine-root
                  /
                 /
           EntranceNode1
               /
              /
        DefaultNode(nodeA)- - - - - -> ClusterNode(nodeA);
 

Here the EntranceNode represents "entrance1" given by ContextUtil.enter("entrance1", "appA").

Both DefaultNode(nodeA) and ClusterNode(nodeA) holds statistics of "nodeA", which is given by SphU.entry("nodeA")

The ClusterNode is uniquely identified by the ResourceId; the DefaultNode is identified by both the resource id and Context. In other words, one resource id will generate multiple DefaultNode for each distinct context, but only one ClusterNode.

the following code shows one resource id in two different context:

    ContextUtil.enter("entrance1", "appA");
    Entry nodeA = SphU.entry("nodeA");
    if (nodeA != null) {
        nodeA.exit();
    }
    ContextUtil.exit();

    ContextUtil.enter("entrance2", "appA");
    nodeA = SphU.entry("nodeA");
    if (nodeA != null) {
        nodeA.exit();
    }
    ContextUtil.exit();
 

Above code will generate the following invocation structure in memory:

                  machine-root
                  /         \
                 /           \
         EntranceNode1   EntranceNode2
               /               \
              /                 \
      DefaultNode(nodeA)   DefaultNode(nodeA)
             |                    |
             +- - - - - - - - - - +- - - - - - -> ClusterNode(nodeA);
 

As we can see, two DefaultNode are created for "nodeA" in two context, but only one ClusterNode is created.

We can also check this structure by calling:
curl http://localhost:8719/tree?type=root

Author:

jialiang.linjl

See Also:

EntranceNode, ContextUtil

Constructor Summary

Constructors

Constructor and Description
NodeSelectorSlot()

Method Summary

Modifier and Type	Method and Description
void	entry(Context context, ResourceWrapper resourceWrapper, Object obj, int count, boolean prioritized, Object... args) Entrance of this slot.
void	exit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) Exit of this slot.

Methods inherited from class com.alibaba.csp.sentinel.slotchain.AbstractLinkedProcessorSlot

fireEntry, fireExit, getNext, setNext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NodeSelectorSlot

public NodeSelectorSlot()

Method Detail

entry

public void entry(Context context,
                  ResourceWrapper resourceWrapper,
                  Object obj,
                  int count,
                  boolean prioritized,
                  Object... args)
           throws Throwable

Description copied from interface: ProcessorSlot

Entrance of this slot.

Parameters:

context - current Context

resourceWrapper - current resource

obj - generics parameter, usually is a Node

count - tokens needed

prioritized - whether the entry is prioritized

args - parameters of the original call

Throws:

Throwable - blocked exception or unexpected error

exit

public void exit(Context context,
                 ResourceWrapper resourceWrapper,
                 int count,
                 Object... args)

Description copied from interface: ProcessorSlot

Exit of this slot.

Parameters:

context - current Context

resourceWrapper - current resource

count - tokens needed

args - parameters of the original call