From 1b39557a476f2177f3d25cd958ad4c9288fe5c7d Mon Sep 17 00:00:00 2001
From: Aditya Thebe <contact@adityathebe.com>
Date: Thu, 2 Jan 2025 14:36:01 +0545
Subject: [PATCH] fix: prevent infinite re-queuing of events with missing
 involved objects

For events of temporary kubernetes resources (like a pod created by a
canary and immediately deleted), we'll not find the involved ever. The
event would then be requeued again & again.

This resulted in ever increasing queue and high db calls.

* fix: mark the scrape context as incremental
* fix: change labels on temp cache metrics
---
 api/cache.go            | 33 +++++++++++++++++----------------
 scrapers/incremental.go | 12 ++++++++----
 2 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/api/cache.go b/api/cache.go
index 27abaa3f..64d497fb 100644
--- a/api/cache.go
+++ b/api/cache.go
@@ -2,7 +2,6 @@ package api
 
 import (
 	"fmt"
-	"strconv"
 	"strings"
 
 	"github.com/flanksource/commons/logger"
@@ -59,7 +58,7 @@ func (t *TempCache) Find(ctx ScrapeContext, lookup v1.ExternalID) (*models.Confi
 	if _, ok := t.notFound[lookup.Key()]; ok {
 		ctx.Counter("temp_cache_missing_hit",
 			"scraper_id", ctx.ScraperID(),
-			"incremental", strconv.FormatBool(ctx.IsIncrementalScrape()),
+			"scrape_type", lo.Ternary(ctx.IsIncrementalScrape(), "incremental", "full"),
 			"query_type", "external_id",
 		).Add(1)
 		return nil, nil
@@ -74,17 +73,18 @@ func (t *TempCache) Find(ctx ScrapeContext, lookup v1.ExternalID) (*models.Confi
 		return t.Get(ctx, alias)
 	}
 
-	ctx.Counter("temp_cache_miss",
-		"scraper_id", ctx.ScraperID(),
-		"incremental", strconv.FormatBool(ctx.IsIncrementalScrape()),
-		"query_type", "external_id",
-	).Add(1)
-
 	var result models.ConfigItem
 	if err := lookup.Find(ctx.DB()).Find(&result).Error; err != nil {
 		return nil, err
 	}
 
+	ctx.Counter("temp_cache_miss",
+		"scraper_id", ctx.ScraperID(),
+		"scrape_type", lo.Ternary(ctx.IsIncrementalScrape(), "incremental", "full"),
+		"query_type", "external_id",
+		"config_type", result.Type,
+	).Add(1)
+
 	if result.ID == "" {
 		t.notFound[lookup.Key()] = struct{}{}
 		return nil, nil
@@ -130,7 +130,7 @@ func (t *TempCache) Get(ctx ScrapeContext, id string, opts ...CacheOption) (*mod
 	if _, notFound := t.notFound[id]; notFound && !optMap[IgnoreNotFound] {
 		ctx.Counter("temp_cache_missing_hit",
 			"scraper_id", ctx.ScraperID(),
-			"incremental", strconv.FormatBool(ctx.IsIncrementalScrape()),
+			"scrape_type", lo.Ternary(ctx.IsIncrementalScrape(), "incremental", "full"),
 			"query_type", "id",
 		).Add(1)
 		return nil, nil
@@ -139,18 +139,12 @@ func (t *TempCache) Get(ctx ScrapeContext, id string, opts ...CacheOption) (*mod
 	if item, ok := t.items[id]; ok {
 		ctx.Counter("temp_cache_hit",
 			"scraper_id", ctx.ScraperID(),
-			"incremental", strconv.FormatBool(ctx.IsIncrementalScrape()),
+			"scrape_type", lo.Ternary(ctx.IsIncrementalScrape(), "incremental", "full"),
 			"query_type", "id",
 		).Add(1)
 		return &item, nil
 	}
 
-	ctx.Counter("temp_cache_miss",
-		"scraper_id", ctx.ScraperID(),
-		"incremental", strconv.FormatBool(ctx.IsIncrementalScrape()),
-		"query_type", "id",
-	).Add(1)
-
 	result := models.ConfigItem{}
 
 	if uuid.Validate(id) == nil {
@@ -167,6 +161,13 @@ func (t *TempCache) Get(ctx ScrapeContext, id string, opts ...CacheOption) (*mod
 		}
 	}
 
+	ctx.Counter("temp_cache_miss",
+		"scraper_id", ctx.ScraperID(),
+		"scrape_type", lo.Ternary(ctx.IsIncrementalScrape(), "incremental", "full"),
+		"query_type", "id",
+		"config_type", result.Type,
+	).Add(1)
+
 	if result.ID != "" {
 		t.Insert(result)
 		return &result, nil
diff --git a/scrapers/incremental.go b/scrapers/incremental.go
index ba09cfb8..127976f6 100644
--- a/scrapers/incremental.go
+++ b/scrapers/incremental.go
@@ -51,7 +51,7 @@ func ConsumeKubernetesWatchJobFunc(sc api.ScrapeContext, config v1.Kubernetes, q
 
 			config := config.DeepCopy()
 
-			sc := sc.WithScrapeConfig(sc.ScrapeConfig(), plugins...)
+			sc := sc.WithScrapeConfig(sc.ScrapeConfig(), plugins...).AsIncrementalScrape()
 			config.BaseScraper = config.BaseScraper.ApplyPlugins(plugins...)
 
 			// Use temp cache if it already exists for scraper
@@ -110,11 +110,15 @@ func ConsumeKubernetesWatchJobFunc(sc api.ScrapeContext, config v1.Kubernetes, q
 					ci, err := sc.TempCache().Get(sc, string(involvedObject.UID), api.IgnoreNotFound)
 					if err != nil {
 						return fmt.Errorf("failed to fetch from cache: %w", err)
-					}
-					if ci == nil {
-						queue.EnqueueWithDelay(kubernetes.NewQueueItem(obj, kubernetes.QueueItemOperationReEnqueue), 30*time.Second)
+					} else if ci == nil {
 						// Remove event object from objects list
 						objs = lo.DropRight(objs, 1)
+
+						// Re-enqueue the event with a delay but only if it wasn't previously enqueued
+						// else the event gets recycled indefinitely
+						if queueItem.Operation != kubernetes.QueueItemOperationReEnqueue {
+							queue.EnqueueWithDelay(kubernetes.NewQueueItem(obj, kubernetes.QueueItemOperationReEnqueue), 30*time.Second)
+						}
 					}
 
 					objectsFromEvents = append(objectsFromEvents, involvedObject)