SERVER-64659 Sorter::File accepts optional SorterFileStats for tracking file open/close operations

(cherry picked from commit 176747132c3be0b0e73adebf55ba4acf6211934f)

3 files changed, 51 insertions, 9 deletions

diff --git a/src/mongo/db/sorter/sorter.cpp b/src/mongo/db/sorter/sorter.cpp
index 39639153d7b..c5f6471c1d5 100644
--- a/src/mongo/db/sorter/sorter.cpp
+++ b/src/mongo/db/sorter/sorter.cpp
@@ -859,14 +859,15 @@ private:
 template <typename Key, typename Value>
 Sorter<Key, Value>::Sorter(const SortOptions& opts)
     : _opts(opts),
-      _file(opts.extSortAllowed
-                ? std::make_shared<Sorter<Key, Value>::File>(opts.tempDir + "/" + nextFileName())
-                : nullptr) {}
+      _file(opts.extSortAllowed ? std::make_shared<Sorter<Key, Value>::File>(
+                                      opts.tempDir + "/" + nextFileName(), opts.sorterFileStats)
+                                : nullptr) {}
 
 template <typename Key, typename Value>
 Sorter<Key, Value>::Sorter(const SortOptions& opts, const std::string& fileName)
     : _opts(opts),
-      _file(std::make_shared<Sorter<Key, Value>::File>(opts.tempDir + "/" + fileName)) {
+      _file(std::make_shared<Sorter<Key, Value>::File>(opts.tempDir + "/" + fileName,
+                                                       opts.sorterFileStats)) {
     invariant(opts.extSortAllowed);
     invariant(!opts.tempDir.empty());
     invariant(!fileName.empty());
@@ -874,6 +875,10 @@ Sorter<Key, Value>::Sorter(const SortOptions& opts, const std::string& fileName)
 
 template <typename Key, typename Value>
 Sorter<Key, Value>::File::~File() {
+    if (_stats && _file.is_open()) {
+        _stats->closed.addAndFetch(1);
+    }
+
     if (_keep) {
         return;
     }
@@ -964,6 +969,10 @@ void Sorter<Key, Value>::File::_open() {
             str::stream() << "Error opening file " << _path.string() << ": "
                           << sorter::myErrnoWithDescription(),
             _file.good());
+
+    if (_stats) {
+        _stats->opened.addAndFetch(1);
+    }
 }
 
 template <typename Key, typename Value>
diff --git a/src/mongo/db/sorter/sorter.h b/src/mongo/db/sorter/sorter.h
index aed12ffdfe2..440da3b54c3 100644
--- a/src/mongo/db/sorter/sorter.h
+++ b/src/mongo/db/sorter/sorter.h
@@ -40,6 +40,7 @@
 #include <vector>
 
 #include "mongo/bson/util/builder.h"
+#include "mongo/platform/atomic_word.h"
 #include "mongo/util/bufreader.h"
 
 /**
@@ -91,6 +92,14 @@
 namespace mongo {
 
 /**
+ * For collecting file usage metrics.
+ */
+struct SorterFileStats {
+    AtomicWord<long long> opened;
+    AtomicWord<long long> closed;
+};
+
+/**
  * Runtime options that control the Sorter's behavior
  */
 struct SortOptions {
@@ -108,7 +117,14 @@ struct SortOptions {
     // extSortAllowed is true.
     std::string tempDir;
 
-    SortOptions() : limit(0), maxMemoryUsageBytes(64 * 1024 * 1024), extSortAllowed(false) {}
+    // If set, allows us to observe Sorter file handle usage.
+    SorterFileStats* sorterFileStats;
+
+    SortOptions()
+        : limit(0),
+          maxMemoryUsageBytes(64 * 1024 * 1024),
+          extSortAllowed(false),
+          sorterFileStats(nullptr) {}
 
     // Fluent API to support expressions like SortOptions().Limit(1000).ExtSortAllowed(true)
 
@@ -131,6 +147,11 @@ struct SortOptions {
         tempDir = newTempDir;
         return *this;
     }
+
+    SortOptions& FileStats(SorterFileStats* newSorterFileStats) {
+        sorterFileStats = newSorterFileStats;
+        return *this;
+    }
 };
 
 /**
@@ -219,7 +240,8 @@ public:
      */
     class File {
     public:
-        File(std::string path) : _path(std::move(path)) {
+        File(std::string path, SorterFileStats* stats = nullptr)
+            : _path(std::move(path)), _stats(stats) {
             invariant(!_path.empty());
         }
 
@@ -266,6 +288,9 @@ public:
 
         // Whether to keep the on-disk file even after this in-memory object has been destructed.
         bool _keep = false;
+
+        // If set, this points to an external metrics holder for tracking file open/close activity.
+        SorterFileStats* _stats;
     };
 
     explicit Sorter(const SortOptions& opts);
diff --git a/src/mongo/db/sorter/sorter_test.cpp b/src/mongo/db/sorter/sorter_test.cpp
index bda75dc17af..2d23292f439 100644
--- a/src/mongo/db/sorter/sorter_test.cpp
+++ b/src/mongo/db/sorter/sorter_test.cpp
@@ -284,10 +284,11 @@ class SortedFileWriterAndFileIteratorTests : public ScopedGlobalServiceContextFo
 public:
     void run() {
         unittest::TempDir tempDir("sortedFileWriterTests");
-        const SortOptions opts = SortOptions().TempDir(tempDir.path());
+        SorterFileStats sorterFileStats;
+        const SortOptions opts = SortOptions().TempDir(tempDir.path()).FileStats(&sorterFileStats);
         auto makeFile = [&] {
-            return std::make_shared<Sorter<IntWrapper, IntWrapper>::File>(opts.tempDir + "/" +
-                                                                          nextFileName());
+            return std::make_shared<Sorter<IntWrapper, IntWrapper>::File>(
+                opts.tempDir + "/" + nextFileName(), opts.sorterFileStats);
         };
 
         {  // small
@@ -300,6 +301,10 @@ public:
             ASSERT_ITERATORS_EQUIVALENT(std::shared_ptr<IWIterator>(sorter.done()),
                                         std::make_shared<IntIterator>(0, 5));
         }
+
+        ASSERT_EQ(sorterFileStats.opened.load(), 1);
+        ASSERT_EQ(sorterFileStats.closed.load(), 1);
+
         {  // big
             SortedFileWriter<IntWrapper, IntWrapper> sorter(opts, makeFile());
             for (int i = 0; i < 10 * 1000 * 1000; i++)
@@ -309,6 +314,9 @@ public:
                                         std::make_shared<IntIterator>(0, 10 * 1000 * 1000));
         }
 
+        ASSERT_EQ(sorterFileStats.opened.load(), 2);
+        ASSERT_EQ(sorterFileStats.closed.load(), 2);
+
         ASSERT(boost::filesystem::is_empty(tempDir.path()));
     }
 };