reclient: use fixed size path for unix domain socket

Bug: b/278846515
Change-Id: Ibfc61acdbfbdbc84a4e1b7fec12169b06236b545
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4570163
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Junji Watanabe <jwata@google.com>

reclient_helper.py

@@ -134,8 +134,11 @@ def set_reproxy_path_flags(out_dir, make_dirs=True):
     os.environ.setdefault("RBE_server_address",
                           "pipe://%s/reproxy.pipe" % pipe_dir)
   else:
-    os.environ.setdefault("RBE_server_address",
-                          "unix://%s/reproxy.sock" % tmp_dir)
+    # unix domain socket has path length limit, so use fixed size path here.
+    # ref: https://www.man7.org/linux/man-pages/man7/unix.7.html
+    os.environ.setdefault(
+        "RBE_server_address", "unix://tmp/reproxy_%s.sock" %
+        hashlib.sha256(tmp_dir.encode()).hexdigest())
 
 
 @contextlib.contextmanager

tests/ninja_reclient_test.py

@@ -86,8 +86,10 @@ class NinjaReclientTest(trial_dir.TestCase):
                            ".reproxy_tmp").encode()).hexdigest())
     else:
       self.assertEqual(
-          os.environ.get('RBE_server_address'), "unix://%s/reproxy.sock" %
-          os.path.join(self.root_dir, "out", "a", ".reproxy_tmp"))
+          os.environ.get('RBE_server_address'),
+          "unix://tmp/reproxy_%s.sock" % hashlib.sha256(
+              os.path.join(self.root_dir, "out", "a",
+                           ".reproxy_tmp").encode()).hexdigest())
 
     mock_ninja.assert_called_once_with(argv)
     mock_call.assert_has_calls([