ssh: rewrite proxy management for multiprocessing usage
We changed sync to use multiprocessing for parallel work. This broke
the ssh proxy code as it's all based on threads. Rewrite the logic to
be multiprocessing safe.
Now instead of the module acting as a stateful object, callers have to
instantiate a new ProxyManager class that holds all the state, an pass
that down to any users.
Bug: https://crbug.com/gerrit/12389
Change-Id: I4b1af116f7306b91e825d3c56fb4274c9b033562
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/305486
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Chris Mcdonald <cjmcdonald@google.com>
diff --git a/git_command.py b/git_command.py
index fabad0e..04953f3 100644
--- a/git_command.py
+++ b/git_command.py
@@ -21,7 +21,6 @@
from git_refs import HEAD
import platform_utils
from repo_trace import REPO_TRACE, IsTrace, Trace
-import ssh
from wrapper import Wrapper
GIT = 'git'
@@ -167,7 +166,7 @@
capture_stderr=False,
merge_output=False,
disable_editor=False,
- ssh_proxy=False,
+ ssh_proxy=None,
cwd=None,
gitdir=None):
env = self._GetBasicEnv()
@@ -175,8 +174,8 @@
if disable_editor:
env['GIT_EDITOR'] = ':'
if ssh_proxy:
- env['REPO_SSH_SOCK'] = ssh.sock()
- env['GIT_SSH'] = ssh.proxy()
+ env['REPO_SSH_SOCK'] = ssh_proxy.sock()
+ env['GIT_SSH'] = ssh_proxy.proxy
env['GIT_SSH_VARIANT'] = 'ssh'
if 'http_proxy' in env and 'darwin' == sys.platform:
s = "'http.proxy=%s'" % (env['http_proxy'],)
@@ -259,7 +258,7 @@
raise GitError('%s: %s' % (command[1], e))
if ssh_proxy:
- ssh.add_client(p)
+ ssh_proxy.add_client(p)
self.process = p
if input:
@@ -271,7 +270,8 @@
try:
self.stdout, self.stderr = p.communicate()
finally:
- ssh.remove_client(p)
+ if ssh_proxy:
+ ssh_proxy.remove_client(p)
self.rc = p.wait()
@staticmethod
diff --git a/git_config.py b/git_config.py
index d7fef8c..978f6a5 100644
--- a/git_config.py
+++ b/git_config.py
@@ -27,7 +27,6 @@
from error import GitError, UploadError
import platform_utils
from repo_trace import Trace
-import ssh
from git_command import GitCommand
from git_refs import R_CHANGES, R_HEADS, R_TAGS
@@ -519,17 +518,23 @@
return self.url.replace(longest, longestUrl, 1)
- def PreConnectFetch(self):
+ def PreConnectFetch(self, ssh_proxy):
"""Run any setup for this remote before we connect to it.
In practice, if the remote is using SSH, we'll attempt to create a new
SSH master session to it for reuse across projects.
+ Args:
+ ssh_proxy: The SSH settings for managing master sessions.
+
Returns:
Whether the preconnect phase for this remote was successful.
"""
+ if not ssh_proxy:
+ return True
+
connectionUrl = self._InsteadOf()
- return ssh.preconnect(connectionUrl)
+ return ssh_proxy.preconnect(connectionUrl)
def ReviewUrl(self, userEmail, validate_certs):
if self._review_url is None:
diff --git a/project.py b/project.py
index 3755806..2f83d79 100644
--- a/project.py
+++ b/project.py
@@ -2045,8 +2045,8 @@
name = self.remote.name
remote = self.GetRemote(name)
- if not remote.PreConnectFetch():
- ssh_proxy = False
+ if not remote.PreConnectFetch(ssh_proxy):
+ ssh_proxy = None
if initial:
if alt_dir and 'objects' == os.path.basename(alt_dir):
diff --git a/ssh.py b/ssh.py
index d06c4eb..0ae8d12 100644
--- a/ssh.py
+++ b/ssh.py
@@ -15,25 +15,20 @@
"""Common SSH management logic."""
