zh_trans: /blog/_posts/2018-07-09-IPVS-In-Cluster-Load-Balancing.md
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congfairy
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---
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title: 基于IPVS的集群内部负载均衡
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cn-approvers:
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- congfairy
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layout: blog
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title: 'IPVS-Based In-Cluster Load Balancing Deep Dive'
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date: 2018-07-09
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---
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<!--
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Author: Jun Du(Huawei), Haibin Xie(Huawei), Wei Liang(Huawei)
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Editor’s note: this post is part of a series of in-depth articles on what’s new in Kubernetes 1.11
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-->
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作者: Jun Du(华为), Haibin Xie(华为), Wei Liang(华为)
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注意: 这篇文章出自系列深度文章介绍Kubernetes 1.11的新特性
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<!--
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Introduction
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Per the Kubernetes 1.11 release blog post , we announced that IPVS-Based In-Cluster Service Load Balancing graduates to General Availability. In this blog, we will take you through a deep dive of the feature.
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-->
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介绍
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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。
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<!--
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What Is IPVS?
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IPVS (IP Virtual Server) is built on top of the Netfilter and implements transport-layer load balancing as part of the Linux kernel.
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IPVS is incorporated into the LVS (Linux Virtual Server), where it runs on a host and acts as a load balancer in front of a cluster of real servers. IPVS can direct requests for TCP- and UDP-based services to the real servers, and make services of the real servers appear as virtual services on a single IP address. Therefore, IPVS naturally supports Kubernetes Service.
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-->
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什么是IPVS?
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IPVS (IP Virtual Server)是在Netfileter上层构建的，并作为Linux内核的一部分，实现传输层负载均衡。
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IPVS集成在LVS（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。
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<!--
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Why IPVS for Kubernetes?
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As Kubernetes grows in usage, the scalability of its resources becomes more and more important. In particular, the scalability of services is paramount to the adoption of Kubernetes by developers/companies running large workloads.
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Kube-proxy, the building block of service routing has relied on the battle-hardened iptables to implement the core supported Service types such as ClusterIP and NodePort. However, iptables struggles to scale to tens of thousands of Services because it is designed purely for firewalling purposes and is based on in-kernel rule lists.
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Even though Kubernetes already support 5000 nodes in release v1.6, the kube-proxy with iptables is actually a bottleneck to scale the cluster to 5000 nodes. One example is that with NodePort Service in a 5000-node cluster, if we have 2000 services and each services have 10 pods, this will cause at least 20000 iptable records on each worker node, and this can make the kernel pretty busy.
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On the other hand, using IPVS-based in-cluster service load balancing can help a lot for such cases. IPVS is specifically designed for load balancing and uses more efficient data structures (hash tables) allowing for almost unlimited scale under the hood.
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-->
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为什么为Kubernetes选择IPVS?
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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。
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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。
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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。
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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。
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<!--
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IPVS-based Kube-proxy
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Parameter Changes
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Parameter: --proxy-mode In addition to existing userspace and iptables modes, IPVS mode is configured via --proxy-mode=ipvs. It implicitly uses IPVS NAT mode for service port mapping.
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-->
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基于IPVS的Kube-proxy
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参数更改
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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。
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<!--
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Parameter: --ipvs-scheduler
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A new kube-proxy parameter has been added to specify the IPVS load balancing algorithm, with the parameter being --ipvs-scheduler. If it’s not configured, then round-robin (rr) is the default value.
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- rr: round-robin
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- lc: least connection
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- dh: destination hashing
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- sh: source hashing
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- sed: shortest expected delay
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- nq: never queue
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In the future, we can implement Service specific scheduler (potentially via annotation), which has higher priority and overwrites the value.
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-->
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参数: --ipvs-scheduler
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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）。
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- rr: round-robin
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- lc: least connection
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- dh: destination hashing
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- sh: source hashing
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- sed: shortest expected delay
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- nq: never queue
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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。
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<!--
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Parameter: --cleanup-ipvs Similar to the --cleanup-iptables parameter, if true, cleanup IPVS configuration and IPTables rules that are created in IPVS mode.
