Add some async read stats (#10947)

Summary:
Add stats for time spent in the ReadAsync call, and async read errors.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10947

Test Plan: Run db_bench and look at stats

Reviewed By: akankshamahajan15

Differential Revision: D41236637

Pulled By: anand1976

fbshipit-source-id: 70539b69a28491d57acead449436a761f7108acf

HISTORY.md

@@ -13,6 +13,7 @@
 
 ### New Features
 * Add basic support for user-defined timestamp to Merge (#10819).
+* Add stats for ReadAsync time spent and async read errors.
 
 ### Public API Changes
 * Marked `block_cache_compressed` as a deprecated feature. Use SecondaryCache instead.

file/random_access_file_reader.cc

@@ -471,6 +471,7 @@ IOStatus RandomAccessFileReader::ReadAsync(
                     (uintptr_t(req.scratch) & (alignment - 1)) == 0;
   read_async_info->is_aligned_ = is_aligned;
 
+  uint64_t elapsed = 0;
   if (use_direct_io() && is_aligned == false) {
     FSReadRequest aligned_req = Align(req, alignment);
     aligned_req.status.PermitUncheckedError();
@@ -491,12 +492,17 @@ IOStatus RandomAccessFileReader::ReadAsync(
 
     assert(read_async_info->buf_.CurrentSize() == 0);
 
+    StopWatch sw(clock_, nullptr /*stats*/, 0 /*hist_type*/, &elapsed,
+                 true /*overwrite*/, true /*delay_enabled*/);
     s = file_->ReadAsync(aligned_req, opts, read_async_callback,
                          read_async_info, io_handle, del_fn, nullptr /*dbg*/);
   } else {
+    StopWatch sw(clock_, nullptr /*stats*/, 0 /*hist_type*/, &elapsed,
+                 true /*overwrite*/, true /*delay_enabled*/);
     s = file_->ReadAsync(req, opts, read_async_callback, read_async_info,
                          io_handle, del_fn, nullptr /*dbg*/);
   }
+  RecordTick(stats_, READ_ASYNC_MICROS, elapsed);
 
 // Suppress false positive clang analyzer warnings.
 // Memory is not released if file_->ReadAsync returns !s.ok(), because
@@ -575,6 +581,8 @@ void RandomAccessFileReader::ReadAsyncCallback(const FSReadRequest& req,
   }
   if (req.status.ok()) {
     RecordInHistogram(stats_, ASYNC_READ_BYTES, req.result.size());
+  } else if (!req.status.IsAborted()) {
+    RecordTick(stats_, ASYNC_READ_ERROR_COUNT, 1);
   }
 #ifndef ROCKSDB_LITE
   if (ShouldNotifyListeners()) {

include/rocksdb/statistics.h

@@ -448,6 +448,11 @@ enum Tickers : uint32_t {
   // # of bytes written into blob cache.
   BLOB_DB_CACHE_BYTES_WRITE,
 
+  // Time spent in the ReadAsync file system call
+  READ_ASYNC_MICROS,
+  // Number of errors returned to the async read callback
+  ASYNC_READ_ERROR_COUNT,
+
   TICKER_ENUM_MAX
 };
 

java/rocksjni/portal.h

@@ -5151,6 +5151,10 @@ class TickerTypeJni {
         return -0x33;
       case ROCKSDB_NAMESPACE::Tickers::BLOB_DB_CACHE_BYTES_WRITE:
         return -0x34;
+      case ROCKSDB_NAMESPACE::Tickers::READ_ASYNC_MICROS:
+        return -0x35;
+      case ROCKSDB_NAMESPACE::Tickers::ASYNC_READ_ERROR_COUNT:
+        return -0x36;
       case ROCKSDB_NAMESPACE::Tickers::TICKER_ENUM_MAX:
         // 0x5F was the max value in the initial copy of tickers to Java.
         // Since these values are exposed directly to Java clients, we keep
@@ -5534,6 +5538,10 @@ class TickerTypeJni {
         return ROCKSDB_NAMESPACE::Tickers::BLOB_DB_CACHE_BYTES_READ;
       case -0x34:
         return ROCKSDB_NAMESPACE::Tickers::BLOB_DB_CACHE_BYTES_WRITE;
+      case -0x35:
+        return ROCKSDB_NAMESPACE::Tickers::READ_ASYNC_MICROS;
+      case -0x36:
+        return ROCKSDB_NAMESPACE::Tickers::ASYNC_READ_ERROR_COUNT;
       case 0x5F:
         // 0x5F was the max value in the initial copy of tickers to Java.
         // Since these values are exposed directly to Java clients, we keep

monitoring/statistics.cc

@@ -233,7 +233,9 @@ const std::vector<std::pair<Tickers, std::string>> TickersNameMap = {
     {BLOB_DB_CACHE_ADD, "rocksdb.blobdb.cache.add"},
     {BLOB_DB_CACHE_ADD_FAILURES, "rocksdb.blobdb.cache.add.failures"},
     {BLOB_DB_CACHE_BYTES_READ, "rocksdb.blobdb.cache.bytes.read"},
-    {BLOB_DB_CACHE_BYTES_WRITE, "rocksdb.blobdb.cache.bytes.write"}};
+    {BLOB_DB_CACHE_BYTES_WRITE, "rocksdb.blobdb.cache.bytes.write"},
+    {READ_ASYNC_MICROS, "rocksdb.read.async.micros"},
+    {ASYNC_READ_ERROR_COUNT, "rocksdb.async.read.error.count"}};
 
 const std::vector<std::pair<Histograms, std::string>> HistogramsNameMap = {
     {DB_GET, "rocksdb.db.get.micros"},