import functools
+import multiprocessing
import os
import re
import signal
import subprocess
import sys
import tempfile
-try:
- import threading as _threading
-except ImportError:
- import dummy_threading as _threading
import time
import platform_utils
from repo_trace import Trace
-_ssh_proxy_path = None
-_ssh_sock_path = None
-_ssh_clients = []
+PROXY_PATH = os.path.join(os.path.dirname(__file__), 'git_ssh')
def _run_ssh_version():
@@ -62,68 +57,104 @@
sys.exit(1)
-def proxy():
- global _ssh_proxy_path
- if _ssh_proxy_path is None:
- _ssh_proxy_path = os.path.join(
- os.path.dirname(__file__),
- 'git_ssh')
- return _ssh_proxy_path
+URI_SCP = re.compile(r'^([^@:]*@?[^:/]{1,}):')
+URI_ALL = re.compile(r'^([a-z][a-z+-]*)://([^@/]*@?[^/]*)/')
-def add_client(p):
- _ssh_clients.append(p)
+class ProxyManager:
+ """Manage various ssh clients & masters that we spawn.
+ This will take care of sharing state between multiprocessing children, and
+ make sure that if we crash, we don't leak any of the ssh sessions.
-def remove_client(p):
- try:
- _ssh_clients.remove(p)
- except ValueError:
- pass
-
-
-def _terminate_clients():
- global _ssh_clients
- for p in _ssh_clients:
- try:
- os.kill(p.pid, signal.SIGTERM)
- p.wait()
- except OSError:
- pass
- _ssh_clients = []
-
-
-_master_processes = []
-_master_keys = set()
-_ssh_master = True
-_master_keys_lock = None
-
-
-def init():
- """Should be called once at the start of repo to init ssh master handling.
-
- At the moment, all we do is to create our lock.
+ The code should work with a single-process scenario too, and not add too much
+ overhead due to the manager.
"""
- global _master_keys_lock
- assert _master_keys_lock is None, "Should only call init once"
- _master_keys_lock = _threading.Lock()
+ # Path to the ssh program to run which will pass our master settings along.
+ # Set here more as a convenience API.
+ proxy = PROXY_PATH
-def _open_ssh(host, port=None):
- global _ssh_master
+ def __init__(self, manager):
+ # Protect access to the list of active masters.
+ self._lock = multiprocessing.Lock()
+ # List of active masters (pid). These will be spawned on demand, and we are
+ # responsible for shutting them all down at the end.
+ self._masters = manager.list()
+ # Set of active masters indexed by "host:port" information.
+ # The value isn't used, but multiprocessing doesn't provide a set class.
+ self._master_keys = manager.dict()
+ # Whether ssh masters are known to be broken, so we give up entirely.
+ self._master_broken = manager.Value('b', False)
+ # List of active ssh sesssions. Clients will be added & removed as
+ # connections finish, so this list is just for safety & cleanup if we crash.
+ self._clients = manager.list()
+ # Path to directory for holding master sockets.
+ self._sock_path = None
- # Bail before grabbing the lock if we already know that we aren't going to
- # try creating new masters below.
- if sys.platform in ('win32', 'cygwin'):
- return False
+ def __enter__(self):
+ """Enter a new context."""
+ return self
- # Acquire the lock. This is needed to prevent opening multiple masters for
- # the same host when we're running "repo sync -jN" (for N > 1) _and_ the
- # manifest <remote fetch="ssh://xyz"> specifies a different host from the
- # one that was passed to repo init.
- _master_keys_lock.acquire()
- try:
+ def __exit__(self, exc_type, exc_value, traceback):
+ """Exit a context & clean up all resources."""
+ self.close()
+ def add_client(self, proc):
+ """Track a new ssh session."""
+ self._clients.append(proc.pid)
+
+ def remove_client(self, proc):
+ """Remove a completed ssh session."""
+ try:
+ self._clients.remove(proc.pid)
+ except ValueError:
+ pass
+
+ def add_master(self, proc):
+ """Track a new master connection."""
+ self._masters.append(proc.pid)
+
+ def _terminate(self, procs):
+ """Kill all |procs|."""
