lvm-json

lvm-json

#!/usr/bin/python

import sys
import json
from lvmjson import *
import argparse

if __name__ == "__main__":

  AVAILABLE_COMMANDS = ["lvs", "vgs", "pvs", "dminfo"]

  ap = argparse.ArgumentParser(description="Take a command and produce JSON output.")
  ap.add_argument("--segments", action="store_const", const=True, default=False, help="list segments. (Makes sense only for lvs.)")
  ap.add_argument("-a", "--all", action="store_const", const=True, default=False, help="list hidden LVs. (Makes sense only for lvs.)")
  ap.add_argument("-v", "--verbose", action="store_true", default=False, help="list more fields. (Makes sense only for lvs.)")
  ap.add_argument("-o", "--options", metavar="FIELDS", type=str, action="append",
          help="Comma separated list of fields to list with optional `+` prefix to add to the list of fields.\n"
               + "This option can be repeated. With `+` prefix the FIELDS are added to previous value, without the prfix it is overridden.")
  ap.add_argument("COMMAND", metavar="COMMAND", nargs=1, help="Command to run. One of `lvs`, `vgs`, `pvs` or `dminfo` (shortcut for `dmsetup info`).")
  ap.add_argument("DEV", metavar="DEV", nargs="*", help="An object to be passed to COMMAND. By default all objects are listed.")
  args = ap.parse_args()

  #import pprint
  #pprint.pprint(args)

  d = {}

  d["all"] = args.all or False
  d["verbose"] = args.verbose or False
  d["segments"] = args.segments or False
  d["options"] = args.options or []

  if not args.COMMAND:
    print >> sys.stderr, "COMMAND is mandatory!"
    sys.exit(1)

  cmd = args.COMMAND[0]
  if cmd not in AVAILABLE_COMMANDS:
    print >> sys.stderr, "COMMAND(%s) must be one of %s." % (cmd, AVAILABLE_COMMANDS)
    sys.exit(1)

  if cmd == "dminfo":
    r = dmsetup_list(args.DEV, d)
  else:
    r = lvm_list_cmd(cmd, args.DEV, d)

  print json.dumps(r, indent=2)

lvmjson.py

import re
import subprocess


_KEY_VALUE_RE=re.compile("([A-Z0-9_]*)='(([^\\\\']|\\\\.)*)'")


def lvm_parse(s):
  """
  Parse output of lvs, pvs or vgs with `--nameprefixes --noheadings` and return list of dictionaries.
  """
  lines=s.splitlines()
  return [dict((match[0], match[1]) for match in _KEY_VALUE_RE.findall(line)) for line in lines]


def _opts(opts):
  answ = ""
  for opt in opts:
    if opt:
      if opt[0] == "+":
        answ = answ+","+opt[1:]
      else:
        answ = opt
  if answ and answ[0] == ",":
    return answ[1:]
  else:
    return answ


def _lvm_cmd(cmd, args, kwargs):
  opts = _opts(kwargs.get("options", []))
  #print "%r" % ((cmd, args, kwargs, opts),)
  return (
      [cmd, "--nameprefixes", "--noheadings"] + args + kwargs.get("devices", [])
      + (["--all"] if kwargs.get("all", False) else [])
      + (["--verbose"] if kwargs.get("verbose", False) else [])
      + (["--segments"] if cmd == "lvs" and kwargs.get("segments", False) else [])
      + (["-o" + opts] if len(opts) > 0 else [])
  )
  
    
def _dmsetup(args, kwargs):
  opts = _opts(kwargs.get("options", []))
  return (
      ["dmsetup", "info", "-c", "--nameprefixes", "--noheadings"] + args + kwargs.get("devices", [])
      + (["-o" + opts] if len(opts) > 0 else [])
  )
    

def _run_cmd(cmd, kwargs):
  p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  out, err = p.communicate()
  r = { "cmd": cmd, "rc": p.returncode, "stdout": out, "stderr": err }
  return r


def lvm_list_cmd(cmd, args, kwargs):
  """
  Return dictionary with cmd, rc, stdout, stderr and parsed
  """
  d = _run_cmd(_lvm_cmd(cmd, args, kwargs), kwargs)
  d["parsed"] = lvm_parse(d["stdout"])
  return d
  
  
def dmsetup_list(args, kwargs):
  """
  Return dictionary with cmd, rc, stdout, stderr and parsed
  """
  d = _run_cmd(_dmsetup(args, kwargs), kwargs)
  d["parsed"] = lvm_parse(d["stdout"])
  return d

Running command ./lvm-json -v lvs /dev/vg_cimrman/lv_home will produce:

{
  "stdout": "  LVM2_LV_NAME='lv_home' LVM2_VG_NAME='vg_cimrman' LVM2_SEG_COUNT='1' LVM2_LV_ATTR='-wi-ao---' LVM2_LV_SIZE='400.00g' LVM2_LV_MAJOR='-1' LVM2_LV_MINOR='-1' LVM2_LV_KERNEL_MAJOR='253' LVM2_LV_KERNEL_MINOR='140' LVM2_POOL_LV='' LVM2_ORIGIN='' LVM2_DATA_PERCENT='' LVM2_METADATA_PERCENT='' LVM2_MOVE_PV='' LVM2_COPY_PERCENT='' LVM2_MIRROR_LOG='' LVM2_CONVERT_LV='' LVM2_LV_UUID='tLwZcy-85bh-CAD0-BlvZ-1u0T-PcPJ-bINxXv'\n",
  "cmd": [
    "lvs",
    "--nameprefixes",
    "--noheadings",
    "/dev/vg_cimrman/lv_home",
    "--verbose"
  ],
  "host": "",
  "stderr": "    Using logical volume(s) on command line\n",
  "rc": 0,
  "parsed": [
    {
      "LVM2_CONVERT_LV": "",
      "LVM2_LV_MINOR": "-1",
      "LVM2_LV_KERNEL_MAJOR": "253",
      "LVM2_LV_ATTR": "-wi-ao---",
      "LVM2_POOL_LV": "",
      "LVM2_DATA_PERCENT": "",
      "LVM2_ORIGIN": "",
      "LVM2_COPY_PERCENT": "",
      "LVM2_MIRROR_LOG": "",
      "LVM2_LV_NAME": "lv_home",
      "LVM2_METADATA_PERCENT": "",
      "LVM2_VG_NAME": "vg_cimrman",
      "LVM2_LV_KERNEL_MINOR": "140",
      "LVM2_SEG_COUNT": "1",
      "LVM2_LV_SIZE": "400.00g",
      "LVM2_MOVE_PV": "",
      "LVM2_LV_UUID": "tLwZcy-85bh-CAD0-BlvZ-1u0T-PcPJ-bINxXv",
      "LVM2_LV_MAJOR": "-1"
    }
  ]
}