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Fix child process reaping #169

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dw opened this issue Mar 26, 2018 · 1 comment

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@dw
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commented Mar 26, 2018

It seems possible that Mitogen can completely avoid installing a SIGCHLD handler, vastly simplifying integration with existing apps, if it takes care to os.waitpid() at the appropriate moments. There are initial pieces of that done today: waitpid() is called by parent.Stream.on_disconnect, however it's not good enough.

  • For SSH it is safe to SIGTERM the child and block on a call to os.waitpid() once.
  • For sudo it's not possible to SIGTERM the child as it is setuid, so conditions exist for os.waitpid() to block indefinitely, hanging the parent's Broker thread.
  • For local() and fork(), it is not safe to immediately SIGTERM the child, as useful work exists to complete in the child after the child has disconnected. For example, when profiling=True, the child must wind up the stack before cProfile output is dumped.

New plan:

  • Implement timers
  • on_disconnect starts a 1 second timer that call a handler
  • Handler calls os.waitpid(..., WNOHANG).
    • After N attempts, it sends SIGTERM if can_signal is True.
    • On the following iteration, it sends SIGKILL
    • On the following iteration, it logs an error and abandons the child.
  • sudo is marked can_signal = False
  • fakessh is updated to remove its dependency on ProcessMonitor
  • Completely remove ProcessMonitor.

@dw dw added the bug label Mar 26, 2018

@dw dw referenced this issue Jan 25, 2019
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commented Mar 12, 2019

Implemented in the frankencommit for #419

@dw dw closed this Mar 12, 2019

dw added a commit that referenced this issue Mar 12, 2019

Refactor Stream, introduce quasi-asynchronous connect, much more
Split Stream into many, many classes

  * mitogen.parent.Connection: Handles connection setup logic only.
    * Maintain references to stdout and stderr streams.
    * Manages TimerList timer to cancel connection attempt after
      deadline
    * Blocking setup code replaced by async equivalents running on the
      broker

  * mitogen.parent.Options: Tracks connection-specific options. This
    keeps the connection class small, but more importantly, it is
    generic to the future desire to build and execute command lines
    without starting a full connection.

  * mitogen.core.Protocol: Handles program behaviour relating to events
    on a stream. Protocol performs no IO of its own, instead deferring
    it to Stream and Side. This makes testing much easier, and means
    libssh can reimplement Stream and Side to reuse MitogenProtocol

  * mitogen.core.MitogenProtocol: Guts of the old Mitogen stream
    implementtion

  * mitogen.core.BufferedWriter: Guts of the old Mitogen buffered
    transmit implementation, made generic

  * mitogen.core.DelineatedProtocol: Guts of the old IoLogger, knows how
    to split up input and pass it on to a
    on_line_received()/on_partial_line_received() callback.

  * mitogen.parent.BootstrapProtocol: Asynchronous equivalent of the old
    blocking connect code. Waits for various prompts (MITO001 etc) and
    writes the bootstrap using a BufferedWriter. On success, switches
    the stream to MitogenProtocol.

  * mitogen.core.Message: move encoding parts of MitogenProtocol out to
    Message (where it belongs) and write a bunch of new tests for
    pickling.

  * The bizarre Stream.construct() is gone now, Option.__init__ is its
    own constructor. Should fix many LGTM errors.

* Update all connection methods:  Every connection method is updated to
  use async logic, defining protocols as required to handle interactive
  prompts like in SSH or su. Add new real integration tests for at least
  doas and su.

* Eliminate manual fd management: File descriptors are trapped in file
  objects at their point of origin, and Side is updated to use file
  objects rather than raw descriptors. This eliminates a whole class of
  bugs where unrelated FDs could be closed by the wrong component. Now
  an FD's open/closed status is fused to it everywhere in the library.

* Halve file descriptor usage: now FD open/close state is tracked by
  its file object, we don't need to duplicate FDs everywhere so that
  receive/transmit side can be closed independently. Instead both sides
  back on to the same file object. Closes #26, Closes #470.

* Remove most uses of dup/dup2: Closes #256. File descriptors are
  trapped in a common file object and shared among classes. The
  remaining few uses for dup/dup2 are as close to minimal as possible.

* Introduce mitogen.parent.Process: uniform interface for subprocesses
  created either via mitogen.fork or the subprocess module. Remove all
  the crap where we steal a pid from subprocess guts. Now we use
  subprocess to manage its processes as it should be. Closes #169 by
  using the new Timers facility to poll for a slow-to-exit subprocess.

* Fix su password race: Closes #363. DelineatedProtocol naturally
  retries partially received lines, preventing the cause of the original
  race.

* Delete old blocking IO utility functions
  iter_read()/write_all()/discard_until().

Closes #26
Closes #147
Closes #169
Closes #256
Closes #363
Closes #419
Closes #470

dw added a commit that referenced this issue Jul 22, 2019

Refactor Stream, introduce quasi-asynchronous connect, much more
Split Stream into many, many classes

  * mitogen.parent.Connection: Handles connection setup logic only.
    * Maintain references to stdout and stderr streams.
    * Manages TimerList timer to cancel connection attempt after
      deadline
    * Blocking setup code replaced by async equivalents running on the
      broker

  * mitogen.parent.Options: Tracks connection-specific options. This
    keeps the connection class small, but more importantly, it is
    generic to the future desire to build and execute command lines
    without starting a full connection.

