Currently, when qemu-dm fails, typically its exit status is lost and
xend doesn't notice. In the patch below I use a fifo (named pipe) to
detect qemu-dm's termination and report the exit status to the
logfile, if possible. (If xend has been restarted since the domain
was created, this isn't possible but we can still know that it failed
and report that fact.)
It would be better to have a failure of qemu crash the domain, by
calling the SCHEDOP_shutdown hypercall with SHUTDOWN_crash. However
if you have on_crash=restart and the configuration is broken in some
way that causes qemu-dm to bomb out straight away this causes xend to
spin endlessly restarting the doomed domain. This is a general
problem with on_*=restart and ought to be fixed separately. When it
is fixed, we can safely arrange for domains whose dm has crashed to be
themselves forcibly crashed.
(As an aside: error reporting in xend is generally very poor and the
multithreaded programming model is IMO a recipe for pain and bugs. We
should be using Twisted.)
Ian.
Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
diff --exclude=.hg --exclude=.config --exclude='*.old' --exclude='*.orig'
--exclude='*~' -ruN ../xen-unstable-3.hg/tools/python/xen/util/oshelp.py
tools/python/xen/util/oshelp.py
--- ../xen-unstable-3.hg/tools/python/xen/util/oshelp.py 1970-01-01
01:00:00.000000000 +0100
+++ tools/python/xen/util/oshelp.py 2008-06-11 16:46:07.000000000 +0100
@@ -0,0 +1,20 @@
+import fcntl
+import os
+
+def fcntl_setfd_cloexec(file, bool):
+ f = fcntl.fcntl(file, fcntl.F_GETFD)
+ if bool: f |= fcntl.FD_CLOEXEC
+ else: f &= ~fcntl.FD_CLOEXEC
+ fcntl.fcntl(file, fcntl.F_SETFD)
+
+def waitstatus_description(st):
+ if os.WIFEXITED(st):
+ es = os.WEXITSTATUS(st)
+ if es: return "exited with nonzero status %i" % es
+ else: return "exited"
+ elif os.WIFSIGNALED(st):
+ s = "died due to signal %i" % os.WTERMSIG(st)
+ if os.WCOREDUMP(st): s += " (core dumped)"
+ return s
+ else:
+ return "failed with unexpected wait status %i" % st
diff --exclude=.hg --exclude=.config --exclude='*.old' --exclude='*.orig'
--exclude='*~' -ruN ../xen-unstable-3.hg/tools/python/xen/util/utils.py
tools/python/xen/util/utils.py
--- ../xen-unstable-3.hg/tools/python/xen/util/utils.py 1970-01-01
01:00:00.000000000 +0100
+++ tools/python/xen/util/utils.py 2008-06-11 15:21:04.000000000 +0100
@@ -0,0 +1,6 @@
+import traceback
+import sys
+
+def exception_string(e):
+ (ty,v,tb) = sys.exc_info()
+ return traceback.format_exception_only(ty,v)
diff --exclude=.hg --exclude=.config --exclude='*.old' --exclude='*.orig'
--exclude='*~' -ruN ../xen-unstable-3.hg/tools/python/xen/xend/XendDomain.py
tools/python/xen/xend/XendDomain.py
--- ../xen-unstable-3.hg/tools/python/xen/xend/XendDomain.py 2008-06-12
12:13:04.000000000 +0100
+++ tools/python/xen/xend/XendDomain.py 2008-06-11 16:42:07.000000000 +0100
@@ -34,7 +34,7 @@
from xen.xend import XendOptions, XendCheckpoint, XendDomainInfo
from xen.xend.PrettyPrint import prettyprint
-from xen.xend import XendConfig
+from xen.xend import XendConfig, image
from xen.xend.XendError import XendError, XendInvalidDomain, VmError
from xen.xend.XendError import VMBadState
from xen.xend.XendLogging import log
@@ -179,6 +179,8 @@
log.exception("Failed to create reference to running "
"domain id: %d" % dom['domid'])
+ image.cleanup_stale_sentinel_fifos()