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Parameter: --ipvs-sync-period Maximum interval of how often IPVS rules are refreshed (e.g. '5s', '1m'). Must be greater than 0.
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Parameter: --ipvs-min-sync-period Minimum interval of how often the IPVS rules are refreshed (e.g. '5s', '1m'). Must be greater than 0.
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-->
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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。
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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。
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参数r: --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。
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<!--
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Parameter: --ipvs-exclude-cidrs A comma-separated list of CIDR's which the IPVS proxier should not touch when cleaning up IPVS rules because IPVS proxier can't distinguish kube-proxy created IPVS rules from user original IPVS rules. If you are using IPVS proxier with your own IPVS rules in the environment, this parameter should be specified, otherwise your original rule will be cleaned.
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-->
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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。
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<!--
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Design Considerations
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IPVS Service Network Topology
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When creating a ClusterIP type Service, IPVS proxier will do the following three things:
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- Make sure a dummy interface exists in the node, defaults to kube-ipvs0
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- Bind Service IP addresses to the dummy interface
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- Create IPVS virtual servers for each Service IP address respectively
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-->
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设计注意事项
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IPVS服务网络拓扑
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创建ClusterIP类型服务时，IPVS proxier将执行以下三项操作：
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- 确保节点中存在虚拟接口，默认为kube-ipvs0
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- 将服务IP地址绑定到虚拟接口
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- 分别为每个服务IP地址创建IPVS虚拟服务器
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<!--
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Here comes an example:
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# kubectl describe svc nginx-service
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Name: nginx-service
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...
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Type: ClusterIP
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IP: 10.102.128.4
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Port: http 3080/TCP
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Endpoints: 10.244.0.235:8080,10.244.1.237:8080
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Session Affinity: None
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# ip addr
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...
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73: kube-ipvs0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 1000
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link/ether 1a:ce:f5:5f:c1:4d brd ff:ff:ff:ff:ff:ff
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inet 10.102.128.4/32 scope global kube-ipvs0
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valid_lft forever preferred_lft forever
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# ipvsadm -ln
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IP Virtual Server version 1.2.1 (size=4096)
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Prot LocalAddress:Port Scheduler Flags
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-> RemoteAddress:Port Forward Weight ActiveConn InActConn
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TCP 10.102.128.4:3080 rr
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-> 10.244.0.235:8080 Masq 1 0 0
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-> 10.244.1.237:8080 Masq 1 0 0
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-->
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举个例子:
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# kubectl describe svc nginx-service
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Name: nginx-service
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...
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Type: ClusterIP
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IP: 10.102.128.4
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Port: http 3080/TCP
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Endpoints: 10.244.0.235:8080,10.244.1.237:8080
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Session Affinity: None
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# ip addr
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...
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73: kube-ipvs0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 1000
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link/ether 1a:ce:f5:5f:c1:4d brd ff:ff:ff:ff:ff:ff
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inet 10.102.128.4/32 scope global kube-ipvs0
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valid_lft forever preferred_lft forever
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# ipvsadm -ln
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IP Virtual Server version 1.2.1 (size=4096)
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Prot LocalAddress:Port Scheduler Flags
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-> RemoteAddress:Port Forward Weight ActiveConn InActConn
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TCP 10.102.128.4:3080 rr
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-> 10.244.0.235:8080 Masq 1 0 0
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-> 10.244.1.237:8080 Masq 1 0 0
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<!--
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Please note that the relationship between a Kubernetes Service and IPVS virtual servers is 1:N. For example, consider a Kubernetes Service that has more than one IP address. An External IP type Service has two IP addresses - ClusterIP and External IP. Then the IPVS proxier will create 2 IPVS virtual servers - one for Cluster IP and another one for External IP. The relationship between a Kubernetes Endpoint (each IP+Port pair) and an IPVS virtual server is 1:1.
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Deleting of a Kubernetes service will trigger deletion of the corresponding IPVS virtual server, IPVS real servers and its IP addresses bound to the dummy interface.
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Port Mapping
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There are three proxy modes in IPVS: NAT (masq), IPIP and DR. Only NAT mode supports port mapping. Kube-proxy leverages NAT mode for port mapping. The following example shows IPVS mapping Service port 3080 to Pod port 8080.
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-->
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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”。
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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。
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端口映射
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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。
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TCP 10.102.128.4:3080 rr
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-> 10.244.0.235:8080 Masq 1 0 0
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-> 10.244.1.237:8080 Masq 1 0
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<!--
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Session Affinity
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IPVS supports client IP session affinity (persistent connection). When a Service specifies session affinity, the IPVS proxier will set a timeout value (180min=10800s by default) in the IPVS virtual server. For example:
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-->
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会话亲和性
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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：
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# kubectl describe svc nginx-service
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Name: nginx-service
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...
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IP: 10.102.128.4
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Port: http 3080/TCP
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Session Affinity: ClientIP
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# ipvsadm -ln
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IP Virtual Server version 1.2.1 (size=4096)
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Prot LocalAddress:Port Scheduler Flags
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-> RemoteAddress:Port Forward Weight ActiveConn InActConn
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TCP 10.102.128.4:3080 rr persistent 10800
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<!--
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Iptables & Ipset in IPVS Proxier
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IPVS is for load balancing and it can't handle other workarounds in kube-proxy, e.g. packet filtering, hairpin-masquerade tricks, SNAT, etc.
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IPVS proxier leverages iptables in the above scenarios. Specifically, ipvs proxier will fall back on iptables in the following 4 scenarios:
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- kube-proxy start with --masquerade-all=true
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- Specify cluster CIDR in kube-proxy startup
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- Support Loadbalancer type service
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- Support NodePort type service
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However, we don't want to create too many iptables rules. So we adopt ipset for the sake of decreasing iptables rules. The following is the table of ipset sets that IPVS proxier maintains:
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-->
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IPVS代理中的Iptables 和 Ipset
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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
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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：
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- kube-proxy以--masquerade-all = true开头
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- 在kube-proxy启动中指定集群CIDR
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- 支持Loadbalancer类型服务
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- 支持NodePort类型的服务
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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：
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<!--
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set name members usage
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KUBE-CLUSTER-IP All Service IP + port masquerade for cases that masquerade-all=true or clusterCIDR specified
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KUBE-LOOP-BACK All Service IP + port + IP masquerade for resolving hairpin issue
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KUBE-EXTERNAL-IP Service External IP + port masquerade for packets to external IPs
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KUBE-LOAD-BALANCER Load Balancer ingress IP + port masquerade for packets to Load Balancer type service
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KUBE-LOAD-BALANCER-LOCAL Load Balancer ingress IP + port with externalTrafficPolicy=local accept packets to Load Balancer with externalTrafficPolicy=local
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KUBE-LOAD-BALANCER-FW Load Balancer ingress IP + port with loadBalancerSourceRanges Drop packets for Load Balancer type Service with loadBalancerSourceRanges specified
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||||
KUBE-LOAD-BALANCER-SOURCE-CIDR Load Balancer ingress IP + port + source CIDR accept packets for Load Balancer type Service with loadBalancerSourceRanges specified
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KUBE-NODE-PORT-TCP NodePort type Service TCP port masquerade for packets to NodePort(TCP)
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KUBE-NODE-PORT-LOCAL-TCP NodePort type Service TCP port with externalTrafficPolicy=local accept packets to NodePort Service with externalTrafficPolicy=local
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||||
KUBE-NODE-PORT-UDP NodePort type Service UDP port masquerade for packets to NodePort(UDP)
|
||||
KUBE-NODE-PORT-LOCAL-UDP NodePort type service UDP port with externalTrafficPolicy=local accept packets to NodePort Service with externalTrafficPolicy=local
|
||||
|
||||
-->
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||||
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||||
设置名称 成员 用法
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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
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KUBE-LOOP-BACK 所有服务IP +端口+ IP 解决数据包欺骗问题
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KUBE-EXTERNAL-IP 服务外部IP +端口 将数据包伪装成外部IP
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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
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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
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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
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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
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KUBE-NODE-PORT-TCP NodePort类型服务TCP 将数据包伪装成NodePort（TCP）
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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
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||||
KUBE-NODE-PORT-UDP NodePort类型服务UDP端口 将数据包伪装成 NodePort(UDP)
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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
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||||
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||||
<!--
|
||||
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||||
In general, for IPVS proxier, the number of iptables rules is static, no matter how many Services/Pods we have.
