Store lock files in /dev/shm/osrm -> ~/.osrm/ instead of /tmp to prevent systemd cleanup by Charmik · Pull Request #7443 · Project-OSRM/osrm-backend

Charmik · 2026-04-03T13:46:52Z

Issue

Move shared memory lock files out of /tmp to prevent cleanup

Lock files used by ftok() to locate System V shared memory segments were
stored in /tmp, which is cleaned by systemd-tmpfiles-clean (Linux, ~10
days) and periodic scripts (macOS, ~3 days). The shared memory segments
themselves survive cleanup as kernel resources, leaving OSRM unable to
reconnect: "lock file does not exist, exiting".

Lock directory is now selected with graceful fallback:

SHM_LOCK_DIR env var (explicit override, unchanged)
/dev/shm/osrm-/ (Linux only — RAM-backed tmpfs, never
cleaned, cleared on reboot together with shared memory segments)
~/.osrm/ (macOS, Windows via %USERPROFILE%)

The selected directory is logged at startup. /tmp is no longer used.

Validated locally on Mac & Linux:

➜  ~  ls -l ~/.osrm
total 0
-rw-r--r--  1 charm  staff  0 Apr  3 16:19 osrm-0.lock
-rw-r--r--  1 charm  staff  0 Apr  3 16:19 osrm-1.lock
-rw-r--r--  1 charm  staff  0 Apr  3 16:19 osrm-datastore.lock

This change was developed with assistance from Claude (Opus 4.6).

Tasklist

self-review code for correctness and following the coding guidelines
add tests (see testing)
update relevant wiki pages
CHANGELOG.md entry (see how to)
review
adjust for comments

Requirements / Relations

None

Copilot

Pull request overview

Updates OSRM shared-memory lock file directory selection to avoid /tmp cleanup on long-running Linux systems (e.g., systemd tmpfiles), and adds unit tests covering the new priority order.

Changes:

Prefer $HOME/.osrm/ for lock files when SHM_LOCK_DIR is not set, with /tmp as a fallback.
Add unit tests for getLockDir() behavior (env override, home default, and tmp fallback).
Update getLockDir() documentation to describe the new priority.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
`src/storage/shared_memory.cpp`	Implements `$HOME/.osrm` default lock directory and ensures the directory exists.
`include/storage/shared_memory.hpp`	Updates API documentation to reflect lock directory priority and rationale.
`unit_tests/storage/shared_memory.cpp`	Adds unit tests validating `getLockDir()` selection logic.

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Copilot · 2026-04-03T15:11:02Z

+        std::filesystem::create_directories(lock_dir);
+        return lock_dir;
+    }
+
    return std::filesystem::temp_directory_path();


getLockDir() unconditionally calls std::filesystem::create_directories(lock_dir) and will throw std::filesystem::filesystem_error if $HOME exists but is not writable (or if ~/.osrm is an existing non-directory). This can abort makeSharedMemory() / Storage::Run() rather than falling back to the system temp directory. Consider using the error_code overload (or catching filesystem_error) and falling back to temp_directory_path() with a clear log / exception message suggesting SHM_LOCK_DIR.

Suggested change

std::filesystem::create_directories(lock_dir);

return lock_dir;

}

return std::filesystem::temp_directory_path();

std::error_code ec;

const bool exists = std::filesystem::exists(lock_dir, ec);

if (!ec)

{

if (exists)

{

if (std::filesystem::is_directory(lock_dir, ec) && !ec)

{

return lock_dir;

}

util::Log(logWARNING)

<< "Cannot use shared memory lock directory " << lock_dir

<< ": path exists but is not a directory. Falling back to temporary "

"directory. Set SHM_LOCK_DIR to override.";

}

else

{

std::filesystem::create_directories(lock_dir, ec);

if (!ec)

{

return lock_dir;

}

util::Log(logWARNING)

<< "Cannot create shared memory lock directory " << lock_dir << ": "

<< ec.message()

<< ". Falling back to temporary directory. Set SHM_LOCK_DIR to override.";

}

}

else

{

util::Log(logWARNING)

<< "Cannot inspect shared memory lock directory " << lock_dir << ": "

