Alternative SHM segment cleanup

commons/zenoh-shm/src/api/cleanup.rs

@@ -0,0 +1,31 @@
+//
+// Copyright (c) 2024 ZettaScale Technology
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License 2.0 which is available at
+// http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+// which is available at https://www.apache.org/licenses/LICENSE-2.0.
+//
+// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+//
+// Contributors:
+//   ZettaScale Zenoh Team, <zenoh@zettascale.tech>
+//
+
+use crate::posix_shm::cleanup::cleanup_orphaned_segments;
+
+/// UNIX: Trigger cleanup for orphaned SHM segments
+/// If process that created named SHM segment crashes or exits by a signal, the segment persists in the system
+/// disregarding if it is used by other Zenoh processes or not. This is the detail of POSIX specification for
+/// shared memory that is hard to bypass. To deal with this we developed a cleanup routine that enumerates all
+/// segments and tries to find processes that are using it. If no such process found, segment will be removed.
+/// There is no ideal signal to trigger this cleanup, so by default, zenoh triggers it in the following moments:
+/// - first POSIX SHM segment creation
+/// - process exit via exit() call or return from maint function
+/// It is OK to additionally trigger this function at any time, but be aware that this can be costly.
+///
+/// For non-unix platforms this function currently does nothing
+#[zenoh_macros::unstable_doc]
+pub fn cleanup_orphaned_shm_segments() {
+    cleanup_orphaned_segments();
+}

commons/zenoh-shm/src/api/mod.rs

@@ -13,6 +13,7 @@
 //
 
 pub mod buffer;
+pub mod cleanup;
 pub mod client;
 pub mod client_storage;
 pub mod common;

commons/zenoh-shm/src/cleanup.rs

@@ -14,6 +14,8 @@
 
 use static_init::dynamic;
 
+use crate::posix_shm::cleanup::cleanup_orphaned_segments;
+
 /// A global cleanup, that is guaranteed to be dropped at normal program exit and that will
 /// execute all registered cleanup routines at this moment
 #[dynamic(lazy, drop)]
@@ -26,6 +28,8 @@ pub(crate) struct Cleanup {
 
 impl Cleanup {
     fn new() -> Self {
+        // on first cleanup subsystem touch we perform zenoh segment cleanup
+        cleanup_orphaned_segments();
         Self {
             cleanups: Default::default(),
         }
@@ -34,14 +38,20 @@ impl Cleanup {
     pub(crate) fn register_cleanup(&self, cleanup_fn: Box<dyn FnOnce() + Send>) {
         self.cleanups.push(Some(cleanup_fn));
     }
-}
 
-impl Drop for Cleanup {
-    fn drop(&mut self) {
+    fn cleanup(&self) {
         while let Some(cleanup) = self.cleanups.pop() {
             if let Some(f) = cleanup {
                 f();
             }
         }
     }
 }
+
+impl Drop for Cleanup {
+    fn drop(&mut self) {
+        // on finalization stage we perform zenoh segment cleanup
+        cleanup_orphaned_segments();
+        self.cleanup();
+    }
+}

