How to Run a Software as a Service on Kubernetes

How to Run a Software as a Service on Kubernetes

The first version of CockroachDB Dedicated, our database-as-a-service product, had our users fill out a Google doc with their cloud deployment preferences. We’ve come a long way since that initial proof of concept (including, yes, building a UI). More importantly, we’ve put implementation patterns in place that make something complicated (like configuring a cloud deployment) scalable. As we’ve written about before, choosing to run CockroachDB Dedicated on Kubernetes is a huge part of that implementation pattern. 

In a recent episode of The Cockroach Hour, CockroachDB Dedicated SREs Juan Leon and Josh Imhoff sat down to talk about some of the tools and processes we use to make that happen. While some of the information is specific to CockroachDB Dedicated, many of the implementation patterns covered in the webinar are applicable to anyone considering running their SaaS product on Kubernetes. In this blog post, we’ll recap some of those lessons, from the unexpected benefits of running on Kubernetes to the provisioning and certification platforms we use alongside it.

Why We Use Kubernetes for our SaaS Product 

About a year ago, Josh wrote a blog about why the SRE team started running CockroachDB Dedicated on Kubernetes. There are a lot of different benefits to Kubernetes. Early on, we really cared primarily about the automation and orchestration abilities (more on that, below). But as time goes on, we’ve found more and more reasons to love K8s. 

Automation and Orchestration Primitives

CockroachDB Dedicated is a managed database as a service, and we needed our customers to be able to scale their CockroachDB clusters up and down at the drop of a hat. Therefore, the powerful automation primitives inherent in Kubernetes was really top of mind for us. 

When we were just starting CockroachDB Dedicated, we did this workflow with Terraform. Terraform spun up the VMs for us, and then CockroachDB on those VMs with supervisor scripts and a touch of homegrown automation. And the benefits of that was it was very simple. You just have the VM and then just Cockroach process running. That's it, which the SRE team liked. There's not tons of moving pieces they got to understand. But the cost was high: it was rather hard to do orchestration tasks.

But we knew we needed to automate these tasks--while maintaining a high level of reliability--and we didn't want to build that ourselves. Kubernetes was the best way to do that, and does an excellent job. 

Bin Packing

Another main benefit to deploying our software as a service on Kubernetes is its bin packing capabilities. Kubernetes lets you pack a bunch of containers on a VM in a way that improves resource utilization. This is one of the motivating reasons for Google's Borg (a tool both Josh and Juan had used previously). Google realized how much resources they could save by bin packing containers through virtual machines.

When we were initially building CockroachDB Dedicated, we didn't care about bin packing at all. We just wanted to run one Cockroach node per VM, because we wanted the whole VM for CockroachDB. We didn't even need that benefit of Kubernetes. And there's a lot of complexity that comes from those two requirements being implemented by Kubernetes and we were taking on that complexity in order to get only some of the benefits of Kubernetes almost.

Kubernetes Provides a Common Interface

Another big benefit we didn't totally expect when first using Kubernetes is the simplicity a common interface offers. Right now, CockroachDB Dedicated runs on GCP and AWS, and we have plans to expand. Kubernetes offers a consistent way of running production across clouds. And that's powerful. 

Other Tools We Use for CockroachDB Dedicated

For Kubernetes monitoring: Prometheus and Grafana 

As far as monitoring goes, we run Prometheus clusters, Prometheus Alertmanager and Grafana in each customer cluster on Kubernetes. So in a given Kubernetes cluster we have dedicated to customer A, we're running Prometheus Alert Manager and Grafana. If it's a multi-region cluster, each region's running Prometheus and they're scraping all the regions, so it's replicated. Then we have a meta-monitoring Prometheus instance that’s just sitting outside of the cluster. It's going to page if the problems for the customer abound.

For Certificates: Vault 

We also needed to automate certs when scaling CockroachDB Dedicated. We use HashiCorp’s Vault (and Kubernetes) for that. Vault is a really powerful secret store. If you have a secret that you want to just store in a specific place, just write a key to Vault, and Vault will keep it and handle encryption for you. It also serves as our certificate authenticator, and manages and distributes project owner tokens. 

We run Vault in a control plane that's used to manage all the clusters. That way, Vault's not in the serving path. Rhwn, we use secrets within each instance to manage the certificate. Alternatively, we could have had CockroachDB talk directly to Vault, but that would introduce security issues. Because then the customer cluster has access to this thing that has keys for all the customers. Vault writes things to Kubernetes, but the customer’s cluster--since it’s accessible by the customer--cannot talk to Vault.

For Provisioning Hardware: Pulumi

We were initially depending on Terraform to provision hardware. But again, we had this future in our heads of service that creates clusters and adds regions to existing clusters and all of that. And we didn't really want our code to be generating Terraform configs, that then get executed by Terraform. We just thought that was a little messy. So we looked at Pulumi, which is very core to Terraform, except that you can configure it with Go code. We’re a Go shop, which made it a great fit for us. 

Conclusion

Your implementation patterns will no doubt vary from CockroachDB’s. But the lessons Josh, Juan, and Jim cover in this webinar are relevant to anyone running--or considering running--their software-as-a-service on Kubernetes. For more details on gotchas and lessons learned (plus a quick conversation about what Kubernetes can do it a serverless world), watch the full webinar here

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