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File descriptor usage is needlessly doubled #470

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dw opened this issue Jan 19, 2019 · 1 comment

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@dw
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commented Jan 19, 2019

This may be a duplicate ticket, but just in case.. Due to #26, at present the receive_side and transmit_side of every stream actually keep a private dup() of the socket/pipe/whatever file descriptor, even though the whole point of Side is to manage the lifetime of a potentially shared descriptor.

This was a 'quick' workaround for there being no clarity early on about when/where close() should be called for an FD. Now that is clearer (any FD added to a broker's poller must be closed on the broker thread), a single Side instance should be assigned to both receive_side and transmit_side, so only one system FD exists.

I think really the only problem right now is that it's burning RAM needlessly, FDs aren't free. But it's still something that needs to be carefully fixed.

see also (same underlying problem) #147

related #256

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commented Mar 9, 2019

Rolled into #419

@dw dw closed this Mar 9, 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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