1. Concept introduction ( original address )
1.Pod
Kubernetes uses Pods to manage containers, and each Pod can contain one or more closely related containers. Pod is a set of closely related containers. They share PID, IPC, Network, and UTS namespace. They are the basic unit of Kubernetes scheduling. Multiple containers in the Pod share the network and file system, which can be combined to complete the service in a simple and efficient way of inter-process communication and file sharing
A pod yaml file
apiVersion: v1 #Version number
kind: Pod #Pod
metadata: #Metadata
name: string #Pod name
namespace: string #The namespace to which the Pod belongs
labels: #Custom labels
-name: string #Custom label name
annotations: #Custom annotation list
- name: string
spec: The detailed definition of the container in #Pod
containers: #Pod list of containers
-name: string #container name
image: string #The image name of the container
imagePullPolicy: [Always | Never | IfNotPresent] #Alawys means to download the mirror image IfnotPresent means to use the local mirror first, otherwise download the mirror, Nerver means to use only the local mirror
command: [string] #Container startup command list, if not specified, use the startup command used during packaging
args: [string] #Container startup command parameter list
workingDir: string #The working directory of the container
volumeMounts: #Mounting to the storage volume configuration inside the container
-name: string #quote the name of the shared storage volume defined by the pod, use the volume name defined in the volumes[] part
mountPath: string #The absolute path of the storage volume mount in the container, which should be less than 512 characters
readOnly: boolean #Whether it is in read-only mode
ports: #List of port library numbers that need to be exposed
-name: string #Port number name
containerPort: int #The port number that the container needs to monitor
hostPort: int #The port number of the host where the container is located, the default is the same as the Container
protocol: string #Port protocol, support TCP and UDP, default TCP
env: #List of environment variables that need to be set before the container runs
-name: string #environment variable name
value: string #The value of the environment variable
resources: #Resource limits and requested settings
limits: #Resource limit settings
cpu: string #Cpu limit, the unit is the number of cores, which will be used for the docker run --cpu-shares parameter
memory: string #Memory limit, the unit can be Mib/Gib, which will be used for the docker run --memory parameter
requests: #Resource request settings
cpu: string #Cpu request, the initial available number of container startup
memory: string #Memory request, the initial available number of container startup
livenessProbe: #Set the health check of a container in the Pod. The container will be automatically restarted when the detection does not respond several times. The check methods are exec, httpGet and tcpSocket. You only need to set one of these methods for a container.
exec: #Set the inspection method in the Pod container to exec
command: [string] #exec command or script that needs to be developed
httpGet: #Set the health check method of a container in the Pod to HttpGet, and you need to specify the Path and port
path: string
port: number
host: string
scheme: string
HttpHeaders:
- name: string
value: string
tcpSocket: #Set the health check mode of a container in the Pod to tcpSocket mode
port: number
initialDelaySeconds: 0 #The first detection time after the container is started, in seconds
timeoutSeconds: 0 #The timeout period of waiting for a response to the container health check probe, in seconds, the default is 1 second
periodSeconds: 0 #The periodical detection time setting for container monitoring inspection, in seconds, the default is once every 10 seconds
successThreshold: 0
failureThreshold: 0
securityContext:
privileged:false
restartPolicy: [Always | Never | OnFailure]#Pod's restart strategy, Always means that once the operation is terminated in any way, the kubelet will restart, OnFailure means that only Pod exits with a non-zero exit code will restart, Nerver means no longer restart the Pod
nodeSelector: obeject #Set NodeSelector means that the Pod is scheduled to the node that contains this label, specified in the format of key: value
imagePullSecrets: #Pull the secret name used when mirroring, specified in key: secretkey format
- name: string
hostNetwork:false #Whether to use the host network mode, the default is false, if set to true, it means to use the host network
volumes: #Define a list of shared storage volumes on the pod
-name: string #Shared storage volume name (there are many types of volumes)
emptyDir: {} #Storage volume of type emtyDir, a temporary directory with the same life cycle as Pod. Null
hostPath: string #Storage volume of type hostPath, indicating the directory of the host where the Pod is mounted
path: string #The directory of the host where the Pod is located, which will be used for the mount directory during the same period
secret: #Storage volume of type secret, mount the cluster and the defined secret object to the inside of the container
scretname: string
items:
- key: string
path: string
configMap: #Storage volume of type configMap, mount the predefined configMap object to the inside of the container
name: string
items:
- key: string
path: string
Among them, it is worth explaining that there are a few points
