Make flat graph an attribute and build it during runtime initialization

core/dbt/context/common.py

@@ -405,7 +405,7 @@ def generate_base(model, model_dict, config, manifest, source_config,
         "exceptions": dbt.exceptions.wrapped_exports(model),
         "execute": provider.execute,
         "flags": dbt.flags,
-        "graph": manifest.to_flat_graph(),
+        "graph": manifest.flat_graph,
         "log": log,
         "model": model_dict,
         "modules": get_context_modules(),

core/dbt/contracts/graph/manifest.py

@@ -185,7 +185,7 @@ def __init__(self, nodes, macros, docs, generated_at, disabled,
         self.generated_at = generated_at
         self.metadata = metadata
         self.disabled = disabled
-        self._flat_graph = None
+        self.flat_graph = None
         super(Manifest, self).__init__()
 
     @staticmethod
@@ -224,18 +224,17 @@ def serialize(self):
             'disabled': [v.serialize() for v in self.disabled],
         }
 
-    def to_flat_graph(self):
-        """This function gets called in context.common by each node, so we want
-        to cache it. Make sure you don't call this until you're done with
-        building your manifest!
+    def build_flat_graph(self):
+        """This attribute is used in context.common by each node, so we want to
+        only build it once and avoid any concurrency issues around it.
+        Make sure you don't call this until you're done with building your
+        manifest!
         """
-        if self._flat_graph is None:
-            self._flat_graph = {
-                'nodes': {
-                    k: v.serialize() for k, v in self.nodes.items()
-                },
-            }
-        return self._flat_graph
+        self.flat_graph = {
+            'nodes': {
+                k: v.serialize() for k, v in self.nodes.items()
+            },
+        }
 
     def find_disabled_by_name(self, name, package=None):
         return dbt.utils.find_in_list_by_name(self.disabled, name, package,

core/dbt/task/runnable.py

@@ -45,6 +45,7 @@ def __init__(self, args, config):
     def _runtime_initialize(self):
         self.manifest = load_manifest(self.config)
         self.linker = compile_manifest(self.config, self.manifest)
+        self.manifest.build_flat_graph()
 
 
 class GraphRunnableTask(ManifestTask):