If a process daemonizes itself, then it should be possible to control that
process's log levels with "ovs-appctl vlog/set" and related commands. The
vlog_init() function registers those commands. But vlog_init() doesn't
normally get called until the first log message is issued. This can take a
while, especially for ovs-controller, where I first noticed the problem.
This commit fixes the problem by calling vlog_init() from
daemonize_start(), which always gets called as a process daemonizes.
Adding a macro to define the vlog module in use adds a level of
indirection, which makes it easier to change how the vlog module must be
defined. A followup commit needs to do that, so getting these widespread
changes out of the way first should make that commit easier to review.
If a monitored daemon dies quickly at startup, the system can waste a lot
of CPU time continually restarting it. This commit prevents a given
daemon from restarting more than once every 10 seconds.
If the monitored daemon dumps core frequently, then this can quickly
exhaust the host's disk space. This commit limits core dumps to at most
one per monitored session (typically, once per boot).
This leaked a small amount of memory each time a daemon process was
created. It is only important if a daemon is otherwise very buggy.
Found with valgrind.
When --monitor is used, administrators sometimes become confused about the
presence of two copies of each process. This commit attempts to clarify
the situation by making the monitoring process change its process name, as
seen in /proc/$pid/cmdline and in "ps", to clearly indicate what is going
on.
CC: Dan Wendlandt <dan@nicira.com>
Before SSH terminates, it waits for the PTYs that it creates for use as
stdin, stdout, and stderr to be closed. When any of the Open vSwitch
daemons were started in the background over an SSH session, they held
those file descriptors open and thus the SSH session hung. This commit
fixes the problem by closing those file descriptors, allowing SSH to
terminate.
There are conflicting pressures in startup of a daemon process:
* The parent process should exit with an error code if the daemon
cannot start up successfully.
* Some startup actions must be performed in the child process, not in
the parent. The most obvious of these are file locking, since
child processes do not inherit locks, and anything that requires
knowing the child process's PID (e.g. unixctl sockets).
Until now, this conflict has usually been handled by giving up part of the
first property, i.e. in some cases the parent process would exit
successfully and the child immediately afterward exit with a failure code.
This commit introduces a better approach, by allowing daemons to perform
startup work in the child and only then signal the parent that they have
successfully started. If the child instead exits without signaling
success, the parent passes this exit code along to its own parent.
This commit also modifies the daemons that can usefully take advantage of
this new feature to do so.
Some systems complain when certain functions' return values are not
checked. This commit fixes those warnings.
Creating ignore() function suggested by Ben Pfaff.
Before this commit, "ovsdb-server --detach" would detach after it opened
the database file, which meant that the child process did not hold the
file lock on the database file (because a forked child process does not
inherit its parents' locks). This commit fixes the problem by making
ovsdb-server open the database only after it has detached. This fix, in
turn, required that daemonize() not chdir to /, because this would break
databases whose names are given relative to the current directory, and so
this commit also changes ovsdb-server to do so later.
Open vSwitch uses an interval timer signal to tell it that its cached idea
of the current time has expired. However, this didn't work in a daemon
detached from the foreground session (invoked with --detach) because a
child created with fork() does not inherit the parent's interval timer and
we did not re-set it after calling fork().
This commit fixes the problem by setting the interval timer back up after
calling fork() from daemonize().
This fix is based on code inspection (which was then verified to be correct
through testing). It may not fix any actual problems in practice, because
time_refresh() is called every time through the poll loop, and the poll
loop typically runs more quickly than the periodic timer fires (1 ms or so
average in ovs-vswitchd, vs. 100 ms timer interval).
The daemon library provides a few short options, but these then take
away their availability from programs that wish to use the library.
Since the daemon options are generally going to be called from a script
(which doesn't care how much typing is involved), we'll only provide
long options.
By default, Open vSwitch daemons change their working directories to the
root directory. This commit provides a --no-chdir option to prevent this
behavior.
