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Client-go code breakdown (4): Work Queue

1. Introduction to WorkQueue In Informer, the Delta FIFO queue triggers Add, Update, and Delete callbacks. In the callback method, the key of the resource object change event that needs to be processed is put into the WorkQueue work queue. Wait for the Control Loop to be retrieved from the work queue, and then retrieve the complete resource object from the Indexer local cache through Lister for processing. Image source: Geek Time – “Kubernetes in a Simple and In-depth manner” The main function of WorkQueue is marking and deduplication, and supports the following features:

Posted by Hao Liang's Blog on Friday, August 21, 2020

Client-go code breakdown (3): Informer mechanism

1. Introduction In Kubernetes, the controller needs to monitor the status of resource objects in the cluster to coordinate the actual status of the resource objects with the desired status defined through yaml. So how does the controller monitor the resource object and make corresponding processing based on the actual status changes of the object? In fact, it is implemented through the Informer mechanism in the Client-go package. Image source: Geek Time – “Kubernetes in a Simple and In-depth manner” From the picture above, we can roughly understand the entire process of the Informer mechanism:

Posted by Hao Liang's Blog on Wednesday, August 12, 2020

Client-go code breakdown (2): Resync mechanism analysis in Informer

1. Informer workflow diagram in Client-go The Reflector in Informer obtains the change events (events) of all resource objects in the cluster from the apiserver through List/watch, puts them into the Delta FIFO queue (saved in the form of Key and Value), and triggers onAdd, onUpdate, and onDelete callbacks. Put the Key into the WorkQueue. At the same time, the Key is updated in the Indexer local cache. Control Loop obtains the Key from the WorkQueue, obtains the Value of the Key from the Indexer, and performs corresponding processing.

Posted by Hao Liang's Blog on Sunday, August 9, 2020