Kubernetes云提供商作用及L4负载均衡Pending问题咨询

Hey there! Let's break down each of your questions clearly, since you're new to Kubernetes and dealing with that frustrating LoadBalancer stuck in Pending state.

1. What exactly does a Cloud Provider do? #

Think of a Cloud Provider as a "translator" between Kubernetes and your underlying cloud infrastructure. It lets K8s interact directly with your cloud service provider's APIs to handle infrastructure-specific tasks automatically, like:

• Provisioning managed L4 load balancers (the exact thing you're trying to set up)
• Creating cloud-native persistent storage volumes (like OVH's block storage)
• Syncing node public/private IPs with K8s
• Cleaning up cloud resources if a node fails

In short, it turns Kubernetes' abstract requests into concrete actions your cloud provider understands, so you don't have to manually click around in the OVH console to tie K8s to your infrastructure.

2. Is a Cloud Provider useful in my environment? #

Absolutely—if you want Kubernetes to automatically provision OVH's managed L4 load balancers. Your cluster runs on OVH VMs via RKE/Rancher, so configuring the official OVH Cloud Provider plugin would let you create LoadBalancer-type Services that automatically spin up OVH's load balancers, fix that Pending state, and handle traffic routing to your nodes.

If you're only using L7 Ingress and ClusterIP Services right now and that meets your needs, it's not strictly required immediately. But if you ever need managed cloud storage, automated load balancer provisioning, or tighter integration with OVH's infrastructure, it'll become essential.

3. Do I have to configure a Cloud Provider to run L4 LoadBalancers? #

No—but it depends on what kind of L4 load balancing you want.

• If you want Kubernetes to automatically create a managed cloud L4 load balancer (like OVH's offering), then yes—K8s can't talk to OVH's APIs directly, so the Cloud Provider plugin is required to bridge that gap.
• If you're willing to set up L4 load balancing yourself (either inside or outside the cluster), you don't need a Cloud Provider at all. We'll cover these alternatives next.

4. What are the alternatives to a Cloud Provider-backed L4 LoadBalancer? #

Here are three practical, beginner-friendly options:

• MetalLB: This is the go-to solution for bare-metal/private cloud clusters. It lets you assign static or dynamic IPs (from a range you control, like your OVH VM's public/private subnet) to LoadBalancer-type Services. It uses ARP/NDP or BGP to advertise these IPs to your network, so external traffic can reach them and route to your Pods. It fully integrates with K8s' LoadBalancer API, so your Service won't stay Pending.
• NodePort + External Load Balancer: Convert your Service to NodePort type, which exposes it on a static port across all cluster nodes. Then set up a standalone L4 load balancer (like HAProxy or NGINX with stream mode enabled) outside the cluster, and configure it to forward traffic to all nodes' NodePort. You'll have to maintain the external load balancer manually, but it's simple for small clusters.
• NGINX Ingress Controller (L4 Mode): Modern NGINX Ingress Controllers support TCP/UDP forwarding (L4 traffic). You can configure a ConfigMap to map specific external ports to your cluster Services, effectively using the Ingress controller as an L4 proxy.

5. Can I build a custom Cloud Provider (like one based on NGINX) instead of using official ones? #

Technically, yes—but this is not recommended, especially for a beginner. Kubernetes requires Cloud Providers to implement a strict set of standard interfaces (like cloudprovider.Interface) that cover load balancing, storage, node management, and more. Building and maintaining a custom Cloud Provider would require deep knowledge of K8s internals and ongoing maintenance to keep up with K8s updates.

Plus, solutions like MetalLB or NGINX as an external load balancer already solve the L4 problem you're facing without needing a custom Cloud Provider. If you're set on extending infrastructure integration, it's far easier to build on existing tools (like the Kubernetes cloud-controller-manager framework) than to start from scratch.

内容的提问来源于stack exchange，提问作者MHogge