builds/vpe-router/lib/charms/layer/execd.py

   1 # Copyright 2014-2016 Canonical Limited.
   2 #
   3 # This file is part of layer-basic, the reactive base layer for Juju.
   4 #
   5 # charm-helpers is free software: you can redistribute it and/or modify
   6 # it under the terms of the GNU Lesser General Public License version 3 as
   7 # published by the Free Software Foundation.
   8 #
   9 # charm-helpers is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Lesser General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Lesser General Public License
  15 # along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 # This module may only import from the Python standard library.
  18 import os
  19 import sys
  20 import subprocess
  21 import time
  22
  23 '''
  24 execd/preinstall
  25
  26 It is often necessary to configure and reconfigure machines
  27 after provisioning, but before attempting to run the charm.
  28 Common examples are specialized network configuration, enabling
  29 of custom hardware, non-standard disk partitioning and filesystems,
  30 adding secrets and keys required for using a secured network.
  31
  32 The reactive framework's base layer invokes this mechanism as
  33 early as possible, before any network access is made or dependencies
  34 unpacked or non-standard modules imported (including the charms.reactive
  35 framework itself).
  36
  37 Operators needing to use this functionality may branch a charm and
  38 create an exec.d directory in it. The exec.d directory in turn contains
  39 one or more subdirectories, each of which contains an executable called
  40 charm-pre-install and any other required resources. The charm-pre-install
  41 executables are run, and if successful, state saved so they will not be
  42 run again.
  43
  44     $CHARM_DIR/exec.d/mynamespace/charm-pre-install
  45
  46 An alternative to branching a charm is to compose a new charm that contains
  47 the exec.d directory, using the original charm as a layer,
  48
  49 A charm author could also abuse this mechanism to modify the charm
  50 environment in unusual ways, but for most purposes it is saner to use
  51 charmhelpers.core.hookenv.atstart().
  52 '''
  53
  54
  55 def default_execd_dir():
  56     return os.path.join(os.environ['CHARM_DIR'], 'exec.d')
  57
  58
  59 def execd_module_paths(execd_dir=None):
  60     """Generate a list of full paths to modules within execd_dir."""
  61     if not execd_dir:
  62         execd_dir = default_execd_dir()
  63
  64     if not os.path.exists(execd_dir):
  65         return
  66
  67     for subpath in os.listdir(execd_dir):
  68         module = os.path.join(execd_dir, subpath)
  69         if os.path.isdir(module):
  70             yield module
  71
  72
  73 def execd_submodule_paths(command, execd_dir=None):
  74     """Generate a list of full paths to the specified command within exec_dir.
  75     """
  76     for module_path in execd_module_paths(execd_dir):
  77         path = os.path.join(module_path, command)
  78         if os.access(path, os.X_OK) and os.path.isfile(path):
  79             yield path
  80
  81
  82 def execd_sentinel_path(submodule_path):
  83     module_path = os.path.dirname(submodule_path)
  84     execd_path = os.path.dirname(module_path)
  85     module_name = os.path.basename(module_path)
  86     submodule_name = os.path.basename(submodule_path)
  87     return os.path.join(execd_path,
  88                         '.{}_{}.done'.format(module_name, submodule_name))
  89
  90
  91 def execd_run(command, execd_dir=None, stop_on_error=True, stderr=None):
  92     """Run command for each module within execd_dir which defines it."""
  93     if stderr is None:
  94         stderr = sys.stdout
  95     for submodule_path in execd_submodule_paths(command, execd_dir):
  96         # Only run each execd once. We cannot simply run them in the
  97         # install hook, as potentially storage hooks are run before that.
  98         # We cannot rely on them being idempotent.
  99         sentinel = execd_sentinel_path(submodule_path)
 100         if os.path.exists(sentinel):
 101             continue
 102
 103         try:
 104             subprocess.check_call([submodule_path], stderr=stderr,
 105                                   universal_newlines=True)
 106             with open(sentinel, 'w') as f:
 107                 f.write('{} ran successfully {}\n'.format(submodule_path,
 108                                                           time.ctime()))
 109                 f.write('Removing this file will cause it to be run again\n')
 110         except subprocess.CalledProcessError as e:
 111             # Logs get the details. We can't use juju-log, as the
 112             # output may be substantial and exceed command line
 113             # length limits.
 114             print("ERROR ({}) running {}".format(e.returncode, e.cmd),
 115                   file=stderr)
 116             print("STDOUT<<EOM", file=stderr)
 117             print(e.output, file=stderr)
 118             print("EOM", file=stderr)
 119
 120             # Unit workload status gets a shorter fail message.
 121             short_path = os.path.relpath(submodule_path)
 122             block_msg = "Error ({}) running {}".format(e.returncode,
 123                                                        short_path)
 124             try:
 125                 subprocess.check_call(['status-set', 'blocked', block_msg],
 126                                       universal_newlines=True)
 127                 if stop_on_error:
 128                     sys.exit(0)  # Leave unit in blocked state.
 129             except Exception:
 130                 pass  # We care about the exec.d/* failure, not status-set.
 131
 132             if stop_on_error:
 133                 sys.exit(e.returncode or 1)  # Error state for pre-1.24 Juju
 134
 135
 136 def execd_preinstall(execd_dir=None):
 137     """Run charm-pre-install for each module within execd_dir."""
 138     execd_run('charm-pre-install', execd_dir=execd_dir)