Is Kubernetes all about scaling a service on a cluster of servers? Or is it also used for managing the same applications on a bunch of servers?
e.g. 100 customers, 100 bare-metal servers, the same dockerized applications on each one. I need to deploy a new version of one of these applications on every server.
Or something like Ansible would be better suited and easier for this use case? I never used Ansible but I understood that I could make a recipe that does a git pull and a docker-compose down && docker-compose up -d on every server in a single command, right?
You could use Kubernetes for this- each customer having their own pod/set, all of which are based on the same template. Kubernetes would help make the overall management a lot easier via abstracting the underlying infrastructure (100 individual services is enough for the cost/benefit ratio of the abstraction to kick in).
That being said, a configuration management tool like Ansible would also fit your use case nicely. Ansible in particular is great for the'I need 100 identical application stacks' scenario.
If your application stack is already containerized, you have the luxury of following either path. It really depends on how much overhead you experience from managing the underlying infrastructure. You can imagine the option range as something like "bare individual VMs w/ Docker >>> Managed container service >>> Managed Kubernetes service".
You can use Kubernetes to run service on every machine. But that is usually done for support services like logging that need to run on every node.
Is it one customer per server? That wouldn't be a very good fit for Kubernetes. Kubernetes is about running containers on cluster of machines, scaling multiple services.
Kubernetes would let you run service per customer on cluster of machines and scale the number of containers for each customer independently. You wouldn't have to setup new server for each customer.
I disagree about it not being a good fit. Even if you run one application per host (and if we're honest, it will always be more when we find flaws). You still get the benefits of very predictable deployments, failovers, lifecycle management, etc.
e.g. 100 customers, 100 bare-metal servers, the same dockerized applications on each one. I need to deploy a new version of one of these applications on every server.
Or something like Ansible would be better suited and easier for this use case? I never used Ansible but I understood that I could make a recipe that does a git pull and a docker-compose down && docker-compose up -d on every server in a single command, right?