feat: Prune resources in reverse of sync wave order (#538)

* Prune resources in reverse of sync wave order

Signed-off-by: Siddhesh Ghadi <sghadi1203@gmail.com>

* Use waveOverride var instead of directly patching live obj

Directly patching live objs results into incorrect wave ordering
as the new wave value from live obj is used to perform reordering during next sync

Signed-off-by: Siddhesh Ghadi <sghadi1203@gmail.com>

---------

Signed-off-by: Siddhesh Ghadi <sghadi1203@gmail.com>

pkg/sync/sync_context.go

@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"sort"
-	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -457,6 +456,18 @@ func (sc *syncContext) Sync() {
 		return
 	}
 
+	// if pruned tasks pending deletion, then wait...
+	prunedTasksPendingDelete := tasks.Filter(func(t *syncTask) bool {
+		if t.pruned() && t.liveObj != nil {
+			return t.liveObj.GetDeletionTimestamp() != nil 
+		} 
+		return false
+	})
+	if prunedTasksPendingDelete.Len() > 0 {
+		sc.setRunningPhase(prunedTasksPendingDelete, true)
+		return
+	}
+
 	// collect all completed hooks which have appropriate delete policy
 	hooksPendingDeletionSuccessful := tasks.Filter(func(task *syncTask) bool {
 		return task.isHook() && task.liveObj != nil && !task.running() && task.deleteOnPhaseSuccessful()
@@ -747,11 +758,42 @@ func (sc *syncContext) getSyncTasks() (_ syncTasks, successful bool) {
 		}
 	}
 
-	// for pruneLast tasks, modify the wave to sync phase last wave of non prune task +1
+	// for prune tasks, modify the waves for proper cleanup i.e reverse of sync wave (creation order)
+	pruneTasks := make(map[int][]*syncTask)
+	for _, task := range tasks {
+	    if task.isPrune() {
+	        pruneTasks[task.wave()] = append(pruneTasks[task.wave()], task)
+	    }
+	}
+
+	var uniquePruneWaves []int
+	for k := range pruneTasks {
+	    uniquePruneWaves = append(uniquePruneWaves, k)
+	}
+	sort.Ints(uniquePruneWaves)
+
+	// reorder waves for pruning tasks using symmetric swap on prune waves
+	n := len(uniquePruneWaves)
+	for i := 0; i < n/2; i++ {
+	    // waves to swap
+	    startWave := uniquePruneWaves[i]
+	    endWave := uniquePruneWaves[n-1-i]
+
+	    for _, task := range pruneTasks[startWave] {
+			task.waveOverride = &endWave
+	    }
+
+	    for _, task := range pruneTasks[endWave] {
+			task.waveOverride = &startWave
+	    }
+	}
+
+	// for pruneLast tasks, modify the wave to sync phase last wave of tasks + 1
+	// to ensure proper cleanup, syncPhaseLastWave should also consider prune tasks to determine last wave
 	syncPhaseLastWave := 0
 	for _, task := range tasks {
 		if task.phase == common.SyncPhaseSync {
-			if task.wave() > syncPhaseLastWave && !task.isPrune() {
+			if task.wave() > syncPhaseLastWave {
 				syncPhaseLastWave = task.wave()
 			}
 		}
@@ -761,12 +803,7 @@ func (sc *syncContext) getSyncTasks() (_ syncTasks, successful bool) {
 	for _, task := range tasks {
 		if task.isPrune() &&
 			(sc.pruneLast || resourceutil.HasAnnotationOption(task.liveObj, common.AnnotationSyncOptions, common.SyncOptionPruneLast)) {
-			annotations := task.liveObj.GetAnnotations()
-			if annotations == nil {
-				annotations = make(map[string]string)
-			}
-			annotations[common.AnnotationSyncWave] = strconv.Itoa(syncPhaseLastWave)
-			task.liveObj.SetAnnotations(annotations)
+			task.waveOverride = &syncPhaseLastWave
 		}
 	}