fix DBImpl instance variable naming

Summary:
got confused while reading `FindObsoleteFiles` due to thinking it's a local variable, so renamed it properly
Closes https://github.com/facebook/rocksdb/pull/3342

Differential Revision: D6684797

Pulled By: ajkr

fbshipit-source-id: a4df0aae1cccce99d4dd4d164aadc85b17707132

db/db_impl.h

@@ -947,7 +947,7 @@ class DBImpl : public DB {
   // from the same write_thread_ without any locks.
   uint64_t logfile_number_;
   std::deque<uint64_t>
-      log_recycle_files;  // a list of log files that we can recycle
+      log_recycle_files_;  // a list of log files that we can recycle
   bool log_dir_synced_;
   // Without two_write_queues, read and writes to log_empty_ are protected by
   // mutex_. Since it is currently updated/read only in write_thread_, it can be

db/db_impl_files.cc

@@ -238,11 +238,11 @@ void DBImpl::FindObsoleteFiles(JobContext* job_context, bool force,
     while (alive_log_files_.begin()->number < min_log_number) {
       auto& earliest = *alive_log_files_.begin();
       if (immutable_db_options_.recycle_log_file_num >
-          log_recycle_files.size()) {
+          log_recycle_files_.size()) {
         ROCKS_LOG_INFO(immutable_db_options_.info_log,
                        "adding log %" PRIu64 " to recycle list\n",
                        earliest.number);
-        log_recycle_files.push_back(earliest.number);
+        log_recycle_files_.push_back(earliest.number);
       } else {
         job_context->log_delete_files.push_back(earliest.number);
       }
@@ -283,8 +283,8 @@ void DBImpl::FindObsoleteFiles(JobContext* job_context, bool force,
   // We're just cleaning up for DB::Write().
   assert(job_context->logs_to_free.empty());
   job_context->logs_to_free = logs_to_free_;
-  job_context->log_recycle_files.assign(log_recycle_files.begin(),
-                                        log_recycle_files.end());
+  job_context->log_recycle_files.assign(log_recycle_files_.begin(),
+                                        log_recycle_files_.end());
   logs_to_free_.clear();
 }
 

db/db_impl_write.cc

@@ -1215,9 +1215,9 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
   }
   uint64_t recycle_log_number = 0;
   if (creating_new_log && immutable_db_options_.recycle_log_file_num &&
-      !log_recycle_files.empty()) {
-    recycle_log_number = log_recycle_files.front();
-    log_recycle_files.pop_front();
+      !log_recycle_files_.empty()) {
+    recycle_log_number = log_recycle_files_.front();
+    log_recycle_files_.pop_front();
   }
   uint64_t new_log_number =
       creating_new_log ? versions_->NewFileNumber() : logfile_number_;