SERVER-15395 Remove lock stats from web interface

3 files changed, 46 insertions, 57 deletions

diff --git a/src/mongo/db/stats/snapshots.cpp b/src/mongo/db/stats/snapshots.cpp
index ccae800a0f5..addf361bcb6 100644
--- a/src/mongo/db/stats/snapshots.cpp
+++ b/src/mongo/db/stats/snapshots.cpp
@@ -62,7 +62,8 @@ namespace mongo {
         verify( _newer._created > _older._created );
         Top::UsageMap u;
 
-        for ( Top::UsageMap::const_iterator i=_newer._usage.begin(); i != _newer._usage.end(); ++i ) {
+        for ( Top::UsageMap::const_iterator i=_newer._usage.begin();
+              i != _newer._usage.end(); ++i ) {
             Top::UsageMap::const_iterator j = _older._usage.find(i->first);
             if (j != _older._usage.end())
                 u[i->first] = Top::CollectionData( j->second , i->second );
@@ -72,55 +73,52 @@ namespace mongo {
         return u;
     }
 
-    Snapshots::Snapshots(int n)
-        : _n(n)
-        , _snapshots(new SnapshotData[n])
-        , _loc(0)
+    Snapshots::Snapshots()
+        : _loc(0)
         , _stored(0)
     {}
 
     const SnapshotData* Snapshots::takeSnapshot() {
         boost::lock_guard<boost::mutex> lk(_lock);
-        _loc = ( _loc + 1 ) % _n;
+        _loc = ( _loc + 1 ) % kNumSnapshots;
         _snapshots[_loc].takeSnapshot();
-        if ( _stored < _n )
+        if ( _stored < kNumSnapshots )
             _stored++;
         return &_snapshots[_loc];
     }
 
-    auto_ptr<SnapshotDelta> Snapshots::computeDelta( int numBack ) {
+    StatusWith<SnapshotDiff> Snapshots::computeDelta() {
         boost::lock_guard<boost::mutex> lk(_lock);
-        auto_ptr<SnapshotDelta> p;
-        if ( numBack < numDeltas() )
-            p.reset( new SnapshotDelta( getPrev(numBack+1) , getPrev(numBack) ) );
-        return p;
-    }
 
-    const SnapshotData& Snapshots::getPrev( int numBack ) {
-        int x = _loc - numBack;
-        if ( x < 0 )
-            x += _n;
-        return _snapshots[x];
+        // We need 2 snapshots to calculate a delta
+        if (_stored < 2) {
+            return StatusWith<SnapshotDiff>(ErrorCodes::BadValue, 
+                                            "Less than 2 snapshots exist");
+        }
+
+        // The following logic depends on there being exactly 2 stored snapshots
+        BOOST_STATIC_ASSERT(kNumSnapshots == 2);
+
+        // Current and previous napshot alternates between indexes 0 and 1
+        int currIdx = _loc;
+        int prevIdx = _loc > 0 ? 0 : 1;
+        SnapshotDelta delta(_snapshots[prevIdx], _snapshots[currIdx]);
+
+        return SnapshotDiff(delta.collectionUsageDiff(), delta.elapsed());
     }
 
     void SnapshotThread::run() {
         Client::initThread("snapshot");
         Client& client = cc();
 
-        long long numLoops = 0;
-
-        const SnapshotData* prev = 0;
-
         while ( ! inShutdown() ) {
             try {
-                const SnapshotData* s = statsSnapshots.takeSnapshot();
-                prev = s;
+                statsSnapshots.takeSnapshot();
             }
             catch ( std::exception& e ) {
                 log() << "ERROR in SnapshotThread: " << e.what() << endl;
             }
 
-            numLoops++;
             sleepsecs(4);
         }
 
diff --git a/src/mongo/db/stats/snapshots.h b/src/mongo/db/stats/snapshots.h
index 59240c9bfea..9c29e7d5eb6 100644
--- a/src/mongo/db/stats/snapshots.h
+++ b/src/mongo/db/stats/snapshots.h
@@ -29,9 +29,11 @@
 */
 
