SERVER-53216 Report number of databases in resource consumption serverStatus section

3 files changed, 51 insertions, 21 deletions

diff --git a/jstests/noPassthrough/aggregate_operation_metrics.js b/jstests/noPassthrough/aggregate_operation_metrics.js
index a1b1ff7a2cc..62533397cf7 100644
--- a/jstests/noPassthrough/aggregate_operation_metrics.js
+++ b/jstests/noPassthrough/aggregate_operation_metrics.js
@@ -57,10 +57,10 @@ let getDBMetrics = (adminDB) => {
     return allMetrics;
 };
 
-let getGlobalCpuTime = (db) => {
-    let ss = db.serverStatus({resourceConsumption: true});
+let getServerStatusMetrics = (db) => {
+    let ss = db.serverStatus();
     assert(ss.hasOwnProperty('resourceConsumption'), ss);
-    return ss.resourceConsumption.cpuNanos;
+    return ss.resourceConsumption;
 };
 
 // Perform very basic reads and writes on two different databases.
@@ -75,10 +75,6 @@ const db2 = primary.getDB(db2Name);
 assert.commandWorked(db2.coll1.insert({a: 1}));
 assert.commandWorked(db2.coll2.insert({a: 1}));
 
-// The 'resourceConsumption' field should not be included in serverStatus by default.
-let ss = db1.serverStatus();
-assert(!ss.hasOwnProperty('resourceConsumption'), ss);
-
 const secondary = rst.getSecondary();
 [primary, secondary].forEach(function(node) {
     jsTestLog("Testing node: " + node);
@@ -88,7 +84,7 @@ const secondary = rst.getSecondary();
     rst.awaitReplication();
     const adminDB = node.getDB('admin');
 
-    let initialCpuTime = getGlobalCpuTime(adminDB);
+    let initialCpuTime = getServerStatusMetrics(adminDB).cpuNanos;
 
     adminDB.aggregate([{$operationMetrics: {clearMetrics: true}}]);
 
@@ -117,6 +113,10 @@ const secondary = rst.getSecondary();
     assertMetricsExist(allMetrics[db1Name]);
     assertMetricsExist(allMetrics[db2Name]);
 
+    let ssMetrics = getServerStatusMetrics(adminDB);
+    assert.eq(ssMetrics.numMetrics, 2);
+    assert.gt(ssMetrics.memUsage, 0);
+
     // Ensure read metrics are attributed to the correct replication state.
     let lastDocBytesRead;
     if (node === primary) {
@@ -148,7 +148,7 @@ const secondary = rst.getSecondary();
     // CPU time aggregation is only supported on Linux.
     if (isLinux) {
         // Ensure the CPU time is increasing.
-        let lastCpuTime = getGlobalCpuTime(adminDB);
+        let lastCpuTime = getServerStatusMetrics(adminDB).cpuNanos;
         assert.gt(lastCpuTime, initialCpuTime);
 
         // Ensure the global CPU time matches the aggregated time for both databases.
@@ -207,6 +207,16 @@ const secondary = rst.getSecondary();
     cursor = adminDB.aggregate([{$operationMetrics: {}}]);
     assert.eq(cursor.itcount(), 0);
 
+    // Ensure the serverStatus metrics are cleared except for cpuNanos.
+    ssMetrics = getServerStatusMetrics(adminDB);
+    assert.eq(0, ssMetrics.numMetrics);
+    assert.eq(0, ssMetrics.memUsage);
+    if (isLinux) {
+        assert.neq(0, ssMetrics.cpuNanos);
+    } else {
+        assert.eq(0, ssMetrics.cpuNanos);
+    }
+
     // Insert something and ensure metrics are still reporting.
     assert.commandWorked(db1.coll3.insert({a: 1}));
     rst.awaitReplication();
diff --git a/src/mongo/db/stats/resource_consumption_metrics.cpp b/src/mongo/db/stats/resource_consumption_metrics.cpp
index 49c879cb272..fbc53138f3c 100644
--- a/src/mongo/db/stats/resource_consumption_metrics.cpp
+++ b/src/mongo/db/stats/resource_consumption_metrics.cpp
@@ -45,21 +45,23 @@ const OperationContext::Decoration<ResourceConsumption::MetricsCollector> getMet
 const ServiceContext::Decoration<ResourceConsumption> getGlobalResourceConsumption =
     ServiceContext::declareDecoration<ResourceConsumption>();
 
