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eio_linux: add subprocess support #472

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merged 2 commits into from
Mar 28, 2023
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talex5
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@talex5 talex5 commented Mar 24, 2023

This combines @patricoferris's code from #435 with the new fork actions from #461.

It needs some review and cleaning up, but might be useful if someone wants to have another go at the high-level API (#330), now that all backends support subprocesses.

I wanted to use clone3, but for now it's just using plain fork combined with pidfd_open. We might need to check that Docker's security policy doesn't block clone3. The first commit is just moving the fork support from eio_posix to eio_unix to share it.

It uses pidfd_send_signal to signal child processes, which requires #define CAML_INTERNALS. I think that's fine, but if not we could instead use plain Unix.kill, with Rcfd ref-counting to ensure we don't signal the wrong process.

This also cleans up the Eio_unix.Private.Pipe handling, to match eio_posix. The same should be done for the other handlers.

  • Split out pipe changes to another PR and fix sockets too.
  • Consider not reporting an exception if you signal a process that's already finished.

@talex5 talex5 added the enhancement New feature or request label Mar 24, 2023
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avsm commented Mar 24, 2023

The clone3/seccomp issue was fixed last year (moby/moby#42836) but need to check thats been rolled out into production Docker instances.

@talex5 talex5 mentioned this pull request Mar 27, 2023
5 tasks
@talex5 talex5 force-pushed the linux-process branch 4 times, most recently from 50a1caa to 4c9716d Compare March 27, 2023 13:46
@talex5 talex5 marked this pull request as ready for review March 27, 2023 13:50
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talex5 commented Mar 27, 2023

The clone3/seccomp issue was fixed last year

Ah, great! I've removed the fork bit and switched to using clone3 directly now.

@talex5 talex5 merged commit dd66ff9 into ocaml-multicore:main Mar 28, 2023
@talex5 talex5 deleted the linux-process branch March 28, 2023 11:43
RyanGibb added a commit to RyanGibb/ocaml-exec-shell that referenced this pull request Apr 3, 2023
RyanGibb added a commit to RyanGibb/ocaml-exec-shell that referenced this pull request Apr 3, 2023
talex5 added a commit to talex5/opam-repository that referenced this pull request Apr 11, 2023
CHANGES:

New features:

- Add eio_posix backend (@talex5 @haesbaert ocaml-multicore/eio#448 ocaml-multicore/eio#477, reviewed by @avsm @patricoferris @polytypic).
  This replaces eio_luv on all platforms except Windows (which will later switch to its own backend). It is a lot faster, provides access to more modern features (such as `openat`), and can safely share OS resources between domains.

- Add subprocess support (@patricoferris @talex5 ocaml-multicore/eio#461 ocaml-multicore/eio#464 ocaml-multicore/eio#472, reviewed by @haesbaert @avsm).
  This is the low-level API support for eio_linux and eio_posix. A high-level cross-platform API will be added in the next release.

- Add `Fiber.fork_seq` (@talex5 ocaml-multicore/eio#460, reviewed by @avsm).
  This is a light-weight alternative to using a single-producer, single-consumer, 0-capacity stream, similar to a Python generator function.

Bug fixes:

- eio_linux: make it safe to share FDs across domains (@talex5 ocaml-multicore/eio#440, reviewed by @haesbaert).
  It was previously not safe to share file descriptors between domains because if one domain used an FD just as another was closing it, and the FD got reused, then the original operation could act on the wrong file.

- eio_linux: release uring if Linux is too old (@talex5 ocaml-multicore/eio#476).
  Avoids a small resource leak.

- eio_linux: improve error handling creating pipes and sockets (@talex5 ocaml-multicore/eio#474, spotted by @avsm).
  If we get an error (e.g. too many FDs) then report it to the calling fiber, instead of exiting the event loop.

- eio_linux: wait for uring to finish before exiting (@talex5 ocaml-multicore/eio#470, reviewed by @avsm).
  If the main fiber raised an exception then it was possible to exit while a cancellation operation was still in progress.

- eio_main: make `EIO_BACKEND` handling more uniform (@talex5 ocaml-multicore/eio#447).
  Previously this environment variable was only used on Linux. Now all platforms check it.

- Tell dune about `EIO_BACKEND` (@talex5 ocaml-multicore/eio#442).
  If this changes, dune needs to re-run the tests.

- eio_linux: add some missing close-on-execs (@talex5 ocaml-multicore/eio#441).

- eio_linux: `read_exactly` fails to update file offset (@talex5 ocaml-multicore/eio#438).

- Work around dune `enabled_if` bug on non-Linux systems (@polytypic ocaml-multicore/eio#475, reviewed by @talex5).

- Use raw system call of `getrandom` for glibc versions before 2.25 (@zenfey ocaml-multicore/eio#482).

Documentation:

- Add `HACKING.md` with hints for working on Eio (@talex5 ocaml-multicore/eio#443, reviewed by @avsm @polytypic).

