Refactor node drain (kubernetes-sigs#11074)

controllers/alias.go

@@ -18,7 +18,6 @@ package controllers
 
 import (
 	"context"
-	"time"
 
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
@@ -65,18 +64,14 @@ type MachineReconciler struct {
 
 	// WatchFilterValue is the label value used to filter events prior to reconciliation.
 	WatchFilterValue string
-
-	// NodeDrainClientTimeout timeout of the client used for draining nodes.
-	NodeDrainClientTimeout time.Duration
 }
 
 func (r *MachineReconciler) SetupWithManager(ctx context.Context, mgr ctrl.Manager, options controller.Options) error {
 	return (&machinecontroller.Reconciler{
-		Client:                 r.Client,
-		APIReader:              r.APIReader,
-		Tracker:                r.Tracker,
-		WatchFilterValue:       r.WatchFilterValue,
-		NodeDrainClientTimeout: r.NodeDrainClientTimeout,
+		Client:           r.Client,
+		APIReader:        r.APIReader,
+		Tracker:          r.Tracker,
+		WatchFilterValue: r.WatchFilterValue,
 	}).SetupWithManager(ctx, mgr, options)
 }
 

go.mod

@@ -33,6 +33,7 @@ require (
 	github.com/valyala/fastjson v1.6.4
 	go.etcd.io/etcd/api/v3 v3.5.15
 	go.etcd.io/etcd/client/v3 v3.5.15
+	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56
 	golang.org/x/oauth2 v0.22.0
 	golang.org/x/text v0.17.0
 	gomodules.xyz/jsonpatch/v2 v2.4.0
@@ -156,7 +157,6 @@ require (
 	go.uber.org/zap v1.27.0 // indirect
 	go4.org v0.0.0-20201209231011-d4a079459e60 // indirect
 	golang.org/x/crypto v0.26.0 // indirect
-	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56 // indirect
 	golang.org/x/net v0.28.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.23.0 // indirect

internal/controllers/machine/drain/cache.go

@@ -0,0 +1,97 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package drain
+
+import (
+	"time"
+
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/client-go/tools/cache"
+)
+
+const (
+	// ttl is the duration for which we keep entries in the cache.
+	ttl = 10 * time.Minute
+
+	// expirationInterval is the interval in which we will remove expired entries
+	// from the cache.
+	expirationInterval = 10 * time.Hour
+)
+
+// CacheEntry is an entry of the drain cache. It stores at which time a Machine was drained the last time.
+type CacheEntry struct {
+	Machine   types.NamespacedName
+	LastDrain time.Time
+}
+
+// Cache caches the time when the last drain was done for a Machine.
+// Specifically we only use it to ensure we only retry drains
+// at a specific interval and not more often.
+type Cache interface {
+	// Add adds the given entry to the Cache.
+	// Note: entries expire after the ttl.
+	Add(entry CacheEntry)
+
+	// Has checks if the given key (still) exists in the Cache.
+	// Note: entries expire after the ttl.
+	Has(machineName types.NamespacedName) (CacheEntry, bool)
+}
+
+// NewCache creates a new cache.
+func NewCache() Cache {
+	r := &drainCache{
+		Store: cache.NewTTLStore(func(obj interface{}) (string, error) {
+			// We only add CacheEntries to the cache, so it's safe to cast to CacheEntry.
+			return obj.(CacheEntry).Machine.String(), nil
+		}, ttl),
+	}
+	go func() {
+		for {
+			// Call list to clear the cache of expired items.
+			// We have to do this periodically as the cache itself only expires
+			// items lazily. If we don't do this the cache grows indefinitely.
+			r.List()
+
+			time.Sleep(expirationInterval)
+		}
+	}()
+	return r
+}
+
+type drainCache struct {
+	cache.Store
+}
+
+// Add adds the given entry to the Cache.
+// Note: entries expire after the ttl.
+func (r *drainCache) Add(entry CacheEntry) {
+	// Note: We can ignore the error here because by only allowing CacheEntries
+	// and providing the corresponding keyFunc ourselves we can guarantee that
+	// the error never occurs.
+	_ = r.Store.Add(entry)
+}
+
+// Has checks if the given key (still) exists in the Cache.
+// Note: entries expire after the ttl.
+func (r *drainCache) Has(machineName types.NamespacedName) (CacheEntry, bool) {
+	// Note: We can ignore the error here because GetByKey never returns an error.
+	item, exists, _ := r.Store.GetByKey(machineName.String())
+	if exists {
+		return item.(CacheEntry), true
+	}
+	return CacheEntry{}, false
+}