Also set the mmap mode to match the read_mode flag.

coderanger · brian-brazil · commit 8586b8de002e · 2018-09-21T11:12:41.000+01:00
Signed-off-by: Noah Kantrowitz &lt;noah@coderanger.net&gt;
diff --git a/prometheus_client/core.py b/prometheus_client/core.py
@@ -509,7 +509,7 @@ def __init__(self, filename, read_mode=False):
         if os.fstat(self._f.fileno()).st_size == 0:
             self._f.truncate(_INITIAL_MMAP_SIZE)
         self._capacity = os.fstat(self._f.fileno()).st_size
-        self._m = mmap.mmap(self._f.fileno(), self._capacity)
+        self._m = mmap.mmap(self._f.fileno(), self._capacity, access=mmap.ACCESS_READ if read_mode else mmap.ACCESS_WRITE)
 
         self._positions = {}
         self._used = _unpack_integer(self._m, 0)[0]
