SERVER-46726 Provide separate setParameter to disable diagnostic work

22 files changed, 299 insertions, 41 deletions

diff --git a/src/mongo/SConscript b/src/mongo/SConscript
index 5b1aecdb10d..ee959b26226 100644
--- a/src/mongo/SConscript
+++ b/src/mongo/SConscript
@@ -159,6 +159,7 @@ baseEnv.Library(
         'util/system_clock_source.cpp',
         'util/system_tick_source.cpp',
         'util/text.cpp',
+        'util/testing_proctor.cpp',
         'util/thread_safety_context.cpp',
         'util/time_support.cpp',
         'util/timer.cpp',
@@ -499,6 +500,7 @@ env.Library(
         'util/ntservice',
         'util/options_parser/options_parser_init',
         'util/periodic_runner_factory',
+        'util/testing_options',
         'util/version_impl',
         'watchdog/watchdog_mongod',
     ],
@@ -704,6 +706,7 @@ env.Library(
         'util/ntservice',
         'util/options_parser/options_parser',
         'util/options_parser/options_parser_init',
+        'util/testing_options',
         'util/version_impl',
     ],
     LIBDEPS=[
diff --git a/src/mongo/db/pipeline/accumulator_js_test.cpp b/src/mongo/db/pipeline/accumulator_js_test.cpp
index 6ce4adae7c9..92e11e592a8 100644
--- a/src/mongo/db/pipeline/accumulator_js_test.cpp
+++ b/src/mongo/db/pipeline/accumulator_js_test.cpp
@@ -62,7 +62,6 @@ private:
 
 
 void MapReduceFixture::setUp() {
-    setTestCommandsEnabled(true);
     ServiceContextMongoDTest::setUp();
     ScriptEngine::setup(false);
 }
diff --git a/src/mongo/db/pipeline/expression_javascript_test.cpp b/src/mongo/db/pipeline/expression_javascript_test.cpp
index 299ee506664..dc0df7cb51d 100644
--- a/src/mongo/db/pipeline/expression_javascript_test.cpp
+++ b/src/mongo/db/pipeline/expression_javascript_test.cpp
@@ -75,7 +75,6 @@ private:
 
 
 void MapReduceFixture::setUp() {
-    setTestCommandsEnabled(true);
     ServiceContextMongoDTest::setUp();
     ScriptEngine::setup(false);
 }
diff --git a/src/mongo/db/query/find_and_modify_request_test.cpp b/src/mongo/db/query/find_and_modify_request_test.cpp
index a5d55fcd503..f9f01b82769 100644
--- a/src/mongo/db/query/find_and_modify_request_test.cpp
+++ b/src/mongo/db/query/find_and_modify_request_test.cpp
@@ -53,7 +53,6 @@ TEST(FindAndModifyRequest, BasicUpdate) {
 }
 
 TEST(FindAndModifyRequest, PipelineUpdate) {
-    setTestCommandsEnabled(true);
     const BSONObj query(BSON("x" << 1));
     const BSONObj pipelineBSON(
         BSON("pipeline" << BSON_ARRAY(BSON("$addFields" << BSON("y" << 1)))));
@@ -660,7 +659,6 @@ TEST(FindAndModifyRequest, ParseWithWriteConcernAsArray) {
 }
 
 TEST(FindAndModifyRequest, ParsesAndSerializesPipelineUpdate) {
-    setTestCommandsEnabled(true);
     BSONObj cmdObj(fromjson(R"json({
             query: { x: 1 },
             update: [{$replaceWith: {y: 1}}]
@@ -684,7 +682,6 @@ TEST(FindAndModifyRequest, ParsesAndSerializesPipelineUpdate) {
 }
 
 TEST(FindAndModifyRequest, RejectsBothArrayFiltersAndPipelineUpdate) {
-    setTestCommandsEnabled(true);
     BSONObj cmdObj(fromjson(R"json({
             query: { x: 1 },
             update: [{$replaceWith: {y: 1}}],
diff --git a/src/mongo/db/s/wait_for_ongoing_chunk_splits_command.cpp b/src/mongo/db/s/wait_for_ongoing_chunk_splits_command.cpp
index f9b1e85a78c..04a0e6dce92 100644
--- a/src/mongo/db/s/wait_for_ongoing_chunk_splits_command.cpp
+++ b/src/mongo/db/s/wait_for_ongoing_chunk_splits_command.cpp
@@ -83,12 +83,6 @@ public:
     }
 };
 