+
# add all managed domains as dormant domains.
for dom in managed:
dom_uuid = dom.get('uuid')
diff --exclude=.hg --exclude=.config --exclude='*.old' --exclude='*.orig'
--exclude='*~' -ruN
../xen-unstable-3.hg/tools/python/xen/xend/XendDomainInfo.py
tools/python/xen/xend/XendDomainInfo.py
--- ../xen-unstable-3.hg/tools/python/xen/xend/XendDomainInfo.py
2008-06-12 12:13:04.000000000 +0100
+++ tools/python/xen/xend/XendDomainInfo.py 2008-06-11 15:02:43.000000000
+0100
@@ -30,6 +30,7 @@
import re
import copy
import os
+import fcntl
import traceback
from types import StringTypes
diff --exclude=.hg --exclude=.config --exclude='*.old' --exclude='*.orig'
--exclude='*~' -ruN ../xen-unstable-3.hg/tools/python/xen/xend/XendLogging.py
tools/python/xen/xend/XendLogging.py
--- ../xen-unstable-3.hg/tools/python/xen/xend/XendLogging.py 2008-06-12
12:13:04.000000000 +0100
+++ tools/python/xen/xend/XendLogging.py 2008-06-12 12:14:14.000000000
+0100
@@ -25,10 +25,10 @@
import types
import logging
import logging.handlers
-import fcntl
from xen.util import mkdir
from xen.xend.server import params
+from xen.util import oshelp
__all__ = [ 'log', 'init', 'getLogFilename' ]
@@ -103,9 +103,7 @@
# entire FileHandler, StreamHandler & RotatingFileHandler classes which
# is even worse
def setCloseOnExec(self):
- flags = fcntl.fcntl(self.stream.fileno(), fcntl.F_GETFD)
- flags |= fcntl.FD_CLOEXEC
- fcntl.fcntl(self.stream.fileno(), fcntl.F_SETFD, flags)
+ oshelp.fcntl_setfd_cloexec(self.stream, True)
def init(filename, level):
diff --exclude=.hg --exclude=.config --exclude='*.old' --exclude='*.orig'
--exclude='*~' -ruN ../xen-unstable-3.hg/tools/python/xen/xend/image.py
tools/python/xen/xend/image.py
--- ../xen-unstable-3.hg/tools/python/xen/xend/image.py 2008-06-12
12:13:04.000000000 +0100
+++ tools/python/xen/xend/image.py 2008-06-12 12:16:14.000000000 +0100
@@ -22,6 +22,12 @@
import math
import time
import signal
+import thread
+import fcntl
+import sys
+import errno
+import glob
+import traceback
import xen.lowlevel.xc
from xen.xend.XendConstants import *
@@ -32,11 +38,23 @@
from xen.xend.xenstore.xswatch import xswatch
from xen.xend import arch
from xen.xend import XendOptions
+from xen.util import oshelp
+from xen.util import utils
xc = xen.lowlevel.xc.xc()
MAX_GUEST_CMDLINE = 1024
+sentinel_path_prefix = '/var/run/xend/dm-'
+sentinel_fifos_inuse = { }
+
+def cleanup_stale_sentinel_fifos():
+ for path in glob.glob(sentinel_path_prefix + '*.fifo'):
+ if path in sentinel_fifos_inuse: continue
+ try: os.unlink(path)
+ except OSError, e:
+ log.warning('could not delete stale fifo %s: %s',
+ path, utils.exception_string(e))
def create(vm, vmConfig):
"""Create an image handler for a vm.
