parse_slave.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

'''
parse_slave.py -- parses SSH cmd for invocation of smallfile_remote.py
Copyright 2012 -- Ben England
Licensed under the Apache License at http://www.apache.org/licenses/LICENSE-2.0
See Appendix on this page for instructions pertaining to license.
'''

import sys
import os
import errno
import time
import pickle
import smallfile


# convert boolean value into 'Y' or 'N'

def usage(msg):  # call if CLI syntax error or invalid parameter
    print('')
    print('ERROR: ' + msg)
    print('usage: smallfile_remote.py ' +
          '[ --network-sync-dir path ] --as-host hostname ')
    sys.exit(1)


# parse command line and return tuple containing:
#   network sync directory
#   host identity of this remote invocation

def parse():

    prm_network_sync_dir = None

    argc = len(sys.argv)
    if argc == 1:
        print('for additional help add the parameter "--help" to the command')
        sys.exit(1)
    j = 1
    while j < argc:
        rawprm = sys.argv[j]
        if rawprm == '-h' or rawprm == '--help':
            usage('normally this process is run automatically ' +
                  'by smallfile_cli.py')
        if rawprm[0:2] != '--':
            usage('parameter names begin with "--"')
        prm = rawprm[2:]
        if j == argc - 1 and argc % 2 != 1:
            usage('all parameters consist of a name and a value')
        val = sys.argv[j + 1]
        if len(rawprm) < 3:
            usage('parameter name not long enough')
        j += 2
        if prm == 'network-sync-dir':
            prm_network_sync_dir = val
        elif prm == 'as-host':
            # --ashost should not be used by end-user
            prm_as_host = smallfile.get_hostname(val)
        else:
            usage('unrecognized parameter name')

    param_pickle_fname = os.path.join(prm_network_sync_dir,
                                      'param.pickle')
    if not os.path.exists(param_pickle_fname):
        time.sleep(1.1)
    params = None
    try:
        with open(param_pickle_fname, 'rb') as pickled_params:
            params = pickle.load(pickled_params)
            params.is_slave = True
            params.as_host = prm_as_host
            params.master_invoke.onhost = prm_as_host
    except IOError as e:
        if e.errno != errno.ENOENT:
            raise e
        usage('could not read parameter pickle file %s'
              % param_pickle_fname)
    return params