Add docs to cover upgrading kube-router

Documentation/upgrading.md

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+# Upgrading kube-router
+
+## Breaking Changes
+
+We follow semantic versioning and try to the best of our abilities to maintain a
+stable interface between patch versions. For example, `v0.1.1` -> `v0.1.2`
+should be a perfectly safe upgrade path, without data service interruption.
+However, major (`vX.0.0`) and minor (`v0.Y.0`) version upgrades may contain
+breaking changes, which will be detailed here and in the release notes.
+
+First check if you are upgrading across one of the
+[breaking change versions](#breaking-change-version-history). If so, read the
+relevant section(s) first before proceeding with the general guidelines below.
+
+## General Guidelines
+
+### Image Pull Policy
+Here we will assume that you have the following in your kube-router DaemonSet:
+```yaml
+imagePullPolicy: Always
+```
+
+If that's not the case, you will need to manually pull the desired image version
+on each of your nodes with a command like: `docker pull
+cloudnativelabs/kube-router:VERSION`
+
+### Without Rolling Updates
+
+This is the default situation with our DaemonSet manifests. We will soon be
+switching these manifests to use Rolling Updates though.
+
+The following example(s) show an upgrade from `v0.0.15` to `v0.0.16`.
+
+First we will modify the kube-router DaemonSet resource's image field:
+```
+kubectl -n kube-system set image ds/kube-router kube-router=cloudnativelabs/kube-router:v0.0.16
+```
+
+This does not actually trigger any version changes yet. It is recommended that
+you upgrade only one node and perform any tests you see fit to ensure nothing
+goes wrong.
+
+For example, we'll test upgrading kube-router on worker-01:
+```sh
+TEST_NODE="worker-01"
+TEST_POD="$(kubectl -n kube-system get pods -o wide|grep -E "^kube-router.*${TEST_NODE}"|awk '{ print $1 }')
+
+kubectl -n kube-system delete pod "${TEST_POD}"
+```
+
+You can watch to make sure the new kube-router pod comes up and stays running
+with:
+```sh
+kubectl -n kube-system get pods -o wide -w
+```
+
+Check the logs with:
+```sh
+TEST_NODE="worker-01"
+TEST_POD="$(kubectl -n kube-system get pods -o wide|grep -E "^kube-router.*${TEST_NODE}"|awk '{ print $1 }')
+
+kubectl -n kube-system logs "${TEST_POD}"
+```
+
+If it all looks good, go ahead and upgrade kube-router on all nodes:
+```sh
+kubectl -n kube-system delete pods -l k8s-app=kube-router
+```
+
+### With Rolling Updates
+
+*TODO*
+
+## Breaking Change Version History
+
+This section covers version specific upgrade instructions.
+
+### v0.0.X alpha versions
+
+While kube-router is in its alpha stage changes can be expected to be rapid.
+Therefor we cannot guarantee that a new alpha release will not break previous
+expected behavior.
+
+### v0.0.17 (aka v0.1.0-rc1)
+
+This version brings changes to hairpin and BGP peering CLI/annotation
+configuration flags/keys.
+
+CLI flag changes:
+- OLD: `--peer-router` -> NEW: `--peer-router-ips`
+- OLD: `--peer-asn` -> NEW: `--peer-router-asns`
+
+CLI flag additions:
+- NEW: `--peer-router-passwords`
+
+Annotation key changes:
+- OLD: `kube-router.io/hairpin-mode=` -> NEW:
+  `io.kube-router.net.service.hairpin=`
+- OLD: `net.kuberouter.nodeasn=` -> NEW: `io.kube-router.net.node.asn=`
+- OLD: `net.kuberouter.node.bgppeer.address=` -> NEW: `io.kube-router.net.peer.ips`
+- OLD: `net.kuberouter.node.bgppeer.asn` -> NEW: `io.kube-router.net.peer.asns`
+
+Annotation key additions:
+- NEW: `io.kube-router.net.peer.passwords`
+
+#### v0.0.17 Upgrade Procedure
+
+For CLI flag changes, all that is required is to change the flag names you use
+above to their new names at the same time that you change the image version.
+```
+kubectl -n kube-system edit ds kube-router
+```
+
+For Annotations, the recommended approach is to copy all the values of
+your current annotations into new annotations with the updated keys.
+
+You can get a quick look at all your service and node annotations with these
+commands:
+```sh
+kubectl describe services --all-namespaces |grep -E '^(Name:|Annotations:)'
+kubectl describe nodes |grep -E '^(Name:|Annotations:)'
+```
+
+For example if you have a service annotation to enable Hairpin mode like:
+```
+Name:              hairpin-service
+Annotations:       kube-router.io/hairpin-mode=
+```
+
+You will then want to make a new annotation with the new key:
+```sh
+kubectl annotate service hairpin-service "io.kube-router.net.service.hairpin="
+```
+
+Once all new annotations are created, proceed with the
+[General Guidelines](#general-guidelines). After the upgrades tested and
+complete, you can delete the old annotations.
+```sh
+kubectl annotate service hairpin-service "kube-router.io/hairpin-mode-"
+```