Directory Watcher. Leaked handles detected at driver shutdown

[FreeSlave]

Running this application with vibe-d 0.9.2

import core.time;
import vibe.core.file;
import vibe.core.log;
import vibe.core.task;
import vibe.core.core;

void main()
{
    runTask({
        auto watcher = watchDirectory("./test", false);
        while(true)
        {
            DirectoryChange[] changes;
            if (watcher.readChanges(changes, dur!"seconds"(-1)))
            {
                foreach(ref change; changes)
                {
                    logInfo("Changed file: %s\n", change);
                }
            }
        }
    });
    runApplication();
}

When I press Ctrl+C on Windows (did not try on other systems yet) it reports:

Warning (thread: main): Leaked handles detected at driver shutdown
   FD 0204 (watcher)

I'm not sure though if I'm doing it right. I think there should be a directory watcher example in 'examples/' directory of the repository.

[FreeSlave]

I checked and similar thing happens on Linux.

Warning (thread: main): leaking eventcore driver because there are still active handles
   FD 6 (watcher)

Warning (thread: main): leaking eventcore driver because there are still active handles
   FD 6 (watcher)

I tried it with VibeHighEventPriority enabled but without any success.

[Geod24]

@FreeSlave : I can't reproduce on OSX. Do you still see it with the latest release ?

[FreeSlave]

@Geod24 I've just tried it on Linux with vibecore 1.18.0

Warning (thread: main): leaking eventcore driver because there are still active handles
  FD 6 (watcher)
Created by;
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/file.d:543 @safe vibe.core.file.DirectoryWatcher vibe.core.file.watchDirectory(vibe.core.path.GenericPath!(vibe.core.path.PosixPathFormat).GenericPath, bool) [0x5640ed43772b]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/file.d:548 @safe vibe.core.file.DirectoryWatcher vibe.core.file.watchDirectory(immutable(char)[], bool) [0x5640ed3f7755]
      source/app.d:10 @safe void app.main().__lambda1() [0x5640ed3ebdf9]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/task.d:718 void vibe.core.task.TaskFuncInfo.set!(void function() @safe*).set(ref void function() @safe*).callDelegate(ref vibe.core.task.TaskFuncInfo) [0x5640ed3f072a]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/task.d:739 void vibe.core.task.TaskFuncInfo.call() [0x5640ed40efc5]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/task.d:446 nothrow void vibe.core.task.TaskFiber.run() [0x5640ed40e28b]
      ??:? void core.thread.context.Callable.opCall() [0x5640ed4a6088]
      ??:? fiber_entryPoint [0x5640ed4dbe7b]
Warning (thread: main): leaking eventcore driver because there are still active handles
  FD 6 (watcher)
    Created by;
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/file.d:543 @safe vibe.core.file.DirectoryWatcher vibe.core.file.watchDirectory(vibe.core.path.GenericPath!(vibe.core.path.PosixPathFormat).GenericPath, bool) [0x5640ed43772b]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/file.d:548 @safe vibe.core.file.DirectoryWatcher vibe.core.file.watchDirectory(immutable(char)[], bool) [0x5640ed3f7755]
      source/app.d:10 @safe void app.main().__lambda1() [0x5640ed3ebdf9]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/task.d:718 void vibe.core.task.TaskFuncInfo.set!(void function() @safe*).set(ref void function() @safe*).callDelegate(ref vibe.core.task.TaskFuncInfo) [0x5640ed3f072a]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/task.d:739 void vibe.core.task.TaskFuncInfo.call() [0x5640ed40efc5]
      ../../.dub/packages/vibe-core-1.18.0/vibe-core/source/vibe/core/task.d:446 nothrow void vibe.core.task.TaskFiber.run() [0x5640ed40e28b]
      ??:? void core.thread.context.Callable.opCall() [0x5640ed4a6088]
      ??:? fiber_entryPoint [0x5640ed4dbe7b]

[FreeSlave]

Note that if I save Task into variable and then manually call join on it in scope(exit), there're no such warnings when I interrupt the app by Ctrl+C.

import core.time;
import vibe.core.file;
import vibe.core.log;
import vibe.core.task;
import vibe.core.core;

void main()
{
    auto watcherTask = runTask({
        auto watcher = watchDirectory("./test", false);
        while(true)
        {
            DirectoryChange[] changes;
            if (watcher.readChanges(changes, dur!"seconds"(-1)))
            {
                foreach(ref change; changes)
                {
                    logInfo("Changed file: %s\n", change);
                }
            }
        }
    });

    scope(exit) {
        watcherTask.join();
    }

    runApplication();
}

[dedupely]

I can attest to this as well. I have the directory watcher in a runTask like you're doing here and it leaks on shutdown.

[s-ludwig]

As far as I can see, this is a leak that has to be fixed on the user side. All tasks should ideally be terminated before returning from main (e.g. by a task.interrupt(); task.join(); sequence) and in this case, the watcher object will still be alive within the stack of that task, causing the leak. It could be argued that for short lived applications (command line tools) such leaks don't matter, because the OS will clean them up anyway. In that case eventcore could offer an optional compile time version EventCoreSilenceLeakWarnings or similar to just avoid showing the warning to the user.

[dedupely]

@s-ludwig EventCoreSilenceLeakWarnings would be great actually.

[s-ludwig]

Forgot to mention here - the latest versions now have that version flag: https://github.com/vibe-d/eventcore?tab=readme-ov-file#version-identifiers