Change random seed for txn stress tests on each run (#5004)

Summary:
Currently the transaction stress tests use thread id as the seed. Since the thread ids are likely to be the same across multiple runs, the seed is thus going to be the same. The patch includes time in calculating the seed to help covering a very different part of state space in each run of the stress tests. To be able to reproduce the bug in case the stress tests failed, it also prints out the time that was used to calculate the seed value.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5004

Differential Revision: D14144356

Pulled By: maysamyabandeh

fbshipit-source-id: 728ed522f550fc8b4f5f9f373259c05fe9a54556

utilities/transactions/transaction_test.cc

@@ -4996,23 +4996,19 @@ TEST_P(TransactionStressTest, ExpiredTransactionDataRace1) {
 namespace {
 // cmt_delay_ms is the delay between prepare and commit
 // first_id is the id of the first transaction
-Status TransactionStressTestInserter(TransactionDB* db,
-                                     const size_t num_transactions,
-                                     const size_t num_sets,
-                                     const size_t num_keys_per_set,
-                                     const uint64_t cmt_delay_ms = 0,
-                                     const uint64_t first_id = 0) {
-  size_t seed = std::hash<std::thread::id>()(std::this_thread::get_id());
-  Random64 _rand(seed);
+Status TransactionStressTestInserter(
+    TransactionDB* db, const size_t num_transactions, const size_t num_sets,
+    const size_t num_keys_per_set, Random64* rand,
+    const uint64_t cmt_delay_ms = 0, const uint64_t first_id = 0) {
   WriteOptions write_options;
   ReadOptions read_options;
   TransactionOptions txn_options;
   // Inside the inserter we might also retake the snapshot. We do both since two
   // separte functions are engaged for each.
-  txn_options.set_snapshot = _rand.OneIn(2);
+  txn_options.set_snapshot = rand->OneIn(2);
 
   RandomTransactionInserter inserter(
-      &_rand, write_options, read_options, num_keys_per_set,
+      rand, write_options, read_options, num_keys_per_set,
       static_cast<uint16_t>(num_sets), cmt_delay_ms, first_id);
 
   for (size_t t = 0; t < num_transactions; t++) {
@@ -5055,15 +5051,19 @@ TEST_P(MySQLStyleTransactionTest, TransactionStressTest) {
   std::vector<port::Thread> threads;
   std::atomic<uint32_t> finished = {0};
   bool TAKE_SNAPSHOT = true;
+  uint64_t time_seed = env->NowMicros();
+  printf("time_seed is %" PRIu64 "\n", time_seed);  // would help to reproduce
 
   std::function<void()> call_inserter = [&] {
+    size_t thd_seed = std::hash<std::thread::id>()(std::this_thread::get_id());
+    Random64 rand(time_seed * thd_seed);
     ASSERT_OK(TransactionStressTestInserter(db, num_transactions_per_thread,
-                                            num_sets, num_keys_per_set));
+                                            num_sets, num_keys_per_set, &rand));
     finished++;
   };
   std::function<void()> call_checker = [&] {
-    size_t seed = std::hash<std::thread::id>()(std::this_thread::get_id());
-    Random64 rand(seed);
+    size_t thd_seed = std::hash<std::thread::id>()(std::this_thread::get_id());
+    Random64 rand(time_seed * thd_seed);
     // Verify that data is consistent
     while (finished < num_workers) {
       Status s = RandomTransactionInserter::Verify(
@@ -5072,8 +5072,8 @@ TEST_P(MySQLStyleTransactionTest, TransactionStressTest) {
     }
   };
   std::function<void()> call_slow_checker = [&] {
-    size_t seed = std::hash<std::thread::id>()(std::this_thread::get_id());
-    Random64 rand(seed);
+    size_t thd_seed = std::hash<std::thread::id>()(std::this_thread::get_id());
+    Random64 rand(time_seed * thd_seed);
     // Verify that data is consistent
     while (finished < num_workers) {
       uint64_t delay_ms = rand.Uniform(100) + 1;
@@ -5083,14 +5083,14 @@ TEST_P(MySQLStyleTransactionTest, TransactionStressTest) {
     }
   };
   std::function<void()> call_slow_inserter = [&] {
-    size_t seed = std::hash<std::thread::id>()(std::this_thread::get_id());
-    Random64 rand(seed);
+    size_t thd_seed = std::hash<std::thread::id>()(std::this_thread::get_id());
+    Random64 rand(time_seed * thd_seed);
     uint64_t id = 0;
     // Verify that data is consistent
     while (finished < num_workers) {
       uint64_t delay_ms = rand.Uniform(500) + 1;
       ASSERT_OK(TransactionStressTestInserter(db, 1, num_sets, num_keys_per_set,
-                                              delay_ms, id++));
+                                              &rand, delay_ms, id++));
     }
   };