commons/zenoh-shm/src/posix_shm/cleanup.rs

@@ -0,0 +1,134 @@
+//
+// Copyright (c) 2023 ZettaScale Technology
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License 2.0 which is available at
+// http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+// which is available at https://www.apache.org/licenses/LICENSE-2.0.
+//
+// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+//
+// Contributors:
+//   ZettaScale Zenoh Team, <zenoh@zettascale.tech>
+//
+
+pub(crate) use platform::cleanup_orphaned_segments;
+
+#[cfg(not(unix))]
+mod platform {
+    pub(crate) fn cleanup_orphaned_segments() {}
+}
+
+#[cfg(unix)]
+mod platform {
+    use std::{borrow::Borrow, collections::HashSet, fs, path::PathBuf};
+
+    use zenoh_result::ZResult;
+
+    #[derive(PartialEq, Eq, Hash)]
+    struct ProcFdDir(PathBuf);
+
+    impl ProcFdDir {
+        fn enumerate_fds(&self) -> ZResult<HashSet<FdFile>> {
+            let fds = self.0.read_dir()?;
+            let fd_map: HashSet<FdFile> = fds
+                .filter_map(Result::ok)
+                .map(|f| std::convert::Into::<FdFile>::into(f.path()))
+                .collect();
+            Ok(fd_map)
+        }
+    }
+
+    impl From<PathBuf> for ProcFdDir {
+        fn from(value: PathBuf) -> Self {
+            Self(value)
+        }
+    }
+
+    #[derive(PartialEq, Eq, Hash)]
+    struct FdFile(PathBuf);
+
+    impl From<PathBuf> for FdFile {
+        fn from(value: PathBuf) -> Self {
+            Self(value)
+        }
+    }
+
+    #[derive(PartialEq, Eq, Hash)]
+    struct ShmFile(PathBuf);
+
+    impl ShmFile {
+        fn cleanup_file(self) {
+            let _ = std::fs::remove_file(self.0);
+        }
+    }
+
+    impl Borrow<PathBuf> for ShmFile {
+        fn borrow(&self) -> &PathBuf {
+            &self.0
+        }
+    }
+
+    impl From<PathBuf> for ShmFile {
+        fn from(value: PathBuf) -> Self {
+            Self(value)
+        }
+    }
+
+    pub(crate) fn cleanup_orphaned_segments() {
+        if let Err(e) = cleanup_orphaned_segments_inner() {
+            tracing::error!("Error performing orphaned SHM segments cleanup: {e}")
+        }
+    }
+
+    fn enumerate_shm_files() -> ZResult<HashSet<ShmFile>> {
+        let shm_files = fs::read_dir("/dev/shm")?;
+        Ok(shm_files
+            .filter_map(Result::ok)
+            .filter_map(|f| {
+                if let Some(ext) = f.path().extension() {
+                    if ext == "zenoh" {
+                        return Some(std::convert::Into::<ShmFile>::into(f.path()));
+                    }
+                }
+                None
+            })
+            .collect())
+    }
+
+    fn enumerate_proc_dirs() -> ZResult<HashSet<ProcFdDir>> {
+        let proc_dirs = fs::read_dir("/proc")?;
+        Ok(proc_dirs
+            .filter_map(Result::ok)
+            .map(|f| std::convert::Into::<ProcFdDir>::into(f.path().join("fd")))
+            .collect())
+    }
+
+    fn enumerate_proc_fds() -> ZResult<HashSet<FdFile>> {
+        let mut fds = HashSet::default();
+        let dirs = enumerate_proc_dirs()?;
+        for dir in dirs {
+            if let Ok(dir_fds) = dir.enumerate_fds() {
+                fds.extend(dir_fds);
+            }
+        }
+        Ok(fds)
+    }
+
+    fn cleanup_orphaned_segments_inner() -> ZResult<()> {
+        let fd_map = enumerate_proc_fds()?;
+        let mut shm_map = enumerate_shm_files()?;
+
+        for fd_file in fd_map {
+            if let Ok(resolved_link) = fd_file.0.read_link() {
+                shm_map.remove(&resolved_link);
+            }
+        }
+
+        for shm_file_to_cleanup in shm_map {
+            shm_file_to_cleanup.cleanup_file();
+        }
+
+        Ok(())
+    }
+}

commons/zenoh-shm/src/posix_shm/mod.rs

@@ -14,3 +14,4 @@
 
 pub mod array;
 tested_crate_module!(segment);
+pub(crate) mod cleanup;

commons/zenoh-shm/src/posix_shm/segment.rs

@@ -106,7 +106,7 @@ where
     fn os_id(id: ID, id_prefix: &str) -> String {
         let os_id_str = format!("{id_prefix}_{id}");
         let crc_os_id_str = ECMA.checksum(os_id_str.as_bytes());
-        format!("{:x}", crc_os_id_str)
+        format!("{:x}.zenoh", crc_os_id_str)
     }
 
     pub fn as_ptr(&self) -> *mut u8 {

zenoh/src/lib.rs

@@ -427,6 +427,7 @@ pub mod shm {
             zshm::{zshm, ZShm},
             zshmmut::{zshmmut, ZShmMut},
         },
+        cleanup::cleanup_orphaned_shm_segments,
         client::{shm_client::ShmClient, shm_segment::ShmSegment},
         client_storage::{ShmClientStorage, GLOBAL_CLIENT_STORAGE},
         common::types::{ChunkID, ProtocolID, SegmentID},