ssh: move proxy usage to the sync subcommand

The only time we really need ssh proxies is when we want to run many
connections and reuse them.  That only happens when running sync.
Every other command makes at most two connections, and even then it's
only one or none.  So the effort of setting up & tearing down ssh
proxies isn't worth it most of the time.

The big reason we want to move this logic to sync is that it's now
using multiprocessing for parallel work.  The current ssh proxy code
is all based on threads, which means none of the logic is working
correctly.  The current ssh design makes it hard to fix when all of
the state lives in the global/module scope.

So the first step to fixing this is top move the setup & teardown to
the one place that really needs it: sync.  No other commands will use
proxies anymore, just direct connections.

Bug: https://crbug.com/gerrit/12389
Change-Id: Ibd351acdec39a87562b3013637c5df4ea34e03c6
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/305485
Reviewed-by: Chris Mcdonald <cjmcdonald@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

git_config.py

@@ -520,6 +520,14 @@ class Remote(object):
     return self.url.replace(longest, longestUrl, 1)
 
   def PreConnectFetch(self):
+    """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.
+
+    Returns:
+      Whether the preconnect phase for this remote was successful.
+    """
     connectionUrl = self._InsteadOf()
     return ssh.preconnect(connectionUrl)
 

main.py

@@ -56,7 +56,6 @@ from error import RepoChangedException
 import gitc_utils
 from manifest_xml import GitcClient, RepoClient
 from pager import RunPager, TerminatePager
-import ssh
 from wrapper import WrapperPath, Wrapper
 
 from subcmds import all_commands
@@ -592,8 +591,6 @@ def _Main(argv):
 
   repo = _Repo(opt.repodir)
   try:
-    try:
-      ssh.init()
     init_http()
     name, gopts, argv = repo._ParseArgs(argv)
     run = lambda: repo._Run(name, gopts, argv) or 0
@@ -604,8 +601,6 @@ def _Main(argv):
       result = tracer.runfunc(run)
     else:
       result = run()
-    finally:
-      ssh.close()
   except KeyboardInterrupt:
     print('aborted by user', file=sys.stderr)
     result = 1

project.py

@@ -1050,6 +1050,7 @@ class Project(object):
                        retry_fetches=0,
                        prune=False,
                        submodules=False,
+                       ssh_proxy=None,
                        clone_filter=None,
                        partial_clone_exclude=set()):
     """Perform only the network IO portion of the sync process.
@@ -1143,6 +1144,7 @@ class Project(object):
               alt_dir=alt_dir, current_branch_only=current_branch_only,
               tags=tags, prune=prune, depth=depth,
               submodules=submodules, force_sync=force_sync,
+              ssh_proxy=ssh_proxy,
               clone_filter=clone_filter, retry_fetches=retry_fetches):
         return False
 
@@ -1994,6 +1996,7 @@ class Project(object):
                    prune=False,
                    depth=None,
                    submodules=False,
+                   ssh_proxy=None,
                    force_sync=False,
                    clone_filter=None,
                    retry_fetches=2,
@@ -2041,16 +2044,14 @@ class Project(object):
     if not name:
       name = self.remote.name
 
-    ssh_proxy = False
     remote = self.GetRemote(name)
-    if remote.PreConnectFetch():
+    if not remote.PreConnectFetch():
-      ssh_proxy = True
+      ssh_proxy = False
 
     if initial:
       if alt_dir and 'objects' == os.path.basename(alt_dir):
         ref_dir = os.path.dirname(alt_dir)
         packed_refs = os.path.join(self.gitdir, 'packed-refs')
-        remote = self.GetRemote(name)
 
         all_refs = self.bare_ref.all
         ids = set(all_refs.values())
@@ -2238,7 +2239,7 @@ class Project(object):
             name=name, quiet=quiet, verbose=verbose, output_redir=output_redir,
             current_branch_only=current_branch_only and depth,
             initial=False, alt_dir=alt_dir,
-            depth=None, clone_filter=clone_filter)
+            depth=None, ssh_proxy=ssh_proxy, clone_filter=clone_filter)
 
     return ok
 

subcmds/sync.py

@@ -57,6 +57,7 @@ from error import RepoChangedException, GitError, ManifestParseError
 import platform_utils
 from project import SyncBuffer
 from progress import Progress
+import ssh
 from wrapper import Wrapper
 from manifest_xml import GitcManifest
 
@@ -357,6 +358,7 @@ later is required to fix a server side protocol bug.
           optimized_fetch=opt.optimized_fetch,
           retry_fetches=opt.retry_fetches,
           prune=opt.prune,
+          ssh_proxy=True,
           clone_filter=self.manifest.CloneFilter,
           partial_clone_exclude=self.manifest.PartialCloneExclude)
 
@@ -983,8 +985,12 @@ later is required to fix a server side protocol bug.
 
     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()
 
       # If we saw an error, exit with code 1 so that other scripts can check.
       if err_event.is_set():