Enable all txn write policies in crash test (#6158)

Summary:
Currently the default txn write policy in crash tests is WRITE_PREPARED. The patch randomly picks the write policy at the start of the crash test.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6158

Test Plan:
```
make -j32 crash_test_with_txn
```

Differential Revision: D18946307

Pulled By: maysamyabandeh

fbshipit-source-id: f77d7a94f99a08791ef9626da153d284bf521950

db_stress_tool/db_stress_common.h

@@ -161,6 +161,7 @@ DECLARE_int32(range_deletion_width);
 DECLARE_uint64(rate_limiter_bytes_per_sec);
 DECLARE_bool(rate_limit_bg_reads);
 DECLARE_bool(use_txn);
+DECLARE_uint64(txn_write_policy);
 DECLARE_int32(backup_one_in);
 DECLARE_int32(checkpoint_one_in);
 DECLARE_int32(ingest_external_file_one_in);

db_stress_tool/db_stress_gflags.cc

@@ -371,6 +371,11 @@ DEFINE_bool(use_txn, false,
             "Use TransactionDB. Currently the default write policy is "
             "TxnDBWritePolicy::WRITE_PREPARED");
 
+DEFINE_uint64(txn_write_policy, 0,
+              "The transaction write policy. Default is "
+              "TxnDBWritePolicy::WRITE_COMMITTED. Note that this should not be "
+              "changed accross crashes.");
+
 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

@@ -1671,8 +1671,9 @@ void StressTest::Open() {
     } else {
 #ifndef ROCKSDB_LITE
       TransactionDBOptions txn_db_options;
-      // For the moment it is sufficient to test WRITE_PREPARED policy
-      txn_db_options.write_policy = TxnDBWritePolicy::WRITE_PREPARED;
+      assert(FLAGS_txn_write_policy <= TxnDBWritePolicy::WRITE_UNPREPARED);
+      txn_db_options.write_policy =
+          static_cast<TxnDBWritePolicy>(FLAGS_txn_write_policy);
       s = TransactionDB::Open(options_, txn_db_options, FLAGS_db,
                               cf_descriptors, &column_families_, &txn_db_);
       db_ = txn_db_;

include/rocksdb/utilities/transaction_db.h

@@ -25,9 +25,7 @@ class TransactionDBMutexFactory;
 
 enum TxnDBWritePolicy {
   WRITE_COMMITTED = 0,  // write only the committed data
-  // TODO(myabandeh): Not implemented yet
   WRITE_PREPARED,  // write data after the prepare phase of 2pc
-  // TODO(myabandeh): Not implemented yet
   WRITE_UNPREPARED  // write data before the prepare phase of 2pc
 };
 

tools/db_crashtest.py

@@ -159,6 +159,8 @@ cf_consistency_params = {
 
 txn_params = {
     "use_txn" : 1,
+    # Avoid lambda to set it once for the entire test
+    "txn_write_policy": random.randint(0, 2),
     "disable_wal": 0,
     # OpenReadOnly after checkpoint is not currnetly compatible with WritePrepared txns
     "checkpoint_one_in": 0,