path: root/src/mongo/db/curop.h

// @file curop.h

/*
 *    Copyright (C) 2010 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */


#pragma once

#include <boost/noncopyable.hpp>

#include "mongo/base/disallow_copying.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/server_options.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/util/concurrency/spin_lock.h"
#include "mongo/util/progress_meter.h"
#include "mongo/util/thread_safe_string.h"
#include "mongo/util/time_support.h"

namespace mongo {

    class Client;
    class Command;
    class CurOp;
    class OperationContext;

    /**
     * stores a copy of a bson obj in a fixed size buffer
     * if its too big for the buffer, says "too big"
     * useful for keeping a copy around indefinitely without wasting a lot of space or doing malloc
     */
    class CachedBSONObjBase {
    public:
        static BSONObj _tooBig; // { $msg : "query not recording (too large)" }
    };

    template <size_t BUFFER_SIZE>
    class CachedBSONObj : public CachedBSONObjBase {
    public:
        enum { TOO_BIG_SENTINEL = 1 } ;

        CachedBSONObj() {
            _size = (int*)_buf;
            reset();
        }

        void reset( int sz = 0 ) {
            _lock.lock();
            _reset( sz );
            _lock.unlock();
        }

        void set( const BSONObj& o ) {
            scoped_spinlock lk(_lock);
            size_t sz = o.objsize();
            if ( sz > sizeof(_buf) ) {
                _reset(TOO_BIG_SENTINEL);
            }
            else {
                memcpy(_buf, o.objdata(), sz );
            }
        }

        int size() const { return *_size; }
        bool have() const { return size() > 0; }
        bool tooBig() const { return size() == TOO_BIG_SENTINEL; }

        BSONObj get() const {
            scoped_spinlock lk(_lock);
            return _get();
        }

        void append( BSONObjBuilder& b , StringData name ) const {
            scoped_spinlock lk(_lock);
            BSONObj temp = _get();
            b.append( name , temp );
        }

    private:
        /** you have to be locked when you call this */
        BSONObj _get() const {
            int sz = size();
            if ( sz == 0 )
                return BSONObj();
            if ( sz == TOO_BIG_SENTINEL )
                return _tooBig;
            return BSONObj( _buf ).copy();
        }

        /** you have to be locked when you call this */
        void _reset( int sz ) { _size[0] = sz; }

        mutable SpinLock _lock;
        int * _size;
        char _buf[BUFFER_SIZE];
    };

    /* lifespan is different than CurOp because of recursives with DBDirectClient */
    class OpDebug {
    public:
        OpDebug() : planSummary(2048) { reset(); }

        void reset();

        std::string report(const CurOp& curop, const SingleThreadedLockStats& lockStats) const;

        /**
         * Appends information about the current operation to "builder"
         *
         * @param curop reference to the CurOp that owns this OpDebug
         * @param lockStats lockStats object containing locking information about the operation
         */
        void append(const CurOp& curop,
                    const SingleThreadedLockStats& lockStats,
                    BSONObjBuilder& builder) const;

        // -------------------
        
        StringBuilder extra; // weird things we need to fix later
        
        // basic options
        int op;
        bool iscommand;
        std::string ns;
        BSONObj query;
        BSONObj updateobj;
        
        // detailed options
        long long cursorid;
        int ntoreturn;
        int ntoskip;
        bool exhaust;

        // debugging/profile info
        long long nscanned;
        long long nscannedObjects;
        bool idhack;         // indicates short circuited code path on an update to make the update faster
        bool scanAndOrder;   // scanandorder query plan aspect was used
        long long  nMatched; // number of records that match the query
        long long  nModified; // number of records written (no no-ops)
        long long  nmoved;   // updates resulted in a move (moves are expensive)
        long long  ninserted;
        long long  ndeleted;
        bool fastmod;
        bool fastmodinsert;  // upsert of an $operation. builds a default object
        bool upsert;         // true if the update actually did an insert
        bool cursorExhausted; // true if the cursor has been closed at end a find/getMore operation
        int keyUpdates;
        long long writeConflicts;
        ThreadSafeString planSummary; // a brief std::string describing the query solution

        // New Query Framework debugging/profiling info
        // TODO: should this really be an opaque BSONObj?  Not sure.
        CachedBSONObj<4096> execStats;

        // error handling
        ExceptionInfo exceptionInfo;
        