-MONGO_INITIALIZER(RegisterWaitForOngoingChunkSplitsCommand)(InitializerContext* context) {
-    if (getTestCommandsEnabled()) {
-        // Leaked intentionally: a Command registers itself when constructed.
-        new WaitForOngoingChunksSplitsCommand();
-    }
-    return Status::OK();
-}
+MONGO_REGISTER_TEST_COMMAND(WaitForOngoingChunksSplitsCommand);
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/dbtests/dbtests.cpp b/src/mongo/dbtests/dbtests.cpp
index 9f4d4b63984..03a3eb6fd01 100644
--- a/src/mongo/dbtests/dbtests.cpp
+++ b/src/mongo/dbtests/dbtests.cpp
@@ -59,6 +59,7 @@
 #include "mongo/util/clock_source_mock.h"
 #include "mongo/util/quick_exit.h"
 #include "mongo/util/signal_handlers_synchronous.h"
+#include "mongo/util/testing_proctor.h"
 #include "mongo/util/text.h"
 
 namespace mongo {
@@ -173,6 +174,7 @@ WriteContextForTests::WriteContextForTests(OperationContext* opCtx, StringData n
 
 int dbtestsMain(int argc, char** argv, char** envp) {
     ::mongo::setTestCommandsEnabled(true);
+    ::mongo::TestingProctor::instance().setEnabled(true);
     ::mongo::setupSynchronousSignalHandlers();
     mongo::dbtests::initWireSpec();
 
diff --git a/src/mongo/executor/SConscript b/src/mongo/executor/SConscript
index a6b306f0596..25b6ec650d5 100644
--- a/src/mongo/executor/SConscript
+++ b/src/mongo/executor/SConscript
@@ -134,7 +134,6 @@ env.Library(
         'hedging_metrics',
     ],
     LIBDEPS_PRIVATE=[
-        '$BUILD_DIR/mongo/db/commands/test_commands_enabled',
         '$BUILD_DIR/mongo/transport/transport_layer_manager',
         'connection_pool_executor',
         'network_interface',
diff --git a/src/mongo/executor/network_interface_integration_test.cpp b/src/mongo/executor/network_interface_integration_test.cpp
index 9a0e31f08b9..36d0b6aae60 100644
--- a/src/mongo/executor/network_interface_integration_test.cpp
+++ b/src/mongo/executor/network_interface_integration_test.cpp
@@ -161,7 +161,6 @@ public:
     }
 
     void setUp() override {
-        setTestCommandsEnabled(true);
         startNet(std::make_unique<WaitForIsMasterHook>(this));
     }
 
diff --git a/src/mongo/executor/network_interface_tl.cpp b/src/mongo/executor/network_interface_tl.cpp
index 48adfb7d4fa..647fc1bfb36 100644
--- a/src/mongo/executor/network_interface_tl.cpp
+++ b/src/mongo/executor/network_interface_tl.cpp
@@ -33,7 +33,6 @@
 
 #include "mongo/executor/network_interface_tl.h"
 
-#include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/db/server_options.h"
 #include "mongo/executor/connection_pool_tl.h"
 #include "mongo/executor/hedging_metrics.h"
@@ -42,6 +41,7 @@
 #include "mongo/transport/transport_layer_manager.h"
 #include "mongo/util/concurrency/idle_thread_block.h"
 #include "mongo/util/net/socket_utils.h"
+#include "mongo/util/testing_proctor.h"
 
 namespace mongo {
 namespace executor {
@@ -129,7 +129,7 @@ NetworkInterfaceTL::NetworkInterfaceTL(std::string instanceName,
     _pool = std::make_shared<ConnectionPool>(
         std::move(typeFactory), std::string("NetworkInterfaceTL-") + _instanceName, _connPoolOpts);
 
