Add rate_limiter to string options

Summary: I want to be able to set this through mongo config.

Test Plan: added unit test

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D34599

db/db_impl.cc

@@ -133,7 +133,7 @@ DBOptions SanitizeOptions(const std::string& dbname, const DBOptions& src) {
   result.env->IncBackgroundThreadsIfNeeded(src.max_background_flushes,
                                            Env::Priority::HIGH);
 
-  if (!result.rate_limiter) {
+  if (result.rate_limiter.get() != nullptr) {
     if (result.bytes_per_sync == 0) {
       result.bytes_per_sync = 1024 * 1024;
     }

util/options_helper.cc

@@ -9,6 +9,7 @@
 #include "rocksdb/cache.h"
 #include "rocksdb/filter_policy.h"
 #include "rocksdb/options.h"
+#include "rocksdb/rate_limiter.h"
 #include "rocksdb/slice_transform.h"
 #include "rocksdb/table.h"
 #include "rocksdb/utilities/convenience.h"
@@ -474,6 +475,9 @@ bool ParseDBOption(const std::string& name, const std::string& value,
       new_options->error_if_exists = ParseBoolean(name, value);
     } else if (name == "paranoid_checks") {
       new_options->paranoid_checks = ParseBoolean(name, value);
+    } else if (name == "rate_limiter_bytes_per_sec") {
+      new_options->rate_limiter.reset(
+          NewGenericRateLimiter(static_cast<int64_t>(ParseUint64(value))));
     } else if (name == "max_open_files") {
       new_options->max_open_files = ParseInt(value);
     } else if (name == "max_total_wal_size") {

util/options_test.cc

@@ -480,7 +480,7 @@ TEST(OptionsTest, GetOptionsFromStringTest) {
       base_options,
       "write_buffer_size=10;max_write_buffer_number=16;"
       "block_based_table_factory={block_cache=1M;block_size=4;};"
-      "create_if_missing=true;max_open_files=1",
+      "create_if_missing=true;max_open_files=1;rate_limiter_bytes_per_sec=1024",
       &new_options));
 
   ASSERT_EQ(new_options.write_buffer_size, 10U);
@@ -495,6 +495,7 @@ TEST(OptionsTest, GetOptionsFromStringTest) {
 
   ASSERT_EQ(new_options.create_if_missing, true);
   ASSERT_EQ(new_options.max_open_files, 1);
+  ASSERT_TRUE(new_options.rate_limiter.get() != nullptr);
 }
 #endif  // !ROCKSDB_LITE