Print info message about files need compaction for debuging purpose

Summary:
When there are files marked for compaction after compactions, print extra messages to help debugging. Example:

2015/06/08-23:12:55.212855 7ff5013ff700 [default] [JOB 121] Generated table #75: 54 keys, 4807 bytes (need compaction)

2015/06/08-23:12:55.556194 7ff5013ff700 (Original Log Time 2015/06/08-23:12:55.556160) [default] compacted to: base level 1 max bytes base
10240 files[0 1 9 32 12 0 0 0] max score 0.96 (2 files need compaction), MB/sec: 0.0 rd, 0.1 wr, level 2, files in(1, 3) out(5) MB in(0.0,
0.0) out(0.0), read-write-amplify(11.3) write-amplify(5.7) OK, records in: 40, records dropped: 0

Test Plan:
Run test and see LOG files.

valgrind test DBTest.TablePropertiesNeedCompactTest

Reviewers: rven, yhchiang, kradhakrishnan, IslamAbdelRahman, igor

Reviewed By: igor

Subscribers: yoshinorim, maykov, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D39771

db/compaction_job.cc

@@ -1067,9 +1067,11 @@ Status CompactionJob::FinishCompactionOutputFile(Iterator* input) {
       info.job_id = job_id_;
       Log(InfoLogLevel::INFO_LEVEL, db_options_.info_log,
           "[%s] [JOB %d] Generated table #%" PRIu64 ": %" PRIu64
-          " keys, %" PRIu64 " bytes",
+          " keys, %" PRIu64 " bytes%s",
           cfd->GetName().c_str(), job_id_, output_number, current_entries,
-          current_bytes);
+          current_bytes,
+          compact_->current_output()->need_compaction ? " (need compaction)"
+                                                      : "");
       EventHelpers::LogAndNotifyTableFileCreation(
           event_logger_, cfd->ioptions()->listeners, fd, info);
     }

db/flush_job.cc

@@ -244,9 +244,12 @@ Status FlushJob::WriteLevel0Table(const autovector<MemTable*>& mems,
       LogFlush(db_options_.info_log);
     }
     Log(InfoLogLevel::INFO_LEVEL, db_options_.info_log,
-        "[%s] [JOB %d] Level-0 flush table #%" PRIu64 ": %" PRIu64 " bytes %s",
+        "[%s] [JOB %d] Level-0 flush table #%" PRIu64 ": %" PRIu64
+        " bytes %s"
+        "%s",
         cfd_->GetName().c_str(), job_context_->job_id, meta.fd.GetNumber(),
-        meta.fd.GetFileSize(), s.ToString().c_str());
+        meta.fd.GetFileSize(), s.ToString().c_str(),
+        meta.marked_for_compaction ? " (needs compaction)" : "");
 
     // output to event logger
     if (s.ok()) {

db/version_set.cc

@@ -1551,8 +1551,15 @@ const char* VersionStorageInfo::LevelSummary(
     // overwrite the last space
     --len;
   }
-  snprintf(scratch->buffer + len, sizeof(scratch->buffer) - len,
-           "] max score %.2f", compaction_score_[0]);
+  len += snprintf(scratch->buffer + len, sizeof(scratch->buffer) - len,
+                  "] max score %.2f", compaction_score_[0]);
+
+  if (!files_marked_for_compaction_.empty()) {
+    snprintf(scratch->buffer + len, sizeof(scratch->buffer) - len,
+             " (%zu files need compaction)",
+             files_marked_for_compaction_.size());
+  }
+
   return scratch->buffer;
 }