.TH WATCHER 1
.SH NAME
watcher \- octopus watcher for network gadget arrival and departure
.SH SYNOPSIS
.B watcher
[
.B \-dv
]
[
.B -i
.I ival
]
[
.B \-t
.I tmout
]
[
.B -r
.I regdir
]
.SH DESCRIPTION
.I Watcher
watches out the registry to detect and notify of arrivals and departures of network gadgets
in the octopus. It opens
.B /mnt/registry/event
to detect changes in the registry (or uses that at
.I regdir
when
.B -r
is given). Also, it scans the directory every
.I ival
milliseconds (60000 by default) to detect entries not refreshed (with modification time
older than
.I tmout
seconds, 60 by default).
.PP
For each new entry in the registry with value
.B ofs
for the
.B name
attribute
.I watcher
plumbs a message notifying the arrival of the terminal whose name is reported by
the
.B sys
attribute as found in the entry. When such entry is gone (either due to lack of refresh or
due to removal from the registry)
.I watcher
plumbs a message notifying the departure of the terminal. Messages are plumbed both
via
.IR plumber (8)
and
vid
.IR ports (4).
.PP
Also, upon departure of a terminal,
.I watcher
kills
the entire process group of the process whose PID was reported in the
.B pid
attribue of the
.B ofs
entry. This is done to force all resources imported from a (no longer working) gone
terminal to be discarded. Besides,
.I watcher
tries to unmount the terminal from
.B /devs
(just in case).
.PP
Only entries with registry names starting with
.B o!
are timed out. That is the naming convention used by
.IR netget (1)
to register network gadgets. Giving zero in
.I tmout
disables the time out mechanism.
.PP
Flag
.B -v
makes the program a little verbose, to report arrivals and departures. Flag
.B -d
makes the program quite verbose, for debugging.
.SH SOURCE
.B /usr/octopus/port/watcher.b
.SH SEE ALSO
.IR netget (1),
.IR mux (4).