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serf_event_handler.py
executable file
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/
serf_event_handler.py
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#!/usr/bin/env python3
# vim:ts=4:sts=4:sw=4:et
#
# Author: Hari Sekhon
# Date: 2016-01-16 15:44:16 +0000 (Sat, 16 Jan 2016)
#
# https://github.com/HariSekhon/DevOps-Python-tools
#
# License: see accompanying Hari Sekhon LICENSE file
#
# If you're using my code you're welcome to connect with me on LinkedIn and optionally send me feedback
# to help improve or steer this or other code I publish
#
# https://www.linkedin.com/in/HariSekhon
#
"""
Serf Handler to return query information or handle specific events
Optionally allows enabling command pass through of any user query or event
Checks first arg against $PATH and if matching executable is found, then executes the full command and returns the
result from standard output. Careful to ensure you've set up security before enabling --cmd!
Framework for new custom handlers, simply inherit SerfEventHandler and override add_options() and handle_event() methods
Docs:
https://www.serfdom.io/intro/getting-started/event-handlers.html
https://www.serfdom.io/docs/agent/event-handlers.html
Call custom events:
https://www.serfdom.io/docs/commands/event.html
Tested on HashiCorp's Serf 0.7.0
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
#from __future__ import unicode_literals
import logging
import os
import re
import sys
libdir = os.path.abspath(os.path.join(os.path.dirname(__file__), 'pylib'))
sys.path.append(libdir)
try:
# pylint: disable=wrong-import-position
from harisekhon.utils import isStr, log, which
from harisekhon import CLI
except ImportError as _:
print('module import failed: %s' % _, file=sys.stderr)
print("Did you remember to build the project by running 'make'?", file=sys.stderr)
print("Alternatively perhaps you tried to copy this program out without it's adjacent libraries?", file=sys.stderr)
sys.exit(4)
__author__ = 'Hari Sekhon'
__version__ = '0.2.3'
class SerfEventHandler(CLI):
def __init__(self):
super(SerfEventHandler, self).__init__()
# allow shorter default 10 sec timeout
# self.timeout_default = 30
self.events = ['member-join', 'member-leave', 'member-failed', 'member-update', 'member-reap', 'user', 'query']
self.node = os.getenv('SERF_SELF_NAME', '')
self.role = os.getenv('SERF_SELF_ROLE', None)
self.event = os.getenv('SERF_EVENT', None)
self.query_name = os.getenv('SERF_QUERY_NAME', None)
self.user_event = os.getenv('SERF_USER_EVENT', None)
# self.user_ltime = os.getenv('SERF_USER_LTIME', 0)
# self.query_ltime = os.getenv('SERF_QUERY_LTIME', 0)
self.command = None
# "expected to exit within a reasonable amount of time" according to docs, this seems like a reasonable
# safeguard and is configurable on the command line via --timeout <secs>
if self.event is None:
log.warn('SERF_EVENT environment variable was None!!')
elif self.event not in self.events:
log.warn("SERF_EVENT environment variable passed unrecognized event type '%s'" % self.event)
def add_option_command_passthru(self):
self.add_opt('--cmd-passthru', dest='cmd', action='store_true',
help='Allow any query or event to run a command if the first arg is found in $PATH')
# this allows easier overriding of add_options while adding command passthrough option back in
def add_options(self):
self.add_option_command_passthru()
def enable_commands(self):
if self.event in ['query', 'event']:
cmd = ''
if self.event == 'query':
cmd = self.query_name
elif self.event == 'user':
cmd = self.user_event
# if the first part of the query is found in $PATH then assume it's a command that was passed
if which(cmd.split()[0]):
self.command = cmd
# override this if subclassing
def handle_event(self):
if isStr(self.command):
print(os.popen(self.command).read(), end='')
for line in sys.stdin:
# do something with the data
log.debug('data: %s' % line.strip())
def run(self):
if self.args:
self.usage()
if log.isEnabledFor(logging.DEBUG):
# this trips the 1024 byte limit and queries fail to respond so only filter and show *SERF* env vars
# log.debug(envs2str())
serf_regex = re.compile('SERF', re.I)
for (key, value) in os.environ.iteritems(): # pylint: disable=unused-variable
if serf_regex.search(key):
log.debug('%(key)s=%(value)s' % locals())
if 'cmd' in dir(self.options) and self.get_opt('cmd'):
self.enable_commands()
self.handle_event()
if __name__ == '__main__':
SerfEventHandler().main()