logging: deprecate libevent category

Creates logic to deprecate logging categories but still
"support" them so the software doesn't quit with unknown category
on startup. Deprecated categories are always false and attempts
to switch them are logged as warnings.

src/logging.cpp

@@ -133,6 +133,11 @@ void BCLog::Logger::EnableCategory(BCLog::LogFlags flag)
 bool BCLog::Logger::EnableCategory(std::string_view str)
 {
     if (const auto flag{GetLogCategory(str)}) {
+        if (*flag & DEPRECATED){
+            LogWarning("The logging category `%s` is deprecated, can not be enabled, and will be removed in a future version", str);
+            // Deprecated does not mean unsupported, which may prevent startup
+            return true;
+        }
         EnableCategory(*flag);
         return true;
     }
@@ -147,6 +152,11 @@ void BCLog::Logger::DisableCategory(BCLog::LogFlags flag)
 bool BCLog::Logger::DisableCategory(std::string_view str)
 {
     if (const auto flag{GetLogCategory(str)}) {
+        if (*flag & DEPRECATED){
+            LogWarning("The logging category `%s` is deprecated and will be removed in a future version", str);
+            // Deprecated does not mean unsupported, which may prevent startup
+            return true;
+        }
         DisableCategory(*flag);
         return true;
     }

src/logging/categories.h

@@ -46,9 +46,10 @@ enum LogFlags : CategoryMask {
     TXPACKAGES = (CategoryMask{1} << 28),
     KERNEL = (CategoryMask{1} << 29),
     PRIVBROADCAST = (CategoryMask{1} << 30),
-    ALL = ~NONE,
+    DEPRECATED = LIBEVENT,
+    // Remove deprecated categories from ALL
+    ALL = ~DEPRECATED,
 };
-
 } // namespace BCLog
 
 #endif // BITCOIN_LOGGING_CATEGORIES_H

src/rpc/node.cpp

@@ -248,26 +248,16 @@ static RPCMethod logging()
                 },
                 RPCExamples{
                     HelpExampleCli("logging", "\"[\\\"all\\\"]\" \"[\\\"http\\\"]\"")
-            + HelpExampleRpc("logging", "[\"all\"], [\"libevent\"]")
+            + HelpExampleRpc("logging", "[\"all\"], [\"leveldb\"]")
                 },
         [](const RPCMethod& self, const JSONRPCRequest& request) -> UniValue
 {
-    BCLog::CategoryMask original_log_categories = LogInstance().GetCategoryMask();
     if (request.params[0].isArray()) {
         EnableOrDisableLogCategories(request.params[0], true);
     }
     if (request.params[1].isArray()) {
         EnableOrDisableLogCategories(request.params[1], false);
     }
-    BCLog::CategoryMask updated_log_categories = LogInstance().GetCategoryMask();
-    BCLog::CategoryMask changed_log_categories = original_log_categories ^ updated_log_categories;
-
-    // Update libevent logging if BCLog::LIBEVENT has changed.
-    if (changed_log_categories & BCLog::LIBEVENT) {
-        // Currently no modules in the codebase produce libevent log messages.
-        // To redirect libevent messages to our own logs see commit 8b2d6edaa9fbfb6344ca51edd0b3655b451cbcac
-        // in https://github.com/bitcoin/bitcoin/pull/6695
-    }
 
     UniValue result(UniValue::VOBJ);
     for (const auto& logCatActive : LogInstance().LogCategoriesList()) {

src/test/logging_tests.cpp

@@ -167,7 +167,11 @@ BOOST_FIXTURE_TEST_CASE(logging_LogPrintMacros_CategoryName, LogSetup)
     for (const auto& category_name : category_names) {
         const auto trimmed_category_name = TrimString(category_name);
         const auto category{*Assert(BCLog::Logger::GetLogCategory(trimmed_category_name))};
-        expected_category_names.emplace_back(category, trimmed_category_name);
+        if (category & BCLog::LogFlags::ALL) {
+            expected_category_names.emplace_back(category, trimmed_category_name);
+        } else {
+            BOOST_CHECK(category & BCLog::LogFlags::DEPRECATED);
+        }
     }
 
     std::vector<std::string> expected;

src/test/util/setup_common.cpp

@@ -165,7 +165,6 @@ BasicTestingSetup::BasicTestingSetup(const ChainType chainType, TestOpts opts)
             "-logthreadnames",
             "-loglevel=trace",
             "-debug",
-            "-debugexclude=libevent",
             "-debugexclude=leveldb",
         },
         opts.extra_args);

test/functional/rpc_misc.py

@@ -120,6 +120,18 @@ class RpcMiscTest(BitcoinTestFramework):
         # Specifying an unknown index name returns an empty result
         assert_equal(node.getindexinfo("foo"), {})
 
+        # Test a deprecated category
+        node.logging(include=['all'])
+        for category, value in node.logging().items():
+            # Everything True except one...
+            assert_equal(value, category != "libevent")
+        with self.nodes[0].assert_debug_log(["The logging category `libevent` is deprecated"]):
+            node.logging(include=['libevent'])
+        assert_equal(node.logging()['libevent'], False)
+        with self.nodes[0].assert_debug_log(["The logging category `libevent` is deprecated"]):
+            node.logging(exclude=['libevent'])
+        assert_equal(node.logging()['libevent'], False)
+
 
 if __name__ == '__main__':
     RpcMiscTest(__file__).main()

test/functional/test_framework/test_node.py

@@ -142,7 +142,6 @@ class TestNode():
             f"-datadir={self.datadir_path}",
             "-logtimemicros",
             "-debug",
-            "-debugexclude=libevent",
             "-debugexclude=leveldb",
             "-debugexclude=rand",
             "-uacomment=testnode%d" % i,  # required for subversion uniqueness across peers