-    if (getTestCommandsEnabled()) {
+    if (TestingProctor::instance().isEnabled()) {
         _counters = std::make_unique<SynchronizedCounters>();
     }
 }
diff --git a/src/mongo/shell/mongo_main.cpp b/src/mongo/shell/mongo_main.cpp
index a7051081d3f..c338fe921d7 100644
--- a/src/mongo/shell/mongo_main.cpp
+++ b/src/mongo/shell/mongo_main.cpp
@@ -55,7 +55,6 @@
 #include "mongo/config.h"
 #include "mongo/db/auth/sasl_command_constants.h"
 #include "mongo/db/client.h"
-#include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/db/log_process_details.h"
 #include "mongo/db/server_options.h"
 #include "mongo/logger/console_appender.h"
@@ -125,14 +124,6 @@ MONGO_INITIALIZER_WITH_PREREQUISITES(SetFeatureCompatibilityVersionLatest,
     return Status::OK();
 }
 
-// Initialize the testCommandsEnabled server parameter to true since the mongo shell does not have
-// any test-only commands that could cause harm to the server, and it may be necessary to enable
-// this to test certain features, for example through benchRun (see SERVER-40419).
-MONGO_INITIALIZER_WITH_PREREQUISITES(EnableShellTestCommands, ("EndStartupOptionSetup"))
-(InitializerContext* context) {
-    setTestCommandsEnabled(true);
-    return Status::OK();
-}
 const auto kAuthParam = "authSource"s;
 
 /**
diff --git a/src/mongo/shell/servers.js b/src/mongo/shell/servers.js
index 6170046a15d..dd2a46dfdcc 100644
--- a/src/mongo/shell/servers.js
+++ b/src/mongo/shell/servers.js
@@ -1126,6 +1126,14 @@ function appendSetParameterArgs(argArray) {
         if (jsTest.options().enableTestCommands) {
             argArray.push(...['--setParameter', "enableTestCommands=1"]);
         }
+
+        // TODO SERVER-46726 include v4.4 once SERVER-46726 is backported to v4.4
+        if (!programMajorMinorVersion || programMajorMinorVersion > 404) {
+            if (jsTest.options().testingDiagnosticsEnabled) {
+                argArray.push(...['--setParameter', "testingDiagnosticsEnabled=1"]);
+            }
+        }
+
         if (jsTest.options().authMechanism && jsTest.options().authMechanism != "SCRAM-SHA-1") {
             if (!argArrayContainsSetParameterValue('authenticationMechanisms=')) {
                 argArray.push(...['--setParameter',
diff --git a/src/mongo/shell/utils.js b/src/mongo/shell/utils.js
index 4b905500e2e..125b9aeac26 100644
--- a/src/mongo/shell/utils.js
+++ b/src/mongo/shell/utils.js
@@ -268,6 +268,11 @@ jsTestOptions = function() {
             // TestData
             enableTestCommands:
                 TestData.hasOwnProperty('enableTestCommands') ? TestData.enableTestCommands : true,
+            // Testing diagnostics should be enabled by default if no testingDiagnosticsEnabled was
+            // present in TestData
+            testingDiagnosticsEnabled: TestData.hasOwnProperty('testingDiagnosticsEnabled')
+                ? TestData.testingDiagnosticsEnabled
+                : true,
             serviceExecutor: TestData.serviceExecutor,
             setParameters: TestData.setParameters,
             setParametersMongos: TestData.setParametersMongos,
diff --git a/src/mongo/unittest/SConscript b/src/mongo/unittest/SConscript
index f7691b0c5cd..517a1de6997 100644
--- a/src/mongo/unittest/SConscript
+++ b/src/mongo/unittest/SConscript
@@ -35,6 +35,7 @@ env.Library(
         'unittest',
     ],
     LIBDEPS_PRIVATE=[
+        '$BUILD_DIR/mongo/db/commands/test_commands_enabled',
         '$BUILD_DIR/mongo/util/options_parser/options_parser',
     ],
 )
@@ -51,6 +52,7 @@ env.Library(
     ],
     LIBDEPS_PRIVATE=[
         '$BUILD_DIR/mongo/client/connection_string',
+        '$BUILD_DIR/mongo/db/commands/test_commands_enabled',
         '$BUILD_DIR/mongo/db/serverinit',
         '$BUILD_DIR/mongo/db/server_options',
         '$BUILD_DIR/mongo/db/server_options_base',
diff --git a/src/mongo/unittest/integration_test_main.cpp b/src/mongo/unittest/integration_test_main.cpp
index f850fdc901e..07f8c95b097 100644
--- a/src/mongo/unittest/integration_test_main.cpp
+++ b/src/mongo/unittest/integration_test_main.cpp
@@ -37,6 +37,7 @@
 