- Improve worker pool example (@talex5 ocaml-multicore/eio#454).

- Add more Conditions documentation (@talex5 ocaml-multicore/eio#436, reviewed by @haesbaert).
  This adds a discussion of conditions to the README and provides examples using them to handle signals.

- Condition: fix the example in the docstring (@avsm ocaml-multicore/eio#468).

Performance:

- Add a network benchmark using an HTTP-like protocol (@talex5 ocaml-multicore/eio#478, reviewed by @avsm @patricoferris).

- Add a benchmark for reading from `/dev/zero` (@talex5 ocaml-multicore/eio#439).

Other changes:

- Add CI for macOS (@talex5 ocaml-multicore/eio#452).

- Add tests for `pread`, `pwrite` and `readdir` (@talex5 ocaml-multicore/eio#451).

- eio_linux: split into multiple files (@talex5 ocaml-multicore/eio#465 ocaml-multicore/eio#466, reviewed by @avsm).

- Update Dockerfile (@talex5 ocaml-multicore/eio#471).

- Use dune.3.7.0 (@patricoferris ocaml-multicore/eio#457).

- Mint exclusive IDs across domains (@TheLortex ocaml-multicore/eio#480, reported by @haesbaert, reviewed by @talex5).
  The tracing currently only works with a single domain anyway, but this will change when OCaml 5.1 is released.
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talex5 commented May 10, 2023

Hmm, it seems they didn't actually allow clone3 in Docker; they just changed it to return ENOSYS instead of EPERM.

talex5 added a commit to talex5/opam-repository that referenced this pull request Jun 2, 2023
CHANGES:

New features:

- Add eio_posix backend (@talex5 @haesbaert ocaml-multicore/eio#448 ocaml-multicore/eio#477, reviewed by @avsm @patricoferris @polytypic).
  This replaces eio_luv on all platforms except Windows (which will later switch to its own backend). It is a lot faster, provides access to more modern features (such as `openat`), and can safely share OS resources between domains.

- Add subprocess support (@patricoferris @talex5 ocaml-multicore/eio#461 ocaml-multicore/eio#464 ocaml-multicore/eio#472, reviewed by @haesbaert @avsm).
  This is the low-level API support for eio_linux and eio_posix. A high-level cross-platform API will be added in the next release.

- Add `Fiber.fork_seq` (@talex5 ocaml-multicore/eio#460, reviewed by @avsm).
  This is a light-weight alternative to using a single-producer, single-consumer, 0-capacity stream, similar to a Python generator function.

Bug fixes:

- eio_linux: make it safe to share FDs across domains (@talex5 ocaml-multicore/eio#440, reviewed by @haesbaert).
  It was previously not safe to share file descriptors between domains because if one domain used an FD just as another was closing it, and the FD got reused, then the original operation could act on the wrong file.

- eio_linux: release uring if Linux is too old (@talex5 ocaml-multicore/eio#476).
  Avoids a small resource leak.

- eio_linux: improve error handling creating pipes and sockets (@talex5 ocaml-multicore/eio#474, spotted by @avsm).
  If we get an error (e.g. too many FDs) then report it to the calling fiber, instead of exiting the event loop.

- eio_linux: wait for uring to finish before exiting (@talex5 ocaml-multicore/eio#470, reviewed by @avsm).
  If the main fiber raised an exception then it was possible to exit while a cancellation operation was still in progress.

- eio_main: make `EIO_BACKEND` handling more uniform (@talex5 ocaml-multicore/eio#447).
  Previously this environment variable was only used on Linux. Now all platforms check it.

- Tell dune about `EIO_BACKEND` (@talex5 ocaml-multicore/eio#442).
  If this changes, dune needs to re-run the tests.

- eio_linux: add some missing close-on-execs (@talex5 ocaml-multicore/eio#441).

- eio_linux: `read_exactly` fails to update file offset (@talex5 ocaml-multicore/eio#438).

- Work around dune `enabled_if` bug on non-Linux systems (@polytypic ocaml-multicore/eio#475, reviewed by @talex5).

- Use raw system call of `getrandom` for glibc versions before 2.25 (@zenfey ocaml-multicore/eio#482).

Documentation:

- Add `HACKING.md` with hints for working on Eio (@talex5 ocaml-multicore/eio#443, reviewed by @avsm @polytypic).

- Improve worker pool example (@talex5 ocaml-multicore/eio#454).

- Add more Conditions documentation (@talex5 ocaml-multicore/eio#436, reviewed by @haesbaert).
  This adds a discussion of conditions to the README and provides examples using them to handle signals.

- Condition: fix the example in the docstring (@avsm ocaml-multicore/eio#468).

Performance:

- Add a network benchmark using an HTTP-like protocol (@talex5 ocaml-multicore/eio#478, reviewed by @avsm @patricoferris).

- Add a benchmark for reading from `/dev/zero` (@talex5 ocaml-multicore/eio#439).

