Add SetLockTimeout for Transactions

Summary: MyRocks wants to be able to change the lock timeout of a transaction that has already started.  Expose existing SetLockTimeout function to users.

Test Plan: unit test

Reviewers: spetrunia, rven, sdong, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D45987

include/rocksdb/utilities/transaction.h

@@ -258,6 +258,11 @@ class Transaction {
   // write to this transaction.
   virtual WriteBatchWithIndex* GetWriteBatch() = 0;
 
+  // Change the value of TransactionOptions.lock_timeout (in milliseconds) for
+  // this transaction.
+  // Has no effect on OptimisticTransactions.
+  virtual void SetLockTimeout(int64_t timeout) = 0;
+
  protected:
   explicit Transaction(const TransactionDB* db) {}
   Transaction() {}

utilities/transactions/transaction_base.h

@@ -146,6 +146,9 @@ class TransactionBaseImpl : public Transaction {
 
   WriteBatchWithIndex* GetWriteBatch() override;
 
+  virtual void SetLockTimeout(int64_t timeout) override { /* Do nothing */
+  }
+
   const Snapshot* GetSnapshot() const override {
     return snapshot_ ? snapshot_->snapshot() : nullptr;
   }

utilities/transactions/transaction_impl.h

@@ -60,7 +60,7 @@ class TransactionImpl : public TransactionBaseImpl {
   // Returns the number of milliseconds a transaction can wait on acquiring a
   // lock or -1 if there is no timeout.
   int64_t GetLockTimeout() const { return lock_timeout_; }
-  void SetLockTimeout(int64_t timeout) { lock_timeout_ = timeout; }
+  void SetLockTimeout(int64_t timeout) override { lock_timeout_ = timeout; }
 
  protected:
   Status TryLock(ColumnFamilyHandle* column_family, const Slice& key,

utilities/transactions/transaction_test.cc

@@ -1530,7 +1530,9 @@ TEST_F(TransactionTest, TimeoutTest) {
 
   delete txn1;
   txn_options.expiration = 6000000;  // 100 minutes
+  txn_options.lock_timeout = 1;      // 1ms
   txn1 = db->BeginTransaction(write_options, txn_options);
+  txn1->SetLockTimeout(100);
 
   TransactionOptions txn_options2;
   txn_options2.expiration = 10;  // 10ms