+ for pid in procs:
+ try:
+ os.kill(pid, signal.SIGTERM)
+ os.waitpid(pid, 0)
+ except OSError:
+ pass
+
+ # The multiprocessing.list() API doesn't provide many standard list()
+ # methods, so we have to manually clear the list.
+ while True:
+ try:
+ procs.pop(0)
+ except:
+ break
+
+ def close(self):
+ """Close this active ssh session.
+
+ Kill all ssh clients & masters we created, and nuke the socket dir.
+ """
+ self._terminate(self._clients)
+ self._terminate(self._masters)
+
+ d = self.sock(create=False)
+ if d:
+ try:
+ platform_utils.rmdir(os.path.dirname(d))
+ except OSError:
+ pass
+
+ def _open_unlocked(self, host, port=None):
+ """Make sure a ssh master session exists for |host| & |port|.
+
+ If one doesn't exist already, we'll create it.
+
+ We won't grab any locks, so the caller has to do that. This helps keep the
+ business logic of actually creating the master separate from grabbing locks.
+ """
# Check to see whether we already think that the master is running; if we
# think it's already running, return right away.
if port is not None:
@@ -131,17 +162,15 @@
else:
key = host
- if key in _master_keys:
+ if key in self._master_keys:
return True
- if not _ssh_master or 'GIT_SSH' in os.environ:
+ if self._master_broken.value or 'GIT_SSH' in os.environ:
# Failed earlier, so don't retry.
return False
# We will make two calls to ssh; this is the common part of both calls.
- command_base = ['ssh',
- '-o', 'ControlPath %s' % sock(),
- host]
+ command_base = ['ssh', '-o', 'ControlPath %s' % self.sock(), host]
if port is not None:
command_base[1:1] = ['-p', str(port)]
@@ -161,7 +190,7 @@
if not isnt_running:
# Our double-check found that the master _was_ infact running. Add to
# the list of keys.
- _master_keys.add(key)
+ self._master_keys[key] = True
return True
except Exception:
# Ignore excpetions. We we will fall back to the normal command and print
@@ -173,7 +202,7 @@
Trace(': %s', ' '.join(command))
p = subprocess.Popen(command)
except Exception as e:
- _ssh_master = False
+ self._master_broken.value = True
print('\nwarn: cannot enable ssh control master for %s:%s\n%s'
% (host, port, str(e)), file=sys.stderr)
return False
@@ -183,75 +212,66 @@
if ssh_died:
return False
- _master_processes.append(p)
- _master_keys.add(key)
+ self.add_master(p)
+ self._master_keys[key] = True
return True
- finally:
- _master_keys_lock.release()
+ def _open(self, host, port=None):
+ """Make sure a ssh master session exists for |host| & |port|.
-def close():
- global _master_keys_lock
+ If one doesn't exist already, we'll create it.
- _terminate_clients()
+ This will obtain any necessary locks to avoid inter-process races.
+ """
+ # Bail before grabbing the lock if we already know that we aren't going to
+ # try creating new masters below.
+ if sys.platform in ('win32', 'cygwin'):
+ return False
- for p in _master_processes:
- try:
- os.kill(p.pid, signal.SIGTERM)
- p.wait()
- except OSError:
- pass
- del _master_processes[:]
- _master_keys.clear()
+ # Acquire the lock. This is needed to prevent opening multiple masters for
+ # the same host when we're running "repo sync -jN" (for N > 1) _and_ the
+ # manifest <remote fetch="ssh://xyz"> specifies a different host from the
+ # one that was passed to repo init.
+ with self._lock:
+ return self._open_unlocked(host, port)
- d = sock(create=False)
- if d:
- try:
- platform_utils.rmdir(os.path.dirname(d))
- except OSError:
- pass
+ def preconnect(self, url):
+ """If |uri| will create a ssh connection, setup the ssh master for it."""
+ m = URI_ALL.match(url)
+ if m:
+ scheme = m.group(1)
+ host = m.group(2)
+ if ':' in host:
+ host, port = host.split(':')
+ else:
+ port = None
+ if scheme in ('ssh', 'git+ssh', 'ssh+git'):
+ return self._open(host, port)
+ return False
- # We're done with the lock, so we can delete it.
