IOStatsContext::ToString() add option to exclude zero counters

Summary: similar to D52809 add option to exclude zero counters.

Test Plan:
[yiwu@dev4504.prn1 ~/rocksdb] ./iostats_context_test
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from IOStatsContextTest
[ RUN      ] IOStatsContextTest.ToString
[       OK ] IOStatsContextTest.ToString (0 ms)
[----------] 1 test from IOStatsContextTest (0 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (0 ms total)
[  PASSED  ] 1 test.

Reviewers: anthony, yhchiang, andrewkr, IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54591

2 files changed, 45 insertions, 13 deletions

diff --git a/util/iostats_context.cc b/util/iostats_context.cc
index 666fddcd1..a3c72db96 100644
--- a/util/iostats_context.cc
+++ b/util/iostats_context.cc
@@ -31,21 +31,24 @@ void IOStatsContext::Reset() {
   logger_nanos = 0;
 }
 
-#define IOSTATS_CONTEXT_OUTPUT(counter) #counter << " = " << counter << ", "
+#define IOSTATS_CONTEXT_OUTPUT(counter)         \
+  if (!exclude_zero_counters || counter > 0) {  \
+    ss << #counter << " = " << counter << ", "; \
+  }
 
-std::string IOStatsContext::ToString() const {
+std::string IOStatsContext::ToString(bool exclude_zero_counters) const {
   std::ostringstream ss;
-  ss << IOSTATS_CONTEXT_OUTPUT(thread_pool_id)
-     << IOSTATS_CONTEXT_OUTPUT(bytes_read)
-     << IOSTATS_CONTEXT_OUTPUT(bytes_written)
-     << IOSTATS_CONTEXT_OUTPUT(open_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(allocate_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(write_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(read_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(range_sync_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(fsync_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(prepare_write_nanos)
-     << IOSTATS_CONTEXT_OUTPUT(logger_nanos);
+  IOSTATS_CONTEXT_OUTPUT(thread_pool_id);
+  IOSTATS_CONTEXT_OUTPUT(bytes_read);
+  IOSTATS_CONTEXT_OUTPUT(bytes_written);
+  IOSTATS_CONTEXT_OUTPUT(open_nanos);
+  IOSTATS_CONTEXT_OUTPUT(allocate_nanos);
+  IOSTATS_CONTEXT_OUTPUT(write_nanos);
+  IOSTATS_CONTEXT_OUTPUT(read_nanos);
+  IOSTATS_CONTEXT_OUTPUT(range_sync_nanos);
+  IOSTATS_CONTEXT_OUTPUT(fsync_nanos);
+  IOSTATS_CONTEXT_OUTPUT(prepare_write_nanos);
+  IOSTATS_CONTEXT_OUTPUT(logger_nanos);
 
   return ss.str();
 }
diff --git a/util/iostats_context_test.cc b/util/iostats_context_test.cc
new file mode 100644
index 000000000..a2884f8a6
--- /dev/null
+++ b/util/iostats_context_test.cc
@@ -0,0 +1,29 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#include "rocksdb/iostats_context.h"
+#include "util/testharness.h"
+
+namespace rocksdb {
+
+TEST(IOStatsContextTest, ToString) {
+  iostats_context.Reset();
+  iostats_context.bytes_read = 12345;
+
+  std::string zero_included = iostats_context.ToString();
+  ASSERT_NE(std::string::npos, zero_included.find("= 0"));
+  ASSERT_NE(std::string::npos, zero_included.find("= 12345"));
+
+  std::string zero_excluded = iostats_context.ToString(true);
+  ASSERT_EQ(std::string::npos, zero_excluded.find("= 0"));
+  ASSERT_NE(std::string::npos, zero_excluded.find("= 12345"));
+}
+
+}  // namespace rocksdb
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}