Sentinel source code analysis part I sentinel overview

Architecture diagram

The whole source code part is based on the use of the production environment

• 1.1 Sentinel Contains console : Configure current limiting rules [ System rules , Authority, etc ]
• 1.2 The console pushes rules to the data source (zookeeper etc. ) to ground
• 1.3 User process installation sentinel Module monitor zk To configure
• 2.1 Request to enter and hand it over to sentinel-adapter Intercept each module
• 2.2 According to Adapter Analytic contextName structure context
• 2.3 according to contextName structure EntranceNode
• 2.4 Find resources ResourceWrapper Corresponding ProcessorSlotChain
• 2.5 ProcessorSlotChain Handle [ Statistics , Current limiting , Rule verification, etc ]
  

Object name	explain
EntranceNode	Entry node
StatisticNode	Statistics node , It contains two sliding window structures of second level and minute level
DefaultNode	Link nodes , It is used to count the data of a resource on the call link , Maintain the tree structure
ClusterNode	Cluster link information
Entry	every time Adapter Module resource calls will create a Entry, Trestle Structure [ Enter the first ]Entry1->Entry2->Entry3[ Exit first ], Contains the resource name 、curNode（ Current statistics node ） When the call of information resources ends, you need entry.exit Restore call stack
Context	Call link context , Maintaining the entry node ,Entry link ,curNode

One context Maintenance request link Entry, Every entry Both contain node, Maintain the tree relationship between resources and the storage of flow limiting information

Schematic diagram of current limiting

• The whole working mechanism of current limiting is handled through the responsibility chain
• Each resource corresponds to a ProcessorSlotChain
• This work chain passes Spi Mechanism discovery , Users can customize the corresponding implementation , And pass @SpiOrder Orchestration priority
  

context And entry Relationship

• context Represents the current thread context
• Unlike cross process tracing , Here we do not consider cross thread and cross process processing
• Multiple resource calls in the same thread , Will form the entry chain ,context Hold the relevant chain
• context Is the thread dimension . but context The name of is resource ResourceWrapper dimension

context And node Relationship

• According to the resource name, it will build EntranceNode
• context Will hold EntranceNode

node Self relationship tree maintenance

• Call resource throttling multiple times in a thread , be node Form a tree structure
• entry Form a linked list stack [ First in, then out ] structure

See the relationship between the three from the dimension of request and resource

• x Axis indicates request , The thread of each request builds a context, but context Could be the same , Generally, it is the resource name
• Each creation context Will get or build from the cache entranceNode, The same resource name corresponds to the same Node
• node It will build a tree structure , Indicates current statistics node Tree structure current limiting information

That's why ProcessorSlotChain Instantiate by resource dimension , Instead of singleton mode

Because of the statistics Slot Statistics are based on resource dimensions , If singleton is used, the current limit statistics of all resources are in the same node

• Above picture Node The same color means the same object

Expansion point - Official schematic diagram

Expand a little bit node Class diagram