SERVER-43767 fix free_mon_controller_test.cpp

1 files changed, 60 insertions, 12 deletions

diff --git a/src/mongo/db/free_mon/free_mon_controller_test.cpp b/src/mongo/db/free_mon/free_mon_controller_test.cpp
index 4db1bfa3c44..13939a35142 100644
--- a/src/mongo/db/free_mon/free_mon_controller_test.cpp
+++ b/src/mongo/db/free_mon/free_mon_controller_test.cpp
@@ -73,6 +73,12 @@
 namespace mongo {
 namespace {
 
+auto makeRandom() {
+    auto seed = SecureRandom::create()->nextInt64();
+    unittest::log() << "PseudoRandom(" << std::showbase << std::hex << seed << std::dec
+                    << std::noshowbase << ")";
+    return PseudoRandom(seed);
+}
 
 class FreeMonMetricsCollectorMock : public FreeMonCollectorInterface {
 public:
@@ -455,7 +461,7 @@ repl::ReplicationCoordinatorMock* FreeMonControllerTest::_getReplCoord() const {
 
 // Positive: Ensure deadlines sort properly
 TEST(FreeMonRetryTest, TestRegistration) {
-    PseudoRandom random(0);
+    auto random = makeRandom();
     RegistrationRetryCounter counter(random);
     counter.reset();
 
@@ -480,20 +486,47 @@ TEST(FreeMonRetryTest, TestRegistration) {
     }
 
     // Validate max timeout
-    for (int j = 0; j < 3; j++) {
-        // Fail requests
-        for (int i = 1; i <= 163; ++i) {
-            ASSERT_TRUE(counter.incrementError());
+
+    auto characterizeJitter = [](Seconds jitter1, Seconds jitter2) {
+        static constexpr size_t kStage1Retries = 10;
+        static constexpr auto kTMax = Days{2};
+        auto t = Seconds(0);
+        auto base = Seconds(1);
+        size_t i = 0;
+        for (; t < kTMax; ++i) {
+            if (i < kStage1Retries) {
+                base *= 2;
+                t += base + jitter1;
+            } else {
+                t += base + jitter2;
+            }
         }
-        ASSERT_FALSE(counter.incrementError());
+        return i;
+    };
+    // If jitter is small as possible, we'd expect trueMax increments before false.
+    const auto trueMax = characterizeJitter(Seconds{2}, Seconds{60});
+    // If jitter is large as possible, we'd expect trueMin increments before false.
+    const auto trueMin = characterizeJitter(Seconds{9}, Seconds{119});
+
+    // unittest::log() << "trueMin:" << trueMin;
+    // unittest::log() << "trueMax:" << trueMax;
 
+    for (int j = 0; j < 30; j++) {
+        // std::cout << "j: " << j << "\n";
+        // Fail requests
+        size_t trueCount = 0;
+        while (counter.incrementError()) {
+            ++trueCount;
+        }
+        ASSERT_GTE(trueCount, trueMin);
+        ASSERT_LTE(trueCount, trueMax);
         counter.reset();
     }
 }
 
 // Positive: Ensure deadlines sort properly
 TEST(FreeMonRetryTest, TestMetrics) {
-    PseudoRandom random(0);
+    auto random = makeRandom();
     MetricsRetryCounter counter(random);
     counter.reset();
 
@@ -519,13 +552,28 @@ TEST(FreeMonRetryTest, TestMetrics) {
     }
 
     // Validate max timeout
-    for (int j = 0; j < 3; j++) {
-        // Fail requests
-        for (int i = 1; i < 9456; ++i) {
-            ASSERT_TRUE(counter.incrementError());
+    static size_t expectation = [] {
+        // There's technically a jitter in the MetricsRetryCounter but its default
+        // magnitude rounds to 0, so we make an exact expectation.
+        size_t iters = 0;
+        static constexpr auto kDurationMax = Days{7};
+        auto t = Seconds{0};
+        auto base = Seconds{1};
+        for (; t < kDurationMax; ++iters) {
+            if (iters < 6)
+                base *= 2;
+            t += base;
         }
-        ASSERT_FALSE(counter.incrementError());
+        return iters;
+    }();
 
+    for (int j = 0; j < 30; j++) {
+        // Fail requests
+        int iters = 0;
+        while (counter.incrementError()) {
+            ++iters;
+        }
+        ASSERT_EQ(iters, expectation);
         counter.reset();
     }
 }