Merge pull request iterative#3270 from mroutis/fix-3164

rwlock: include actionable in error message

dvc/rwlock.py

@@ -5,7 +5,6 @@
 from contextlib import contextmanager
 
 from voluptuous import Schema, Invalid
-from funcy.py3 import lmap, lfilter, lmapcat
 
 from .exceptions import DvcException
 from .lock import LockError
@@ -61,38 +60,25 @@ def _infos_to_str(infos):
     )
 
 
-def _check_no_writers(lock, info, path_infos):
-    for path_info in path_infos:
-        blocking_urls = lfilter(path_info.overlaps, lock["write"])
-        if not blocking_urls:
-            continue
+def _check_blockers(lock, info, *, mode, waiters):
+    for path_info in waiters:
+        blockers = [
+            info
+            for path, infos in lock[mode].items()
+            if path_info.overlaps(path)
+            if info not in (infos if type(infos) is list else [infos])
+        ]
 
-        writers = lmap(lock["write"].get, blocking_urls)
-        writers = lfilter(lambda i: info != i, writers)
-        if not writers:
+        if not blockers:
             continue
 
         raise LockError(
-            "'{}' is busy, it is being written to by:\n{}".format(
-                str(path_info), _infos_to_str(writers)
-            )
-        )
-
-
-def _check_no_readers(lock, info, path_infos):
-    for path_info in path_infos:
-        blocking_urls = lfilter(path_info.overlaps, lock["read"])
-        if not blocking_urls:
-            continue
-
-        readers = lmapcat(lock["read"].get, blocking_urls)
-        readers = lfilter(lambda i: info != i, readers)
-        if not readers:
-            continue
-
-        raise LockError(
-            "'{}' is busy, it is being read by:\n{}".format(
-                str(path_info), _infos_to_str(readers)
+            "'{path}' is busy, it is being blocked by:\n"
+            "{blockers}\n"
+            "\n"
+            "If there are no processes with such PIDs, you can manually remove"
+            "'.dvc/tmp/rwlock' and try again.".format(
+                path=str(path_info), blockers=_infos_to_str(blockers)
             )
         )
 
@@ -171,8 +157,9 @@ def rwlock(tmp_dir, cmd, read, write):
     info = {"pid": os.getpid(), "cmd": cmd}
 
     with _edit_rwlock(tmp_dir) as lock:
-        _check_no_writers(lock, info, read + write)
-        _check_no_readers(lock, info, write)
+
+        _check_blockers(lock, info, mode="write", waiters=read + write)
+        _check_blockers(lock, info, mode="read", waiters=write)
 
         rchanges = _acquire_read(lock, info, read)
         wchanges = _acquire_write(lock, info, write)