Add support for negative logging categories in the log gateway

Development/cmake/NmosCppTest.cmake

@@ -56,6 +56,7 @@ set(NMOS_CPP_TEST_NMOS_TEST_SOURCES
     nmos/test/json_validator_test.cpp
     nmos/test/jwt_generator_test.cpp
     nmos/test/jwt_validation_test.cpp
+    nmos/test/log_gate_test.cpp
     nmos/test/mdns_test.cpp
     nmos/test/node_interfaces_test.cpp
     nmos/test/paging_utils_test.cpp

Development/nmos/log_gate.h

@@ -63,14 +63,36 @@ namespace nmos
 
                 const auto& pertinent_categories = nmos::fields::logging_categories(model.settings);
 
+                // categories prefixed with '!' specify messages that should not be logged;
+                // a negative match takes precedence over any positive match, and when only
+                // negative categories are specified, all other messages are pertinent
+                const auto is_negative = [](const web::json::value& category)
+                {
+                    const auto& s = category.as_string();
+                    return !s.empty() && U('!') == s.front();
+                };
+                const bool default_pertinent = 0 != pertinent_categories.size()
+                    && pertinent_categories.end() == boost::range::find_if(pertinent_categories, [&](const web::json::value& category)
+                    {
+                        return !is_negative(category);
+                    });
+
                 if (categories.empty())
                 {
                     static const auto no_category = web::json::value::string(utility::string_t());
-                    return pertinent_categories.end() != boost::range::find(pertinent_categories, no_category);
+                    return default_pertinent || pertinent_categories.end() != boost::range::find(pertinent_categories, no_category);
                 }
 
                 // this could be made more efficient if there may be many pertinent categories
-                return categories.end() != boost::range::find_if(categories, [&](const nmos::category& c)
+                if (categories.end() != boost::range::find_if(categories, [&](const nmos::category& c)
+                {
+                    return pertinent_categories.end() != boost::range::find(pertinent_categories, web::json::value::string(utility::s2us("!" + c)));
+                }))
+                {
+                    return false;
+                }
+
+                return default_pertinent || categories.end() != boost::range::find_if(categories, [&](const nmos::category& c)
                 {
                     return pertinent_categories.end() != boost::range::find(pertinent_categories, web::json::value::string(utility::s2us(c)));
                 });

Development/nmos/settings.h

@@ -100,6 +100,8 @@ namespace nmos
         const web::json::field_as_integer_or logging_level{ U("logging_level"), 0 }; // 0, rather than slog::severities::info or slog::nil_severity, just to avoid a #include
 
         // logging_categories [registry, node]: array of logging categories to be included in the error log
+        // categories prefixed with '!' are excluded, even if another category matches positively;
+        // when only excluded categories are specified, all other log messages are included
         const web::json::field_as_array logging_categories{ U("logging_categories") }; // when omitted, all log messages are included
 
         // Configuration settings and defaults for the NMOS APIs

Development/nmos/test/log_gate_test.cpp

@@ -0,0 +1,69 @@
+// The first "test" is of course whether the header compiles standalone
+#include "nmos/log_gate.h"
+
+#include <sstream>
+#include "bst/test/test.h"
+
+namespace
+{
+    struct test_gate : nmos::experimental::log_gate
+    {
+        test_gate(std::ostream& error_log, std::ostream& access_log, nmos::experimental::log_model& model)
+            : nmos::experimental::log_gate(error_log, access_log, model) {}
+        using nmos::experimental::log_gate::pertinent;
+    };
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////
+BST_TEST_CASE(testLogGatePertinentCategories)
+{
+    using web::json::value_of;
+
+    std::ostringstream error_log;
+    std::ostringstream access_log;
+    nmos::experimental::log_model model;
+    test_gate gate(error_log, access_log, model);
+
+    const std::list<nmos::category> no_categories;
+    const std::list<nmos::category> access{ "access" };
+    const std::list<nmos::category> send_query_ws_events{ "send_query_ws_events" };
+    const std::list<nmos::category> both{ "send_query_ws_events", "access" };
+
+    // when logging_categories is omitted, all messages are pertinent
+    BST_REQUIRE(gate.pertinent(no_categories));
+    BST_REQUIRE(gate.pertinent(access));
+    BST_REQUIRE(gate.pertinent(both));
+
+    // when logging_categories is empty, no messages are pertinent
+    model.settings[nmos::fields::logging_categories] = web::json::value::array();
+    BST_REQUIRE(!gate.pertinent(no_categories));
+    BST_REQUIRE(!gate.pertinent(access));
+    BST_REQUIRE(!gate.pertinent(both));
+
+    // positive categories select the messages to be logged
+    model.settings[nmos::fields::logging_categories] = value_of({ U("send_query_ws_events") });
+    BST_REQUIRE(!gate.pertinent(no_categories));
+    BST_REQUIRE(gate.pertinent(send_query_ws_events));
+    BST_REQUIRE(!gate.pertinent(access));
+    BST_REQUIRE(gate.pertinent(both));
+
+    // the empty string selects messages with no category
+    model.settings[nmos::fields::logging_categories] = value_of({ U("") });
+    BST_REQUIRE(gate.pertinent(no_categories));
+    BST_REQUIRE(!gate.pertinent(access));
+
+    // a category prefixed with '!' excludes matching messages, even if another
+    // category matches positively
+    model.settings[nmos::fields::logging_categories] = value_of({ U("send_query_ws_events"), U("!access") });
+    BST_REQUIRE(gate.pertinent(send_query_ws_events));
+    BST_REQUIRE(!gate.pertinent(access));
+    BST_REQUIRE(!gate.pertinent(both));
+    BST_REQUIRE(!gate.pertinent(no_categories));
+
+    // when only excluded categories are specified, all other messages are pertinent
+    model.settings[nmos::fields::logging_categories] = value_of({ U("!access") });
+    BST_REQUIRE(gate.pertinent(no_categories));
+    BST_REQUIRE(gate.pertinent(send_query_ws_events));
+    BST_REQUIRE(!gate.pertinent(access));
+    BST_REQUIRE(!gate.pertinent(both));
+}