Kubernetes 博客

Wednesday, December 05, 2018

New Contributor Workshop Shanghai

Authors: Josh Berkus (Red Hat), Yang Li (The Plant), Puja Abbassi (Giant Swarm), XiangPeng Zhao (ZTE)

Kubecon Shanghai New Contributor Summit attendees. Photo by Jerry Zhang

Kubecon Shanghai New Contributor Summit attendees. Photo by Jerry Zhang

We recently completed our first New Contributor Summit in China, at the first KubeCon in China. It was very exciting to see all of the Chinese and Asian developers (plus a few folks from around the world) interested in becoming contributors. Over the course of a long day, they learned how, why, and where to contribute to Kubernetes, created pull requests, attended a panel of current contributors, and got their CLAs signed.

This was our second New Contributor Workshop (NCW), building on the one created and led by SIG Contributor Experience members in Copenhagen. Because of the audience, it was held in both Chinese and English, taking advantage of the superb simultaneous interpretation services the CNCF sponsored. Likewise, the NCW team included both English and Chinese-speaking members of the community: Yang Li, XiangPeng Zhao, Puja Abbassi, Noah Abrahams, Tim Pepper, Zach Corleissen, Sen Lu, and Josh Berkus. In addition to presenting and helping students, the bilingual members of the team translated all of the slides into Chinese. Fifty-one students attended.

Noah Abrahams explains Kubernetes communications channels. Photo by Jerry Zhang

Noah Abrahams explains Kubernetes communications channels. Photo by Jerry Zhang

The NCW takes participants through the stages of contributing to Kubernetes, starting from deciding where to contribute, followed by an introduction to the SIG system and our repository structure. We also have “guest speakers” from Docs and Test Infrastructure who cover contributing in those areas. We finally wind up with some hands-on exercises in filing issues and creating and approving PRs.

Those hands-on exercises use a repository known as the contributor playground, created by SIG Contributor Experience as a place for new contributors to try out performing various actions on a Kubernetes repo. It has modified Prow and Tide automation, uses Owners files like in the real repositories. This lets students learn how the mechanics of contributing to our repositories work without disrupting normal development.

Yang Li talks about getting your PRs reviewed. Photo by Josh Berkus

Yang Li talks about getting your PRs reviewed. Photo by Josh Berkus

Both the “Great Firewall” and the language barrier prevent contributing Kubernetes from China from being straightforward. What’s more, because open source business models are not mature in China, the time for employees work on open source projects is limited.

Chinese engineers are eager to participate in the development of Kubernetes, but many of them don’t know where to start since Kubernetes is such a large project. With this workshop, we hope to help those who want to contribute, whether they wish to fix some bugs they encountered, improve or localize documentation, or they need to work with Kubernetes at their work. We are glad to see more and more Chinese contributors joining the community in the past few years, and we hope to see more of them in the future.

“I have been participating in the Kubernetes community for about three years,” said XiangPeng Zhao. “In the community, I notice that more and more Chinese developers are showing their interest in contributing to Kubernetes. However, it’s not easy to start contributing to such a project. I tried my best to help those who I met in the community, but I think there might still be some new contributors leaving the community due to not knowing where to get help when in trouble. Fortunately, the community initiated NCW at KubeCon Copenhagen and held a second one at KubeCon Shanghai. I was so excited to be invited by Josh Berkus to help organize this workshop. During the workshop, I met community friends in person, mentored attendees in the exercises, and so on. All of this was a memorable experience for me. I also learned a lot as a contributor who already has years of contributing experience. I wish I had attended such a workshop when I started contributing to Kubernetes years ago.”

Panel of contributors. Photo by Jerry Zhang

Panel of contributors. Photo by Jerry Zhang

The workshop ended with a panel of current contributors, featuring Lucas Käldström, Janet Kuo, Da Ma, Pengfei Ni, Zefeng Wang, and Chao Xu. The panel aimed to give both new and current contributors a look behind the scenes on the day-to-day of some of the most active contributors and maintainers, both from China and around the world. Panelists talked about where to begin your contributor’s journey, but also how to interact with reviewers and maintainers. They further touched upon the main issues of contributing from China and gave attendees an outlook into exciting features they can look forward to in upcoming releases of Kubernetes.

After the workshop, Xiang Peng Zhao chatted with some attendees on WeChat and Twitter about their experiences. They were very glad to have attended the NCW and had some suggestions on improving the workshop. One attendee, Mohammad, said, “I had a great time at the workshop and learned a lot about the entire process of k8s for a contributor.” Another attendee, Jie Jia, said, “The workshop was wonderful. It systematically explained how to contribute to Kubernetes. The attendee could understand the process even if s/he knew nothing about that before. For those who were already contributors, they could also learn something new. Furthermore, I could make new friends from inside or outside of China in the workshop. It was awesome!”

SIG Contributor Experience will continue to run New Contributor Workshops at each upcoming Kubecon, including Seattle, Barcelona, and the return to Shanghai in June 2019. If you failed to get into one this year, register for one at a future Kubecon. And, when you meet an NCW attendee, make sure to welcome them to the community.

