From fad478f608a62b0f572ab0679ebcbe165c9d8ebf Mon Sep 17 00:00:00 2001
From: Angus Lees <gus@inodes.org>
Date: Thu, 18 May 2017 16:48:29 +1000
Subject: [PATCH] Attempt to topologically sort resources before updating
The goal is to make a best-effort attempt at reducing the number of
"crash-restart" loops required to bring up a group of interdependent
resources.
The current implementation is very simple and just sorts into 3 tiers:
- Namespace, ThirdPartyResource, StorageClass
- everything else
- Pods or similar (Pod/Job/Deployment/DaemonSet/StatefulSet)
---
cmd/update.go | 4 ++++
utils/sort.go | 59 ++++++++++++++++++++++++++++++++++++++++++++++
utils/sort_test.go | 34 ++++++++++++++++++++++++++
3 files changed, 97 insertions(+)
create mode 100644 utils/sort.go
create mode 100644 utils/sort_test.go
diff --git a/cmd/update.go b/cmd/update.go
index 8ffc485d..655afe59 100644
--- a/cmd/update.go
+++ b/cmd/update.go
@@ -10,6 +10,8 @@ import (
"k8s.io/client-go/pkg/api/errors"
"k8s.io/client-go/pkg/runtime"
"k8s.io/client-go/pkg/util/diff"
+
+ "github.com/ksonnet/kubecfg/utils"
)
const (
@@ -47,6 +49,8 @@ var updateCmd = &cobra.Command{
return err
}
+ utils.SortDepFirst(objs)
+
for _, obj := range objs {
desc := fmt.Sprintf("%s/%s", obj.GetKind(), fqName(obj))
glog.Info("Updating ", desc)
diff --git a/utils/sort.go b/utils/sort.go
new file mode 100644
index 00000000..554f4c24
--- /dev/null
+++ b/utils/sort.go
@@ -0,0 +1,59 @@
+package utils
+
+import (
+ "sort"
+
+ "k8s.io/client-go/pkg/api/unversioned"
+ "k8s.io/client-go/pkg/runtime"
+)
+
+var (
+ gkNamespace = unversioned.GroupKind{Group: "", Kind: "Namespace"}
+ gkTpr = unversioned.GroupKind{Group: "extensions", Kind: "ThirdPartyResource"}
+ gkStorageClass = unversioned.GroupKind{Group: "storage.k8s.io", Kind: "StorageClass"}
+
+ gkPod = unversioned.GroupKind{Group: "", Kind: "Pod"}
+ gkJob = unversioned.GroupKind{Group: "batch", Kind: "Job"}
+ gkDeployment = unversioned.GroupKind{Group: "extensions", Kind: "Deployment"}
+ gkDaemonSet = unversioned.GroupKind{Group: "extensions", Kind: "DaemonSet"}
+ gkStatefulSet = unversioned.GroupKind{Group: "apps", Kind: "StatefulSet"}
+)
+
+// These kinds all start pods.
+// TODO: expand this list.
+func isPodOrSimilar(gk unversioned.GroupKind) bool {
+ return gk == gkPod ||
+ gk == gkJob ||
+ gk == gkDeployment ||
+ gk == gkDaemonSet ||
+ gk == gkStatefulSet
+}
+
+// Arbitrary numbers used to do a simple topological sort of resources.
+// TODO: expand this list.
+func depTier(o *runtime.Unstructured) int {
+ gk := o.GroupVersionKind().GroupKind()
+ if gk == gkNamespace || gk == gkTpr || gk == gkStorageClass {
+ return 10
+ } else if isPodOrSimilar(gk) {
+ return 100
+ } else {
+ return 50
+ }
+}
+
+type dependentObjects []*runtime.Unstructured
+
+func (l dependentObjects) Len() int { return len(l) }
+func (l dependentObjects) Swap(i, j int) { l[i], l[j] = l[j], l[i] }
+func (l dependentObjects) Less(i, j int) bool {
+ return depTier(l[i]) < depTier(l[j])
+}
+
+// SortDepFirst *best-effort* sorts the objects so that known
+// dependencies appear earlier in the list. The idea is to prevent
+// *some* of the "crash-restart" loops when creating inter-dependent
+// resources.
+func SortDepFirst(objs []*runtime.Unstructured) {
+ sort.Sort(dependentObjects(objs))
+}
diff --git a/utils/sort_test.go b/utils/sort_test.go
new file mode 100644
index 00000000..c579badc
--- /dev/null
+++ b/utils/sort_test.go
@@ -0,0 +1,34 @@
+package utils
+
+import (
+ "testing"
+
+ "k8s.io/client-go/pkg/runtime"
+)
+
+func newObj(apiVersion, kind string) *runtime.Unstructured {
+ return &runtime.Unstructured{
+ Object: map[string]interface{}{
+ "apiVersion": apiVersion,
+ "kind": kind,
+ },
+ }
+}
+
+func TestSort(t *testing.T) {
+ objs := []*runtime.Unstructured{
+ newObj("extensions/v1beta1", "Deployment"),
+ newObj("v1", "ConfigMap"),
+ newObj("v1", "Namespace"),
+ newObj("v1", "Service"),
+ }
+
+ SortDepFirst(objs)
+
+ if objs[0].GetKind() != "Namespace" {
+ t.Error("Namespace should be sorted first")
+ }
+ if objs[3].GetKind() != "Deployment" {
+ t.Error("Deployment should be sorted after other objects")
+ }
+}
--
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