- The apiVersion version in k8s, you can use the command kubectl api-versions to view, here are three common
- alpha: development version, may contain errors, support for this feature may be discarded at any time
- beta: The beta version, the software has been well tested, the enabling function is considered safe, the details may be changed, but the function will not be deleted in subsequent versions
- stable: stable version, which will appear in subsequent software versions
- Harbor defaults to the https protocol. If you want to pull the image of the harbor through the http protocol, you need to modify the /etc/docker/daemon.json file on each node of k8s
{
"insecure-registries":["http://your-harbor-url"]
}
Then restart docker
systemctl dadmon-reload systemctl restart docker
2.Deployment
- Define Deployment to create Pod and ReplicaSet
- Rolling upgrade and rollback application
- Expansion and shrinkage
- Pause and resume deployment
A deployment yaml file (limited to space, many contents have been omitted)
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: string #Deployment name
spec:
replicas: 3 #number of target replicas
strategy:
rollingUpdate:
maxSurge: 1 #Upgrade 1 pod at the same time during rolling upgrade
maxUnavailable: 1 #Maximum number of unavailable pods allowed during rolling upgrade
template:
metadata:
labels:
app: string #template name
sepc: #define a container template, which can contain multiple containers
containers:
- name: string
image: string
ports:
- name: http
containerPort: 8080 #Exposing port to service
How to upgrade and roll back applications in k8s
When performing a rolling upgrade, first update the mirror version in the yaml file, and then set the values of maxSurge and maxUnavailable according to the setting requirements to complete
How does k8s complete expansion and contraction
Republish after modifying the value of replicas
3.Service
apiVersion: v1
kind: Service
matadata: #metadata
name: string #service name
namespace: string #namespace
labels: #Custom label attribute list
- name: string
annotations: #Custom annotation attribute list
- name: string
spec: #Detailed description
selector: [] #label selector configuration, select Pod with label as the management scope
type: string #service type, specify the access method of service, the default is clusterIp
clusterIP: string #Virtual service address
sessionAffinity: string #Whether to support session
ports: #service The list of ports that need to be exposed
-name: string #Port name
protocol: string #Port protocol, support TCP and UDP, default TCP
port: int #The port number that the service monitors
targetPort: int #The port number that needs to be forwarded to the backend Pod
nodePort: int #When type = NodePort, specify the port number mapped to the physical machine
status: #When spce.type=LoadBalancer, set the address of the external load balancer
loadBalancer: #External load balancer
ingress: #external load balancer
ip: string #IP address value of external load balancer
hostname: string #The host name of the external load balancer
2. Relationship analysis ( original address )
Deploy controls RS, and RS controls Pod. This whole set provides stable and reliable Service.
Analysis The
following is the analysis process
First, we start with the smallest scheduling unit pod.
There is currently a pod in my k8s cluster, its name is mq-svc-5b96bf78d9-brpjw
[root@VM_0_17_centos ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
mq-svc-5b96bf78d9-brpjw 1/1 Running 0 51m to
see its details
[root@VM_0_17_centos ~]# kubectl describe pod mq-svc-5b96bf78d9-brpjw
Name: mq-svc-5b96bf78d9-brpjw
Namespace: default
Node: 10.0.0.17/10.0.0.17
Start Time: Fri, 17 Aug 2018 17:24:44 +0800
Labels: pod-template-hash=1652693485
qcloud-app=mq-svc
Annotations: <none>
Status: Running
IP: 172.16.0.39
Controlled By: ReplicaSet/mq-svc-5b96bf78d9
Containers:
queue-mq:
Container ID: docker://700cdc55c111a413faaa8cabb8680009d2663701ccbe84b8a50ea6e6fe1d538c
Image: rabbitmq:management
Image ID: docker-pullable://rabbitmq@sha256:0b36ea1a8df9e53228aaeee277680de2cc97c7d675bc2d5dbe1cc9e3836a9d9f
Port: <none>
Host Port: <none>
State: Running
Started: Fri, 17 Aug 2018 17:24:49 +0800
Ready: True
Restart Count: 0
Limits:
cpu: 500m
memory: 1Gi
Requests:
cpu: 250m
memory: 256Mi
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-vzhz4 (ro)
Conditions:
Type Status
Initialized True
Ready True
PodScheduled True
Volumes:
default-token-vzhz4:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-vzhz4
Optional: false
QoS Class: Burstable
Node-Selectors: <none>
Tolerations: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 51m default-scheduler Successfully assigned mq-svc-5b96bf78d9-brpjw to 10.0.0.17
Normal SuccessfulMountVolume 51m kubelet, 10.0.0.17 MountVolume.SetUp succeeded for volume "default-token-vzhz4"
Normal Pulling 51m kubelet, 10.0.0.17 pulling image "rabbitmq:management"
Normal Pulled 51m kubelet, 10.0.0.17 Successfully pulled image "rabbitmq:management"
Normal Created 51m kubelet, 10.0.0.17 Created container
Normal Started 51m kubelet, 10.0.0.17 Started The container
actually has sensitive information. The pod is managed by a ReplicaSet named mq-svc-5b96bf78d9, so we believe that RS is a higher-level component specifically used to manage pods. One RS will manage a batch of pods.
Controlled By: ReplicaSet/mq-svc-5b96bf78d9
And the practices that take place in pods are also operations on containers, such as pulling images, starting containers, etc.