Other changes:

- Add CI for macOS (@talex5 ocaml-multicore/eio#452).

- Add tests for `pread`, `pwrite` and `readdir` (@talex5 ocaml-multicore/eio#451).

- eio_linux: split into multiple files (@talex5 ocaml-multicore/eio#465 ocaml-multicore/eio#466, reviewed by @avsm).

- Update Dockerfile (@talex5 ocaml-multicore/eio#471).

- Use dune.3.7.0 (@patricoferris ocaml-multicore/eio#457).

- Mint exclusive IDs across domains (@TheLortex ocaml-multicore/eio#480, reported by @haesbaert, reviewed by @talex5).
  The tracing currently only works with a single domain anyway, but this will change when OCaml 5.1 is released.
talex5 added a commit to talex5/opam-repository that referenced this pull request Jun 2, 2023
CHANGES:

New features:

- Add eio_posix backend (@talex5 @haesbaert ocaml-multicore/eio#448 ocaml-multicore/eio#477, reviewed by @avsm @patricoferris @polytypic).
  This replaces eio_luv on all platforms except Windows (which will later switch to its own backend). It is a lot faster, provides access to more modern features (such as `openat`), and can safely share OS resources between domains.

- Add subprocess support (@patricoferris @talex5 ocaml-multicore/eio#461 ocaml-multicore/eio#464 ocaml-multicore/eio#472, reviewed by @haesbaert @avsm).
  This is the low-level API support for eio_linux and eio_posix. A high-level cross-platform API will be added in the next release.

- Add `Fiber.fork_seq` (@talex5 ocaml-multicore/eio#460, reviewed by @avsm).
  This is a light-weight alternative to using a single-producer, single-consumer, 0-capacity stream, similar to a Python generator function.

Bug fixes:

- eio_linux: make it safe to share FDs across domains (@talex5 ocaml-multicore/eio#440, reviewed by @haesbaert).
  It was previously not safe to share file descriptors between domains because if one domain used an FD just as another was closing it, and the FD got reused, then the original operation could act on the wrong file.

- eio_linux: release uring if Linux is too old (@talex5 ocaml-multicore/eio#476).
  Avoids a small resource leak.

- eio_linux: improve error handling creating pipes and sockets (@talex5 ocaml-multicore/eio#474, spotted by @avsm).
  If we get an error (e.g. too many FDs) then report it to the calling fiber, instead of exiting the event loop.

- eio_linux: wait for uring to finish before exiting (@talex5 ocaml-multicore/eio#470, reviewed by @avsm).
  If the main fiber raised an exception then it was possible to exit while a cancellation operation was still in progress.

- eio_main: make `EIO_BACKEND` handling more uniform (@talex5 ocaml-multicore/eio#447).
  Previously this environment variable was only used on Linux. Now all platforms check it.

- Tell dune about `EIO_BACKEND` (@talex5 ocaml-multicore/eio#442).
  If this changes, dune needs to re-run the tests.

- eio_linux: add some missing close-on-execs (@talex5 ocaml-multicore/eio#441).

- eio_linux: `read_exactly` fails to update file offset (@talex5 ocaml-multicore/eio#438).

- Work around dune `enabled_if` bug on non-Linux systems (@polytypic ocaml-multicore/eio#475, reviewed by @talex5).

- Use raw system call of `getrandom` for glibc versions before 2.25 (@zenfey ocaml-multicore/eio#482).

Documentation:

- Add `HACKING.md` with hints for working on Eio (@talex5 ocaml-multicore/eio#443, reviewed by @avsm @polytypic).

- Improve worker pool example (@talex5 ocaml-multicore/eio#454).

- Add more Conditions documentation (@talex5 ocaml-multicore/eio#436, reviewed by @haesbaert).
  This adds a discussion of conditions to the README and provides examples using them to handle signals.

- Condition: fix the example in the docstring (@avsm ocaml-multicore/eio#468).

Performance:

- Add a network benchmark using an HTTP-like protocol (@talex5 ocaml-multicore/eio#478, reviewed by @avsm @patricoferris).

- Add a benchmark for reading from `/dev/zero` (@talex5 ocaml-multicore/eio#439).

Other changes:

- Add CI for macOS (@talex5 ocaml-multicore/eio#452).

- Add tests for `pread`, `pwrite` and `readdir` (@talex5 ocaml-multicore/eio#451).

- eio_linux: split into multiple files (@talex5 ocaml-multicore/eio#465 ocaml-multicore/eio#466, reviewed by @avsm).

- Update Dockerfile (@talex5 ocaml-multicore/eio#471).

- Use dune.3.7.0 (@patricoferris ocaml-multicore/eio#457).

- Mint exclusive IDs across domains (@TheLortex ocaml-multicore/eio#480, reported by @haesbaert, reviewed by @talex5).
  The tracing currently only works with a single domain anyway, but this will change when OCaml 5.1 is released.
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