Use lockfile to prevent race conditions

mdboom · mdboom · commit ca750bf2e01f · 2015-10-19T11:36:20.000-04:00
Creation of the font cache has race conditions
diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
@@ -1405,10 +1405,9 @@ def findfont(prop, fontext='ttf'):
 else:
     _fmcache = None
 
-    if not 'TRAVIS' in os.environ:
-        cachedir = get_cachedir()
-        if cachedir is not None:
-            _fmcache = os.path.join(cachedir, 'fontList.json')
+    cachedir = get_cachedir()
+    if cachedir is not None:
+        _fmcache = os.path.join(cachedir, 'fontList.json')
 
     fontManager = None
 
@@ -1419,8 +1418,14 @@ def findfont(prop, fontext='ttf'):
 
     def _rebuild():
         global fontManager
+        import lockfile
+
         fontManager = FontManager()
+
         if _fmcache:
+            with lockfile.Lockfile(_fmcache):
+                json_dump(fontManager, _fmcache)
+
             json_dump(fontManager, _fmcache)
         verbose.report("generated new fontManager")
 
diff --git a/setup.py b/setup.py
@@ -68,6 +68,7 @@
     setupext.Numpy(),
     setupext.Dateutil(),
     setupext.Pytz(),
+    setupext.Lockfile(),
     setupext.Cycler(),
     setupext.Tornado(),
     setupext.Pyparsing(),
diff --git a/setupext.py b/setupext.py
@@ -1171,6 +1171,24 @@ def get_install_requires(self):
         return ['pytz']
 
 
+class LockFile(SetupPackage):
+    name = 'lockfile'
+
+    def check(self):
+        try:
+            import lockfile
+        except ImportError:
+            return (
+                'lockfile was not found. '
+                'pip will attempt to install it '
+                'after matplotlib.')
+
+        return 'using lockfile version %s' % lockfile.__version__
+
+    def get_install_requires(self):
+        return ['lockfile']
+
+
 class Cycler(SetupPackage):
     name = "cycler"
 
