Add chapter about backups

slides/k8s/cluster-backup.md

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+# Backing up clusters
+
+- Backups can have multiple purposes:
+
+  - disaster recovery (servers or storage are destroyed or unreachable)
+
+  - error recovery (human or process has altered or corrupted data)
+
+  - cloning environments (for testing, validation ...)
+
+- Let's see the strategies and tools available with Kubernetes!
+
+---
+
+## Important
+
+- Kubernetes helps us with disaster recovery
+
+  (it gives us replication primitives)
+
+- Kubernetes helps us to clone / replicate environments
+
+  (all resources can be described with manifests)
+
+- Kubernetes *does not* help us with error recovery
+
+- This is the job of the storage layer
+
+- We still need to do e.g. database backups
+
+  (with snapshots, or tools like mysqldump, pgdump, etc.)
+
+---
+
+## In a perfect world ...
+
+- The deployment of our Kubernetes clusters is automated
+
+  (recreating a cluster takes less than a minute of human time)
+
+- All the resources (Deployments, Services...) on our clusters are under version control
+
+  (never use `kubectl run`; always apply YAML files coming from a repository)
+
+- Stateful components are either:
+
+  - stored on systems with regular snapshots
+
+  - backed up regularly to an external, durable storage
+
+  - outside of Kubernetes
+
+---
+
+## Kubernetes cluster deployment
+
+- If our deployment system isn't fully automated, it should at least be documented
+
+- Litmus test: how long does it take to deploy a cluster ...
+
+  - for a senior engineer?
+
+  - for a new hire?
+
+- Does it require external intervention?
+
+  (e.g. provisioning servers, signing TLS certs ...)
+
+---
+
+## Plan B
+
+- Full machine backups of the control plane can help
+
+- If the control plane is in pods (or containers), pay attention to storage drivers
+
+  (if the backup mechanism is not container-aware, the backups can take way more resources than they should, or even be unusable!)
+
+- If the previous sentence worries you:
+
+  **automate the deployment of your clusters!**
+
+---
+
+## Managing our Kubernetes resources
+
+- Ideal scenario:
+
+  - never create a resource directly on a cluster
+
+  - push to a code repository
+
+  - a special branch (`production` or even `master`) gets automatically deployed
+
+- Some folks call this "GitOps"
+
+  (it's the logical evolution of configuration management and infrastructure as code)
+
+---
+
+## GitOps in theory
+
+- What do we keep in version control?
+
+- For very simple scenarios: source code, Dockerfiles, scripts
+
+- For real applications: add resources (as YAML files)
+
+- For applications deployed multiple times: Helm, Kustomize ...
+
+  (staging and production count as "multiple times")
+
+---
+
+## GitOps tooling
+
+- Various tools exist (Weave Flux, GitKube...)
+
+- These tools are still very young
+
+- You still need to write YAML for all your resources
+
+- There is no tool to:
+
+  - list *all* resources in a namespace
+
+  - get resource YAML in a canonical form
+
+  - diff YAML descriptions with current state
+
+---
+
+## GitOps in practice
+
+- Start describing your resources with YAML
+
+- Leverage a tool like Kustomize or Helm
+
+- Make sure that you can easily deploy to a new namespace
+
+  (or even better: to a new cluster)
+
+- When tooling matures, you will be ready
+
+---
+
+## Plan B
+
+- What if we can't describe everything with YAML?
+
+- What if we manually create resources and forget to commit them to source control?
+
+- What about global resources, that don't live in a namespace?
+
+- How can we be sure that we saved *everything*?