- _master_keys_lock = None
+ m = URI_SCP.match(url)
+ if m:
+ host = m.group(1)
+ return self._open(host)
-
-URI_SCP = re.compile(r'^([^@:]*@?[^:/]{1,}):')
-URI_ALL = re.compile(r'^([a-z][a-z+-]*)://([^@/]*@?[^/]*)/')
-
-
-def preconnect(url):
- m = URI_ALL.match(url)
- if m:
- scheme = m.group(1)
- host = m.group(2)
- if ':' in host:
- host, port = host.split(':')
- else:
- port = None
- if scheme in ('ssh', 'git+ssh', 'ssh+git'):
- return _open_ssh(host, port)
return False
- m = URI_SCP.match(url)
- if m:
- host = m.group(1)
- return _open_ssh(host)
+ def sock(self, create=True):
+ """Return the path to the ssh socket dir.
- return False
-
-def sock(create=True):
- global _ssh_sock_path
- if _ssh_sock_path is None:
- if not create:
- return None
- tmp_dir = '/tmp'
- if not os.path.exists(tmp_dir):
- tmp_dir = tempfile.gettempdir()
- if version() < (6, 7):
- tokens = '%r@%h:%p'
- else:
- tokens = '%C' # hash of %l%h%p%r
- _ssh_sock_path = os.path.join(
- tempfile.mkdtemp('', 'ssh-', tmp_dir),
- 'master-' + tokens)
- return _ssh_sock_path
+ This has all the master sockets so clients can talk to them.
+ """
+ if self._sock_path is None:
+ if not create:
+ return None
+ tmp_dir = '/tmp'
+ if not os.path.exists(tmp_dir):
+ tmp_dir = tempfile.gettempdir()
+ if version() < (6, 7):
+ tokens = '%r@%h:%p'
+ else:
+ tokens = '%C' # hash of %l%h%p%r
+ self._sock_path = os.path.join(
+ tempfile.mkdtemp('', 'ssh-', tmp_dir),
+ 'master-' + tokens)
+ return self._sock_path
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 2856806..fb25c22 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -358,7 +358,7 @@
optimized_fetch=opt.optimized_fetch,
retry_fetches=opt.retry_fetches,
prune=opt.prune,
- ssh_proxy=True,
+ ssh_proxy=self.ssh_proxy,
clone_filter=self.manifest.CloneFilter,
partial_clone_exclude=self.manifest.PartialCloneExclude)
@@ -380,7 +380,11 @@
finish = time.time()
return (success, project, start, finish)
- def _Fetch(self, projects, opt, err_event):
+ @classmethod
+ def _FetchInitChild(cls, ssh_proxy):
+ cls.ssh_proxy = ssh_proxy
+
+ def _Fetch(self, projects, opt, err_event, ssh_proxy):
ret = True
jobs = opt.jobs_network if opt.jobs_network else self.jobs
@@ -410,8 +414,14 @@
break
return ret
+ # We pass the ssh proxy settings via the class. This allows multiprocessing
+ # to pickle it up when spawning children. We can't pass it as an argument
+ # to _FetchProjectList below as multiprocessing is unable to pickle those.
+ Sync.ssh_proxy = None
+
# NB: Multiprocessing is heavy, so don't spin it up for one job.
if len(projects_list) == 1 or jobs == 1:
+ self._FetchInitChild(ssh_proxy)
if not _ProcessResults(self._FetchProjectList(opt, x) for x in projects_list):
ret = False
else:
@@ -429,7 +439,8 @@
else:
pm.update(inc=0, msg='warming up')
chunksize = 4
- with multiprocessing.Pool(jobs) as pool:
+ with multiprocessing.Pool(
+ jobs, initializer=self._FetchInitChild, initargs=(ssh_proxy,)) as pool:
results = pool.imap_unordered(
functools.partial(self._FetchProjectList, opt),
projects_list,
@@ -438,6 +449,11 @@
ret = False
pool.close()
+ # Cleanup the reference now that we're done with it, and we're going to
+ # release any resources it points to. If we don't, later multiprocessing
+ # usage (e.g. checkouts) will try to pickle and then crash.