-static const char kPrimaryMetrics[] = "primaryMetrics";
-static const char kSecondaryMetrics[] = "secondaryMetrics";
+static const char kCpuNanos[] = "cpuNanos";
+static const char kCursorSeeks[] = "cursorSeeks";
 static const char kDocBytesRead[] = "docBytesRead";
+static const char kDocBytesWritten[] = "docBytesWritten";
 static const char kDocUnitsRead[] = "docUnitsRead";
+static const char kDocUnitsReturned[] = "docUnitsReturned";
+static const char kDocUnitsWritten[] = "docUnitsWritten";
 static const char kIdxEntryBytesRead[] = "idxEntryBytesRead";
+static const char kIdxEntryBytesWritten[] = "idxEntryBytesWritten";
 static const char kIdxEntryUnitsRead[] = "idxEntryUnitsRead";
+static const char kIdxEntryUnitsWritten[] = "idxEntryUnitsWritten";
 static const char kKeysSorted[] = "keysSorted";
+static const char kMemUsage[] = "memUsage";
+static const char kNumMetrics[] = "numMetrics";
+static const char kPrimaryMetrics[] = "primaryMetrics";
+static const char kSecondaryMetrics[] = "secondaryMetrics";
 static const char kSorterSpills[] = "sorterSpills";
-static const char kCpuNanos[] = "cpuNanos";
-static const char kDocBytesWritten[] = "docBytesWritten";
-static const char kDocUnitsWritten[] = "docUnitsWritten";
-static const char kIdxEntryBytesWritten[] = "idxEntryBytesWritten";
-static const char kIdxEntryUnitsWritten[] = "idxEntryUnitsWritten";
-static const char kDocUnitsReturned[] = "docUnitsReturned";
-static const char kCursorSeeks[] = "cursorSeeks";
 
 inline void appendNonZeroMetric(BSONObjBuilder* builder, const char* name, long long value) {
     if (value != 0) {
@@ -74,10 +76,10 @@ class ResourceConsumptionSSS : public ServerStatusSection {
 public:
     ResourceConsumptionSSS() : ServerStatusSection("resourceConsumption") {}
 
-    // Do not include this metric by default. It is likely to be misleading for diagnostic purposes
-    // because it does not include the CPU time for every operation or every command.
+    // Do not include this section unless metrics aggregation is enabled. It will not have populated
+    // data otherwise.
     bool includeByDefault() const override {
-        return false;
+        return ResourceConsumption::isMetricsAggregationEnabled();
     }
 
     BSONObj generateSection(OperationContext* opCtx, const BSONElement& configElem) const override {
@@ -87,6 +89,14 @@ public:
         }
         BSONObjBuilder builder;
         builder.append(kCpuNanos, durationCount<Nanoseconds>(resourceConsumption.getCpuTime()));
+
+        // The memory usage we report only estimates the amount of memory from the metrics
+        // themselves, and does not include the overhead of the map container or its keys.
+        auto numMetrics = resourceConsumption.getNumDbMetrics();
+        builder.append(
+            kMemUsage,
+            static_cast<long long>(numMetrics * sizeof(ResourceConsumption::AggregatedMetrics)));
+        builder.append(kNumMetrics, static_cast<long long>(numMetrics));
         return builder.obj();
     }
 } resourceConsumptionMetricSSM;
@@ -334,6 +344,11 @@ ResourceConsumption::MetricsMap ResourceConsumption::getDbMetrics() const {
     return _dbMetrics;
 }
 
+size_t ResourceConsumption::getNumDbMetrics() const {
+    stdx::lock_guard<Mutex> lk(_mutex);
+    return _dbMetrics.size();
+}
+
 ResourceConsumption::MetricsMap ResourceConsumption::getAndClearDbMetrics() {
     stdx::lock_guard<Mutex> lk(_mutex);
     MetricsMap newMap;
diff --git a/src/mongo/db/stats/resource_consumption_metrics.h b/src/mongo/db/stats/resource_consumption_metrics.h
index 1dc401aef88..5e098b5c730 100644
--- a/src/mongo/db/stats/resource_consumption_metrics.h
+++ b/src/mongo/db/stats/resource_consumption_metrics.h
@@ -450,6 +450,11 @@ public:
     MetricsMap getDbMetrics() const;
 
     /**
+     *  Returns the number of databases with aggregated metrics.
+     */
+    size_t getNumDbMetrics() const;
+
+    /**
      * Returns the per-database metrics map and then clears the contents. This attempts to swap and
      * return the metrics map rather than making a full copy like getDbMetrics.
      */