Patchwork [21,of,21,V2] speedy: detect store corruption

diff --git a/hgext/speedy/server.py b/hgext/speedy/server.py
--- a/hgext/speedy/server.py
+++ b/hgext/speedy/server.py
@@ -147,19 +147,45 @@ 
         'deerialize': serialize.identity,
         },
 }
-def makeserver(repo):
-    """Return an initialized metaserver instance.
 
-    Updates all indices to the last revision along the way.
+def makeindexstores(repo):
+    """Return a list with the initialized indice stores.
+
+    Updates all indices to the tip of the serverrepo.
+
+    If the store appears to be in an inconsistent state, rebuilds it.
+
+    A simple locking mechanism is used to ensure the consistency of the store.
+    Before modifying the store a lock is acquired (the LOCK file is created
+    on disk). This lock is later released (the file removed) only if
+    the transaction completes successfully.
+    If the lock could not be acquired (it was already taken by someone else) it
+    is very likely that previous transction was aborted and the store is not
+    in the consistent state. In this case all indices are erased and recreated.
     """
     opener = scmutil.opener(os.path.join(repo.path, 'hgext/speedyserver'))
     opener.makedirs()
-    lastrev = len(repo) - 1
-    indices = {}
+    lock = store.lock(os.path.join(repo.path, 'hgext/speedyserver/LOCK'))
+    recreate = False
+    try:
+        lock.acquire()
+    except store.LockHeld:
+        recreate = True
+    istores = []
+    updaterev = len(repo) - 1
     for name, cfg in indicecfg.iteritems():
         istore = store.indexstore(name, opener, **cfg)
-        istore.update(repo, lastrev)
-        indices[name] = istore.view()
+        if recreate:
+            istore.clear()
+        istore.update(repo, updaterev)
+        istores.append(istore)
+    lock.release()
+    return istores
+
+def makeserver(repo):
+    """Return an initialized metaserver instance."""
+    istores = makeindexstores(repo)
+    indices = dict([(istore.name, istore.view()) for istore in istores])
     return metaserver(repo, indices)
 
 @command('metaserve', [], _(''))
@@ -174,4 +200,3 @@ 
     serviceopts = collections.defaultdict(lambda: '')
     ui.status(_('listening on port %d\n' % port))
     cmdutil.service(serviceopts, runfn=server.serve_forever)
-
diff --git a/hgext/speedy/store.py b/hgext/speedy/store.py
--- a/hgext/speedy/store.py
+++ b/hgext/speedy/store.py
@@ -57,3 +57,25 @@ 
     def view(self):
         """Return a dict-like object for read access to the index elements."""
         return self._dict
+
+class LockHeld(Exception):
+    """Raised by `lock.acquire` if the lock is already taken."""
+    pass
+
+class lock(object):
+    """Simple file-based lock used to ensure store consistency."""
+
+    def __init__(self, path):
+        self.path = path
+
+    def acquire(self):
+        try:
+            ld = os.open(self.path, os.O_CREAT | os.O_WRONLY | os.O_EXCL)
+            os.close(ld)
+        except (OSError, IOError), why:
+            if why.errno == errno.EEXIST:
+                raise LockHeld
+            raise
+
+    def release(self):
+        os.remove(self.path)
diff --git a/tests/test-speedy.t b/tests/test-speedy.t
--- a/tests/test-speedy.t
+++ b/tests/test-speedy.t
@@ -235,6 +235,20 @@ 
 
   $ cd ..
 
+Testing store corruption detection
+
+  $ cd $TESTTMP/serverrepo
+
+  $ touch .hg/hgext/speedyserver/LOCK
+  $ rm -rf .hg/hgext/speedyserver/files .hg/hgext/speedyserver/filechgs
+
+  $ cd $TESTTMP/localrepo
+
+  $ hg log "glob:d2/*" --exclude "**.py"
+  chgx
+  chgpushed
+  chg4
+
 Testing socket server
 
 Writing server config file
@@ -364,3 +378,4 @@ 
   $ kill `cat pidfile` 2> /dev/null
   $ cat err
   handling request
+