3 files changed, 46 insertions, 0 deletions

diff --git a/src/mongo/logv2/attribute_storage.h b/src/mongo/logv2/attribute_storage.h
index 656302ba4de..141c10752a2 100644
--- a/src/mongo/logv2/attribute_storage.h
+++ b/src/mongo/logv2/attribute_storage.h
@@ -678,6 +678,8 @@ private:
 // Wrapper around internal pointer of AttributeStorage so it does not need any template parameters
 class TypeErasedAttributeStorage {
 public:
+    using const_iterator = const detail::NamedAttribute*;
+
     TypeErasedAttributeStorage() : _size(0) {}
 
     template <typename... Args>
@@ -695,6 +697,13 @@ public:
         return _size;
     }
 
+    const_iterator begin() const {
+        return _data;
+    }
+    const_iterator end() const {
+        return _data + _size;
+    }
+
     // Applies a function to every stored named attribute in order they are captured
     template <typename Func>
     void apply(Func&& f) const {
diff --git a/src/mongo/logv2/log_detail.cpp b/src/mongo/logv2/log_detail.cpp
index 766c79488e4..e7863215590 100644
--- a/src/mongo/logv2/log_detail.cpp
+++ b/src/mongo/logv2/log_detail.cpp
@@ -31,12 +31,15 @@
 
 #include "mongo/platform/basic.h"
 
+#include <fmt/format.h>
+
 #include "mongo/logv2/attributes.h"
 #include "mongo/logv2/log.h"
 #include "mongo/logv2/log_domain.h"
 #include "mongo/logv2/log_domain_internal.h"
 #include "mongo/logv2/log_options.h"
 #include "mongo/logv2/log_source.h"
+#include "mongo/util/testing_proctor.h"
 
 namespace mongo::logv2::detail {
 
@@ -99,12 +102,39 @@ private:
     std::deque<std::string> _storage;
 };
 
+static void checkUniqueAttrs(int32_t id, const TypeErasedAttributeStorage& attrs) {
+    if (attrs.size() <= 1)
+        return;
+    // O(N^2), but N is small and this avoids alloc, sort, and operator<.
+    auto first = attrs.begin();
+    auto last = attrs.end();
+    while (first != last) {
+        auto it = first;
+        ++first;
+        if (std::find_if(first, last, [&](auto&& a) { return a.name == it->name; }) == last)
+            continue;
+        StringData sep;
+        std::string msg;
+        for (auto&& a : attrs) {
+            msg.append(sep.rawData(), sep.size())
+                .append("\"")
+                .append(a.name.rawData(), a.name.size())
+                .append("\"");
+            sep = ","_sd;
+        }
+        uasserted(4793301, format(FMT_STRING("LOGV2 (id={}) attribute collision: [{}]"), id, msg));
+    }
+}
+
 void doLogImpl(int32_t id,
                LogSeverity const& severity,
                LogOptions const& options,
                StringData message,
                TypeErasedAttributeStorage const& attrs) {
     dassert(options.component() != LogComponent::kNumLogComponents);
+    if (TestingProctor::instance().isEnabled())
+        checkUniqueAttrs(id, attrs);
+
     auto& source = options.domain().internal().source();
     auto record = source.open_record(id,
                                      severity,
diff --git a/src/mongo/logv2/logv2_test.cpp b/src/mongo/logv2/logv2_test.cpp
index e5c702a1f7c..f863c7db555 100644
--- a/src/mongo/logv2/logv2_test.cpp
+++ b/src/mongo/logv2/logv2_test.cpp
@@ -1318,6 +1318,13 @@ TEST_F(LogV2ContainerTest, StringMapUint32) {
     });
 }
 
+TEST_F(LogV2Test, AttrNameCollision) {
+    ASSERT_THROWS_CODE(
+        LOGV2(4793300, "Collision {k1}", "Collision", "k1"_attr = "v1", "k1"_attr = "v2"),
+        AssertionException,
+        4793301);
+}
+
 TEST_F(LogV2Test, Unicode) {
     auto lines = makeLineCapture(JSONFormatter());