MOD: trim last space and comma in perf context and iostat context ToString()

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/5755

Differential Revision: D17165190

Pulled By: riversand963

fbshipit-source-id: a3a4633961bfe019bf360f97a4c4d36464e7fa0b

monitoring/iostats_context.cc

@@ -54,7 +54,9 @@ std::string IOStatsContext::ToString(bool exclude_zero_counters) const {
   IOSTATS_CONTEXT_OUTPUT(prepare_write_nanos);
   IOSTATS_CONTEXT_OUTPUT(logger_nanos);
 
-  return ss.str();
+  std::string str = ss.str();
+  str.erase(str.find_last_not_of(", ") + 1);
+  return str;
 }
 
 }  // namespace rocksdb

monitoring/perf_context.cc

@@ -529,7 +529,10 @@ std::string PerfContext::ToString(bool exclude_zero_counters) const {
   PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(bloom_filter_full_true_positive);
   PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(block_cache_hit_count);
   PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(block_cache_miss_count);
-  return ss.str();
+
+  std::string str = ss.str();
+  str.erase(str.find_last_not_of(", ") + 1);
+  return str;
 #endif
 }