Getting started with kubernetes to real-world resource management and Qos

1.1 resource definition

• Spec.container[].Resources.requests.cpuThe size of the requested cpu resource, such as 0.1 cpu and 100m, means 1/10 cpu is allocated;
• Spec.container[].Resources.requests.memoryRequest memory size in M, Mi, G, Gi;
• Spec.container[].Resources.limits.cpuLimit the size of the cpu to no more than the threshold, the limit in cggroup;
• Spec.container[].Resources.limits.memoryLimit the size of memory beyond the threshold, beyond which OOM will occur;

1. Start learning how to define resource resources for a pod. For example, using nginx-demo as an example, containers request 250 m cpu resources, limit 500 m, request 128 Mi memory resources, and limit 256 Mi memory resources. Of course, you can also define resources for multiple containers, which together are the total resources for a pod, as follows:

[root@node-1 demo]#cat nginx-resource.yaml apiVersion: v1 kind: Pod metadata: name: nginx-demo labels: name: nginx-demo spec: containers: - name: nginx-demo image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: requests: cpu: 0.25 memory: 128Mi limits: cpu: 500m memory: 256Mi

2. Apply the configuration definition of the pod (if the previous pod still exists, first delete the kubectl delete pod <pod-name>), or name the pod another name

[root@node-1 demo]# kubectl apply -f nginx-resource.yaml pod/nginx-demo created

3. View the allocation details of pod resources

[root@node-1 demo]# kubectl get pods NAME READY STATUS RESTARTS AGE demo-7b86696648-8bq7h 1/1 Running 0 12d demo-7b86696648-8qp46 1/1 Running 0 12d demo-7b86696648-d6hfw 1/1 Running 0 12d nginx-demo 1/1 Running 0 94s [root@node-1 demo]# kubectl describe pods nginx-demo Name: nginx-demo Namespace: default Priority: 0 Node: node-3/10.254.100.103 Start Time: Sat, 28 Sep 2019 12:10:49 +0800 Labels: name=nginx-demo Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-demo"},"name":"nginx-demo","namespace":"default"},"sp... Status: Running IP: 10.244.2.13 Containers: nginx-demo: Container ID: docker://55d28fdc992331c5c58a51154cd072cd6ae37e03e05ae829a97129f85eb5ed79 Image: nginx:1.7.9 Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451 Port: 80/TCP Host Port: 0/TCP State: Running Started: Sat, 28 Sep 2019 12:10:51 +0800 Ready: True Restart Count: 0 Limits: #Limit resources cpu: 500m memory: 256Mi Requests: #Request Resources cpu: 250m memory: 128Mi Environment: <none> ...ellipsis...

4. How are Pod's resources allocated?There is no doubt that it is allocated from nodes. When we create a pod with requests set, kube-scheduler of kubernetes performs two scheduling processes: filter filtering and weight weighting, and kube-scheduler filters the eligible nodes based on the requested resources, then sorts them, filters the nodes that best satisfy the running pod, and thenRun pod on a specific node.Scheduling algorithms and details can be referred to below Introduction of kubernetes scheduling algorithm .The following are the allocation details of node-3 node resources:

[root@node-1 ~]# kubectl describe node node-3 ...ellipsis... Capacity: #Total resource condition of resources on nodes, 1 cpu, 2 g memory, 110 pod s cpu: 1 ephemeral-storage: 51473888Ki hugepages-2Mi: 0 memory: 1882352Ki pods: 110 Allocatable: #Allowable allocation of resources by nodes, partially reserved resources are drained in the Allocatable category cpu: 1 ephemeral-storage: 47438335103 hugepages-2Mi: 0 memory: 1779952Ki pods: 110 System Info: Machine ID: 0ea734564f9a4e2881b866b82d679dfc System UUID: FFCD2939-1BF2-4200-B4FD-8822EBFFF904 Boot ID: 293f49fd-8a7c-49e2-8945-7a4addbd88ca Kernel Version: 3.10.0-957.21.3.el7.x86_64 OS Image: CentOS Linux 7 (Core) Operating System: linux Architecture: amd64 Container Runtime Version: docker://18.6.3 Kubelet Version: v1.15.3 Kube-Proxy Version: v1.15.3 PodCIDR: 10.244.2.0/24 Non-terminated Pods: (3 in total) #When running pod resources on a node, there are more than one pod in addition to nginx-demo Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits AGE --------- ---- ------------ ---------- --------------- ------------- --- default nginx-demo 250m (25%) 500m (50%) 128Mi (7%) 256Mi (14%) 63m kube-system kube-flannel-ds-amd64-jp594 100m (10%) 100m (10%) 50Mi (2%) 50Mi (2%) 14d kube-system kube-proxy-mh2gq 0 (0%) 0 (0%) 0 (0%) 0 (0%) 12d Allocated resources: #Allocated cpu and memory resources (Total limits may be over 100 percent, i.e., overcommitted.) Resource Requests Limits -------- -------- ------ cpu 350m (35%) 600m (60%) memory 178Mi (10%) 306Mi (17%) ephemeral-storage 0 (0%) 0 (0%) Events: <none>

1.2 Resource Allocation Principles

The resource requests and limits defined by Pod work on kube-sheduler, the dispatcher of kubernetes. In fact, the cpu and memory-defined resources are applied on containers and the cggroup on containers is used to isolate resources. Next, we describe the principles of resource allocation.

• Spec.containers[].Resources.requests.cpuUsed in CpuShares to indicate the weight assigned to the cpu and the proportion allocated during a race
• Spec.containers[].Resources.requests.memoryMainly used for kube-scheduler scheduler, not for container settings
• Spec.containers[].Resources.limits.cpuActs on CpuQuota and CpuPeriod, in microseconds, calculated as CpuQuota/CpuPeriod, which represents the percentage of maximum usable cpu, such as 500m, which allows 50% of a cpu's resources to be used
• Spec.containers[].Resources.limits.memoryActs on the emory, indicating the maximum available Memory size of the container, beyond which OOM will occur

Taking nginx-demo as an example, this paper studies the parameters that requests and limits defined in pod apply to docker in effect:

1. View the node where the pod is located and nginx-demo is dispatched to the node-3 node

[root@node-1 ~]# kubectl get pods -o wide nginx-demo NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx-demo 1/1 Running 0 96m 10.244.2.13 node-3 <none> <none>

2. To get the id number of the container, you can get the id of the container by using the containerID of kubectl describe pods nginx-demo, or you can get the id number of the container by logging on to the node-3 node through name filtering. By default, there are two pods: one created by pause mirror and the other by applying mirror.

[root@node-3 ~]# docker container list |grep nginx 55d28fdc9923 84581e99d807 "nginx -g 'daemon of..." 2 hours ago Up 2 hours k8s_nginx-demonginx-demo_default_66958ef7-507a-41cd-a688-7a4976c6a71e_0 2fe0498ea9b5 k8s.gcr.io/pause:3.1 "/pause" 2 hours ago Up 2 hours k8s_POD_nginx-demo_default_66958ef7-507a-41cd-a688-7a4976c6a71e_0

