Kubernetes focuses on kubelet's responsibilities

kubelet

---

One... Runs on each node kubelet Service process , Default listening 10250 port .

• Receive and execute master Instructions sent ( In fact, it is watch Mechanism to monitor , If these pod There is a change , He will perform certain operations , The specific operation is management pod The middle container )
• management Pod And Pod In the container
• Every kubelet The process will be in progress APIServer To register the node's own information , Regularly send to master The node reports the resource usage of the node , And pass cAdvisor Monitor the resources of nodes and containers .（pod Health status passes pleg Go and report , The resource usage of the node passes cadvisor Report ）

 

 

Node management

---

kubelet It has the function of node management , It can register nodes , Update node status , So it's starting kubelet When , If you add register-node, Then the current node will be automatically registered to apiserver. 

Node management mainly includes node self registration and node status update ∶

• kubelet You can set the startup parameters --register-node To determine whether to API Server Register yourself
• If kubelet No self registration mode selected , You need to configure it yourself Node Resource information , Also need to be informed kubelet On Cluster APIServer The location of
• kubelet Passed at startup APIServer Register node information , And regularly report to APIServer Send a new message to the node ,APIServer After receiving a new message , Write the information etcd.

 

 

Pod management

---

Related to node management, more importantly pod Management of , Because the registration management of nodes is one-time , Then there is kublet Constantly report the status , More importantly, application management , That is to say pod.

kubelet How to manage pod？ It first needs to know what to start on the node pod, This involves how to get pod detailed list ,kubelet There are several ways to get pod detailed list , The first way is to file , That is to say static pod, Scan the directory to find pod Inventory file , That's all pod Start it up .

Second, it can be done through http endpoint To load the pod, You can give it a startup parameter called manifest-url, This url yes http-endpoint, You put all pod Put the list there , He will also read that url To load the pod detailed list .

The last is apiservre 了 , When apiserver After starting , It will start itself api gateway ,kubelet Connect to apiserver, They're going to monitor apiserver All the above pod, Of course, it is related to this node , After scheduling .（kubelet Will go to watch apiservre,apiserver There are pod Created , And related to this node , On this node kubelet Will go to work ）

obtain Pod detailed list ∶

• file ∶ Launch parameters --config Files in the specified configuration directory （ Default /etc/Kubernetes/manifests/）. This document is every 20 Check again in seconds （ Configurable ）.
• HTTP endpoint（URL）∶ Launch parameters --manifest-url Set up . Every time 20 Check this endpoint every second （ Configurable ）.
• APIServer∶ adopt APIServer monitor etcd Catalog , Sync Pod detailed list .
• HTTP Server∶ kubelet Listen HTTP request , And respond to simple API To submit a new Pod detailed list .