Fix the potential memory leak in trace_replay (#5955)

Summary:
In the previous PR https://github.com/facebook/rocksdb/issues/5934 , in the while loop, if/else if is used without ending with else to free the object referenced by ra, it might cause potential memory leak (warning during compiling). Fix it by changing the last "else if" to "else".
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5955

Test Plan: pass make asan check, pass the USE_CLANG=1 TEST_TMPDIR=/dev/shm/rocksdb OPT=-g make -j64 analyze.

Differential Revision: D18071612

Pulled By: zhichao-cao

fbshipit-source-id: 51c00023d0c97c2921507254329aed55d56e1786

trace_replay/trace_replay.cc

@@ -315,11 +315,10 @@ Status Replayer::MultiThreadReplay(uint32_t threads_num) {
   ReadOptions roptions;
   uint64_t ops = 0;
   while (s.ok()) {
-    ReplayerWorkerArg* ra = new ReplayerWorkerArg;
+    std::unique_ptr<ReplayerWorkerArg> ra(new ReplayerWorkerArg);
     ra->db = db_;
     s = ReadTrace(&(ra->trace_entry));
     if (!s.ok()) {
-      delete ra;
       break;
     }
     ra->woptions = woptions;
@@ -329,23 +328,29 @@ Status Replayer::MultiThreadReplay(uint32_t threads_num) {
         replay_epoch + std::chrono::microseconds(
                            (ra->trace_entry.ts - header.ts) / fast_forward_));
     if (ra->trace_entry.type == kTraceWrite) {
-      thread_pool.Schedule(&Replayer::BGWorkWriteBatch, ra, nullptr, nullptr);
+      thread_pool.Schedule(&Replayer::BGWorkWriteBatch, ra.release(), nullptr,
+                           nullptr);
       ops++;
     } else if (ra->trace_entry.type == kTraceGet) {
-      thread_pool.Schedule(&Replayer::BGWorkGet, ra, nullptr, nullptr);
+      thread_pool.Schedule(&Replayer::BGWorkGet, ra.release(), nullptr,
+                           nullptr);
       ops++;
     } else if (ra->trace_entry.type == kTraceIteratorSeek) {
-      thread_pool.Schedule(&Replayer::BGWorkIterSeek, ra, nullptr, nullptr);
+      thread_pool.Schedule(&Replayer::BGWorkIterSeek, ra.release(), nullptr,
+                           nullptr);
       ops++;
     } else if (ra->trace_entry.type == kTraceIteratorSeekForPrev) {
-      thread_pool.Schedule(&Replayer::BGWorkIterSeekForPrev, ra, nullptr,
-                           nullptr);
+      thread_pool.Schedule(&Replayer::BGWorkIterSeekForPrev, ra.release(),
+                           nullptr, nullptr);
       ops++;
     } else if (ra->trace_entry.type == kTraceEnd) {
       // Do nothing for now.
       // TODO: Add some validations later.
-      delete ra;
       break;
+    } else {
+      // Other trace entry types that are not implemented for replay.
+      // To finish the replay, we continue the process.
+      continue;
     }
   }