+ del Sync.ssh_proxy
+
pm.end()
self._fetch_times.Save()
@@ -447,7 +463,7 @@
return (ret, fetched)
def _FetchMain(self, opt, args, all_projects, err_event, manifest_name,
- load_local_manifests):
+ load_local_manifests, ssh_proxy):
"""The main network fetch loop.
Args:
@@ -457,6 +473,7 @@
err_event: Whether an error was hit while processing.
manifest_name: Manifest file to be reloaded.
load_local_manifests: Whether to load local manifests.
+ ssh_proxy: SSH manager for clients & masters.
"""
rp = self.manifest.repoProject
@@ -467,7 +484,7 @@
to_fetch.extend(all_projects)
to_fetch.sort(key=self._fetch_times.Get, reverse=True)
- success, fetched = self._Fetch(to_fetch, opt, err_event)
+ success, fetched = self._Fetch(to_fetch, opt, err_event, ssh_proxy)
if not success:
err_event.set()
@@ -498,7 +515,7 @@
if previously_missing_set == missing_set:
break
previously_missing_set = missing_set
- success, new_fetched = self._Fetch(missing, opt, err_event)
+ success, new_fetched = self._Fetch(missing, opt, err_event, ssh_proxy)
if not success:
err_event.set()
fetched.update(new_fetched)
@@ -985,12 +1002,15 @@
self._fetch_times = _FetchTimes(self.manifest)
if not opt.local_only:
- try:
- ssh.init()
- self._FetchMain(opt, args, all_projects, err_event, manifest_name,
- load_local_manifests)
- finally:
- ssh.close()
+ with multiprocessing.Manager() as manager:
+ with ssh.ProxyManager(manager) as ssh_proxy:
+ # Initialize the socket dir once in the parent.
+ ssh_proxy.sock()
+ self._FetchMain(opt, args, all_projects, err_event, manifest_name,
+ load_local_manifests, ssh_proxy)
+
+ if opt.network_only:
+ return
# If we saw an error, exit with code 1 so that other scripts can check.
if err_event.is_set():
diff --git a/tests/test_ssh.py b/tests/test_ssh.py
index 5a4f27e..ffb5cb9 100644
--- a/tests/test_ssh.py
+++ b/tests/test_ssh.py
@@ -14,6 +14,8 @@
"""Unittests for the ssh.py module."""
+import multiprocessing
+import subprocess
import unittest
from unittest import mock
@@ -39,14 +41,34 @@
with mock.patch('ssh._run_ssh_version', return_value='OpenSSH_1.2\n'):
self.assertEqual(ssh.version(), (1, 2))
+ def test_context_manager_empty(self):
+ """Verify context manager with no clients works correctly."""
+ with multiprocessing.Manager() as manager:
+ with ssh.ProxyManager(manager):
+ pass
+
+ def test_context_manager_child_cleanup(self):
+ """Verify orphaned clients & masters get cleaned up."""
+ with multiprocessing.Manager() as manager:
+ with ssh.ProxyManager(manager) as ssh_proxy:
+ client = subprocess.Popen(['sleep', '964853320'])
+ ssh_proxy.add_client(client)
+ master = subprocess.Popen(['sleep', '964853321'])
+ ssh_proxy.add_master(master)
+ # If the process still exists, these will throw timeout errors.
+ client.wait(0)
+ master.wait(0)
+
def test_ssh_sock(self):
"""Check sock() function."""
+ manager = multiprocessing.Manager()
+ proxy = ssh.ProxyManager(manager)
with mock.patch('tempfile.mkdtemp', return_value='/tmp/foo'):
# old ssh version uses port
with mock.patch('ssh.version', return_value=(6, 6)):
- self.assertTrue(ssh.sock().endswith('%p'))
- ssh._ssh_sock_path = None
+ self.assertTrue(proxy.sock().endswith('%p'))
+
+ proxy._sock_path = None
# new ssh version uses hash
with mock.patch('ssh.version', return_value=(6, 7)):
- self.assertTrue(ssh.sock().endswith('%C'))
- ssh._ssh_sock_path = None
+ self.assertTrue(proxy.sock().endswith('%C'))
