groundwork (#140)

kubernetes/migration/migrate.go

@@ -0,0 +1,231 @@
+package migration
+// This package provides a set of functions to help handle migrations of CoreDNS Corefiles to be compatible with new
+// versions of CoreDNS. The task of upgrading CoreDNS is the responsibility of a variety of Kubernetes management tools
+// (e.g. kubeadm and others), and the precise behavior may be different for each one. This library abstracts some basic
+// helper functions that make this easier to implement.
+
+import (
+	"github.com/coredns/deployment/kubernetes/migration/corefile"
+)
+
+// Deprecated returns a list of deprecated plugins or directives present in the Corefile. Each Notice returned is a
+// warning, e.g. "plugin 'foo' is deprecated." An empty list returned means there are no deprecated plugins/options
+// present in the Corefile.
+func Deprecated(fromCoreDNSVersion, toCoreDNSVersion, corefileStr string) ([]Notice, error) {
+	return getStatus(fromCoreDNSVersion, toCoreDNSVersion, corefileStr, deprecated)
+}
+
+// Removed returns a list of removed plugins or directives present in the Corefile. Each Notice returned is a warning,
+// e.g. "plugin 'foo' is no longer supported." An empty list returned means there are no removed plugins/options
+// present in the Corefile.
+func Removed(fromCoreDNSVersion, toCoreDNSVersion, corefileStr string) ([]Notice, error) {
+	return getStatus(fromCoreDNSVersion, toCoreDNSVersion, corefileStr, removed)
+}
+
+// Unsupported returns a list of plugins that are not recognized/supported by the migration tool (but may still be valid in CoreDNS).
+func Unsupported(fromCoreDNSVersion, toCoreDNSVersion, corefileStr string) ([]Notice, error) {
+	return getStatus(fromCoreDNSVersion, toCoreDNSVersion, corefileStr, unsupported)
+}
+
+func getStatus(fromCoreDNSVersion, toCoreDNSVersion, corefileStr, status string) ([]Notice, error) {
+	notices := []Notice{}
+	cf, err := corefile.New(corefileStr)
+	if err != nil {
+		return notices, err
+	}
+	v := fromCoreDNSVersion
+	for {
+		v = Versions[v].nextVersion
+		for _, s := range cf.Servers {
+			for _, p := range s.Plugins {
+				vp, present := Versions[v].plugins[p.Name]
+				if status == unsupported {
+					if present {
+						continue
+					}
+					notices = append(notices, Notice{Plugin: p.Name, Severity: status, Version: v})
+					continue
+				}
+				if !present {
+					continue
+				}
+				if vp.status == status {
+					notices = append(notices, Notice{
+						Plugin:     p.Name,
+						Severity:   status,
+						Version:    v,
+						ReplacedBy: vp.replacedBy,
+						Additional: vp.additional,
+					})
+					continue
+				}
+				for _, o := range p.Options {
+					vo, present := Versions[v].plugins[p.Name].options[o.Name]
+					if status == unsupported {
+						if present {
+							continue
+						}
+						notices = append(notices, Notice{
+							Plugin:     p.Name,
+							Option:     o.Name,
+							Severity:   status,
+							Version:    v,
+							ReplacedBy: vo.replacedBy,
+							Additional: vo.additional,
+						})
+						continue
+					}
+					if !present {
+						continue
+					}
+					if vo.status == status {
+						notices = append(notices, Notice{Plugin: p.Name, Option: o.Name, Severity: status, Version: v})
+						continue
+					}
+				}
+			}
+		}
+		if v == toCoreDNSVersion {
+			break
+		}
+	}
+	return notices, nil
+}
+
+// Migrate returns version of the Corefile migrated to toCoreDNSVersion, or an error if it cannot.
+func Migrate(fromCoreDNSVersion, toCoreDNSVersion, corefileStr string, deprecations bool) (string, error) {
+	cf, err := corefile.New(corefileStr)
+	if err != nil {
+		return "", err
+	}
+	v := fromCoreDNSVersion
+	for {
+		v = Versions[v].nextVersion
+		newSrvs := []*corefile.Server{}
+		for _, s := range cf.Servers {
+			newPlugs := []*corefile.Plugin{}
+			for _, p := range s.Plugins {
+				vp, present := Versions[v].plugins[p.Name]
+				if !present {
+					newPlugs = append(newPlugs, p)
+					continue
+				}
+				if !deprecations && vp.status == deprecated {
+					newPlugs = append(newPlugs, p)
+					continue
+				}
+				if vp.action != nil {
+					p, err := vp.action(p)
+					if err != nil {
+						return "", err
+					}
+					if p == nil {
+						// remove plugin, skip options processing
+						continue
+					}
+				}
+				newOpts := []*corefile.Option{}
+				for _, o := range p.Options {
+					vo, present := Versions[v].plugins[p.Name].options[o.Name]
+					if !present {
+						newOpts = append(newOpts, o)
+						continue
+					}
+					if !deprecations && vo.status == deprecated {
+						newOpts = append(newOpts, o)
+						continue
+					}
+					if vo.action == nil {
+						newOpts = append(newOpts, o)
+						continue
+					}
+					o, err := vo.action(o)
+					if err != nil {
+						return "", err
+					}
+					if o == nil {
+						// remove option
+						continue
+					}
+					newOpts = append(newOpts, o)
+				}
+				newPlugs = append(newPlugs,
+					&corefile.Plugin{
+						Name:    p.Name,
+						Args:    p.Args,
+						Options: newOpts,
+					})
+			}
+			newSrvs = append(newSrvs,
+				&corefile.Server{
+					DomPorts: s.DomPorts,
+					Plugins:  newPlugs,
+				},
+			)
+		}
+		cf = corefile.Corefile{Servers: newSrvs}
+		if v == toCoreDNSVersion {
+			break
+		}
+	}
+	return cf.ToString(), nil
+}
+
+// Default returns true if the Corefile is the default for a given version of Kubernetes.
+// Or, if k8sVersion is empty, Default returns true if the Corefile is the default for any version of Kubernetes.
+func Default(k8sVersion, corefileStr string) bool {
+	cf, err := corefile.New(corefileStr)
+	if err != nil {
+		return false
+	}
+	NextVersion:
+	for _, v := range Versions {
+		if k8sVersion != "" && k8sVersion != v.k8sRelease {
+			continue
+		}
+		defCf, err := corefile.New(v.defaultConf)
+		if err != nil {
+			continue
+		}
+		// check corefile against k8s release default
+		if len(cf.Servers) != len(defCf.Servers) {
+			continue NextVersion
+		}
+		for _, s := range cf.Servers {
+			defS, found := s.FindMatch(defCf.Servers)
+			if !found {
+				continue NextVersion
+			}
+			if len(s.Plugins) != len(defS.Plugins) {
+				continue NextVersion
+			}
+			for _, p := range s.Plugins {
+				defP, found := p.FindMatch(defS.Plugins)
+				if !found {
+					continue NextVersion
+				}
+				if len(p.Options) != len(defP.Options) {
+					continue NextVersion
+				}
+				for _, o := range p.Options {
+					_, found := o.FindMatch(defP.Options)
+					if !found {
+						continue NextVersion
+					}
+				}
+			}
+		}
+		return true
+	}
+	return false
+}
+
+// Released returns true if dockerImageID matches any released image of CoreDNS.
+func Released(dockerImageID string) bool {
+	for _, v := range Versions {
+		if v.dockerImageID == dockerImageID {
+			return true
+		}
+	}
+	return false
+}