From 46c464e3bf0941b0d22f5557f1012e2dd2a692aa Mon Sep 17 00:00:00 2001
From: Johannes Meyer <johannes.meyer@icinga.com>
Date: Fri, 8 Oct 2021 16:22:24 +0200
Subject: [PATCH] VolatileStateResults: Prevent loops and handle empty results

---
 library/Icingadb/Redis/VolatileStateResults.php | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/library/Icingadb/Redis/VolatileStateResults.php b/library/Icingadb/Redis/VolatileStateResults.php
index f1b30f64..d65e8bef 100644
--- a/library/Icingadb/Redis/VolatileStateResults.php
+++ b/library/Icingadb/Redis/VolatileStateResults.php
@@ -15,9 +15,12 @@ use RuntimeException;
 
 class VolatileStateResults extends ResultSet
 {
+    /** @var bool Whether Redis updates were applied */
+    private $updatesApplied = false;
+
     public function current()
     {
-        if ($this->position === null && ! $this->isCacheDisabled) {
+        if (! $this->updatesApplied && ! $this->isCacheDisabled) {
             $this->rewind();
         }
 
@@ -26,7 +29,7 @@ class VolatileStateResults extends ResultSet
 
     public function key()
     {
-        if ($this->position === null && ! $this->isCacheDisabled) {
+        if (! $this->updatesApplied && ! $this->isCacheDisabled) {
             $this->rewind();
         }
 
@@ -35,7 +38,8 @@ class VolatileStateResults extends ResultSet
 
     public function rewind()
     {
-        if ($this->position === null && ! $this->isCacheDisabled) {
+        if (! $this->updatesApplied && ! $this->isCacheDisabled) {
+            $this->updatesApplied = true;
             $this->advance();
 
             Benchmark::measure('Applying Redis updates');
@@ -75,6 +79,10 @@ class VolatileStateResults extends ResultSet
             }
         }
 
+        if (empty($states)) {
+            return;
+        }
+
         foreach ($this->fetchStates("icinga:{$type}:state", array_keys($states)) as $id => $data) {
             foreach ($data as $key => $value) {
                 $data[$key] = $behaviors->retrieveProperty($value, $key);