`streamlit run` does not work when the python file is in root directory.

Summary

Running something like streamlit run /foo.py crashes.

Steps to reproduce

$ pip install streamlit
$ sudo touch /foo.py
$ .local/bin/streamlit run /foo.py 
Traceback (most recent call last):
  File "/usr/local/google/home/ayushranjan/.local/bin/streamlit", line 8, in <module>
    sys.exit(main())
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/web/cli.py", line 205, in main_run
    _main_run(target, args, flag_options=kwargs)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/web/cli.py", line 240, in _main_run
    bootstrap.run(file, command_line, args, flag_options)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/web/bootstrap.py", line 360, in run
    _install_pages_watcher(main_script_path)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/web/bootstrap.py", line 336, in _install_pages_watcher
    watch_dir(
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/watcher/path_watcher.py", line 154, in watch_dir
    return _watch_path(
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/watcher/path_watcher.py", line 129, in _watch_path
    watcher_class(
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/watcher/event_based_path_watcher.py", line 92, in __init__
    path_watcher.watch_path(
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/streamlit/watcher/event_based_path_watcher.py", line 170, in watch_path
    folder_handler.watch = self._observer.schedule(
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/api.py", line 302, in schedule
    emitter.start()
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/utils/__init__.py", line 93, in start
    self.on_thread_start()
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/inotify.py", line 118, in on_thread_start
    self._inotify = InotifyBuffer(path, self.watch.is_recursive)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/inotify_buffer.py", line 35, in __init__
    self._inotify = Inotify(path, recursive)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/inotify_c.py", line 167, in __init__
    self._add_dir_watch(path, recursive, event_mask)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/inotify_c.py", line 372, in _add_dir_watch
    self._add_watch(full_path, mask)
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/inotify_c.py", line 386, in _add_watch
    Inotify._raise_error()
  File "/usr/local/google/home/ayushranjan/.local/lib/python3.10/site-packages/watchdog/observers/inotify_c.py", line 406, in _raise_error
    raise OSError(err, os.strerror(err))
FileNotFoundError: [Errno 2] No such file or directory

Expected behavior:

This crash should not happen since there is not documented constraints of where the python file can be placed.

Actual behavior:

Crashes as shown in reproducer.

Is this a regression?

I am not sure. Have not bisected across versions.

Debug info

• Streamlit version: 1.12.2
• Python version: 3.10.5
• OS: gLinux

Technical details of crash

The reason this crash happens is because streamlit tries to recursively add inotify watchers on everything inside the parent directory of the python file. In this case, the parent directory is root itself. As a result, streamlit attempts to add inotify watchers in /proc filesystem. This fails because watchdog/observers package uses a directory file descriptor to read the contents of each directory. At some point, it comes across /proc/<selfpid>/task/<selftid>/fd directory. getdents64(2) results on this directory naturally includes the directory file descriptor which was used for getdents64(2). Then the directory FD is closed. But watchdog package remembers the entry and tries to add inotify watcher on that entry. But that entry no longer exists because the directory FD has been closed. Here are some strace logs (which were collected using gvisor) which show this phenomenon happening:

...
strace.go:603] [   2:   2] streamlit E openat(AT_FDCWD /, 0x3eb19c6cf290 /proc/2/task/2/fd, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NONBLOCK, 0o0)
strace.go:641] [   2:   2] streamlit X openat(AT_FDCWD /, 0x3eb19c6cf290 /proc/2/task/2/fd, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NONBLOCK, 0o0) = 4 (0x4) (7.951µs)
strace.go:597] [   2:   2] streamlit E fstat(0x4 /proc/2/task/2/fd, 0x3e131b2c4c20)
strace.go:635] [   2:   2] streamlit X fstat(0x4 /proc/2/task/2/fd, 0x3e131b2c4c20 {dev=14, ino=135, mode=S_IFDIR|0o555, nlink=2, uid=0, gid=0, rdev=0, size=0, blksize=4096, blocks=0, atime=2022-08-22 21:56:35.52712683 -0700 PDT, mtime=2022-08-22 21:56:35.52712683 -0700 PDT, ctime=2022-08-22 21:56:35.52712683 -0700 PDT}) = 0 (0x0) (1.498µs)
strace.go:600] [   2:   2] streamlit E getdents64(0x4 /proc/2/task/2/fd, 0x29f049765960, 0x8000)
strace.go:638] [   2:   2] streamlit X getdents64(0x4 /proc/2/task/2/fd, 0x29f049765960, 0x8000) = 168 (0xa8) (5.062µs)
strace.go:597] [   2:   2] streamlit E stat(0x3eb19c6cfa50 /proc/2/task/2/fd/0, 0x3e131b2c4c00)
strace.go:635] [   2:   2] streamlit X stat(0x3eb19c6cfa50 /proc/2/task/2/fd/0, 0x3e131b2c4c00 {dev=26, ino=3, mode=S_IFCHR|0o666, nlink=1, uid=0, gid=0, rdev=0, size=0, blksize=4096, blocks=0, atime=2022-08-17 17:56:13.882378514 -0700 PDT, mtime=2022-08-17 17:56:13.882378514 -0700 PDT, ctime=2022-08-17 17:56:13.882378514 -0700 PDT}) = 0 (0x0) (14.659µs)
strace.go:597] [   2:   2] streamlit E stat(0x3eb19c6cfa90 /proc/2/task/2/fd/1, 0x3e131b2c4c00)
strace.go:635] [   2:   2] streamlit X stat(0x3eb19c6cfa90 /proc/2/task/2/fd/1, 0x3e131b2c4c00 {dev=26, ino=2, mode=S_IFIFO|0o666, nlink=1, uid=268582982, gid=5000, rdev=0, size=0, blksize=4096, blocks=0, atime=2022-08-22 21:56:22.962273084 -0700 PDT, mtime=2022-08-22 21:56:22.962273084 -0700 PDT, ctime=2022-08-22 21:56:22.962273084 -0700 PDT}) = 0 (0x0) (10.111µs)
strace.go:597] [   2:   2] streamlit E stat(0x3eb19c6cfa50 /proc/2/task/2/fd/2, 0x3e131b2c4c00)
strace.go:635] [   2:   2] streamlit X stat(0x3eb19c6cfa50 /proc/2/task/2/fd/2, 0x3e131b2c4c00 {dev=26, ino=1, mode=S_IFIFO|0o666, nlink=1, uid=268582982, gid=5000, rdev=0, size=0, blksize=4096, blocks=0, atime=2022-08-22 21:56:24.822271459 -0700 PDT, mtime=2022-08-22 21:56:24.822271459 -0700 PDT, ctime=2022-08-22 21:56:24.822271459 -0700 PDT}) = 0 (0x0) (9.985µs)
strace.go:597] [   2:   2] streamlit E stat(0x3eb19c6cfa90 /proc/2/task/2/fd/3, 0x3e131b2c4c00)
strace.go:635] [   2:   2] streamlit X stat(0x3eb19c6cfa90 /proc/2/task/2/fd/3, 0x3e131b2c4c00 {dev=1, ino=1, mode=0o600, nlink=1, uid=0, gid=0, rdev=0, size=0, blksize=4096, blocks=0, atime=1969-12-31 16:00:00 -0800 PST, mtime=1969-12-31 16:00:00 -0800 PST, ctime=1969-12-31 16:00:00 -0800 PST}) = 0 (0x0) (7.327µs)
strace.go:597] [   2:   2] streamlit E stat(0x3eb19c6cfa50 /proc/2/task/2/fd/4, 0x3e131b2c4c00)
strace.go:635] [   2:   2] streamlit X stat(0x3eb19c6cfa50 /proc/2/task/2/fd/4, 0x3e131b2c4c00 {dev=14, ino=135, mode=S_IFDIR|0o555, nlink=2, uid=0, gid=0, rdev=0, size=0, blksize=4096, blocks=0, atime=2022-08-22 21:56:35.52712683 -0700 PDT, mtime=2022-08-22 21:56:35.52712683 -0700 PDT, ctime=2022-08-22 21:56:35.52712683 -0700 PDT}) = 0 (0x0) (9.26µs)
strace.go:600] [   2:   2] streamlit E getdents64(0x4 /proc/2/task/2/fd, 0x29f049765960, 0x8000)
strace.go:638] [   2:   2] streamlit X getdents64(0x4 /proc/2/task/2/fd, 0x29f049765960, 0x8000) = 0 (0x0) (4.754µs)
strace.go:594] [   2:   2] streamlit E close(0x4 /proc/2/task/2/fd)
strace.go:632] [   2:   2] streamlit X close(0x4 /proc/2/task/2/fd) = 0 (0x0) (2.102µs)
strace.go:597] [   2:   2] streamlit E lstat(0x3eb19c6cf390 /proc/2/task/2/fd/4, 0x3e131b2c5330)
strace.go:635] [   2:   2] streamlit X lstat(0x3eb19c6cf390 /proc/2/task/2/fd/4, 0x3e131b2c5330) = 0 (0x0) errno=2 (no such file or directory) (5.88µs)
strace.go:600] [   2:   2] streamlit E inotify_add_watch(0x3, 0x3eb19c6cf390 /proc/2/task/2/fd/4, 0x20007ce)
strace.go:638] [   2:   2] streamlit X inotify_add_watch(0x3, 0x3eb19c6cf390 /proc/2/task/2/fd/4, 0x20007ce) = 0 (0x0) errno=2 (no such file or directory) (5.137µs)
...

[vdonato]

Hm, so I think that even with a workaround, we’ll want to fix this rather than add an item to our docs about it (although the docs item is necessary until a fix is merged).

I do think doing so is relative low priority given that we do have an easy workaround for it, though.

[kajarenc]

Hello, @ayushr2, and thanks for the detailed response!

I think this is the same bug, we discussed here https://github.com/streamlit/streamlit/issues/4842

Yes, we not support running streamlit from the OS root directory since 1.10 .

We recommend specifying WORKDIR in Dockerfile https://docs.streamlit.io/knowledge-base/tutorials/deploy/docker

CC: @snehankekre it would be great to add a paragraph in documentation, that says that we don’t support running streamlit from the root of OS