sync: Fetch after applying bundle and retry after errors

After a $GIT_URL/clone.bundle has been applied to the new local
repository, perform an incremental fetch using `git fetch` to ensure
the local repository is up-to-date. This allows the hosting server
to offer stale /clone.bundle files to bootstrap a new client.

If a single git fetch fails, it may succeed again after a short
delay.  Transient failures are typical in environments where the
remote Git server happens to have limits on how many requests it
can serve at once (the anonymous git daemon, or an HTTP server).
Wait a randomized delay between 30 and 45 seconds and retry the
failed project once.  This delay gives the site time to recover
from a transient traffic spike, and the randomization makes it less
likely that a spike occurs again from all of the same clients.

Change-Id: I97fb0fcb33630fb78ac1a21d1a4a3e2268ab60c0
Signed-off-by: Shawn O. Pearce <sop@google.com>

project.py

@@ -16,10 +16,12 @@ import traceback
 import errno
 import filecmp
 import os
+import random
 import re
 import shutil
 import stat
 import sys
+import time
 import urllib2
 
 from color import Coloring
@@ -894,9 +896,25 @@ class Project(object):
       is_new = not self.Exists
     if is_new:
       self._InitGitDir()
-
     self._InitRemote()
-    if not self._RemoteFetch(initial=is_new, quiet=quiet):
+
+    if is_new:
+      alt = os.path.join(self.gitdir, 'objects/info/alternates')
+      try:
+        fd = open(alt, 'rb')
+        try:
+          alt_dir = fd.readline().rstrip()
+        finally:
+          fd.close()
+      except IOError:
+        alt_dir = None
+    else:
+      alt_dir = None
+
+    if alt_dir is None and self._ApplyCloneBundle(initial=is_new, quiet=quiet):
+      is_new = False
+
+    if not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir):
       return False
 
     #Check that the requested ref was found after fetch
@@ -1307,7 +1325,8 @@ class Project(object):
 
   def _RemoteFetch(self, name=None, tag=None,
                    initial=False,
-                   quiet=False):
+                   quiet=False,
+                   alt_dir=None):
     if not name:
       name = self.remote.name
 
@@ -1316,29 +1335,9 @@ class Project(object):
     if remote.PreConnectFetch():
       ssh_proxy = True
 
-    bundle_dst = os.path.join(self.gitdir, 'clone.bundle')
-    bundle_tmp = os.path.join(self.gitdir, 'clone.bundle.tmp')
-    use_bundle = False
-    if os.path.exists(bundle_dst) or os.path.exists(bundle_tmp):
-      use_bundle = True
-
     if initial:
-      alt = os.path.join(self.gitdir, 'objects/info/alternates')
-      try:
-        fd = open(alt, 'rb')
-        try:
-          ref_dir = fd.readline()
-          if ref_dir and ref_dir.endswith('\n'):
-            ref_dir = ref_dir[:-1]
-        finally:
-          fd.close()
-      except IOError, e:
-        ref_dir = None
-
-      if ref_dir and 'objects' == os.path.basename(ref_dir):
-        if use_bundle:
-          use_bundle = False
-        ref_dir = os.path.dirname(ref_dir)
+      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)
 
@@ -1374,10 +1373,8 @@ class Project(object):
             old_packed += line
 
         _lwrite(packed_refs, tmp_packed)
-
       else:
-        ref_dir = None
-        use_bundle = True
+        alt_dir = None
 
     cmd = ['fetch']
 
@@ -1386,59 +1383,74 @@ class Project(object):
     depth = self.manifest.manifestProject.config.GetString('repo.depth')
     if depth and initial:
       cmd.append('--depth=%s' % depth)
-      use_bundle = False
 
     if quiet:
       cmd.append('--quiet')
     if not self.worktree:
       cmd.append('--update-head-ok')
+    cmd.append(name)
+    if tag is not None:
+      cmd.append('tag')
+      cmd.append(tag)
 
-    if use_bundle and not os.path.exists(bundle_dst):
-      bundle_url = remote.url + '/clone.bundle'
-      bundle_url = GitConfig.ForUser().UrlInsteadOf(bundle_url)
-      if GetSchemeFromUrl(bundle_url) in ('http', 'https'):
-        use_bundle = self._FetchBundle(
-          bundle_url,
-          bundle_tmp,
-          bundle_dst,
-          quiet=quiet)
-      else:
-        use_bundle = False
-
-    if use_bundle:
-      if not quiet:
-        cmd.append('--quiet')
-      cmd.append(bundle_dst)
-      for f in remote.fetch:
-        cmd.append(str(f))
-      cmd.append('refs/tags/*:refs/tags/*')
-    else:
-      cmd.append(name)
-      if tag is not None:
-        cmd.append('tag')
-        cmd.append(tag)
-
-    ok = GitCommand(self,
-                    cmd,
-                    bare = True,
-                    ssh_proxy = ssh_proxy).Wait() == 0
+    ok = False
+    for i in range(2):
+      if GitCommand(self, cmd, bare=True, ssh_proxy=ssh_proxy).Wait() == 0:
+        ok = True
+        break
+      time.sleep(random.randint(30, 45))
 
     if initial:
-      if ref_dir:
+      if alt_dir:
         if old_packed != '':
           _lwrite(packed_refs, old_packed)
         else:
           os.remove(packed_refs)
       self.bare_git.pack_refs('--all', '--prune')
+    return ok
 
+  def _ApplyCloneBundle(self, initial=False, quiet=False):
+    if initial and self.manifest.manifestProject.config.GetString('repo.depth'):
+      return False
+
+    remote = self.GetRemote(self.remote.name)
+    bundle_url = remote.url + '/clone.bundle'
+    bundle_url = GitConfig.ForUser().UrlInsteadOf(bundle_url)
+    if GetSchemeFromUrl(bundle_url) not in ('http', 'https'):
+      return False
+
+    bundle_dst = os.path.join(self.gitdir, 'clone.bundle')
+    bundle_tmp = os.path.join(self.gitdir, 'clone.bundle.tmp')
+
+    exist_dst = os.path.exists(bundle_dst)
+    exist_tmp = os.path.exists(bundle_tmp)
+
+    if not initial and not exist_dst and not exist_tmp:
+      return False
+
+    if not exist_dst:
+      exist_dst = self._FetchBundle(bundle_url, bundle_tmp, bundle_dst, quiet)
+    if not exist_dst:
+      return False
+
+    cmd = ['fetch']
+    if quiet:
+      cmd.append('--quiet')
+    if not self.worktree:
+      cmd.append('--update-head-ok')
+    cmd.append(bundle_dst)
+    for f in remote.fetch:
+      cmd.append(str(f))
+    cmd.append('refs/tags/*:refs/tags/*')
+
+    ok = GitCommand(self, cmd, bare=True).Wait() == 0
     if os.path.exists(bundle_dst):
       os.remove(bundle_dst)
     if os.path.exists(bundle_tmp):
       os.remove(bundle_tmp)
-
     return ok
 
-  def _FetchBundle(self, srcUrl, tmpPath, dstPath, quiet=False):
+  def _FetchBundle(self, srcUrl, tmpPath, dstPath, quiet):
     keep = True
     done = False
     dest = open(tmpPath, 'a+b')