  * mitogen.core.Protocol: Handles program behaviour relating to events
    on a stream. Protocol performs no IO of its own, instead deferring
    it to Stream and Side. This makes testing much easier, and means
    libssh can reimplement Stream and Side to reuse MitogenProtocol

  * mitogen.core.MitogenProtocol: Guts of the old Mitogen stream
    implementtion

  * mitogen.core.BufferedWriter: Guts of the old Mitogen buffered
    transmit implementation, made generic

  * mitogen.core.DelineatedProtocol: Guts of the old IoLogger, knows how
    to split up input and pass it on to a
    on_line_received()/on_partial_line_received() callback.

  * mitogen.parent.BootstrapProtocol: Asynchronous equivalent of the old
    blocking connect code. Waits for various prompts (MITO001 etc) and
    writes the bootstrap using a BufferedWriter. On success, switches
    the stream to MitogenProtocol.

  * mitogen.core.Message: move encoding parts of MitogenProtocol out to
    Message (where it belongs) and write a bunch of new tests for
    pickling.

  * The bizarre Stream.construct() is gone now, Option.__init__ is its
    own constructor. Should fix many LGTM errors.

* Update all connection methods:  Every connection method is updated to
  use async logic, defining protocols as required to handle interactive
  prompts like in SSH or su. Add new real integration tests for at least
  doas and su.

* Eliminate manual fd management: File descriptors are trapped in file
  objects at their point of origin, and Side is updated to use file
  objects rather than raw descriptors. This eliminates a whole class of
  bugs where unrelated FDs could be closed by the wrong component. Now
  an FD's open/closed status is fused to it everywhere in the library.

* Halve file descriptor usage: now FD open/close state is tracked by
  its file object, we don't need to duplicate FDs everywhere so that
  receive/transmit side can be closed independently. Instead both sides
  back on to the same file object. Closes #26, Closes #470.

* Remove most uses of dup/dup2: Closes #256. File descriptors are
  trapped in a common file object and shared among classes. The
  remaining few uses for dup/dup2 are as close to minimal as possible.

* Introduce mitogen.parent.Process: uniform interface for subprocesses
  created either via mitogen.fork or the subprocess module. Remove all
  the crap where we steal a pid from subprocess guts. Now we use
  subprocess to manage its processes as it should be. Closes #169 by
  using the new Timers facility to poll for a slow-to-exit subprocess.

* Fix su password race: Closes #363. DelineatedProtocol naturally
  retries partially received lines, preventing the cause of the original
  race.

* Delete old blocking IO utility functions
  iter_read()/write_all()/discard_until().

Closes #26
Closes #147
Closes #169
Closes #256
Closes #363
Closes #419
Closes #470

dw added a commit that referenced this issue Jul 22, 2019

Refactor Stream, introduce quasi-asynchronous connect, much more
Split Stream into many, many classes

  * mitogen.parent.Connection: Handles connection setup logic only.
    * Maintain references to stdout and stderr streams.
    * Manages TimerList timer to cancel connection attempt after
      deadline
    * Blocking setup code replaced by async equivalents running on the
      broker

  * mitogen.parent.Options: Tracks connection-specific options. This
    keeps the connection class small, but more importantly, it is
    generic to the future desire to build and execute command lines
    without starting a full connection.

  * mitogen.core.Protocol: Handles program behaviour relating to events
    on a stream. Protocol performs no IO of its own, instead deferring
    it to Stream and Side. This makes testing much easier, and means
    libssh can reimplement Stream and Side to reuse MitogenProtocol

  * mitogen.core.MitogenProtocol: Guts of the old Mitogen stream
    implementtion

  * mitogen.core.BufferedWriter: Guts of the old Mitogen buffered
    transmit implementation, made generic

  * mitogen.core.DelineatedProtocol: Guts of the old IoLogger, knows how
    to split up input and pass it on to a
    on_line_received()/on_partial_line_received() callback.

  * mitogen.parent.BootstrapProtocol: Asynchronous equivalent of the old
    blocking connect code. Waits for various prompts (MITO001 etc) and
    writes the bootstrap using a BufferedWriter. On success, switches
    the stream to MitogenProtocol.

  * mitogen.core.Message: move encoding parts of MitogenProtocol out to
    Message (where it belongs) and write a bunch of new tests for
    pickling.

  * The bizarre Stream.construct() is gone now, Option.__init__ is its
    own constructor. Should fix many LGTM errors.

* Update all connection methods:  Every connection method is updated to
  use async logic, defining protocols as required to handle interactive
  prompts like in SSH or su. Add new real integration tests for at least
  doas and su.

* Eliminate manual fd management: File descriptors are trapped in file
  objects at their point of origin, and Side is updated to use file
  objects rather than raw descriptors. This eliminates a whole class of
  bugs where unrelated FDs could be closed by the wrong component. Now
  an FD's open/closed status is fused to it everywhere in the library.

* Halve file descriptor usage: now FD open/close state is tracked by
  its file object, we don't need to duplicate FDs everywhere so that
  receive/transmit side can be closed independently. Instead both sides
  back on to the same file object. Closes #26, Closes #470.

* Remove most uses of dup/dup2: Closes #256. File descriptors are
  trapped in a common file object and shared among classes. The
  remaining few uses for dup/dup2 are as close to minimal as possible.

* Introduce mitogen.parent.Process: uniform interface for subprocesses
  created either via mitogen.fork or the subprocess module. Remove all
  the crap where we steal a pid from subprocess guts. Now we use
  subprocess to manage its processes as it should be. Closes #169 by
  using the new Timers facility to poll for a slow-to-exit subprocess.

* Fix su password race: Closes #363. DelineatedProtocol naturally
  retries partially received lines, preventing the cause of the original
  race.

* Delete old blocking IO utility functions
  iter_read()/write_all()/discard_until().

Closes #26
Closes #147
Closes #169
Closes #256
Closes #363
Closes #419
Closes #470
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