Nifi: how does nifi processors get flowfiles from upstream connections?

[#1]

I want to write Custom processor , and i want to know how does :fileQueue,inProcess,recentlyProcessed,queueLock this elemenst work inside processors . (can you link me any good article whcih can show me whole cycle of this processSessions and upsetrem connections.)

[#2]

@sally sally

Here is what you want to read. I recommend reading both links - it's same webpage and its not too long.

https://nifi.apache.org/docs/nifi-docs/html/nifi-in-depth.html#flowfile-repository

https://nifi.apache.org/docs/nifi-docs/html/nifi-in-depth.html#DeeperView --> specific answer to your question.