@@ -318,6 +336,13 @@
args = args + self.dmargs
return args
+ def _openSentinel(self, sentinel_path_fifo):
+ self.sentinel_fifo = file(sentinel_path_fifo, 'r')
+ self.sentinel_lock = thread.allocate_lock()
+ oshelp.fcntl_setfd_cloexec(self.sentinel_fifo, True)
+ sentinel_fifos_inuse[sentinel_path_fifo] = 1
+ self.sentinel_path_fifo = sentinel_path_fifo
+
def createDeviceModel(self, restore = False):
if self.device_model is None:
return
@@ -333,21 +358,29 @@
env['XAUTHORITY'] = self.xauthority
if self.vncconsole:
args = args + ([ "-vncviewer" ])
+ unique_id = "%i-%i" % (self.vm.getDomid(), time.time())
+ sentinel_path = sentinel_path_prefix + unique_id
+ sentinel_path_fifo = sentinel_path + '.fifo'
+ os.mkfifo(sentinel_path_fifo, 0600)
+ sentinel_write = file(sentinel_path_fifo, 'r+')
+ self._openSentinel(sentinel_path_fifo)
+ self.vm.storeDom("image/device-model-fifo", sentinel_path_fifo)
xstransact.Mkdir("/local/domain/0/device-model/%i" %
self.vm.getDomid())
xstransact.SetPermissions("/local/domain/0/device-model/%i" %
self.vm.getDomid(),
{ 'dom': self.vm.getDomid(), 'read': True, 'write':
True })
log.info("spawning device models: %s %s", self.device_model, args)
# keep track of pid and spawned options to kill it later
- logfile = "/var/log/xen/qemu-dm-%s.log" %
str(self.vm.info['name_label'])
- if os.path.exists(logfile):
- if os.path.exists(logfile + ".1"):
- os.unlink(logfile + ".1")
- os.rename(logfile, logfile + ".1")
+ self.logfile = "/var/log/xen/qemu-dm-%s.log" %
str(self.vm.info['name_label'])
+ if os.path.exists(self.logfile):
+ if os.path.exists(self.logfile + ".1"):
+ os.unlink(self.logfile + ".1")
+ os.rename(self.logfile, self.logfile + ".1")
null = os.open("/dev/null", os.O_RDONLY)
- logfd = os.open(logfile, os.O_WRONLY|os.O_CREAT|os.O_TRUNC)
-
+ logfd = os.open(self.logfile,
os.O_WRONLY|os.O_CREAT|os.O_TRUNC|os.O_APPEND)
+
+ sys.stderr.flush()
pid = os.fork()
if pid == 0: #child
try:
@@ -356,18 +389,26 @@
os.dup2(logfd, 2)
os.close(null)
os.close(logfd)
+ self.sentinel_fifo.close()
try:
os.execve(self.device_model, args, env)
- except:
- os._exit(127)
+ except Exception, e:
+ print >>sys.stderr, (
+ 'failed to set up fds or execute dm %s: %s' %
+ (self.device_model, utils.exception_string(e)))
+ os._exit(126)
except:
os._exit(127)
else:
self.pid = pid
os.close(null)
os.close(logfd)
+ sentinel_write.close()
self.vm.storeDom("image/device-model-pid", self.pid)
log.info("device model pid: %d", self.pid)
+ # we would very much prefer not to have a thread here and instead
+ # have a callback but sadly we don't have Twisted in xend
+ self.sentinel_thread = thread.start_new_thread(self._sentinel_watch,())
def signalDeviceModel(self, cmd, ret, par = None):
if self.device_model is None:
@@ -413,47 +454,119 @@
xstransact.Store("/local/domain/0/device-model/%i"
% self.vm.getDomid(), ('command', 'continue'))
+ def _dmfailed(self, message):
+ log.warning("domain %s: %s", self.vm.getName(), message)
+ # ideally we would like to forcibly crash the domain with
+ # something like
+ # xc.domain_shutdown(self.vm.getDomid(), DOMAIN_CRASH)
+ # but this can easily lead to very rapid restart loops against
+ # which we currently have no protection
+
def recreate(self):
if self.device_model is None:
return
- self.pid = self.vm.gatherDom(('image/device-model-pid', int))
+ name = self.vm.getName()
+ sentinel_path_fifo = self.vm.readDom('image/device-model-fifo')
+ fifo_fd = -1
+ log.debug("rediscovering %s", sentinel_path_fifo)
+ if sentinel_path_fifo is None:
+ log.debug("%s device model no sentinel, cannot rediscover", name)
+ else:
+ try:
+ # We open it O_WRONLY because that fails ENXIO if no-one
+ # has it open for reading (see SuSv3). The dm process got
+ # a read/write descriptor from our earlier invocation.
