Issue #1017 Only warn if the "base" LMDB env is opened twice

Otherwise, if a user ignores the first error, they are then spammed with misleading errors on their subsequent interactions.

See the Github issue for a couple of examples that this change seeks to avoid.

cpp/arcticdb/storage/lmdb/lmdb_storage.cpp

@@ -278,7 +278,7 @@ LmdbStorage::LmdbStorage(const LibraryPath &library_path, OpenMode mode, const C
 
     lib_dir_ = root_path / lib_path_str;
 
-    warn_if_lmdb_already_open(root_path, lib_path_str);
+    warn_if_lmdb_already_open();
 
     if (!fs::exists(lib_dir_)) {
         util::check_arg(mode > OpenMode::READ, "Missing dir {} for lib={}. mode={}",
@@ -326,27 +326,19 @@ LmdbStorage::LmdbStorage(const LibraryPath &library_path, OpenMode mode, const C
     ARCTICDB_DEBUG(log::storage(), "Opened lmdb storage at {} with map size {}", lib_dir_.string(), format_bytes(mapsize));
 }
 
-void LmdbStorage::warn_if_lmdb_already_open(const fs::path &root_path, const std::string &lib_path_str) {
-    uint64_t& count_for_pid = ++times_path_opened[(root_path / lib_path_str).string()];
-    if (count_for_pid != 1) {
+void LmdbStorage::warn_if_lmdb_already_open() {
+    uint64_t& count_for_pid = ++times_path_opened[lib_dir_.string()];
+    // Only warn for the "base" config library to avoid spamming users with more warnings if they decide to ignore it and continue
+    if (count_for_pid != 1 && lib_dir_.string().find(CONFIG_LIBRARY_NAME) != std::string::npos) {
+        std::filesystem::path user_facing_path = lib_dir_;
         // Strip magic name from warning as it will confuse users
-        if (lib_dir_.string().find(CONFIG_LIBRARY_NAME) == std::string::npos) {
-            log::storage().warn(fmt::format(
-                    "LMDB path at {} has already been opened in this process which is not supported by LMDB. "
-                    "To continue safely, you should delete all Library objects over the LMDB path in this "
-                    "process and then try again. This indicates a bug in ArcticDB. Please report at "
-                    "https://github.com/man-group/ArcticDB. Current process ID=[{}]",
-                    lib_dir_.string(), getpid()));
-        } else {
-            std::filesystem::path user_facing_path = lib_dir_;
-            user_facing_path.remove_filename();
-            log::storage().warn(fmt::format(
-                    "LMDB path at {} has already been opened in this process which is not supported by LMDB. "
-                    "You should only open a single Arctic instance over a given LMDB path. "
-                    "To continue safely, you should delete this Arctic instance and any others over the LMDB path in this "
-                    "process and then try again. Current process ID=[{}]",
-                    user_facing_path.string(), getpid()));
-        }
+        user_facing_path.remove_filename();
+        log::storage().warn(fmt::format(
+                "LMDB path at {} has already been opened in this process which is not supported by LMDB. "
+                "You should only open a single Arctic instance over a given LMDB path. "
+                "To continue safely, you should delete this Arctic instance and any others over the LMDB path in this "
+                "process and then try again. Current process ID=[{}]",
+                user_facing_path.string(), getpid()));
     }
 }
 

cpp/arcticdb/storage/lmdb/lmdb_storage.hpp

@@ -60,7 +60,7 @@ class LmdbStorage final : public Storage {
 
     std::string do_key_path(const VariantKey&) const final { return {}; };
 
-    void warn_if_lmdb_already_open(const fs::path &root_path, const std::string &lib_path_str);
+    void warn_if_lmdb_already_open();
 
     // _internal methods assume the write mutex is already held
     void do_write_internal(Composite<KeySegmentPair>&& kvs, ::lmdb::txn& txn);

python/tests/integration/arcticdb/test_lmdb.py

@@ -208,3 +208,10 @@ def test_arctic_instances_across_same_lmdb_multiprocessing(tmpdir):
     ac["test"].write("a", pd.DataFrame())
     with mp.Pool(5) as p:
         p.starmap(create_arctic_instance, [(tmpdir, i) for i in range(20)])
+
+
+def test_lmdb_warnings_when_reopened(tmpdir):
+    ac = Arctic(f"lmdb://{tmpdir}")
+    lib = ac.create_library("test")
+    ac = Arctic(f"lmdb://{tmpdir}")  # expect to warn
+    lib = ac["test"]