3. View docker container details

[root@node-3 ~]# docker container inspect 55d28fdc9923 [ ...Partial Output Omitting... { "Image": "sha256:84581e99d807a703c9c03bd1a31cd9621815155ac72a7365fd02311264512656", "ResolvConfPath": "/var/lib/docker/containers/2fe0498ea9b5dfe1eb63eba09b1598a8dfd60ef046562525da4dcf7903a25250/resolv.conf", "HostConfig": { "Binds": [ "/var/lib/kubelet/pods/66958ef7-507a-41cd-a688-7a4976c6a71e/volumes/kubernetes.io~secret/default-token-5qwmc:/var/run/secrets/kubernetes.io/serviceaccount:ro", "/var/lib/kubelet/pods/66958ef7-507a-41cd-a688-7a4976c6a71e/etc-hosts:/etc/hosts", "/var/lib/kubelet/pods/66958ef7-507a-41cd-a688-7a4976c6a71e/containers/nginx-demo/1cc072ca:/dev/termination-log" ], "ContainerIDFile": "", "LogConfig": { "Type": "json-file", "Config": { "max-size": "100m" } }, "UTSMode": "", "UsernsMode": "", "ShmSize": 67108864, "Runtime": "runc", "ConsoleSize": [ 0, 0 ], "Isolation": "", "CpuShares": 256, CPU Weight assigned to requests.cpu upper "Memory": 268435456, The size of the memory allocation used for limits.memory upper "NanoCpus": 0, "CgroupParent": "kubepods-burstable-pod66958ef7_507a_41cd_a688_7a4976c6a71e.slice", "BlkioWeight": 0, "BlkioWeightDevice": null, "BlkioDeviceReadBps": null, "BlkioDeviceWriteBps": null, "BlkioDeviceReadIOps": null, "BlkioDeviceWriteIOps": null, "CpuPeriod": 100000, CPU The allocated usage ratio, and CpuQuota Working together in limits.cpu upper "CpuQuota": 50000, "CpuRealtimePeriod": 0, "CpuRealtimeRuntime": 0, "CpusetCpus": "", "CpusetMems": "", "Devices": [], "DeviceCgroupRules": null, "DiskQuota": 0, "KernelMemory": 0, "MemoryReservation": 0, "MemorySwap": 268435456, "MemorySwappiness": null, "OomKillDisable": false, "PidsLimit": 0, "Ulimits": null, "CpuCount": 0, "CpuPercent": 0, "IOMaximumIOps": 0, "IOMaximumBandwidth": 0, }, } ]

1.3. cpu resource testing

CPU limitation in pod is mainly throughRequests.cpuandLimits.cpuLimits is defined as a CPU size that cannot be exceeded. We verify through the stress mirror that stress is a compression tool for both CPU and memory by specifying the args parameter to define the size of the compression cpu.The CPU and memory for monitoring pods can be viewed by kubectl top, depending on monitoring components such as metric-server or promethus, which are not currently installed, and we view them by docker stats.

1. Define a pod with stress mirror, assign 0.25 cores and limit 0.5 cores usage ratio

[root@node-1 demo]# cat cpu-demo.yaml apiVersion: v1 kind: Pod metadata: name: cpu-demo namespace: default annotations: kubernetes.io/description: "demo for cpu requests and" spec: containers: - name: stress-cpu image: vish/stress resources: requests: cpu: 250m limits: cpu: 500m args: - -cpus - "1"

2. Applying yaml file to generate pod

[root@node-1 demo]# kubectl apply -f cpu-demo.yaml pod/cpu-demo created

3. View pod resource allocation details

[root@node-1 demo]# kubectl describe pods cpu-demo Name: cpu-demo Namespace: default Priority: 0 Node: node-2/10.254.100.102 Start Time: Sat, 28 Sep 2019 14:33:12 +0800 Labels: <none> Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{"kubernetes.io/description":"demo for cpu requests and"},"name":"cpu-demo","nam... kubernetes.io/description: demo for cpu requests and Status: Running IP: 10.244.1.14 Containers: stress-cpu: Container ID: docker://14f93767ad37b92beb91e3792678f60c9987bbad3290ae8c29c35a2a80101836 Image: progrium/stress Image ID: docker-pullable://progrium/stress@sha256:e34d56d60f5caae79333cee395aae93b74791d50e3841986420d23c2ee4697bf Port: <none> Host Port: <none> Args: -cpus 1 State: Waiting Reason: CrashLoopBackOff Last State: Terminated Reason: Error Exit Code: 1 Started: Sat, 28 Sep 2019 14:34:28 +0800 Finished: Sat, 28 Sep 2019 14:34:28 +0800 Ready: False Restart Count: 3 Limits: #cpu restricted usage ratio cpu: 500m Requests: #cpu request size cpu: 250m

4. Log on to a specific node and view the container's resource usage details through docker container stats

Viewed over top on the node to which the pod belongs, the cpu usage limit is 50%.

From the above validation, we can conclude that we define the use of a core in the stress container and thatLimits.cpuLimit the usable cpu size to 500m, and test verifies that pod resources are strictly limited to 50% either inside the container or on the host machine (there is only one cpu on the node machine and 25% if there are two).

1.4 memory Resource Test

1. Verify by stress mirror testRequests.memoryandLimits.memoryThe effective range,Limits.memoryDefine the size of memory resources available to the container. OOM occurs when the container exceeds the size set by the memory. Define a test container with a maximum memory of 512M and a pressure mirror with vm-bytes to define a side memory size of 256Mi

[root@node-1 demo]# cat memory-demo.yaml apiVersion: v1 kind: Pod metadata: name: memory-stress-demo annotations: kubernetes.io/description: "stress demo for memory limits" spec: containers: - name: memory-stress-limits image: polinux/stress resources: requests: memory: 128Mi limits: memory: 512Mi command: ["stress"] args: ["--vm", "1", "--vm-bytes", "256M", "--vm-hang", "1"]

2. Applying yaml file to generate pod

[root@node-1 demo]# kubectl apply -f memory-demo.yaml pod/memory-stress-demo created [root@node-1 demo]# kubectl get pods memory-stress-demo -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES memory-stress-demo 1/1 Running 0 41s 10.244.1.19 node-2 <none> <none>

3. View the allocation of resources

[root@node-1 demo]# kubectl describe pods memory-stress-demo Name: memory-stress-demo Namespace: default Priority: 0 Node: node-2/10.254.100.102 Start Time: Sat, 28 Sep 2019 15:13:06 +0800 Labels: <none> Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{"kubernetes.io/description":"stress demo for memory limits"},"name":"memory-str... kubernetes.io/description: stress demo for memory limits Status: Running IP: 10.244.1.16 Containers: memory-stress-limits: Container ID: docker://c7408329cffab2f10dd860e50df87bd8671e65a0f8abb4dae96d059c0cb6bb2d Image: polinux/stress Image ID: docker-pullable://polinux/stress@sha256:6d1825288ddb6b3cec8d3ac8a488c8ec2449334512ecb938483fc2b25cbbdb9a Port: <none> Host Port: <none> Command: stress Args: --vm 1 --vm-bytes 256Mi --vm-hang 1 State: Waiting Reason: CrashLoopBackOff Last State: Terminated Reason: Error Exit Code: 1 Started: Sat, 28 Sep 2019 15:14:08 +0800 Finished: Sat, 28 Sep 2019 15:14:08 +0800 Ready: False Restart Count: 3 Limits: #Memory Limit Size memory: 512Mi Requests: #Memory Request Size memory: 128Mi Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qwmc (ro)

4. Check the usage of container memory resources, allocate 256M memory, the maximum usage is 512Mi, and the utilization rate is 50%. At this time, the container is running normally without exceeding the limit size.

5. What happens when the internal size of the container exceeds the memory size? We will set the--vm-byte to 513M, the container will try to run, OOM will occur when the internal memory exceeds, kube-controller-manager will keep trying to restart the container, and the number of RESTARTS will keep increasing.

[root@node-1 demo]# cat memory-demo.yaml apiVersion: v1 kind: Pod metadata: name: memory-stress-demo annotations: kubernetes.io/description: "stress demo for memory limits" spec: containers: - name: memory-stress-limits image: polinux/stress resources: requests: memory: 128Mi limits: memory: 512Mi command: ["stress"] args: ["--vm", "1", "--vm-bytes", "520M", "--vm-hang", "1"] . #520M memory in container //View the state of the container as OOMKilled, RESTARTS keeps increasing, and keeps trying to restart [root@node-1 demo]# kubectl get pods memory-stress-demo NAME READY STATUS RESTARTS AGE memory-stress-demo 0/1 OOMKilled 3 60s

Quality of Service (QOS) is mainly used as an important factor for pod dispatch and expulsion. Different QOS have different quality of service and corresponding priority, which are mainly divided into three types of QOS:

• BestEffort does its best to allocate resources, does not specify the Qos assigned by resource by default, and has the lowest priority;
• Burstable volatile resources, at least those allocated to requests, common QOS;
• Guaranteed fully guarantees resources, with requests and limits defining the same resources with the highest priority.

2.1 BestEffort best efforts

1. There is no resource defined in the Pod. The default Qos policy is BestEffort with the lowest priority. When the resource comparison is progressing and evice s need to be expelled, the Pod defined by BestEffort should be expelled first. Define a BestEffort pod as follows

[root@node-1 demo]# cat nginx-qos-besteffort.yaml apiVersion: v1 kind: Pod metadata: name: nginx-qos-besteffort labels: name: nginx-qos-besteffort spec: containers: - name: nginx-qos-besteffort image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: {}

2. Create a pod and view the Qos policy, qosClass is BestEffort

[root@node-1 demo]# kubectl apply -f nginx-qos-besteffort.yaml pod/nginx-qos-besteffort created //View Qos Policy [root@node-1 demo]# kubectl get pods nginx-qos-besteffort -o yaml apiVersion: v1 kind: Pod metadata: annotations: kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-qos-besteffort"},"name":"nginx-qos-besteffort","namespace":"default"},"spec":{"containers":[{"image":"nginx:1.7.9","imagePullPolicy":"IfNotPresent","name":"nginx-qos-besteffort","ports":[{"containerPort":80,"name":"nginx-port-80","protocol":"TCP"}],"resources":{}}]}} creationTimestamp: "2019-09-28T11:12:03Z" labels: name: nginx-qos-besteffort name: nginx-qos-besteffort namespace: default resourceVersion: "1802411" selfLink: /api/v1/namespaces/default/pods/nginx-qos-besteffort uid: 56e4a2d5-8645-485d-9362-fe76aad76e74 spec: containers: - image: nginx:1.7.9 imagePullPolicy: IfNotPresent name: nginx-qos-besteffort ports: - containerPort: 80 name: nginx-port-80 protocol: TCP resources: {} terminationMessagePath: /dev/termination-log ...ellipsis... status: hostIP: 10.254.100.102 phase: Running podIP: 10.244.1.21 qosClass: BestEffort #Qos Policy startTime: "2019-09-28T11:12:03Z"

3. Delete Test Pod

[root@node-1 demo]# kubectl delete pods nginx-qos-besteffort pod "nginx-qos-besteffort" deleted

2.2 Burstable can fluctuate

1. Pod's quality of service is Burstable, second only to Guaranteed's. At least one container needs to define requests, and requests define less resources than limits

[root@node-1 demo]# cat nginx-qos-burstable.yaml apiVersion: v1 kind: Pod metadata: name: nginx-qos-burstable labels: name: nginx-qos-burstable spec: containers: - name: nginx-qos-burstable image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: requests: cpu: 100m memory: 128Mi limits: cpu: 200m memory: 256Mi

2. Apply yaml file to generate pod and view Qos type

[root@node-1 demo]# kubectl apply -f nginx-qos-burstable.yaml pod/nginx-qos-burstable created //View Qos Types [root@node-1 demo]# kubectl describe pods nginx-qos-burstable Name: nginx-qos-burstable Namespace: default Priority: 0 Node: node-2/10.254.100.102 Start Time: Sat, 28 Sep 2019 19:27:37 +0800 Labels: name=nginx-qos-burstable Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-qos-burstable"},"name":"nginx-qos-burstable","namespa... Status: Running IP: 10.244.1.22 Containers: nginx-qos-burstable: Container ID: docker://d1324b3953ba6e572bfc63244d4040fee047ed70138b5a4bad033899e818562f Image: nginx:1.7.9 Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451 Port: 80/TCP Host Port: 0/TCP State: Running Started: Sat, 28 Sep 2019 19:27:39 +0800 Ready: True Restart Count: 0 Limits: cpu: 200m memory: 256Mi Requests: cpu: 100m memory: 128Mi Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qwmc (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-5qwmc: Type: Secret (a volume populated by a Secret) SecretName: default-token-5qwmc Optional: false QoS Class: Burstable #Quality of service is volatile Burstable Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 95s default-scheduler Successfully assigned default/nginx-qos-burstable to node-2 Normal Pulled 94s kubelet, node-2 Container image "nginx:1.7.9" already present on machine Normal Created 94s kubelet, node-2 Created container nginx-qos-burstable Normal Started 93s kubelet, node-2 Started container nginx-qos-burstable

2.3 Guaranteed Full Guaranteed

1. The cpu and memory defined in resource must contain requests and limits. The value of requests and limits must be the same, with the highest priority. This type of Qos is guaranteed first when dispatch and expulsion occur. Define a container for nginx-qos-guaranteed as follows.Requests.cpuandLimits.cpuSame, SameRequests.memoryandLimits.memory.

[root@node-1 demo]# cat nginx-qos-guaranteed.yaml apiVersion: v1 kind: Pod metadata: name: nginx-qos-guaranteed labels: name: nginx-qos-guaranteed spec: containers: - name: nginx-qos-guaranteed image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: requests: cpu: 200m memory: 256Mi limits: cpu: 200m memory: 256Mi

2. Guaranteed can be fully guaranteed by applying yaml file to generate pod and viewing the Qos type of pod

[root@node-1 demo]# kubectl apply -f nginx-qos-guaranteed.yaml pod/nginx-qos-guaranteed created [root@node-1 demo]# kubectl describe pods nginx-qos-guaranteed Name: nginx-qos-guaranteed Namespace: default Priority: 0 Node: node-2/10.254.100.102 Start Time: Sat, 28 Sep 2019 19:37:15 +0800 Labels: name=nginx-qos-guaranteed Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-qos-guaranteed"},"name":"nginx-qos-guaranteed","names... Status: Running IP: 10.244.1.23 Containers: nginx-qos-guaranteed: Container ID: docker://cf533e0e331f49db4e9effb0fbb9249834721f8dba369d281c8047542b9f032c Image: nginx:1.7.9 Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451 Port: 80/TCP Host Port: 0/TCP State: Running Started: Sat, 28 Sep 2019 19:37:16 +0800 Ready: True Restart Count: 0 Limits: cpu: 200m memory: 256Mi Requests: cpu: 200m memory: 256Mi Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qwmc (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-5qwmc: Type: Secret (a volume populated by a Secret) SecretName: default-token-5qwmc Optional: false QoS Class: Guaranteed #Quality of service is fully guaranteed for Guaranteed Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 25s default-scheduler Successfully assigned default/nginx-qos-guaranteed to node-2 Normal Pulled 24s kubelet, node-2 Container image "nginx:1.7.9" already present on machine Normal Created 24s kubelet, node-2 Created container nginx-qos-guaranteed Normal Started 24s kubelet, node-2 Started container nginx-qos-guaranteed

This chapter is kubernetes series tutorials In the sixth article, by introducing resource resource allocation and quality of service Qos, node usage suggestions for resource are given:

• requests and limits resource definitions recommend no more than 1:2 to avoid resource contention and OOM due to excessive resource allocation.
• There is no resource defined by default in pod. It is recommended to define a limitrange for namespace to ensure that pod can allocate resources.
• To prevent excessive resources on the node from occurring due to machine hang ing or OOM, it is recommended to set up retention and expulsion of resources on the node, such as reservation of resources--system-reserved=cpu=200m,memory=1G, expulsion condition--eviction hard=Memory.available<500Mi.

Container computing resource management: https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/

pod memory resource management: https://kubernetes.io/docs/tasks/configure-pod-container/assign-memory-resource/

pod cpu resource management: https://kubernetes.io/docs/tasks/configure-pod-container/assign-cpu-resource/

Quality of Service QOS: https://kubernetes.io/docs/tasks/configure-pod-container/quality-service-pod/

Docker's CPU limitations: https://www.cnblogs.com/sparkdev/p/8052522.html

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