[couchdb-ioq] 02/02: Allow dynamic classes in is_valid_class

[ch...@apache.org]

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chewbranca pushed a commit to branch allow-for-dynamic-ioq-classes
in repository https://gitbox.apache.org/repos/asf/couchdb-ioq.git

commit d6e7a78ccffba459860df6ffcfd9e022569118de
Author: Russell Branca <ch...@apache.org>
AuthorDate: Fri Apr 12 22:36:18 2019 +0000

    Allow dynamic classes in is_valid_class
    
    This adds support for dynamic classes in IOQ2. Before this change, the
    allowed set of classes was fixed and hardcoded, with no way for 3rd
    party IO traffic to be prioritized, and similarly, no way for 3rd party
    IO traffic to bypass IOQ based on config settings. This change switches
    to checking to see if there's a declared IO priority value in the
    classes config, and if so it is treated as a valid value. It's worth
    noting that because `ioq_config:set_class_config` uses the
    `is_valid_class` check, you must use `config:set` directly to declare an
    initial priority for the dynamic channel before being able to use the
    `ioq_config` helpers.
    
    This change was motivated by not being able to bypass search in the
    Dreyfus project, as it piggy-backed off of `interactive` and
    `view_update` channels. That was rectified in [1], and now Dreyfus uses
    the `search` IOQ channel. As that is not used in CouchDB directly, this
    commit adds the dynamic class support based off of config values, rather
    than specifically hardcoding search, so that it can be used by any 3rd
    party services running IO traffic through IOQ.
    
    [1] https://github.com/cloudant-labs/dreyfus/pull/46/commits/75d86c49c86f4e7e299d2d05a741c4ef68a144fb
---
 src/ioq_config.erl        | 15 +++++++++++++--
 test/ioq_config_tests.erl | 31 +++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/src/ioq_config.erl b/src/ioq_config.erl
index 33a3030..6b324e3 100644
--- a/src/ioq_config.erl
+++ b/src/ioq_config.erl
@@ -135,8 +135,19 @@ set_user_config(User, Value, Reason) ->
     ok = set_config(?IOQ2_USERS_CONFIG, User, Value, Reason).
 
 
-is_valid_class(Class) ->
-    lists:member(Class, ioq_classes()).
+is_valid_class(Class) when is_atom(Class) ->
+    case lists:member(Class, ioq_classes()) of
+        true ->
+            true;
+        false ->
+            SClass = atom_to_list(Class),
+            case config:get(?IOQ2_CLASSES_CONFIG, SClass, undefined) of
+                undefined ->
+                    false;
+                _ ->
+                    true
+            end
+    end.
 
 
 check_float_value(Value) when is_float(Value) ->
diff --git a/test/ioq_config_tests.erl b/test/ioq_config_tests.erl
index a7fd491..2b6e153 100644
--- a/test/ioq_config_tests.erl
+++ b/test/ioq_config_tests.erl
@@ -260,3 +260,34 @@ check_bypass_configs(_) ->
     ok = ioq_config:set_bypass(interactive, true, "Bypassing interactive"),
     Value = config:get_boolean("ioq2.bypass", "interactive", false),
     ?_assertEqual(true, Value).
+
+
+valid_classes_test_() ->
+    {
+        "Test ioq_config is_valid_class logic",
+        {
+            foreach,
+            fun() -> test_util:start_applications([config, couch_log]) end,
+            fun(_) -> test_util:stop_applications([config, couch_log]) end,
+            [
+                fun check_default_classes/1,
+                fun check_undeclared_class/1,
+                fun check_declared_class/1
+            ]
+        }
+    }.
+
+
+check_default_classes(_) ->
+    Classes = [C || {C, _P} <- ?DEFAULT_CLASS_PRIORITIES],
+    [?_assert(ioq_config:is_valid_class(C)) || C <- Classes].
+
+
+check_undeclared_class(_) ->
+    ?_assert(not ioq_config:is_valid_class(search)).
+
+
+check_declared_class(_) ->
+    config:set(?IOQ2_CLASSES_CONFIG, "search", "1.0", false),
+    ?_assert(ioq_config:is_valid_class(search)).
+