Add SHM_LOCK_DIR environment variable for containerized deployments (memory leak fix)

CHANGELOG.md

@@ -4,6 +4,7 @@
       - FIXED: Update Node.js binding path from `lib/binding` to `lib/binding_napi_v8` to match node-pre-gyp versioning conventions [#7272](https://github.com/Project-OSRM/osrm-backend/pull/7272)
       - FIXED: Reduce MSVC compiler warnings by suppressing informational warnings while preserving bug-indicating warnings [#7253](https://github.com/Project-OSRM/osrm-backend/issues/7253)
     - Misc:
+      - ADDED: `SHM_LOCK_DIR` environment variable for shared memory lock file directory [#7312](https://github.com/Project-OSRM/osrm-backend/pull/7312)
       - FIXED: Fix JSON rendering of large OSM IDs (avoids scientific notation) and handle NaN/Infinity gracefully [#7016](https://github.com/Project-OSRM/osrm-backend/issues/7016)
       - CHANGED: Add std::format compatibility layer with fallback to fmt::format [#7261](https://github.com/Project-OSRM/osrm-backend/pull/7261)
       - FIXED: Update node_osrm to C++20 to fix ABI mismatch with libosrm (was overlooked in #6877) [#7261](https://github.com/Project-OSRM/osrm-backend/pull/7261)

docs/routed.md

@@ -1,5 +1,13 @@
 ## Environment Variables
 
+### SHM_LOCK_DIR
+
+If the SHM_LOCK_DIR environment variable is set, OSRM will use it as the
+directory for shared memory lock files instead of the system temporary directory.
+This is useful in containerized environments (Docker/Kubernetes) where the lock
+file directory should persist across container restarts when loading from shared
+memory.
+
 ### SIGNAL_PARENT_WHEN_READY
 
 If the SIGNAL_PARENT_WHEN_READY environment variable is set osrm-routed will

include/storage/shared_memory.hpp

@@ -18,6 +18,7 @@
 #endif
 
 #include <cstdint>
+#include <cstdlib>
 
 #include <algorithm>
 #include <filesystem>
@@ -29,13 +30,27 @@
 namespace osrm::storage
 {
 
+// Returns directory for OSRM lock files (SHM_LOCK_DIR env var or system temp)
+inline std::filesystem::path getLockDir()
+{
+    if (const char *lock_dir = std::getenv("SHM_LOCK_DIR"))
+    {
+        std::filesystem::path dir(lock_dir);
+        if (!std::filesystem::exists(dir))
+        {
+            throw util::exception("SHM_LOCK_DIR directory does not exist: " + dir.string() +
+                                  SOURCE_REF);
+        }
+        return dir;
+    }
+    return std::filesystem::temp_directory_path();
+}
+
 struct OSRMLockFile
 {
     template <typename IdentifierT> std::filesystem::path operator()(const IdentifierT &id)
     {
-        std::filesystem::path temp_dir = std::filesystem::temp_directory_path();
-        std::filesystem::path lock_file = temp_dir / ("osrm-" + std::to_string(id) + ".lock");
-        return lock_file;
+        return getLockDir() / ("osrm-" + std::to_string(id) + ".lock");
     }
 };
 

src/storage/storage.cpp

@@ -188,8 +188,7 @@ int Storage::Run(int max_wait, const std::string &dataset_name, bool only_metric
 
     util::LogPolicy::GetInstance().Unmute();
 
-    std::filesystem::path lock_path =
-        std::filesystem::temp_directory_path() / "osrm-datastore.lock";
+    std::filesystem::path lock_path = getLockDir() / "osrm-datastore.lock";
     if (!std::filesystem::exists(lock_path))
     {
         std::ofstream ofs(lock_path);