From bb5d6a308dbd733eabfc11be9934068649fb1041 Mon Sep 17 00:00:00 2001
From: Kishore Nallan <kishorenc@gmail.com>
Date: Tue, 19 Jul 2022 16:33:27 +0530
Subject: [PATCH] Finer locking during collection creation.

---
 src/collection_manager.cpp       |  2 ++
 test/collection_manager_test.cpp | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/collection_manager.cpp b/src/collection_manager.cpp
index 48011ed2..8b293309 100644
--- a/src/collection_manager.cpp
+++ b/src/collection_manager.cpp
@@ -292,6 +292,7 @@ Option<Collection*> CollectionManager::create_collection(const std::string& name
                                                          const std::string& fallback_field_type,
                                                          const std::vector<std::string>& symbols_to_index,
                                                          const std::vector<std::string>& token_separators) {
+    std::unique_lock lock(mutex);
 
     if(store->contains(Collection::get_meta_key(name))) {
         return Option<Collection*>(409, std::string("A collection with name `") + name + "` already exists.");
@@ -340,6 +341,7 @@ Option<Collection*> CollectionManager::create_collection(const std::string& name
         return Option<Collection*>(500, "Could not write to on-disk storage.");
     }
 
+    lock.unlock();
     add_to_collections(new_collection);
 
     return Option<Collection*>(new_collection);
diff --git a/test/collection_manager_test.cpp b/test/collection_manager_test.cpp
index 06cd86e2..b8faad9e 100644
--- a/test/collection_manager_test.cpp
+++ b/test/collection_manager_test.cpp
@@ -104,6 +104,35 @@ TEST_F(CollectionManagerTest, CollectionCreation) {
     ASSERT_EQ("1", next_collection_id);
 }
 
+TEST_F(CollectionManagerTest, ParallelCollectionCreation) {
+    std::vector<std::thread> threads;
+    for(size_t i = 0; i < 10; i++) {
+        threads.emplace_back([i, &collectionManager = collectionManager]() {
+            nlohmann::json coll_json = R"({
+                "name": "parcoll",
+                "fields": [
+                    {"name": "title", "type": "string"}
+                ]
+            })"_json;
+            coll_json["name"] = coll_json["name"].get<std::string>() + std::to_string(i+1);
+            auto coll_op = collectionManager.create_collection(coll_json);
+            ASSERT_TRUE(coll_op.ok());
+        });
+    }
+
+    for(auto& thread : threads){
+        thread.join();
+    }
+
+    int64_t prev_id = INT32_MAX;
+
+    for(auto coll: collectionManager.get_collections()) {
+        // collections are sorted by ID, in descending order
+        ASSERT_TRUE(coll->get_collection_id() < prev_id);
+        prev_id = coll->get_collection_id();
+    }
+}
+
 TEST_F(CollectionManagerTest, ShouldInitCollection) {
     nlohmann::json collection_meta1 =
             nlohmann::json::parse("{\"name\": \"foobar\", \"id\": 100, \"fields\": [{\"name\": \"org\", \"type\": "