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 51m default-scheduler Successfully assigned mq-svc-5b96bf78d9-brpjw to 10.0.0.17
Normal SuccessfulMountVolume 51m kubelet, 10.0.0.17 MountVolume.SetUp succeeded for volume "default-token-vzhz4"
Normal Pulling 51m kubelet, 10.0.0.17 pulling image "rabbitmq:management"
Normal Pulled 51m kubelet, 10.0.0.17 Successfully pulled image "rabbitmq:management"
Normal Created 51m kubelet, 10.0.0.17 Created container
Normal Started 51m kubelet, 10.0.0.17 Started container
Next, let’s take a look at the details of this RS
[root@VM_0_17_centos ~]# kubectl describe rs mq-svc-5b96bf78d9
Name: mq-svc-5b96bf78d9
Namespace: default
Selector: pod-template-hash=1652693485,qcloud-app =mq-svc
Labels: pod-template-hash=1652693485
qcloud-app=mq-svc
Annotations: deployment.changecourse=Updating
deployment.kubernetes.io/desired-replicas=1
deployment.kubernetes.io/max-replicas=2
deployment .kubernetes.io/revision=2
description=Service based on rabbitmq.
Controlled By: Deployment/mq-svc
Replicas: 1 current / 1 desired
Pods Status: 1 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: pod-template-hash=1652693485
qcloud-app=mq-svc
Containers:
queue-mq:
Image: rabbitmq:management
Port: <none>
Host Port: <none>
Limits:
cpu: 500m
memory: 1Gi
Requests:
cpu: 250m
memory: 256Mi
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 50m replicaset-controller Created pod: mq-svc-5b96bf78d9-r8n8t
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-l4zj2
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-m8tmv
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-m8tmv
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-r9wkj
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-8wzpq
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-d8gwc
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-d8gwc
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-8wzpq
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-l4zj2
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-r9wkj
Normal SuccessfulDelete 45m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-r8n8t
Key Information
Controlled By: Deployment/mq-svc
This RS is controlled by the Deployment named mq-svc. From this point of view, Deployment is a component that is one level higher than RS for managing RS.
Events that occur at the RS level are all operations on pods, pods are created, and pods are deleted
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 50m replicaset-controller Created pod: mq-svc-5b96bf78d9-r8n8t
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-l4zj2
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-m8tmv
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-m8tmv
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-r9wkj
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-8wzpq
Normal SuccessfulCreate 49m replicaset-controller Created pod: mq-svc-5b96bf78d9-d8gwc
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-d8gwc
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-8wzpq
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-l4zj2
Normal SuccessfulDelete 49m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-r9wkj
Normal SuccessfulDelete 45m replicaset-controller Deleted pod: mq-svc-5b96bf78d9-r8n8t
接下来，我们来看看Delpoyment
[root@VM_0_17_centos ~]# kubectl describe deploy mq-svc
Name: mq-svc
Namespace: default
CreationTimestamp: Fri, 17 Aug 2018 17:21:13 +0800
Labels: qcloud-app=mq-svc
Annotations: deployment.changecourse=Updating
deployment.kubernetes.io/revision=2
description=Service based on rabbitmq.
Selector: qcloud-app=mq-svc
Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 10
RollingUpdateStrategy: 0 max unavailable, 1 max surge
Pod Template:
Labels: qcloud-app=mq-svc
Containers:
queue-mq:
Image: rabbitmq:management
Port: <none>
Host Port: <none>
Limits:
cpu: 500m
memory: 1Gi
Requests:
cpu: 250m
memory: 256Mi
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Progressing True NewReplicaSetAvailable
Available True MinimumReplicasAvailable
OldReplicaSets: <none>
NewReplicaSet: mq-svc-5b96bf78d9 (1/1 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 58m deployment-controller Scaled up replica set mq-svc-5b96bf78d9 to 2
Normal ScalingReplicaSet 57m deployment-controller Scaled up replica set mq-svc-5b96bf78d9 to 3
Normal ScalingReplicaSet 57m deployment-controller Scaled up replica set mq-svc-5b96bf78d9 to 4
Normal ScalingReplicaSet 57m deployment-controller Scaled down replica set mq-svc-5b96bf78d9 to 3
Normal ScalingReplicaSet 57m deployment-controller Scaled up replica set mq-svc-5b96bf78d9 to 6
Normal ScalingReplicaSet 57m deployment-controller Scaled down replica set mq-svc-5b96bf78d9 to 4
Normal ScalingReplicaSet 56m deployment-controller Scaled down replica set mq-svc-5b96bf78d9 to 2
Normal ScalingReplicaSet 53m deployment-controller Scaled down replica set mq-svc-5b96bf78d9 1 It
can be seen that at the deployment level, it is no longer controlled by other components, and the transition of his state is generated as an API is called. We have seen that the events that occur at the deployment level are generally creating a service, rolling a service upgrade, or operating an RS scaling Pod cluster.
Finally, it is also very clear here that service is actually a stable service provided to the outside on this whole set of foundations.