        // response info
        int executionTime;
        int nreturned;
        int responseLength;
    };

    /**
     * Container for data used to report information about an OperationContext.
     *
     * Every OperationContext in a server with CurOp support has a stack of CurOp
     * objects. The entry at the top of the stack is used to record timing and
     * resource statistics for the executing operation or suboperation.
     *
     * All of the accessor methods on CurOp may be called by the thread executing
     * the associated OperationContext at any time, or by other threads that have
     * locked the context's owning Client object.
     *
     * The mutator methods on CurOp whose names end _inlock may only be called by the thread
     * executing the associated OperationContext and Client, and only when that thread has also
     * locked the Client object.  All other mutators may only be called by the thread executing
     * CurOp, but do not require holding the Client lock.  The exception to this is the kill()
     * method, which is self-synchronizing.
     *
     * The OpDebug member of a CurOp, accessed via the debug() accessor should *only* be accessed
     * from the thread executing an operation, and as a result its fields may be accessed without
     * any synchronization.
     */
    class CurOp {
        MONGO_DISALLOW_COPYING(CurOp);
    public:
        static CurOp* get(const OperationContext* opCtx);
        static CurOp* get(const OperationContext& opCtx);

        /**
         * Constructs a nested CurOp at the top of the given "opCtx"'s CurOp stack.
         */
        explicit CurOp(OperationContext* opCtx);
        ~CurOp();

        bool haveQuery() const { return _query.have(); }
        BSONObj query() const { return _query.get();  }
        void appendQuery( BSONObjBuilder& b , StringData name ) const { _query.append( b , name ); }

        void enter_inlock(const char* ns, int dbProfileLevel);

        /**
         * Sets the type of the current operation to "op".
         */
        void setOp_inlock(int op);

        /**
         * Marks the current operation as being a command.
         */
        void markCommand_inlock() { _isCommand = true; }

        /**
         * Returns a structure containing data used for profiling, accessed only by a thread
         * currently executing the operation context associated with this CurOp.
         */
        OpDebug& debug()           { return _debug; }

        /**
         * Gets the name of the namespace on which the current operation operates.
         */
        std::string getNS() const { return _ns; }

        bool shouldDBProfile( int ms ) const {
            if ( _dbprofile <= 0 )
                return false;

            return _dbprofile >= 2 || ms >= serverGlobalParams.slowMS;
        }

        /**
         * Raises the profiling level for this operation to "dbProfileLevel" if it was previously
         * less than "dbProfileLevel".
         *
         * This belongs on OpDebug, and so does not have the _inlock suffix.
         */
        void raiseDbProfileLevel(int dbProfileLevel);

        /**
         * Gets the type of the current operation.
         */
        int getOp() const { return _op; }

        /**
         * Returns true if the current operation is known to be a command.
         */
        bool isCommand() const { return _isCommand; }

        //
        // Methods for controlling CurOp "max time".
        //

        /**
         * Sets the amount of time operation this should be allowed to run, units of microseconds.
         * The special value 0 is "allow to run indefinitely".
         */
        void setMaxTimeMicros(uint64_t maxTimeMicros);

        /**
         * Returns true if a time limit has been set on this operation, and false otherwise.
         */
        bool isMaxTimeSet() const;

        /**
         * Checks whether this operation has been running longer than its time limit.  Returns
         * false if not, or if the operation has no time limit.
         */
        bool maxTimeHasExpired();

        /**
         * Returns the number of microseconds remaining for this operation's time limit, or the
         * special value 0 if the operation has no time limit.
         *
         * Calling this method is more expensive than calling its sibling "maxTimeHasExpired()",
         * since an accurate measure of remaining time needs to be calculated.
         */
        uint64_t getRemainingMaxTimeMicros() const;

        //
        // Methods for getting/setting elapsed time.
        //

        void ensureStarted();
        bool isStarted() const { return _start > 0; }
        long long startTime() { // micros
            ensureStarted();
            return _start;
        }
        void done() {
            _end = curTimeMicros64();
        }

        long long totalTimeMicros() {
            massert( 12601 , "CurOp not marked done yet" , _end );
            return _end - startTime();
        }
        int totalTimeMillis() { return (int) (totalTimeMicros() / 1000); }
        long long elapsedMicros() {
            return curTimeMicros64() - startTime();
        }
        int elapsedMillis() {
            return (int) (elapsedMicros() / 1000);
        }
        int elapsedSeconds() { return elapsedMillis() / 1000; }

        void setQuery_inlock(const BSONObj& query) { _query.set( query ); }

        Command * getCommand() const { return _command; }
        void setCommand_inlock(Command* command) { _command = command; }