 #include "mongo/base/initializer.h"
 #include "mongo/client/connection_string.h"
+#include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/db/server_options_base.h"
 #include "mongo/db/server_options_helpers.h"
 #include "mongo/db/service_context.h"
@@ -51,6 +52,7 @@
 #include "mongo/util/options_parser/startup_options.h"
 #include "mongo/util/quick_exit.h"
 #include "mongo/util/signal_handlers_synchronous.h"
+#include "mongo/util/testing_proctor.h"
 
 using namespace mongo;
 
@@ -72,7 +74,9 @@ ConnectionString getFixtureConnectionString() {
 
 int main(int argc, char** argv, char** envp) {
     setupSynchronousSignalHandlers();
+    TestingProctor::instance().setEnabled(true);
     runGlobalInitializersOrDie(argc, argv, envp);
+    setTestCommandsEnabled(true);
     setGlobalServiceContext(ServiceContext::make());
     quickExit(unittest::Suite::run(std::vector<std::string>(), "", "", 1));
 }
diff --git a/src/mongo/unittest/unittest_main.cpp b/src/mongo/unittest/unittest_main.cpp
index 1472cdbe2f8..39e59923d10 100644
--- a/src/mongo/unittest/unittest_main.cpp
+++ b/src/mongo/unittest/unittest_main.cpp
@@ -33,6 +33,7 @@
 
 #include "mongo/base/initializer.h"
 #include "mongo/base/status.h"
+#include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/logger/logger.h"
 #include "mongo/logv2/log_domain_global.h"
 #include "mongo/logv2/log_manager.h"
@@ -43,6 +44,7 @@
 #include "mongo/util/options_parser/option_section.h"
 #include "mongo/util/options_parser/options_parser.h"
 #include "mongo/util/signal_handlers_synchronous.h"
+#include "mongo/util/testing_proctor.h"
 
 using mongo::Status;
 
@@ -52,7 +54,9 @@ int main(int argc, char** argv, char** envp) {
     ::mongo::clearSignalMask();
     ::mongo::setupSynchronousSignalHandlers();
 
+    ::mongo::TestingProctor::instance().setEnabled(true);
     ::mongo::runGlobalInitializersOrDie(argc, argv, envp);
+    ::mongo::setTestCommandsEnabled(true);
 
     moe::OptionSection options;
 
diff --git a/src/mongo/util/SConscript b/src/mongo/util/SConscript
index 2ec5e638b83..dd5edaf76c8 100644
--- a/src/mongo/util/SConscript
+++ b/src/mongo/util/SConscript
@@ -158,6 +158,18 @@ env.Library(
 )
 
 env.Library(
+    target="testing_options",
+    source=[
+        "testing_options.cpp",
+        env.Idlc('testing_options.idl')[0],
+    ],
+    LIBDEPS=[
+        "$BUILD_DIR/mongo/base",
+        "$BUILD_DIR/mongo/idl/server_parameter",
+    ],
+)
+
+env.Library(
     target="periodic_runner",
     source=[
         "periodic_runner.cpp",
@@ -316,7 +328,6 @@ if get_option('use-diagnostic-latches') == 'on':
         ],
         LIBDEPS=[
             '$BUILD_DIR/mongo/base',
-            '$BUILD_DIR/mongo/db/commands/test_commands_enabled',
             '$BUILD_DIR/mongo/db/service_context',
         ],
         LIBDEPS_PRIVATE=[
diff --git a/src/mongo/util/latch_analyzer.cpp b/src/mongo/util/latch_analyzer.cpp
index 760ecd265cb..c7ef2e57a1e 100644
--- a/src/mongo/util/latch_analyzer.cpp
+++ b/src/mongo/util/latch_analyzer.cpp
@@ -42,12 +42,12 @@
 
 #include "mongo/base/init.h"
 #include "mongo/db/client.h"
-#include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/db/service_context.h"
 #include "mongo/logv2/log.h"
 #include "mongo/platform/mutex.h"
 #include "mongo/util/fail_point.h"
 #include "mongo/util/latch_analyzer.h"
+#include "mongo/util/testing_proctor.h"
 
 namespace mongo {
 
@@ -126,7 +126,7 @@ struct LatchSetState {
     using LatchIdentitySet = std::deque<const latch_detail::Identity*>;
 