Links:

2018.07.09

IPVS-Based In-Cluster Load Balancing Deep Dive

作者: Jun Du(华为), Haibin Xie(华为), Wei Liang(华为)

注意: 这篇文章出自 系列深度文章 介绍 Kubernetes 1.11 的新特性

介绍

根据 Kubernetes 1.11 发布的博客文章, 我们宣布基于 IPVS 的集群内部服务负载均衡已达到一般可用性。 在这篇博客中,我们将带您深入了解该功能。

什么是 IPVS ?

IPVS (IP Virtual Server)是在 Netfilter 上层构建的,并作为 Linux 内核的一部分,实现传输层负载均衡。

IPVS 集成在 LVS(Linux Virtual Server,Linux 虚拟服务器)中,它在主机上运行,并在物理服务器集群前作为负载均衡器。IPVS 可以将基于 TCP 和 UDP 服务的请求定向到真实服务器,并使真实服务器的服务在单个IP地址上显示为虚拟服务。 因此,IPVS 自然支持 Kubernetes 服务。

为什么为 Kubernetes 选择 IPVS ?

随着 Kubernetes 的使用增长,其资源的可扩展性变得越来越重要。特别是,服务的可扩展性对于运行大型工作负载的开发人员/公司采用 Kubernetes 至关重要。

Kube-proxy 是服务路由的构建块,它依赖于经过强化攻击的 iptables 来实现支持核心的服务类型,如 ClusterIP 和 NodePort。 但是,iptables 难以扩展到成千上万的服务,因为它纯粹是为防火墙而设计的,并且基于内核规则列表。

尽管 Kubernetes 在版本v1.6中已经支持5000个节点,但使用 iptables 的 kube-proxy 实际上是将集群扩展到5000个节点的瓶颈。 一个例子是,在5000节点集群中使用 NodePort 服务,如果我们有2000个服务并且每个服务有10个 pod,这将在每个工作节点上至少产生20000个 iptable 记录,这可能使内核非常繁忙。

另一方面,使用基于 IPVS 的集群内服务负载均衡可以为这种情况提供很多帮助。 IPVS 专门用于负载均衡,并使用更高效的数据结构(哈希表),允许几乎无限的规模扩张。

基于 IPVS 的 Kube-proxy

参数更改

参数: –proxy-mode 除了现有的用户空间和 iptables 模式,IPVS 模式通过–proxy-mode = ipvs 进行配置。 它隐式使用 IPVS NAT 模式进行服务端口映射。

参数: –ipvs-scheduler

添加了一个新的 kube-proxy 参数来指定 IPVS 负载均衡算法,参数为 –ipvs-scheduler。 如果未配置,则默认为 round-robin 算法(rr)。

  • rr: round-robin
  • lc: least connection
  • dh: destination hashing
  • sh: source hashing
  • sed: shortest expected delay
  • nq: never queue

将来,我们可以实现特定于服务的调度程序(可能通过注释),该调度程序具有更高的优先级并覆盖该值。

参数: –cleanup-ipvs 类似于 –cleanup-iptables 参数,如果为 true,则清除在 IPVS 模式下创建的 IPVS 配置和 IPTables 规则。

参数: –ipvs-sync-period 刷新 IPVS 规则的最大间隔时间(例如’5s’,’1m’)。 必须大于0。

参数: –ipvs-min-sync-period 刷新 IPVS 规则的最小间隔时间间隔(例如’5s’,’1m’)。 必须大于0。

参数: –ipvs-exclude-cidrs 清除 IPVS 规则时 IPVS 代理不应触及的 CIDR 的逗号分隔列表,因为 IPVS 代理无法区分 kube-proxy 创建的 IPVS 规则和用户原始规则 IPVS 规则。 如果您在环境中使用 IPVS proxier 和您自己的 IPVS 规则,则应指定此参数,否则将清除原始规则。

设计注意事项

IPVS 服务网络拓扑

创建 ClusterIP 类型服务时,IPVS proxier 将执行以下三项操作:

  • 确保节点中存在虚拟接口,默认为 kube-ipvs0
  • 将服务 IP 地址绑定到虚拟接口
  • 分别为每个服务 IP 地址创建 IPVS 虚拟服务器

这是一个例子:

# kubectl describe svc nginx-service
Name:           nginx-service
...
Type:           ClusterIP
IP:             10.102.128.4
Port:           http    3080/TCP
Endpoints:      10.244.0.235:8080,10.244.1.237:8080
Session Affinity:   None

# ip addr
...
73: kube-ipvs0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 1a:ce:f5:5f:c1:4d brd ff:ff:ff:ff:ff:ff
    inet 10.102.128.4/32 scope global kube-ipvs0
       valid_lft forever preferred_lft forever

# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn     
TCP  10.102.128.4:3080 rr
  -> 10.244.0.235:8080            Masq    1      0          0         
  -> 10.244.1.237:8080            Masq    1      0          0   