 #pragma once
-#include "mongo/platform/basic.h"
+
+#include "mongo/base/status_with.h"
 #include "mongo/db/jsobj.h"
-#include "top.h"
+#include "mongo/db/stats/top.h"
+#include "mongo/platform/basic.h"
 #include "mongo/util/background.h"
 
 /**
@@ -63,10 +65,6 @@ namespace mongo {
     public:
         SnapshotDelta( const SnapshotData& older , const SnapshotData& newer );
 
-        unsigned long long start() const {
-            return _older._created;
-        }
-
         unsigned long long elapsed() const {
             return _elapsed;
         }
@@ -80,21 +78,27 @@ namespace mongo {
         unsigned long long _elapsed;
     };
 
+    struct SnapshotDiff {
+        Top::UsageMap usageDiff;
+        unsigned long long timeElapsed;
+
+        SnapshotDiff() = default;
+        SnapshotDiff(Top::UsageMap map, unsigned long long elapsed)
+            : usageDiff(std::move(map)), timeElapsed(elapsed) {}
+    };
+
     class Snapshots {
     public:
-        Snapshots(int n=100);
+        Snapshots();
 
         const SnapshotData* takeSnapshot();
 
-        int numDeltas() const { return _stored-1; }
-
-        const SnapshotData& getPrev( int numBack = 0 );
-        std::auto_ptr<SnapshotDelta> computeDelta( int numBack = 0 );
+        StatusWith<SnapshotDiff> computeDelta();
 
     private:
         mongo::mutex _lock;
-        int _n;
-        boost::scoped_array<SnapshotData> _snapshots;
+        static const int kNumSnapshots = 2;
+        SnapshotData _snapshots[kNumSnapshots];
         int _loc;
         int _stored;
     };
diff --git a/src/mongo/db/stats/snapshots_webplugins.cpp b/src/mongo/db/stats/snapshots_webplugins.cpp
index 281ed1dbf5c..cc604c6e983 100644
--- a/src/mongo/db/stats/snapshots_webplugins.cpp
+++ b/src/mongo/db/stats/snapshots_webplugins.cpp
@@ -38,26 +38,11 @@ namespace {
 
     using namespace html;
 
-    using std::auto_ptr;
     using std::fixed;
     using std::setprecision;
     using std::string;
     using std::stringstream;
 
-    class WriteLockStatus : public WebStatusPlugin {
-    public:
-        WriteLockStatus() : WebStatusPlugin( "write lock" , 51 , "% time in write lock, by 4 sec periods" ) {}
-        virtual void init() {}
-
-        virtual void run(OperationContext* txn, stringstream& ss) {
-            ss << "<a "
-               "href=\"http://dochub.mongodb.org/core/concurrency\" "
-               "title=\"snapshot: was the db in the write lock when this page was generated?\">";
-            ss << "write locked now:</a> " << (txn->lockState()->isW() ? "true" : "false") << "\n";
-        }
-
-    } writeLockStatus;
-
     class DBTopStatus : public WebStatusPlugin {
     public:
         DBTopStatus() : WebStatusPlugin( "dbtop" , 50 , "(occurrences|percent of elapsed)" ) {}
@@ -95,8 +80,9 @@ namespace {
         }
 
         void run(OperationContext* txn, stringstream& ss) {
-            auto_ptr<SnapshotDelta> delta = statsSnapshots.computeDelta();
-            if ( ! delta.get() )
+            StatusWith<SnapshotDiff> diff = statsSnapshots.computeDelta();
+
+            if ( ! diff.isOK() )
                 return;
 
             ss << "<table border=1 cellpadding=2 cellspacing=0>";
@@ -113,9 +99,10 @@ namespace {
                "<th colspan=2>Removes</th>";
             ss << "</tr>\n";
 
-            Top::UsageMap usage = delta->collectionUsageDiff();
+            const Top::UsageMap& usage = diff.getValue().usageDiff;
+            unsigned long long elapsed = diff.getValue().timeElapsed;
             for ( Top::UsageMap::const_iterator i=usage.begin(); i != usage.end(); ++i ) {
-                display( ss , (double) delta->elapsed() , i->first , i->second );
+                display( ss , (double) elapsed , i->first , i->second );
             }
 
             ss << "</table>";