def reload_process(self):
"""
Execute the reload_cmd command.
Sometimes a daemon might watch its own config file for changes and
reload on its own, so reload_cmd is not mandatory.
Users of supervisord can use a "reload_cmd" value of:
supervisordctl reload haproxy
.. but the default is to kill haproxy and start a new process (killing
all of the existing connections), so be warned about that.
Also of note to supervisord users::
Unfortunately supervisor doesn't offer a way to provide a custom
restart command, so doing an uninterrupted haproxy restart via
supervisor isn't possible. Instead make sure you have autorestart
set to unexpected (the default) rather than true (which is what I
usually do) - that way if you want a clean haproxy restart you can
just do it yourself at the commandline using the -sf option as
normal.
from http://mark.aufflick.com/blog/2012/03/25/supervisord-supervisorctl-cheat-sheet
"""
# maybe it watches its own config and reloads voluntarily
if self.reload_cmd is not None and self.reload_cmd is not "":
log.debug("Running reload_cmd: {}".format(self.reload_cmd))
args = shlex.split(self.reload_cmd)
process = subprocess.Popen(args)
log.debug("Okay, done launching reload_cmd.")
def write_config(self, config):
"""
Write the config file with the given content.
"""
log.debug("Writing config to {}".format(self.dest))
with open(self.dest, "w") as config_fh:
config_fh.write(config)
def sleep(self):
"""
Sleep before checking again. The better way to do this would be to
implement in consul some concept of event-based notification hooks that
would call a script. And then pyconfd wouldn't have to be a daemon.
"""
seconds = 5
log.debug("Sleeping for {} seconds".format(seconds))
# seconds to sleep (fractional values are okay)
gevent.sleep(seconds)
log.debug("Done sleeping for {} seconds.".format(seconds))
def generate(self, template_input):
"""
Populate the template from the given input.
"""
log.debug("Reading the template.")
template_content = self._get_template_content()
# populate the template
log.debug("Populating the template.")
template = jinja2.Template(template_content)
populated = template.render(**template_input)
return populated
def loop(self):
"""
Executes this plugin. Waits an interval amount of time before checking
the config. Updates config files when necessary. Restarts programs.
"""
executing = True
while executing:
try:
# in case self.get() fails
data = None
# determines if config is new
skip = False
# grab config data via custom method
log.debug("Getting the data.")
data = self.get()
except Exception as exc:
log.error("Error getting data: {}".format(exc))
else: # didn't fail
# somehow i doubt jinja responds well to None
if data is None:
data = {}
# never skip the first time (it's None)
if self._last_config is not None:
# skip when new config same as old config
if self._last_config == data:
skip = True
# don't skip if the template has changed, even if data is old
if skip:
# never skip if the template last time was None (initial loop)
if self._last_template is None:
skip = False
else:
# don't skip if the template content is new
content = self._get_template_content()
if content != self._last_template:
skip = False
if not skip:
try:
# populate the template
populated = self.generate(data)
except Exception as exc:
# TODO: log error, don't bail
log.error("Failed to populate the template: {}".format(exc))
else:
self.write_config(populated)
self.reload_process()
self._last_template = self._get_template_content()
else:
log.debug("No new data. Skipping.")
finally:
# only set latest config if it was actually used
if not skip:
self._last_config = data
# wait predefined time
self.sleep()