<< ec.message()

<< ". Falling back to temporary directory. Set SHM_LOCK_DIR to override.";

}

}

std::error_code ec;

auto temp_dir = std::filesystem::temp_directory_path(ec);

if (ec)

{

throw util::exception("Could not determine a shared memory lock directory; "

"failed to use HOME/USERPROFILE and temp_directory_path(): " +

ec.message() +

". Set SHM_LOCK_DIR to a writable directory." + SOURCE_REF);

}

return temp_dir;

added check of error_code

Copilot · 2026-04-03T15:11:02Z

+ * Priority: SHM_LOCK_DIR env var > $HOME/.osrm/ > system temp directory.
+ * Using $HOME/.osrm/ by default avoids lock files being cleaned by
+ * systemd-tmpfiles-clean, which would break shared memory access.


The doc comment describes the default as $HOME/.osrm/, but on Windows the implementation also falls back to %USERPROFILE%. Consider updating the comment to reflect the Windows behavior (or avoid platform-specific env var names in the public header).

Suggested change

* Priority: SHM_LOCK_DIR env var > $HOME/.osrm/ > system temp directory.

* Using $HOME/.osrm/ by default avoids lock files being cleaned by

* systemd-tmpfiles-clean, which would break shared memory access.

* Priority: SHM_LOCK_DIR env var > user-specific .osrm directory in the

* home/profile directory > system temp directory.

* Using a user-specific .osrm directory by default avoids lock files being

* cleaned by system temp directory cleanup tools, which would break shared

* memory access.

added "home/profile directory"

Copilot · 2026-04-03T15:11:02Z

+    const char *home = std::getenv("HOME");
+    // Skip if HOME is not set (e.g. in containers)
+    if (!home)
+        return;
+
+    auto lock_dir = getLockDir();
+    auto expected = std::filesystem::path(home) / ".osrm";
+    BOOST_CHECK_EQUAL(lock_dir, expected);
+    BOOST_CHECK(std::filesystem::exists(lock_dir));


This test calls getLockDir() using the real HOME and can create ~/.osrm on the developer/CI machine. To keep unit tests hermetic, consider setting HOME to a temporary directory for the duration of the test (and restoring it afterward).

added auto temp_home = std::filesystem::temp_directory_path() / "osrm-test-home";

Copilot · 2026-04-03T15:11:03Z

+    // Ensure SHM_LOCK_DIR is not set
+    ::unsetenv("SHM_LOCK_DIR");
+


The test unsets SHM_LOCK_DIR but does not restore its previous value. If the environment running the test had SHM_LOCK_DIR set, this can leak across test cases and cause order-dependent failures. Consider an RAII env-var guard that saves/restores the previous value.

added RAII EnvGuard

Copilot · 2026-04-03T15:11:03Z

+    auto temp = std::filesystem::temp_directory_path() / "osrm-test-lock-dir";
+    std::filesystem::create_directories(temp);
+
+    ::setenv("SHM_LOCK_DIR", temp.c_str(), 1);
+    auto lock_dir = getLockDir();
+    BOOST_CHECK_EQUAL(lock_dir, temp);
+
+    ::unsetenv("SHM_LOCK_DIR");
+    std::filesystem::remove(temp);


setenv/unsetenv are POSIX APIs and will not compile on Windows; additionally std::filesystem::path::c_str() is wchar_t* on Windows. If these unit tests are built cross-platform, consider using a small portability wrapper (e.g., _putenv_s on Windows) and passing temp.string().

fixed, but didn't test windows

Copilot · 2026-04-03T15:11:03Z

+
+#include <boost/test/unit_test.hpp>
+
+#include <cstdlib>


This file uses std::filesystem and std::string directly but only includes <cstdlib>. Consider adding explicit includes for <filesystem> and <string> to avoid relying on transitive headers.