+ fifo_fd = os.open(sentinel_path_fifo,
os.O_WRONLY|os.O_NONBLOCK)
+ except OSError, e:
+ if e.errno == errno.ENXIO:
+ self._dmfailed("%s device model no longer running"%name)
+ elif e.errno == errno.ENOENT:
+ log.debug("%s device model sentinel %s absent!",
+ name, sentinel_path_fifo)
+ else:
+ raise
+ if fifo_fd >= 0:
+ self._openSentinel(sentinel_path_fifo)
+ os.close(fifo_fd)
+ self.pid = self.vm.gatherDom(('image/device-model-pid', int))
+ log.debug("%s device model rediscovered, pid %s sentinel fifo %s",
+ name, self.pid, sentinel_path_fifo)
+ self.sentinel_thread =
thread.start_new_thread(self._sentinel_watch,())
+
+ def _sentinel_watch(self):
+ log.info("waiting for sentinel_fifo")
+ try: self.sentinel_fifo.read(1)
+ except OSError, e: pass
+ self.sentinel_lock.acquire()
+ try:
+ if self.pid:
+ (p,st) = os.waitpid(self.pid, os.WNOHANG)
+ if p == self.pid:
+ message = oshelp.waitstatus_description(st)
+ else:
+ # obviously it is malfunctioning, kill it now
+ try:
+ os.kill(self.pid, signal.SIGKILL)
+ message = "malfunctioning (closed sentinel), killed"
+ except:
+ message = "malfunctioning or died ?"
+ message = "pid %d: %s" % (self.pid, message)
+ else:
+ message = "no longer running"
+ except Exception, e:
+ message = "waitpid failed: %s" % utils.exception_string(e)
+ message = "device model failure: %s" % message
+ try: message += "; see %s " % self.logfile
+ except: pass
+ self._dmfailed(message)
+ self.pid = None
+ self.sentinel_lock.release()
def destroyDeviceModel(self):
if self.device_model is None:
return
+ self
if self.pid:
+ self.sentinel_lock.acquire()
try:
- os.kill(self.pid, signal.SIGHUP)
- except OSError, exn:
- log.exception(exn)
- try:
- # Try to reap the child every 100ms for 10s. Then SIGKILL it.
- for i in xrange(100):
- (p, rv) = os.waitpid(self.pid, os.WNOHANG)
- if p == self.pid:
- break
- time.sleep(0.1)
- else:
- log.warning("DeviceModel %d took more than 10s "
- "to terminate: sending SIGKILL" % self.pid)
+ try:
+ os.kill(self.pid, signal.SIGHUP)
+ except OSError, exn:
+ log.exception(exn)
+ try:
+ # Try to reap the child every 100ms for 10s. Then SIGKILL
it.
+ for i in xrange(100):
+ (p, rv) = os.waitpid(self.pid, os.WNOHANG)
+ if p == self.pid:
+ break
+ time.sleep(0.1)
+ else:
+ log.warning("DeviceModel %d took more than 10s "
+ "to terminate: sending SIGKILL" % self.pid)
+ os.kill(self.pid, signal.SIGKILL)
+ os.waitpid(self.pid, 0)
+ except OSError, exn:
+ # This is expected if Xend has been restarted within the
+ # life of this domain. In this case, we can kill the
process,
+ # but we can't wait for it because it's not our child.
+ # We just make really sure it's going away (SIGKILL) first.
os.kill(self.pid, signal.SIGKILL)
- os.waitpid(self.pid, 0)
- except OSError, exn:
- # This is expected if Xend has been restarted within the
- # life of this domain. In this case, we can kill the process,
- # but we can't wait for it because it's not our child.
- # We just make really sure it's going away (SIGKILL) first.
- os.kill(self.pid, signal.SIGKILL)
- self.pid = None
- state = xstransact.Remove("/local/domain/0/device-model/%i"
- % self.vm.getDomid())
+ state = xstransact.Remove("/local/domain/0/device-model/%i"
+ % self.vm.getDomid())
+ finally:
+ self.pid = None
+ self.sentinel_lock.release()
try:
os.unlink('/var/run/tap/qemu-read-%d' % self.vm.getDomid())
os.unlink('/var/run/tap/qemu-write-%d' % self.vm.getDomid())
except:
pass
-
+ try:
+ del sentinel_fifos_inuse[self.sentinel_path_fifo]
+ os.unlink(self.sentinel_path_fifo)
+ except:
+ pass
class LinuxImageHandler(ImageHandler):
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