Enable unordered_write in stress tests (#6164)

Summary:
With WritePrepared transactions configured with two_write_queues, unordered_write will offer the same guarantees as vanilla rocksdb and thus can be enabled in stress tests.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6164

Test Plan:
```
make -j32 crash_test_with_txn

Differential Revision: D18991899

Pulled By: maysamyabandeh

fbshipit-source-id: eece5e96b4169b67d7931e5c0afca88540a113e1

db_stress_tool/db_stress_common.h

@@ -162,6 +162,7 @@ DECLARE_uint64(rate_limiter_bytes_per_sec);
 DECLARE_bool(rate_limit_bg_reads);
 DECLARE_bool(use_txn);
 DECLARE_uint64(txn_write_policy);
+DECLARE_bool(unordered_write);
 DECLARE_int32(backup_one_in);
 DECLARE_int32(checkpoint_one_in);
 DECLARE_int32(ingest_external_file_one_in);

db_stress_tool/db_stress_gflags.cc

@@ -376,6 +376,11 @@ DEFINE_uint64(txn_write_policy, 0,
               "TxnDBWritePolicy::WRITE_COMMITTED. Note that this should not be "
               "changed accross crashes.");
 
+DEFINE_bool(unordered_write, false,
+            "Turn on the unordered_write feature. This options is currently "
+            "tested only in combination with use_txn=true and "
+            "txn_write_policy=TxnDBWritePolicy::WRITE_PREPARED.");
+
 DEFINE_int32(backup_one_in, 0,
              "If non-zero, then CreateNewBackup() will be called once for "
              "every N operations on average.  0 indicates CreateNewBackup() "

db_stress_tool/db_stress_test_base.cc

@@ -1674,6 +1674,12 @@ void StressTest::Open() {
       assert(FLAGS_txn_write_policy <= TxnDBWritePolicy::WRITE_UNPREPARED);
       txn_db_options.write_policy =
           static_cast<TxnDBWritePolicy>(FLAGS_txn_write_policy);
+      if (FLAGS_unordered_write) {
+        assert(txn_db_options.write_policy == TxnDBWritePolicy::WRITE_PREPARED);
+        options_.unordered_write = true;
+        options_.two_write_queues = true;
+        txn_db_options.skip_concurrency_control = true;
+      }
       s = TransactionDB::Open(options_, txn_db_options, FLAGS_db,
                               cf_descriptors, &column_families_, &txn_db_);
       db_ = txn_db_;
@@ -1773,6 +1779,10 @@ void StressTest::Reopen(ThreadState* thread) {
 #ifndef ROCKSDB_LITE
   if (thread->rand.OneIn(2)) {
     Status s = db_->Close();
+    if (!s.ok()) {
+      fprintf(stderr, "Non-ok close status: %s\n", s.ToString().c_str());
+      fflush(stderr);
+    }
     assert(s.ok());
   }
 #endif

tools/db_crashtest.py

@@ -161,6 +161,7 @@ txn_params = {
     "use_txn" : 1,
     # Avoid lambda to set it once for the entire test
     "txn_write_policy": random.randint(0, 2),
+    "unordered_write": random.randint(0, 1),
     "disable_wal": 0,
     # OpenReadOnly after checkpoint is not currnetly compatible with WritePrepared txns
     "checkpoint_one_in": 0,
@@ -185,6 +186,10 @@ def finalize_and_sanitize(src_params):
             dest_params.get("use_txn") == 1:
         dest_params["delpercent"] += dest_params["delrangepercent"]
         dest_params["delrangepercent"] = 0
+    # Only under WritePrepared txns, unordered_write would provide the same guarnatees as vanilla rocksdb
+    if dest_params.get("unordered_write", 0) == 1:
+        dest_params["txn_write_policy"] = 1
+        dest_params["allow_concurrent_memtable_write"] = 1
     if dest_params.get("disable_wal", 0) == 1:
         dest_params["atomic_flush"] = 1
     if dest_params.get("open_files", 1) != -1: