· ☕ 2 分钟

x-forwarded-client-cert

https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_conn_man/headers#x-forwarded-client-cert

x-forwarded-client-cert (XFCC) is a proxy header which indicates certificate information of part or all of the clients or proxies that a request has flowed through, on its way from the client to the server. A proxy may choose to sanitize/append/forward the XFCC header before proxying the request.

The XFCC header value is a comma (",") separated string. Each substring is an XFCC element, which holds information added by a single proxy. A proxy can append the current client certificate information as an XFCC element, to the end of the request’s XFCC header after a comma.

· ☕ 2 分钟

https://istio.io/latest/docs/ops/common-problems/network-issues/#double-tls

Double TLS (TLS origination for a TLS request)

When configuring Istio to perform TLS origination, you need to make sure that the application sends plaintext requests to the sidecar, which will then originate the TLS.

TLS Origination

TLS origination occurs when an Istio proxy (sidecar or egress gateway) is configured to accept unencrypted internal HTTP connections, encrypt the requests, and then forward them to HTTPS servers that are secured using simple or mutual TLS. This is the opposite of TLS termination where an ingress proxy accepts incoming TLS connections, decrypts the TLS, and passes unencrypted requests on to internal mesh services.

· ☕ 1 分钟

How Does the CPU Manager Work?

When CPU manager is enabled with the “static” policy, it manages a shared pool of CPUs. Initially this shared pool contains all the CPUs in the compute node. When a container with integer CPU request in a Guaranteed pod is created by the Kubelet, CPUs for that container are removed from the shared pool and assigned exclusively for the lifetime of the container. Other containers are migrated off these exclusively allocated CPUs.

· ☕ 1 分钟

注意：kubelet修改cpu_manager策略配置，一定要停掉kubelet服务，并删除/var/lib/kubelet/cpu_manager_state 文件，再重启kubelet，否则会导致kubelet服务重启失败。

· ☕ 1 分钟

Memory Manager Goals

  • 保证最少 NUMA Node 去满足 POD 的内存需求: Offer guaranteed memory (and hugepages) allocation over a minimum number of NUMA nodes for containers (within a pod).

  • 长远是让pod中的所有 container 运行在尽量少的 NUMA NODE 中： Guaranteeing the affinity of memory and hugepages to the same NUMA node for the whole group of containers (within a pod). This is a long-term goal which will be achieved along with PR #1752 and the implementation of hintprovider.GetPodLevelTopologyHints() API in the Memory Manager.- Offer guaranteed memory (and hugepages) allocation over a minimum number of NUMA nodes for containers (within a pod).

· ☕ 2 分钟

K8s Memory Manager

Requriement

Your Kubernetes server must be at or later than version v1.21. To check the version, enter kubectl version.

To align memory resources with other requested resources in a Pod Spec:

Starting from v1.22, the Memory Manager is enabled by default through MemoryManager feature gate.

· ☕ 2 分钟

Topology Manager Scopes and Policies

Topology Manager provides two distinct knobs: scope and policy.

The scope defines the granularity at which you would like resource alignment to be performed (e.g. at the pod or container level). And the policy defines the actual strategy used to carry out the alignment (e.g. best-effort, restricted, single-numa-node, etc.).

Topology Manager Scopes

The Topology Manager can deal with the alignment of resources in a couple of distinct scopes:

· ☕ 1 分钟

kubectl debug

https://kubernetes.io/docs/tasks/debug-application-cluster/debug-running-pod/#ephemeral-container

https://towardsdatascience.com/the-easiest-way-to-debug-kubernetes-workloads-ff2ff5e3cc75

1
2
3

kubectl explain pod.spec.ephemeralContainers

kubectl debug -it ephemeral-demo --image=busybox --target=ephemeral-demo

Process Namespace Sharing

https://towardsdatascience.com/the-easiest-way-to-debug-kubernetes-workloads-ff2ff5e3cc75

kubectl debug -it some-app –image=busybox –share-processes –copy-to=some-app-debug

· ☕ 1 分钟 
➜  2305 pidstat -t -p 2305 1
Linux 5.4.0-74-generic (labile-T30) 	2021年06月24日 	_x86_64_	(2 CPU)

18时37分39秒   UID      TGID       TID    %usr %system  %guest   %wait    %CPU   CPU  Command
18时37分40秒 64055      2305         -    1.00    2.00   14.00    3.00   17.00     1  qemu-system-x86
18时37分40秒 64055         -      2305    1.00    1.00    0.00    3.00    2.00     1  |__qemu-system-x86
18时37分40秒 64055         -      2307    0.00    0.00    0.00    0.00    0.00     0  |__qemu-system-x86
18时37分40秒 64055         -      2312    0.00    0.00    0.00    0.00    0.00     0  |__IO mon_iothread
18时37分40秒 64055         -      2313    0.00    0.00    9.00    5.00    9.00     1  |__CPU 0/KVM
18时37分40秒 64055         -      2314    0.00    2.00    5.00    5.00    7.00     0  |__CPU 1/KVM
18时37分40秒 64055         -      2316    0.00    0.00    0.00    1.00    0.00     1  |__SPICE Worker
18时37分40秒 64055         -     76701    0.00    0.00    0.00    0.00    0.00     0  |__worker

perf kvm stat live

18:42:23.185815

Analyze events for all VMs, all VCPUs:

             VM-EXIT    Samples  Samples%     Time%    Min Time    Max Time         Avg time 

           MSR_WRITE        648    60.67%     5.04%      0.47us 181016.17us    715.22us ( +-  44.28% )
                 HLT        207    19.38%    92.36%      2.05us 3684299.87us  40991.17us ( +-  43.93% )
  EXTERNAL_INTERRUPT         85     7.96%     1.43%      0.34us  43275.57us   1540.36us ( +-  50.18% )
    PREEMPTION_TIMER         78     7.30%     0.25%      0.66us  12804.28us    294.09us ( +-  69.79% )
   PENDING_INTERRUPT         49     4.59%     0.93%      0.60us  84909.22us   1735.07us ( +-  99.87% )
   PAUSE_INSTRUCTION          1     0.09%     0.00%      0.82us      0.82us      0.82us ( +-   0.00% )

Total Samples:1068, Total events handled time:9187522.33us.
· ☕ 1 分钟

Website docs

Github