dinit/TODO

For version 0.9.0:
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* "chain-to" can result in an unbreakable loop if the chain is circular. Chained services should not be
  started during shutdown to prevent this (also avoids a race condition where the chained service is left
  running when everything else has shutdown).
* Check that desired_state is getting set correctly. (Currently we don't decide whether a service
  will restart until it stops...)
* Add dinit command line option to run as pid 1 but not as system manager (i.e., in a container).
  Currently dinit can be used as pid 1 in a container but it may try to shut down the system when
  it terminates. (This results in a harmless warning, but is not ideal).

For version 0.10.+:
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* for non-system init, fail if the control socket exists, with option to override this and re-
  create the socket instead (as system init does).
* report process launch failure reason (stage & errno) via dinitctl.
* Show "activated" state in "dinitctl list" output
* Service description sanity checks:
  - Service type not specified
    - maybe default to 'internal' if command not specified
    - if command specified but type not, report an error
    - other checks?
  - errors should also be reported by dinitcheck

For version 1.0 (i.e. longer-term plans):
-----------------------------------------
* Service description parse errors should report line number
* dinitcheck should perform lint checks - do named files exist? etc
* Limit memory use by control connections. Currently clients can queue commands without limit.
* Consider using mlockall (if system process).
* Dinitctl command to get full status of a service.
* "triggered" service type: external process notifies Dinit when the service
  has started. (maybe?)
  - key thing is we want some way to eg mount filesystem once the disk comes up,
    configure network when device comes up, etc, potentially relying an an external
    tool/daemon.
* on shutdown, after repeated intervals with no activity, display information
  about services we are waiting on (or, do this when prompted via ^C or C-A-D).
* Documentation must be complete (see section below).
* Proper support for socket activation?
* Chaining of service process input/output?
* Be able to boot and shutdown Linux and FreeBSD (or OpenBSD).

For later (post 1.0):
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* On linux when running with PID != 1, write PID to /proc/sys/kernel/cad_pid so
  that we still receive SIGINT from ctrl+alt+del (must be done after /proc is
  mounted, possibly could be left to a service script)
* Perhaps need a way to prevent script services from re-starting.
  (eg there's no need to mount filesystems twice; there might be various other
   system initialisations that can't or shouldn't really be "undone" and so do
   not need to be re-done).
* Internationalisation
* A service can prevent shutdown/reboot by failing to stop. Maybe make
  multiple CTRL-ALT-DEL presses (or ^C since that's more portable) commence
  immediate shutdown (or launch a simple control interface).
* When we take down a service or tty session, it would be ideal if we could kill
  the whole process tree, not just the leader process (need cgroups or pid
  namespace or other mechanism).
* Allow logging tasks to memory (growing or circular buffer) and later
  switching to disk logging (allows for filesystem mounted readonly on boot).
  But perhaps this really the responsibility of another daemon.
* Allow running services with different resource limits, chroot, cgroups,
  namespaces (pid/fs/uid), etc
* Support chaining service output to another process (logger) input; if the
  service dies the file descriptor of its stdout isn't closed and is reassigned
  when the service is restarted, so that minimal output is lost.
  - even more, it would be nice if a single logger process could be responsible
    for receiving output from multiple services. This would require some kind of
    protocol for passing new output descriptors to the logger (for when a
    service starts).

Even later / Maybe never:
-------------------------
* Support recognising /etc/init.d services automatically (as script services, with
  no dependency management - or upstart compatible dependency management)
  Also BSD's rc.d style scripts (PROVIDE, REQUIRE).
* Place some reasonable, soft limit on the number of services to be started
  simultaneously, to prevent thrashing. Services that are taking a long time
  to start don't count to the limit. Maybe use CPU/IO usage as a controlling
  factor.
* Cron-like tasks (if started, they run a sub-task periodically. Stopping the
  task will wait until the sub-task is complete). 
* Allow to run services attached to virtual tty, allow connection to that tty (ala "screen").
* SystemD-like handling of filesystem mounts (see autofs documentation in kernel)
  i.e. a mount point gets an autofs attached, and lazily gets mounted when accessed
  (or is mounted in parallel). Probably put the functionality in a separate daemon.


Documentation:
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* Design philosophy/rationale document
* More system integration documentation?