[couchdb] 01/01: Pre-calculate application start order

[da...@apache.org]

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davisp pushed a commit to branch start-app-order
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit 9ddfe07a2d69dcddba1002d069f966845e3f6e0d
Author: Paul J. Davis <pa...@gmail.com>
AuthorDate: Tue May 16 11:12:24 2017 -0500

    Pre-calculate application start order
    
    This allows us to make some better assertions/logging when starting our
    application list on what should and should not already be started.
---
 src/couch/src/test_util.erl | 42 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 6 deletions(-)

diff --git a/src/couch/src/test_util.erl b/src/couch/src/test_util.erl
index 3c4d170..efaf49c 100644
--- a/src/couch/src/test_util.erl
+++ b/src/couch/src/test_util.erl
@@ -83,18 +83,18 @@ stop_couch(_) ->
     stop_couch().
 
 start_applications(Apps) ->
-    start_applications(Apps, []).
+    StartOrder = calculate_start_order(Apps),
+    start_applications(StartOrder, []).
 
 start_applications([], Acc) ->
     lists:reverse(Acc);
+start_applications([App|Apps], Acc) when App == kernel; App == stdlib ->
+    start_applications(Apps, Acc);
 start_applications([App|Apps], Acc) ->
     case application:start(App) of
     {error, {already_started, _}} ->
-        start_applications(Apps, Acc);
-    {error, {not_started, Dep}} ->
-        start_applications([Dep, App | Apps], Acc);
-    {error, {not_running, Dep}} ->
-        start_applications([Dep, App | Apps], Acc);
+        io:format(standard_error, "Application ~s was left running!~n", [App]),
+        start_applications(Apps, [App|Acc]);
     ok ->
         start_applications(Apps, [App|Acc])
     end.
@@ -258,3 +258,33 @@ load_applications_with_stats() ->
 stats_file_to_app(File) ->
     [_Desc, _Priv, App|_] = lists:reverse(filename:split(File)),
     erlang:list_to_atom(App).
+
+calculate_start_order(Apps) ->
+    calculate_start_order(Apps, []).
+
+calculate_start_order([], StartOrder) ->
+    lists:reverse(StartOrder);
+calculate_start_order([App | RestApps], StartOrder) ->
+    NewStartOrder = load_app_deps(App, StartOrder),
+    calculate_start_order(RestApps, NewStartOrder).
+
+load_app_deps(App, StartOrder) ->
+    case lists:member(App, StartOrder) of
+        true ->
+            StartOrder;
+        false ->
+            case application:load(App) of
+                ok -> ok;
+                {error, {already_loaded, App}} -> ok
+            end,
+            {ok, Apps} = application:get_key(App, applications),
+            Deps = case App of
+                kernel -> Apps;
+                stdlib -> Apps;
+                _ -> lists:usort([kernel, stdlib | Apps])
+            end,
+            NewStartOrder = lists:foldl(fun(Dep, Acc) ->
+                load_app_deps(Dep, Acc)
+            end, StartOrder, Deps),
+            [App | NewStartOrder]
+    end.

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