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||||
|
||||
-->
|
||||
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||||
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。
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||||
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||||
<!--
|
||||
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||||
Run kube-proxy in IPVS Mode
|
||||
|
||||
Currently, local-up scripts, GCE scripts, and kubeadm support switching IPVS proxy mode via exporting environment variables (KUBE_PROXY_MODE=ipvs) or specifying flag (--proxy-mode=ipvs). Before running IPVS proxier, please ensure IPVS required kernel modules are already installed.
|
||||
|
||||
ip_vs
|
||||
ip_vs_rr
|
||||
ip_vs_wrr
|
||||
ip_vs_sh
|
||||
nf_conntrack_ipv4
|
||||
|
||||
Finally, for Kubernetes v1.10, feature gate SupportIPVSProxyMode is set to true by default. For Kubernetes v1.11, the feature gate is entirely removed. However, you need to enable --feature-gates=SupportIPVSProxyMode=true explicitly for Kubernetes before v1.10.
|
||||
|
||||
-->
|
||||
|
||||
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。
|
||||
|
||||
<!--
|
||||
|
||||
Get Involved
|
||||
|
||||
The simplest way to get involved with Kubernetes is by joining one of the many Special Interest Groups (SIGs) that align with your interests. Have something you’d like to broadcast to the Kubernetes community? Share your voice at our weekly community meeting, and through the channels below.
|
||||
|
||||
Thank you for your continued feedback and support.
|
||||
|
||||
Post questions (or answer questions) on Stack Overflow
|
||||
|
||||
Join the community portal for advocates on K8sPort
|
||||
|
||||
Follow us on Twitter @Kubernetesio for latest updates
|
||||
|
||||
Chat with the community on Slack
|
||||
|
||||
Share your Kubernetes story
|
||||
|
||||
-->
|
||||
|
||||
参与其中
|
||||
|
||||
参与Kubernetes的最简单方法是加入众多[特别兴趣小组]（https://github.com/kubernetes/community/blob/master/sig-list.md）（SIG）中与您的兴趣一致的小组。 你有什么想要向Kubernetes社区广播的吗？ 在我们的每周[社区会议]（https://github.com/kubernetes/community/blob/master/communication.md#weekly-meeting）或通过以下渠道分享您的声音。
|
||||
|
||||
感谢您的持续反馈和支持。
|
||||
|
||||
在[Stack Overflow]上发布问题（或回答问题）（http://stackoverflow.com/questions/tagged/kubernetes）
|
||||
|
||||
加入[K8sPort]（http://k8sport.org/）的倡导者社区门户网站
|
||||
|
||||
在Twitter上关注我们[@Kubernetesio]（https://twitter.com/kubernetesio）获取最新更新
|
||||
|
||||
在[Slack]（http://slack.k8s.io/）上与社区聊天
|
||||
|
||||
分享您的Kubernetes [故事]（https://docs.google.com/a/linuxfoundation.org/forms/d/e/1FAIpQLScuI7Ye3VQHQTwBASrgkjQDSS5TP0g3AXfFhwSM9YpHgxRKFA/viewform）
|
||||
Reference in New Issue
Block a user