fix(engine): don't attempt search when ETS checkpoint is loading

The checkpoint file can be quite large (1.2G in my case) and it may take
quite a while to load it (8.2s in my case). During that time, all the
GenServer calls with the default timeout of 5000ms might timeout,
leading to the whole GenServer termination and general instability of
the search functionality.

This adds guards for state.loaded? which return {:error, :loading} if
it's not loaded.

Author: katafrakt

apps/engine/lib/engine/search/store/state.ex

@@ -83,6 +83,10 @@ defmodule Engine.Search.Store.State do
     end
   end
 
+  def exact(%__MODULE__{loaded?: false}, _subject, _constraints) do
+    {:error, :loading}
+  end
+
   def exact(%__MODULE__{} = state, subject, constraints) do
     type = Keyword.get(constraints, :type, :_)
     subtype = Keyword.get(constraints, :subtype, :_)
@@ -93,6 +97,10 @@ defmodule Engine.Search.Store.State do
     end
   end
 
+  def prefix(%__MODULE__{loaded?: false}, _prefix, _constraints) do
+    {:error, :loading}
+  end
+
   def prefix(%__MODULE__{} = state, prefix, constraints) do
     type = Keyword.get(constraints, :type, :_)
     subtype = Keyword.get(constraints, :subtype, :_)
@@ -106,6 +114,10 @@ defmodule Engine.Search.Store.State do
     end
   end
 
+  def fuzzy(%__MODULE__{loaded?: false}, _subject, _constraints) do
+    {:error, :loading}
+  end
+
   def fuzzy(%__MODULE__{} = state, subject, constraints) do
     case Fuzzy.match(state.fuzzy, subject) do
       [] ->
@@ -122,6 +134,10 @@ defmodule Engine.Search.Store.State do
     end
   end
 
+  def all(%__MODULE__{loaded?: false}, _) do
+    {:error, :loading}
+  end
+
   def all(%__MODULE__{} = state, constraints) do
     type = Keyword.get(constraints, :type, :_)
     subtype = Keyword.get(constraints, :subtype, :_)
@@ -146,13 +162,21 @@ defmodule Engine.Search.Store.State do
     (type == :_ or t == type) and (subtype == :_ or st == subtype)
   end
 
+  def siblings(%__MODULE__{loaded?: false}, _entry) do
+    {:error, :loading}
+  end
+
   def siblings(%__MODULE__{} = state, entry) do
     case state.backend.siblings(entry) do
       l when is_list(l) -> {:ok, l}
       error -> error
     end
   end
 
+  def parent(%__MODULE__{loaded?: false}, _entry) do
+    {:error, :loading}
+  end
+
   def parent(%__MODULE__{} = state, entry) do
     case state.backend.parent(entry) do
       %Entry{} = entry -> {:ok, entry}