        /**
         * Appends information about this CurOp to "builder".
         *
         * If called from a thread other than the one executing the operation associated with this
         * CurOp, it is necessary to lock the associated Client object before executing this method.
         */
        void reportState(BSONObjBuilder* builder);

        /**
         * Sets the message and the progress meter for this CurOp.
         *
         * While it is necessary to hold the lock while this method executes, the
         * "hit" and "finished" methods of ProgressMeter may be called safely from
         * the thread executing the operation without locking the Client.
         */
        ProgressMeter& setMessage_inlock(const char * msg,
                                  std::string name = "Progress",
                                  unsigned long long progressMeterTotal = 0,
                                  int secondsBetween = 3);

        /**
         * Gets the message for this CurOp.
         */
        const std::string& getMessage() const { return _message; }
        const ProgressMeter& getProgressMeter() { return _progressMeter; }
        CurOp *parent() const { return _parent; }
        void yielded() { _numYields++; }  // Should be _inlock()?

        /**
         * Returns the number of times yielded() was called.  Callers on threads other
         * than the one executing the operation must lock the client.
         */
        int numYields() const { return _numYields; }

        long long getExpectedLatencyMs() const { return _expectedLatencyMs; }
        void setExpectedLatencyMs( long long latency ) { _expectedLatencyMs = latency; }

        /**
         * this should be used very sparingly
         * generally the Context should set this up
         * but sometimes you want to do it ahead of time
         */
        void setNS_inlock( StringData ns );

    private:
        class CurOpStack;

        static const OperationContext::Decoration<CurOpStack> _curopStack;

        CurOp(OperationContext*, CurOpStack*);

        CurOpStack* _stack;
        CurOp* _parent = nullptr;
        Command * _command;
        long long _start;
        long long _end;
        int _op;
        bool _isCommand;
        int _dbprofile;                  // 0=off, 1=slow, 2=all
        std::string _ns;
        CachedBSONObj<512> _query;       // CachedBSONObj is thread safe
        OpDebug _debug;
        std::string _message;
        ProgressMeter _progressMeter;
        int _numYields;
        
        // this is how much "extra" time a query might take
        // a writebacklisten for example will block for 30s 
        // so this should be 30000 in that case
        long long _expectedLatencyMs; 

        // Time limit for this operation.  0 if the operation has no time limit.
        uint64_t _maxTimeMicros;

        /** Nested class that implements tracking of a time limit for a CurOp object. */
        class MaxTimeTracker {
            MONGO_DISALLOW_COPYING(MaxTimeTracker);
        public:
            /** Newly-constructed MaxTimeTracker objects have the time limit disabled. */
            MaxTimeTracker();

            /** Disables the time tracker. */
            void reset();

            /** Returns whether or not time tracking is enabled. */
            bool isEnabled() const { return _enabled; }

            /**
             * Enables time tracking.  The time limit is set to be "durationMicros" microseconds
             * from "startEpochMicros" (units of microseconds since the epoch).
             *
             * "durationMicros" must be nonzero.
             */
            void setTimeLimit(uint64_t startEpochMicros, uint64_t durationMicros);

            /**
             * Checks whether the time limit has been hit.  Returns false if not, or if time
             * tracking is disabled.
             */
            bool checkTimeLimit();

            /**
             * Returns the number of microseconds remaining for the time limit, or the special
             * value 0 if time tracking is disabled.
             *
             * Calling this method is more expensive than calling its sibling "checkInterval()",
             * since an accurate measure of remaining time needs to be calculated.
             */
            uint64_t getRemainingMicros() const;
        private:
            // Whether or not time tracking is enabled for this operation.
            bool _enabled;

            // Point in time at which the time limit is hit.  Units of microseconds since the
            // epoch.
            uint64_t _targetEpochMicros;

            // Approximate point in time at which the time limit is hit.   Units of milliseconds
            // since the server process was started.
            int64_t _approxTargetServerMillis;
        } _maxTimeTracker;

    };
}