请注意,Kubernetes 服务和 IPVS 虚拟服务器之间的关系是“1:N”。 例如,考虑具有多个 IP 地址的 Kubernetes 服务。 外部 IP 类型服务有两个 IP 地址 - 集群IP和外部 IP。 然后,IPVS 代理将创建2个 IPVS 虚拟服务器 - 一个用于集群 IP,另一个用于外部 IP。 Kubernetes 的 endpoint(每个IP +端口对)与 IPVS 虚拟服务器之间的关系是“1:1”。

删除 Kubernetes 服务将触发删除相应的 IPVS 虚拟服务器,IPVS 物理服务器及其绑定到虚拟接口的 IP 地址。

端口映射

IPVS 中有三种代理模式:NAT(masq),IPIP 和 DR。 只有 NAT 模式支持端口映射。 Kube-proxy 利用 NAT 模式进行端口映射。 以下示例显示 IPVS 服务端口3080到Pod端口8080的映射。

TCP  10.102.128.4:3080 rr
  -> 10.244.0.235:8080            Masq    1      0          0         
  -> 10.244.1.237:8080            Masq    1      0       

会话关系

IPVS 支持客户端 IP 会话关联(持久连接)。 当服务指定会话关系时,IPVS 代理将在 IPVS 虚拟服务器中设置超时值(默认为180分钟= 10800秒)。 例如:

# kubectl describe svc nginx-service
Name:           nginx-service
...
IP:             10.102.128.4
Port:           http    3080/TCP
Session Affinity:   ClientIP

# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  10.102.128.4:3080 rr persistent 10800

IPVS 代理中的 Iptables 和 Ipset

IPVS 用于负载均衡,它无法处理 kube-proxy 中的其他问题,例如 包过滤,数据包欺骗,SNAT 等

IPVS proxier 在上述场景中利用 iptables。 具体来说,ipvs proxier 将在以下4种情况下依赖于 iptables:

  • kube-proxy 以 –masquerade-all = true 开头
  • 在 kube-proxy 启动中指定集群 CIDR
  • 支持 Loadbalancer 类型服务
  • 支持 NodePort 类型的服务

但是,我们不想创建太多的 iptables 规则。 所以我们采用 ipset 来减少 iptables 规则。 以下是 IPVS proxier 维护的 ipset 集表:

设置名称 成员 用法
KUBE-CLUSTER-IP 所有服务 IP + 端口 masquerade-all=true 或 clusterCIDR 指定的情况下进行伪装 KUBE-LOOP-BACK 所有服务 IP +端口+ IP 解决数据包欺骗问题
KUBE-EXTERNAL-IP 服务外部 IP +端口 将数据包伪装成外部 IP
KUBE-LOAD-BALANCER 负载均衡器入口 IP +端口 将数据包伪装成 Load Balancer 类型的服务
KUBE-LOAD-BALANCER-LOCAL 负载均衡器入口 IP +端口 以及 externalTrafficPolicy=local 接受数据包到 Load Balancer externalTrafficPolicy=local KUBE-LOAD-BALANCER-FW 负载均衡器入口 IP +端口 以及 loadBalancerSourceRanges 使用指定的 loadBalancerSourceRanges 丢弃 Load Balancer类型Service的数据包 KUBE-LOAD-BALANCER-SOURCE-CIDR 负载均衡器入口 IP +端口 + 源 CIDR 接受 Load Balancer 类型 Service 的数据包,并指定loadBalancerSourceRanges KUBE-NODE-PORT-TCP NodePort 类型服务 TCP 将数据包伪装成 NodePort(TCP)
KUBE-NODE-PORT-LOCAL-TCP NodePort 类型服务 TCP 端口,带有 externalTrafficPolicy=local 接受数据包到 NodePort 服务 使用 externalTrafficPolicy=local KUBE-NODE-PORT-UDP NodePort 类型服务 UDP 端口 将数据包伪装成 NodePort(UDP)
KUBE-NODE-PORT-LOCAL-UDP NodePort 类型服务 UDP 端口 使用 externalTrafficPolicy=local 接受数据包到NodePort服务 使用 externalTrafficPolicy=local

通常,对于 IPVS proxier,无论我们有多少 Service/ Pod,iptables 规则的数量都是静态的。

在 IPVS 模式下运行 kube-proxy

目前,本地脚本,GCE 脚本和 kubeadm 支持通过导出环境变量(KUBE_PROXY_MODE=ipvs)或指定标志(–proxy-mode=ipvs)来切换 IPVS 代理模式。 在运行IPVS 代理之前,请确保已安装 IPVS 所需的内核模块。

ip_vs
ip_vs_rr
ip_vs_wrr
ip_vs_sh
nf_conntrack_ipv4

最后,对于 Kubernetes v1.10,“SupportIPVSProxyMode” 默认设置为 “true”。 对于 Kubernetes v1.11 ,该选项已完全删除。 但是,您需要在v1.10之前为Kubernetes 明确启用 –feature-gates = SupportIPVSProxyMode = true。

参与其中

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