SERVER-59700 Add programming support for tracepoints

1 files changed, 134 insertions, 0 deletions

diff --git a/src/mongo/util/tracing_support_test.cpp b/src/mongo/util/tracing_support_test.cpp
new file mode 100644
index 00000000000..804069cf8e6
--- /dev/null
+++ b/src/mongo/util/tracing_support_test.cpp
@@ -0,0 +1,134 @@
+/**
+ *    Copyright (C) 2021-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::kTest
+
+#include <memory>
+
+#include "mongo/base/init.h"
+#include "mongo/bson/bsonmisc.h"
+#include "mongo/logv2/log.h"
+#include "mongo/unittest/death_test.h"
+#include "mongo/unittest/unittest.h"
+#include "mongo/util/clock_source_mock.h"
+#include "mongo/util/tracing_support.h"
+
+/*
+ * We use `NOLINT` throughout this file since usages of `TracerProvider` aren't meant to be used in
+ * production, but we still wanted to be able to commit unit tests.
+ */
+
+namespace mongo {
+namespace {
+std::unique_ptr<ClockSource> makeClockSource() {
+    return std::make_unique<ClockSourceMock>();
+}
+
+void advanceTime(std::shared_ptr<Tracer>& tracer, Milliseconds duration) {
+    ClockSourceMock* clk = dynamic_cast<ClockSourceMock*>(tracer->getClockSource());
+    clk->advance(duration);
+}
+
+// Uses the mocked clock source to initialize the trace provider.
+MONGO_INITIALIZER_GENERAL(InitializeTraceProviderForTest, (), ("InitializeTraceProvider"))
+(InitializerContext*) {
+    TracerProvider::initialize(makeClockSource());  // NOLINT
+}
+
+static constexpr auto kTracerName = "MyTracer";
+}  // namespace
+
+DEATH_TEST(TracingSupportTest, CannotInitializeTwice, "invariant") {
+    TracerProvider::initialize(makeClockSource());  // NOLINT
+}
+
+DEATH_TEST(TracingSupportTest, SpansMustCloseInOrder, "invariant") {
+    auto tracer = TracerProvider::get().getTracer(kTracerName);  // NOLINT
+    auto outerSpan = tracer->startSpan("outer span");
+    auto innerSpan = tracer->startSpan("inner span");
+    outerSpan.reset();
+}
+
+TEST(TracingSupportTest, TraceIsInitiallyEmpty) {
+    auto tracer = TracerProvider::get().getTracer(kTracerName);  // NOLINT
+    ASSERT_FALSE(tracer->getLatestTrace());
+}
+
+TEST(TracingSupportTest, TraceIsEmptyWithActiveSpans) {
+    auto tracer = TracerProvider::get().getTracer(kTracerName);  // NOLINT
+    auto span = tracer->startSpan("some span");
+    ASSERT_FALSE(tracer->getLatestTrace());
+}
+
+TEST(TracingSupportTest, BasicUsage) {
+    const auto kSpanDuration = Seconds(5);
+    auto tracer = TracerProvider::get().getTracer(kTracerName);  // NOLINT
+    const auto startTime = tracer->getClockSource()->now();
+
+    {
+        auto rootSpan = tracer->startSpan("root");
+        advanceTime(tracer, kSpanDuration);
+        {
+            auto childSpan = tracer->startSpan("child");
+            advanceTime(tracer, kSpanDuration);
+            {
+                {
+                    auto grandChildOne = tracer->startSpan("grand child #1");
+                    advanceTime(tracer, kSpanDuration);
+                }
+                {
+                    auto grandChildTwo = tracer->startSpan("grand child #2");
+                    advanceTime(tracer, kSpanDuration);
+                }
+            }
+        }
+    }
+
+    const auto trace = tracer->getLatestTrace();
+    ASSERT_TRUE(trace);
+
+    const auto expected = BSON(
+        "tracer"
+        << kTracerName << "root"
+        << BSON("started"
+                << startTime << "spans"
+                << BSON("child" << BSON(
+                            "started"
+                            << startTime + kSpanDuration << "spans"
+                            << BSON("grand child #1"
+                                    << BSON("started" << startTime + 2 * kSpanDuration << "stopped"
+                                                      << startTime + 3 * kSpanDuration)
+                                    << "grand child #2"
+                                    << BSON("started" << startTime + 3 * kSpanDuration << "stopped"
+                                                      << startTime + 4 * kSpanDuration))
+                            << "stopped" << startTime + 4 * kSpanDuration))
+                << "stopped" << startTime + 4 * kSpanDuration));
+    ASSERT_BSONOBJ_EQ(expected, trace.get());
+}
+
+}  // namespace mongo