Suggested change

#include <cstdlib>

#include <cstdlib>

#include <filesystem>

#include <string>

Lock files used by ftok() to locate System V shared memory segments were stored in /tmp, which is cleaned by systemd-tmpfiles-clean (Linux, ~10 days) and periodic scripts (macOS, ~3 days). The shared memory segments themselves survive cleanup as kernel resources, leaving OSRM unable to reconnect: "lock file does not exist, exiting". Lock directory is now selected with graceful fallback: 1. SHM_LOCK_DIR env var (explicit override, unchanged) 2. /dev/shm/osrm-<uid>/ (Linux only — RAM-backed tmpfs, never cleaned, cleared on reboot together with shared memory segments) 3. ~/.osrm/ (macOS, Windows via %USERPROFILE%) The selected directory is logged at startup. /tmp is no longer used.

DennisOSRM requested a review from Copilot April 3, 2026 15:06

Copilot started reviewing on behalf of DennisOSRM April 3, 2026 15:07 View session

Copilot AI reviewed Apr 3, 2026

View reviewed changes

Charmik force-pushed the move-shared-memory-lock-to-home-dir branch from ab27c49 to 95088d8 Compare April 6, 2026 18:30

Charmik force-pushed the move-shared-memory-lock-to-home-dir branch from 95088d8 to ded37fe Compare April 6, 2026 18:51

Charmik changed the title ~~Store lock files in ~/.osrm/ instead of /tmp to prevent systemd cleanup~~ Store lock files in /dev/shm/osrm -> ~/.osrm/ instead of /tmp to prevent systemd cleanup Apr 7, 2026

Merge branch 'master' into move-shared-memory-lock-to-home-dir

75b28c2

DennisOSRM enabled auto-merge (squash) April 10, 2026 17:03

DennisOSRM approved these changes Apr 10, 2026

View reviewed changes

DennisOSRM merged commit 738d412 into Project-OSRM:master Apr 10, 2026
23 checks passed

-        std::filesystem::create_directories(lock_dir);
-        return lock_dir;
-    }
-    return std::filesystem::temp_directory_path();
+        std::error_code ec;
+        const bool exists = std::filesystem::exists(lock_dir, ec);
+        if (!ec)
+        {
+            if (exists)
+            {
+                if (std::filesystem::is_directory(lock_dir, ec) && !ec)
+                {
+                    return lock_dir;
+                }
+                util::Log(logWARNING)
+                    << "Cannot use shared memory lock directory " << lock_dir
+                    << ": path exists but is not a directory. Falling back to temporary "
+                       "directory. Set SHM_LOCK_DIR to override.";
+            }
+            else
+            {
+                std::filesystem::create_directories(lock_dir, ec);
+                if (!ec)
+                {
+                    return lock_dir;
+                }
+                util::Log(logWARNING)
+                    << "Cannot create shared memory lock directory " << lock_dir << ": "
+                    << ec.message()
+                    << ". Falling back to temporary directory. Set SHM_LOCK_DIR to override.";
+            }
+        }
+        else
+        {
+            util::Log(logWARNING)
+                << "Cannot inspect shared memory lock directory " << lock_dir << ": "
+                << ec.message()
+                << ". Falling back to temporary directory. Set SHM_LOCK_DIR to override.";
+        }
+    }
+    std::error_code ec;
+    auto temp_dir = std::filesystem::temp_directory_path(ec);
+    if (ec)
+    {
+        throw util::exception("Could not determine a shared memory lock directory; "
+                              "failed to use HOME/USERPROFILE and temp_directory_path(): " +
+                              ec.message() +
+                              ". Set SHM_LOCK_DIR to a writable directory." + SOURCE_REF);
+    }
+    return temp_dir;

- * Priority: SHM_LOCK_DIR env var > $HOME/.osrm/ > system temp directory.
- * Using $HOME/.osrm/ by default avoids lock files being cleaned by
- * systemd-tmpfiles-clean, which would break shared memory access.
+ * Priority: SHM_LOCK_DIR env var > user-specific .osrm directory in the
+ * home/profile directory > system temp directory.
+ * Using a user-specific .osrm directory by default avoids lock files being
+ * cleaned by system temp directory cleanup tools, which would break shared
+ * memory access.

		// Ensure SHM_LOCK_DIR is not set
		::unsetenv("SHM_LOCK_DIR");

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Charmik commented Apr 3, 2026 •

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