SERVER-57009 Additional debugging information in case of crash during FCV change

2 files changed, 30 insertions, 3 deletions

diff --git a/src/mongo/db/s/shard_server_catalog_cache_loader.cpp b/src/mongo/db/s/shard_server_catalog_cache_loader.cpp
index 2456f90b31e..c1efae18af7 100644
--- a/src/mongo/db/s/shard_server_catalog_cache_loader.cpp
+++ b/src/mongo/db/s/shard_server_catalog_cache_loader.cpp
@@ -1157,8 +1157,16 @@ void ShardServerCatalogCacheLoader::CollAndChunkTaskList::addTask(collAndChunkTa
         return;
     }
 
+    const auto& lastTask = _tasks.back();
     if (task.dropped) {
-        invariant(_tasks.back().maxQueryVersion == task.minQueryVersion);
+        invariant(lastTask.maxQueryVersion == task.minQueryVersion,
+                  str::stream() << "The version of the added task is not contiguous with that of "
+                                << "the previous one: LastTask {"
+                                << lastTask.toString()
+                                << "}, "
+                                << "AddedTask {"
+                                << task.toString()
+                                << "}");
 
         // As an optimization, on collection drop, clear any pending tasks in order to prevent any
         // throw-away work from executing. Because we have no way to differentiate whether the
@@ -1172,8 +1180,13 @@ void ShardServerCatalogCacheLoader::CollAndChunkTaskList::addTask(collAndChunkTa
         }
     } else {
         // Tasks must have contiguous versions, unless a complete reload occurs.
-        invariant(_tasks.back().maxQueryVersion == task.minQueryVersion ||
-                  !task.minQueryVersion.isSet());
+        invariant(lastTask.maxQueryVersion == task.minQueryVersion || !task.minQueryVersion.isSet(),
+                  str::stream() << "The added task is not the first and its version is not "
+                                << "contiguous with that of the previous one: LastTask {"
+                                << lastTask.toString()
+                                << "}, AddedTask {"
+                                << task.toString()
+                                << "}");
 
         _tasks.emplace_back(std::move(task));
     }
diff --git a/src/mongo/db/s/shard_server_catalog_cache_loader.h b/src/mongo/db/s/shard_server_catalog_cache_loader.h
index d42245cfddc..5f1ba9ef40c 100644
--- a/src/mongo/db/s/shard_server_catalog_cache_loader.h
+++ b/src/mongo/db/s/shard_server_catalog_cache_loader.h
@@ -142,6 +142,20 @@ private:
 
         // The term in which the loader scheduled this task.
         uint32_t termCreated;
+
+        std::string toString() const {
+            std::stringstream ss;
+            ss << "CollAndChunkTask -"
+               << " taskNum: " << taskNum << ", collectionAndChangedChunksSize: "
+               << (collectionAndChangedChunks ? collectionAndChangedChunks->changedChunks.size()
+                                              : -1)
+               << ", minQueryVersion: "
+               << (minQueryVersion.isSet() ? minQueryVersion.toString() : "(unset)")
+               << ", maxQueryVersion: "
+               << (maxQueryVersion.isSet() ? maxQueryVersion.toString() : "(unset)")
+               << ", dropped: " << dropped << ", termCreated: " << termCreated;
+            return ss.str();
+        }
     };
 
     /**