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#!/usr/bin/env python

# 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__ = '0.2.2'

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 = None

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()