+
+---
+
+## Backing up etcd
+
+- All objects are saved in etcd
+
+- etcd data should be relatively small
+
+  (and therefore, quick and easy to back up)
+
+- Two options to back up etcd:
+
+  - snapshot the data directory
+
+  - use `etcdctl snapshot`
+
+---
+
+## Making an etcd snapshot
+
+- The basic command is simple:
+  ```bash
+  etcdctl snapshot save <filename>
+  ```
+
+- But we also need to specify:
+
+  - an environment variable to specify that we want etcdctl v3
+
+  - the address of the server to back up
+
+  - the path to the key, certificate, and CA certificate
+    <br/>(if our etcd uses TLS certificates)
+
+---
+
+## Snapshotting etcd on kubeadm
+
+- The following command will work on clusters deployed with kubeadm
+
+  (and maybe others)
+
+- It should be run on a master node
+
+```bash
+docker run --rm --net host -v $PWD:/vol \
+    -v /etc/kubernetes/pki/etcd:/etc/kubernetes/pki/etcd:ro \
+    -e ETCDCTL_API=3 k8s.gcr.io/etcd:3.3.10 \
+    etcdctl --endpoints=https://[127.0.0.1]:2379 \
+            --cacert=/etc/kubernetes/pki/etcd/ca.crt \
+            --cert=/etc/kubernetes/pki/etcd/healthcheck-client.crt \
+            --key=/etc/kubernetes/pki/etcd/healthcheck-client.key \
+            snapshot save /vol/snapshot
+```
+
+- It will create a file named `snapshot` in the current directory
+
+---
+
+## How can we remember all these flags?
+
+- Look at the static pod manifest for etcd
+
+  (in `/etc/kubernetes/manifests`)
+
+- The healthcheck probe is calling `etcdctl` with all the right flags 
+  😉👍✌️
+
+- Exercise: write the YAML for a batch job to perform the backup
+
+---
+
+## Restoring an etcd snapshot
+
+- ~~Execute exactly the same command, but replacing `save` with `restore`~~
+
+  (Believe it or not, doing that will *not* do anything useful!)
+
+- The `restore` command does *not* load a snapshot into a running etcd server
+
+- The `restore` command creates a new data directory from the snapshot
+
+  (it's an offline operation; it doesn't interact with an etcd server)
+
+---
+
+## When using kubeadm
+
+1. Create a new data directory from the snapshot:
+   ```bash
+   sudo rm -rf /var/lib/etcd
+   docker run --rm -v /var/lib:/var/lib -v $PWD:/vol \
+          -e ETCDCTL_API=3 k8s.gcr.io/etcd:3.3.10 \
+          etcdctl snapshot restore /vol/snapshot --data-dir=/var/lib/etcd
+   ```
+
+2. Provision the control plane, using that data directory:
+   ```bash
+   sudo kubeadm init \
+        --ignore-preflight-errors=DirAvailable--var-lib-etcd
+   ```
+
+3. Rejoin the other nodes
+
+---
+
+## The fine print
+
+- This only saves etcd state
+
+- It **does not** save persistent volumes and local node data
+
+- Some critical components (like the pod network) might need to be reset
+
+- As a result, our pods might have to be recreated, too
+
+- If we have proper liveness checks, this should happen automatically
+
+---
+
+## More information
+
+- [Kubernetes documentation](https://kubernetes.io/docs/tasks/administer-cluster/configure-upgrade-etcd/#built-in-snapshot) about etcd backups
+
+- [etcd documentation](https://coreos.com/etcd/docs/latest/op-guide/recovery.html#snapshotting-the-keyspace) about snapshots and restore
+
+- [A good blog post by elastisys](https://elastisys.com/2018/12/10/backup-kubernetes-how-and-why/) explaining how to restore a snapshot
+
+- [Another good blog post by consol labs](https://labs.consol.de/kubernetes/2018/05/25/kubeadm-backup.html) on the same topic
+
+---
+
+## Stateful services
+
+- It's totally fine to keep your production databases outside of Kubernetes
+
+  *Especially if you have only one database server!*
+
+- Feel free to put development and staging databases on Kubernetes
+
+  (as long as they don't hold important data)
+
+- Using Kubernetes for stateful services makes sense if you have *many*
+
+  (because then you can leverage Kubernetes automation)