/usr/sbin/fence_mpath is in fence-agents 4.0.22-2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
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import sys
import stat
import re
import os
import logging
import atexit
sys.path.append("/usr/share/fence")
from fencing import fail_usage, run_command, atexit_handler, check_input, process_input, show_docs
from fencing import fence_action, all_opt, run_delay
#BEGIN_VERSION_GENERATION
RELEASE_VERSION="4.0.22"
BUILD_DATE="(built Sat, 06 Feb 2016 12:34:18 +0100)"
REDHAT_COPYRIGHT="Copyright (C) Red Hat, Inc. 2004-2010 All rights reserved."
#END_VERSION_GENERATION
def get_status(conn, options):
del conn
status = "off"
for dev in options["devices"]:
is_block_device(dev)
if options["--key"] in get_registration_keys(options, dev):
status = "on"
else:
logging.debug("No registration for key "\
+ options["--key"] + " on device " + dev + "\n")
if options["--action"] == "monitor":
dev_read(options)
return status
def set_status(conn, options):
del conn
count = 0
if options["--action"] == "on":
for dev in options["devices"]:
is_block_device(dev)
register_dev(options, dev)
if options["--key"] not in get_registration_keys(options, dev):
count += 1
logging.debug("Failed to register key "\
+ options["--key"] + "on device " + dev + "\n")
continue
dev_write(options, dev)
if get_reservation_key(options, dev) is None \
and not reserve_dev(options, dev) \
and get_reservation_key(options, dev) is None:
count += 1
logging.debug("Failed to create reservation (key="\
+ options["--key"] + ", device=" + dev + ")\n")
else:
dev_keys = dev_read(options)
for dev in options["devices"]:
is_block_device(dev)
if options["--key"] in get_registration_keys(options, dev):
preempt_abort(options, dev_keys[dev], dev)
for dev in options["devices"]:
if options["--key"] in get_registration_keys(options, dev):
count += 1
logging.debug("Failed to remove key "\
+ options["--key"] + " on device " + dev + "\n")
continue
if not get_reservation_key(options, dev):
count += 1
logging.debug("No reservation exists on device " + dev + "\n")
if count:
logging.error("Failed to verify " + str(count) + " device(s)")
sys.exit(1)
#run command, returns dict, ret["err"] = exit code; ret["out"] = output
def run_cmd(options, cmd):
ret = {}
if options.has_key("--use-sudo"):
prefix = options["--sudo-path"] + " "
else:
prefix = ""
(ret["err"], ret["out"], _) = run_command(options, prefix + cmd)
ret["out"] = "".join([i for i in ret["out"] if i is not None])
return ret
# check if device exist and is block device
def is_block_device(dev):
if not os.path.exists(dev):
fail_usage("Failed: device \"" + dev + "\" does not exist")
if not stat.S_ISBLK(os.stat(dev).st_mode):
fail_usage("Failed: device \"" + dev + "\" is not a block device")
# cancel registration
def preempt_abort(options, host, dev):
cmd = options["--mpathpersist-path"] + " -o --preempt-abort --prout-type=5 --param-rk=" + host +" --param-sark=" + options["--key"] +"-d " + dev
return not bool(run_cmd(options, cmd)["err"])
def register_dev(options, dev):
cmd = options["--mpathpersist-path"] + " -o --register --param-sark=" + options["--key"] + " -d " + dev
#cmd return code != 0 but registration can be successful
return not bool(run_cmd(options, cmd)["err"])
def reserve_dev(options, dev):
cmd = options["--mpathpersist-path"] + " -o --reserv --prout-type=5 --param-rk=" + options["--key"] + " -d " + dev
return not bool(run_cmd(options, cmd)["err"])
def get_reservation_key(options, dev):
cmd = options["--mpathpersist-path"] + " -i -r -d " + dev
out = run_cmd(options, cmd)
if out["err"]:
fail_usage("Cannot get reservation key")
match = re.search(r"\s+key\s*=\s*0x(\S+)\s+", out["out"], re.IGNORECASE)
return match.group(1) if match else None
def get_registration_keys(options, dev):
keys = []
cmd = options["--mpathpersist-path"] + " -i -k -d " + dev
out = run_cmd(options, cmd)
if out["err"]:
fail_usage("Cannot get registration keys")
for line in out["out"].split("\n"):
match = re.search(r"\s+0x(\S+)\s*", line)
if match:
keys.append(match.group(1))
return keys
def dev_write(options, dev):
file_path = options["--store-path"] + "/mpath.devices"
if not os.path.isdir(options["--store-path"]):
os.makedirs(options["--store-path"])
try:
store_fh = open(file_path, "a+")
except IOError:
fail_usage("Failed: Cannot open file \""+ file_path + "\"")
out = store_fh.read()
if not re.search(r"^" + dev + r"\s+", out):
store_fh.write(dev + "\t" + options["--key"] + "\n")
store_fh.close()
def dev_read(options):
dev_key = {}
file_path = options["--store-path"] + "/mpath.devices"
try:
store_fh = open(file_path, "r")
except IOError:
fail_usage("Failed: Cannot open file \"" + file_path + "\"")
# get not empty lines from file
for (device, key) in [line.strip().split() for line in store_fh if line.strip()]:
dev_key[device] = key
store_fh.close()
return dev_key
def define_new_opts():
all_opt["devices"] = {
"getopt" : "d:",
"longopt" : "devices",
"help" : "-d, --devices=[devices] List of devices to use for current operation",
"required" : "1",
"shortdesc" : "List of devices to use for current operation. Devices can \
be comma-separated list of device-mapper multipath devices (eg. /dev/dm-3). \
Each device must support SCSI-3 persistent reservations.",
"order": 1
}
all_opt["key"] = {
"getopt" : "k:",
"longopt" : "key",
"help" : "-k, --key=[key] Key to use for the current operation",
"required" : "1",
"shortdesc" : "Key to use for the current operation. This key should be \
unique to a node and have to be written in /etc/multipath.conf. For the \"on\" action, the key specifies the key use to \
register the local node. For the \"off\" action, this key specifies the key to \
be removed from the device(s).",
"order": 1
}
all_opt["mpathpersist_path"] = {
"getopt" : ":",
"longopt" : "mpathpersist-path",
"help" : "--mpathpersist-path=[path] Path to mpathpersist binary",
"required" : "0",
"shortdesc" : "Path to mpathpersist binary",
"default" : "/usr/sbin/mpathpersist",
"order": 200
}
all_opt["store_path"] = {
"getopt" : ":",
"longopt" : "store-path",
"help" : "--store-path=[path] Path to directory containing cached keys",
"required" : "0",
"shortdesc" : "Path to directory where fence agent can store information",
"default" : "/var/run/cluster",
"order": 200
}
def main():
atexit.register(atexit_handler)
device_opt = ["no_login", "no_password", "devices", "key", "sudo", \
"fabric_fencing", "on_target", "store_path", "mpathpersist_path", "force_on"]
define_new_opts()
options = check_input(device_opt, process_input(device_opt), other_conditions=True)
docs = {}
docs["shortdesc"] = "Fence agent for multipath persistent reservation"
docs["longdesc"] = "fence_mpath is an I/O fencing agent that uses SCSI-3 \
persistent reservations to control access multipath devices. Underlying \
devices must support SCSI-3 persistent reservations (SPC-3 or greater) as \
well as the \"preempt-and-abort\" subcommand.\nThe fence_mpath agent works by \
having an unique key for each pair of node and device that has to be set also \
in /etc/multipath.conf. Once registered, a single node will become the reservation holder \
by creating a \"write exclusive, registrants only\" reservation on the \
device(s). The result is that only registered nodes may write to the \
device(s). When a node failure occurs, the fence_mpath agent will remove the \
key belonging to the failed node from the device(s). The failed node will no \
longer be able to write to the device(s). A manual reboot is required."
docs["vendorurl"] = "https://www.sourceware.org/dm/"
show_docs(options, docs)
run_delay(options)
# Input control BEGIN
if not "--key" in options:
fail_usage("Failed: key is required")
if options["--action"] == "validate-all":
sys.exit(0)
options["devices"] = options["--devices"].split(",")
if not options["devices"]:
fail_usage("Failed: No devices found")
# Input control END
result = fence_action(None, options, set_status, get_status)
sys.exit(result)
if __name__ == "__main__":
main()
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