     LatchSetState() {
-        if (getTestCommandsEnabled()) {
+        if (TestingProctor::instance().isEnabled()) {
             identities = std::make_unique<LatchIdentitySet>();
         }
     }
@@ -139,7 +139,7 @@ struct LatchSetState {
 
     // This is an ordered list of latch Identities. Each acquired Latch will add itself to the end
     // of this list and each released Latch will remove itself from the end. This is populated when
-    // getTestCommandsEnabled() is true, i.e. in a testing environment.
+    // TestingProctor::instance().isEnabled() is true, i.e. in a testing environment.
     std::unique_ptr<LatchIdentitySet> identities;
 };
 
@@ -166,7 +166,7 @@ void LatchAnalyzer::setAllowExitOnViolation(bool allowExitOnViolation) {
 }
 
 bool LatchAnalyzer::allowExitOnViolation() {
-    return _allowExitOnViolation.load() && (getTestCommandsEnabled());
+    return _allowExitOnViolation.load() && TestingProctor::instance().isEnabled();
 }
 
 LatchAnalyzer& LatchAnalyzer::get(ServiceContext* serviceContext) {
diff --git a/src/mongo/util/latch_analyzer_test.cpp b/src/mongo/util/latch_analyzer_test.cpp
index 9b4844d1311..8105925597a 100644
--- a/src/mongo/util/latch_analyzer_test.cpp
+++ b/src/mongo/util/latch_analyzer_test.cpp
@@ -41,17 +41,7 @@ namespace {
 
 using Level = HierarchicalAcquisitionLevel;
 
-class LatchAnalyzerTest : public ServiceContextTest {
-    void setUp() override {
-        ServiceContextTest::setUp();
-        setTestCommandsEnabled(true);
-    }
-
-    void tearDown() override {
-        setTestCommandsEnabled(false);
-        ServiceContextTest::tearDown();
-    }
-};
+class LatchAnalyzerTest : public ServiceContextTest {};
 
 DEATH_TEST_REGEX_F(LatchAnalyzerTest, AddInvalidWasAbsent, "Fatal assertion.*31360") {
 
