Revert "projector: fix RunPaths result aliasing (#4479)" (#4506)

Summary:
Some Google-internal, non-TensorBoard code depends on the projector and
monkey patches out its internals in a way that is not compatible with
the changes in #4479. This is clearly not ideal and should probably be
fixed downstream, but pending investigation we revert #4479 to unbreak.

This reverts commit 638014e.

Test Plan:
Test sync at this tree passes all tests.

wchargin-branch: projector-revert-4479

tensorboard/plugins/projector/projector_plugin.py

@@ -242,8 +242,9 @@ def __init__(self, context):
         self.multiplexer = context.multiplexer
         self.logdir = context.logdir
         self.readers = {}
-        self._run_paths = None
+        self.run_paths = None
         self._configs = {}
+        self.old_num_run_paths = None
         self.config_fpaths = None
         self.tensor_cache = LRUCache(_TENSOR_CACHE_CAPACITY)
 
@@ -256,7 +257,8 @@ def __init__(self, context):
         # active. If such a thread exists, do not start a duplicate thread.
         self._thread_for_determining_is_active = None
 
-        self._update_run_paths()
+        if self.multiplexer:
+            self.run_paths = self.multiplexer.RunPaths()
 
     def get_plugin_apps(self):
         asset_prefix = "tf_projector_plugin"
@@ -320,52 +322,44 @@ def frontend_metadata(self):
             disable_reload=True,
         )
 
-    def _update_run_paths(self):
-        """Updates `self._run_paths`, testing for updates.
-
-        Returns:
-          `True` if this call changed the value of `self._run_paths`,
-          else `False`.
-        """
-        if self.multiplexer:
-            run_paths = dict(self.multiplexer.RunPaths())
-        else:
-            run_paths = None
-        changed = run_paths != self._run_paths
-        self._run_paths = run_paths
-        return changed
-
     def _determine_is_active(self):
         """Determines whether the plugin is active.
 
         This method is run in a separate thread so that the plugin can
         offer an immediate response to whether it is active and
         determine whether it should be active in a separate thread.
         """
-        self._update_configs()
-        if self._configs:
+        if self.configs:
             self._is_active = True
         self._thread_for_determining_is_active = None
 
-    def _update_configs(self):
-        """Updates `self._configs`."""
-        run_paths_changed = self._update_run_paths()
-        run_path_pairs = list(self._run_paths.items())
+    @property
+    def configs(self):
+        """Returns a map of run paths to `ProjectorConfig` protos."""
+        run_path_pairs = list(self.run_paths.items())
         self._append_plugin_asset_directories(run_path_pairs)
         # Also accept the root logdir as a model checkpoint directory,
         # so that the projector still works when there are no runs.
         # (Case on `run` rather than `path` to avoid issues with
         # absolute/relative paths on any filesystems.)
-        if "." not in self._run_paths:
+        if not any(run == "." for (run, path) in run_path_pairs):
             run_path_pairs.append((".", self.logdir))
-        if run_paths_changed or _latest_checkpoints_changed(
+        if self._run_paths_changed() or _latest_checkpoints_changed(
             self._configs, run_path_pairs
         ):
             self.readers = {}
             self._configs, self.config_fpaths = self._read_latest_config_files(
                 run_path_pairs
             )
             self._augment_configs_with_checkpoint_info()
+        return self._configs
+
+    def _run_paths_changed(self):
+        num_run_paths = len(list(self.run_paths.keys()))
+        if num_run_paths != self.old_num_run_paths:
+            self.old_num_run_paths = num_run_paths
+            return True
+        return False
 
     def _augment_configs_with_checkpoint_info(self):
         for run, config in self._configs.items():
@@ -530,7 +524,7 @@ def _append_plugin_asset_directories(self, run_path_pairs):
             if metadata.PROJECTOR_FILENAME not in assets:
                 continue
             assets_dir = os.path.join(
-                self._run_paths[run],
+                self.run_paths[run],
                 metadata.PLUGINS_DIR,
                 metadata.PLUGIN_ASSETS_NAME,
             )
@@ -548,8 +542,7 @@ def _serve_file(self, file_path, request):
     @wrappers.Request.application
     def _serve_runs(self, request):
         """Returns a list of runs that have embeddings."""
-        self._update_configs()
-        return Respond(request, list(self._configs.keys()), "application/json")
+        return Respond(request, list(self.configs.keys()), "application/json")
 
     @wrappers.Request.application
     def _serve_config(self, request):
@@ -558,12 +551,12 @@ def _serve_config(self, request):
             return Respond(
                 request, 'query parameter "run" is required', "text/plain", 400
             )
-        self._update_configs()
-        config = self._configs.get(run)
-        if config is None:
+        if run not in self.configs:
             return Respond(
                 request, 'Unknown run: "%s"' % run, "text/plain", 400
             )
+
+        config = self.configs[run]
         return Respond(
             request, json_format.MessageToJson(config), "application/json"
         )
@@ -591,12 +584,12 @@ def _serve_metadata(self, request):
                 400,
             )
 
-        self._update_configs()
-        config = self._configs.get(run)
-        if config is None:
+        if run not in self.configs:
             return Respond(
                 request, 'Unknown run: "%s"' % run, "text/plain", 400
             )
+
+        config = self.configs[run]
         fpath = self._get_metadata_file_for_tensor(name, config)
         if not fpath:
             return Respond(
@@ -651,12 +644,13 @@ def _serve_tensor(self, request):
                 400,
             )
 
-        self._update_configs()
-        config = self._configs.get(run)
-        if config is None:
+        if run not in self.configs:
             return Respond(
                 request, 'Unknown run: "%s"' % run, "text/plain", 400
             )
+
+        config = self.configs[run]
+
         tensor = self.tensor_cache.get((run, name))
         if tensor is None:
             # See if there is a tensor file in the config.
@@ -717,12 +711,12 @@ def _serve_bookmarks(self, request):
                 request, 'query parameter "name" is required', "text/plain", 400
             )
 
-        self._update_configs()
-        config = self._configs.get(run)
-        if config is None:
+        if run not in self.configs:
             return Respond(
                 request, 'Unknown run: "%s"' % run, "text/plain", 400
             )
+
+        config = self.configs[run]
         fpath = self._get_bookmarks_file_for_tensor(name, config)
         if not fpath:
             return Respond(
@@ -760,14 +754,14 @@ def _serve_sprite_image(self, request):
                 request, 'query parameter "name" is required', "text/plain", 400
             )
 
-        self._update_configs()
-        config = self._configs.get(run)
-        if config is None:
+        if run not in self.configs:
             return Respond(
                 request, 'Unknown run: "%s"' % run, "text/plain", 400
             )
 
+        config = self.configs[run]
         embedding_info = self._get_embedding(name, config)
+
         if not embedding_info or not embedding_info.sprite.image_path:
             return Respond(
                 request,