dinit/TODO

now:
* improve error message when service unable to open logfile
* dinitcheck:
  * consumer-of:
    * check consumed service exists, is output-producing, has log-type=pipe
  * logfile:
    * check directory is writable
* add preferred alias for "smooth-recovery": "silent-restart"
* "start-interruptible" should work for process & bgprocess services too
* check services cannot be "after"/"before" themselves
* standardise error messages, exception messages. General format, quote types, punctuation, capitalisation
* review exceptions thrown by load_service.h process_service_line - include setting name where possible

For version 0.17:
-----------------
* [DONE] Limit memory use by control connections. Currently clients have command responses queued without
  limit; it would be better to stop accepting new commands once a certain amount of response is
  buffered. 
* [DONE] Externally triggered services (to represent devices etc). Such services will not reach STARTED
  state unless the external trigger occurs (eg "dinitctl trigger servicename", details to be
  determined).
* [DONE] process input/output chaining (for logging); "log-type = pipe".
* [DONE] Documentation for "log-type = buffer" and "log-type = pipe".
* [DONE] dinitctl command to signal running service process.
* [DONE] "offline" dinitctl enable/disable - i.e. enable or disable a service when dinit isn't running.


For version 1.0 (release requirements):
---------------------------------------
* Be able to boot and shutdown Linux and FreeBSD (or OpenBSD).
* Documentation must be complete (mostly done; will need updates as other items are completed).
* dinitcheck should be able to resolve variable substitutions using variables from running dinit.


For later (post 1.0):
---------------------
* jails support
* 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)
* Proper support for socket activation?
* 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).
* on shutdown, after a long interval with no activity, display information about
  services we are waiting on (and/or, do this when prompted via ^C or C-A-D?)
* 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 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. [Done!]
  - 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.