diff --git a/src/mongo/util/testing_options.cpp b/src/mongo/util/testing_options.cpp
new file mode 100644
index 00000000000..8f886eedf9f
--- /dev/null
+++ b/src/mongo/util/testing_options.cpp
@@ -0,0 +1,66 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kDefault
+
+#include "mongo/base/init.h"
+#include "mongo/logv2/log.h"
+#include "mongo/util/testing_options_gen.h"
+#include "mongo/util/testing_proctor.h"
+
+namespace mongo {
+namespace {
+
+/**
+ * The following initializer must always run before "DisableTestingDiagnosticsByDefault" to ensure
+ * it is allowed to set (enables/disables) testing diagnostics.
+ */
+MONGO_INITIALIZER_GENERAL(TestingDiagnostics,
+                          ("EndServerParameterRegistration"),
+                          ("DisableTestingDiagnosticsByDefault"))
+(InitializerContext*) {
+    // Initialize testing diagnostics only if it has not been already initialized, or it must be
+    // enabled by the initializer (i.e., "testingDiagnosticsEnabled=true"). This ensures testing
+    // diagnostics cannot be set beyond this point.
+    if (!TestingProctor::instance().isInitialized() || gTestingDiagnosticsEnabledAtStartup) {
+        TestingProctor::instance().setEnabled(gTestingDiagnosticsEnabledAtStartup);
+    }
+
+    if (TestingProctor::instance().isEnabled()) {
+        LOGV2_OPTIONS(4672602,
+                      {logv2::LogTag::kStartupWarnings},
+                      "Testing behaviors are enabled. This has serious implications for both "
+                      "performance and security.");
+    }
+
+    return Status::OK();
+}
+
+}  // namespace
+}  // namespace mongo
diff --git a/src/mongo/util/testing_options.idl b/src/mongo/util/testing_options.idl
new file mode 100644
index 00000000000..dfb3e0c0d9f
--- /dev/null
+++ b/src/mongo/util/testing_options.idl
@@ -0,0 +1,38 @@
+# Copyright (C) 2020-present MongoDB, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the Server Side Public License, version 1,
+# as published by MongoDB, Inc.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# Server Side Public License for more details.
+#
+# You should have received a copy of the Server Side Public License
+# along with this program. If not, see
+# <http://www.mongodb.com/licensing/server-side-public-license>.
+#
+# As a special exception, the copyright holders give permission to link the
+# code of portions of this program with the OpenSSL library under certain
+# conditions as described in each individual source file and distribute
+# linked combinations including the program with the OpenSSL library. You
+# must comply with the Server Side Public License in all respects for
+# all of the code used other than as permitted herein. If you modify file(s)
+# with this exception, you may extend this exception to your version of the
+# file(s), but you are not obligated to do so. If you do not wish to do so,
+# delete this exception statement from your version. If you delete this
+# exception statement from all source files in the program, then also delete
+# it in the license file.
+#
+
+global:
+  cpp_namespace: "mongo"
+
+server_parameters:
+  testingDiagnosticsEnabled:
+    description: 'Start with test-only diagnostic behavior enabled'
+    set_at: startup
+    cpp_vartype: bool
+    cpp_varname: gTestingDiagnosticsEnabledAtStartup
+    default: false
diff --git a/src/mongo/util/testing_proctor.cpp b/src/mongo/util/testing_proctor.cpp
new file mode 100644
index 00000000000..f9f378fb687
--- /dev/null
+++ b/src/mongo/util/testing_proctor.cpp
@@ -0,0 +1,80 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kDefault
+
+#include "mongo/util/testing_proctor.h"
+
+#include "mongo/base/init.h"
+#include "mongo/logv2/log.h"
+#include "mongo/util/assert_util.h"
+#include "mongo/util/static_immortal.h"
+
+namespace mongo {
+
+TestingProctor& TestingProctor::instance() {
+    static StaticImmortal<TestingProctor> proctor{};
+    return proctor.value();
+}
+
+bool TestingProctor::isEnabled() const {
+    uassert(ErrorCodes::NotYetInitialized,
+            "Cannot check whether testing diagnostics is enabled before it is initialized",
+            isInitialized());
+    return _diagnosticsEnabled.get();
+}
+
+void TestingProctor::setEnabled(bool enable) {
+    if (!isInitialized()) {
+        _diagnosticsEnabled = enable;
+        return;
+    }
+
+    uassert(ErrorCodes::AlreadyInitialized,
+            "Cannot alter testing diagnostics once initialized",
+            _diagnosticsEnabled.get() == enable);
+
+    LOGV2(4672601, "Overriding testing diagnostics", "enabled"_attr = enable);
+}
+
+namespace {
+
+/**
+ * The initializer ensures that testing diagnostics is always initialized (by default to disabled),
+ * especially for those executables that never call into `setEnabled()` (e.g., the mongo shell).
+ */
+MONGO_INITIALIZER(DisableTestingDiagnosticsByDefault)(InitializerContext*) {
+    if (!TestingProctor::instance().isInitialized()) {
+        TestingProctor::instance().setEnabled(false);
+    }
+    return Status::OK();
+}
+
+}  // namespace
+}  // namespace mongo
diff --git a/src/mongo/util/testing_proctor.h b/src/mongo/util/testing_proctor.h
new file mode 100644
index 00000000000..48a59cb0697
--- /dev/null
+++ b/src/mongo/util/testing_proctor.h
@@ -0,0 +1,67 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <boost/optional.hpp>
+
+namespace mongo {
+
+/**
+ * Provides the apparatus to control the passive testing behavior and diagnostics. Testing
+ * diagnostics can be controlled via the "testingDiagnosticsEnabled" server parameter, or
+ * directly through calling "TestingProctor::instance().setEnabled()".
+ */
+class TestingProctor {
+public:
+    static TestingProctor& instance();
+
+    bool isInitialized() const noexcept {
+        return _diagnosticsEnabled.has_value();
+    }
+
+    /**
+     * Throws "ErrorCodes::NotYetInitialized" if called before any invocation of "setEnabled()" to
+     * initialize "_diagnosticsEnabled".
+     */
+    bool isEnabled() const;
+
+    /**
+     * Enables/disables testing diagnostics. Once invoked for the first time during the lifetime of
+     * a process, its impact (i.e., enabled or disabled diagnostics) cannot be altered. Throws
+     * "ErrorCodes::AlreadyInitialized" if the caller provides a value for "enable" that does not
+     * match what is stored in "_diagnosticsEnabled".
+     */
+    void setEnabled(bool enable);
+
+private:
+    boost::optional<bool> _diagnosticsEnabled;
+};
+
+}  // namespace mongo