From fdcfe25f2df7719806196f1d1ceea3f245dbbebe Mon Sep 17 00:00:00 2001
From: Matt Kneiser <matt.kneiser@mongodb.com>
Date: Mon, 13 Feb 2023 18:25:10 +0000
Subject: SERVER-73861 Log when capped collection size changes

---
 src/mongo/db/catalog/collection_options.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/mongo/db/catalog/collection_options.cpp b/src/mongo/db/catalog/collection_options.cpp
index 9aa647fd41c..8f81f9dfb96 100644
--- a/src/mongo/db/catalog/collection_options.cpp
+++ b/src/mongo/db/catalog/collection_options.cpp
@@ -42,24 +42,37 @@
 #include "mongo/db/query/collation/collator_interface.h"
 #include "mongo/db/query/query_feature_flags_gen.h"
 #include "mongo/idl/command_generic_argument.h"
+#include "mongo/logv2/log.h"
 #include "mongo/util/overloaded_visitor.h"
 #include "mongo/util/str.h"
 
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kStorage
+
 namespace mongo {
 namespace {
 long long adjustCappedSize(long long cappedSize) {
     if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
         !feature_flags::gfeatureFlagCappedCollectionsRelaxedSize.isEnabled(
             serverGlobalParams.featureCompatibility)) {
+        auto originalCappedSize = cappedSize;
         cappedSize += 0xff;
         cappedSize &= 0xffffffffffffff00LL;
+        LOGV2(7386100,
+              "Capped collection maxSize being rounded up to nearest 256-byte size.",
+              "originalSize"_attr = originalCappedSize,
+              "adjustedSize"_attr = cappedSize);
     }
     return cappedSize;
 }
 
 long long adjustCappedMaxDocs(long long cappedMaxDocs) {
     if (cappedMaxDocs <= 0 || cappedMaxDocs == std::numeric_limits<long long>::max()) {
+        auto originalCappedMaxDocs = cappedMaxDocs;
         cappedMaxDocs = 0x7fffffff;
+        LOGV2(7386101,
+              "Capped collection maxDocs being rounded off.",
+              "originalMaxDocs"_attr = originalCappedMaxDocs,
+              "adjustedMaxDocs"_attr = cappedMaxDocs);
     }
     return cappedMaxDocs;
 }
-- 
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