Merge pull request #14869 from Yancey1989/fix_dist_unittest

fix dist unit test

python/paddle/fluid/tests/unittests/test_dist_base.py

@@ -227,6 +227,7 @@ class TestDistBase(unittest.TestCase):
     def setUp(self):
         self._trainers = 2
         self._pservers = 2
+        self._port_set = set()
         self._ps_endpoints = "127.0.0.1:%s,127.0.0.1:%s" % (
             self._find_free_port(), self._find_free_port())
         self._python_interp = sys.executable
@@ -242,9 +243,17 @@ class TestDistBase(unittest.TestCase):
         self._after_setup_config()
 
     def _find_free_port(self):
-        with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as s:
-            s.bind(('', 0))
-            return s.getsockname()[1]
+        def __free_port():
+            with closing(socket.socket(socket.AF_INET,
+                                       socket.SOCK_STREAM)) as s:
+                s.bind(('', 0))
+                return s.getsockname()[1]
+
+        while True:
+            port = __free_port()
+            if port not in self._port_set:
+                self._port_set.add(port)
+                return port
 
     def start_pserver(self, model_file, check_error_log, required_envs):
         ps0_ep, ps1_ep = self._ps_endpoints.split(",")