// background.cpp


/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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.
 */

#include "mongo/platform/basic.h"

#include "mongo/db/background.h"

#include <iostream>
#include <string>

#include "mongo/base/disallow_copying.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/map_util.h"
#include "mongo/util/mongoutils/str.h"
#include "mongo/util/string_map.h"

namespace mongo {

using std::shared_ptr;

namespace {

class BgInfo {
    MONGO_DISALLOW_COPYING(BgInfo);

public:
    BgInfo() : _opsInProgCount(0) {}

    void recordBegin();
    int recordEnd();
    void awaitNoBgOps(stdx::unique_lock<stdx::mutex>& lk);

    int getOpsInProgCount() const {
        return _opsInProgCount;
    }

private:
    int _opsInProgCount;
    stdx::condition_variable _noOpsInProg;
};

typedef StringMap<std::shared_ptr<BgInfo>> BgInfoMap;
typedef BgInfoMap::const_iterator BgInfoMapIterator;

// Static data for this file is never destroyed.
stdx::mutex& m = *(new stdx::mutex());
BgInfoMap& dbsInProg = *(new BgInfoMap());
BgInfoMap& nsInProg = *(new BgInfoMap());

void BgInfo::recordBegin() {
    ++_opsInProgCount;
}

int BgInfo::recordEnd() {
    dassert(_opsInProgCount > 0);
    --_opsInProgCount;
    if (0 == _opsInProgCount) {
        _noOpsInProg.notify_all();
    }
    return _opsInProgCount;
}

void BgInfo::awaitNoBgOps(stdx::unique_lock<stdx::mutex>& lk) {
    while (_opsInProgCount > 0)
        _noOpsInProg.wait(lk);
}

void recordBeginAndInsert(BgInfoMap& bgiMap, StringData key) {
    std::shared_ptr<BgInfo>& bgInfo = bgiMap[key];
    if (!bgInfo)
        bgInfo.reset(new BgInfo);
    bgInfo->recordBegin();
}

void recordEndAndRemove(BgInfoMap& bgiMap, StringData key) {
    BgInfoMapIterator iter = bgiMap.find(key);
    fassert(17431, iter != bgiMap.end());
    if (0 == iter->second->recordEnd()) {
        bgiMap.erase(iter);
    }
}

void awaitNoBgOps(stdx::unique_lock<stdx::mutex>& lk, BgInfoMap* bgiMap, StringData key) {
    std::shared_ptr<BgInfo> bgInfo = mapFindWithDefault(*bgiMap, key, std::shared_ptr<BgInfo>());
    if (!bgInfo)
        return;
    bgInfo->awaitNoBgOps(lk);
}

}  // namespace

bool BackgroundOperation::inProgForDb(StringData db) {
    stdx::lock_guard<stdx::mutex> lk(m);
    return dbsInProg.find(db) != dbsInProg.end();
}

int BackgroundOperation::numInProgForDb(StringData db) {
    stdx::lock_guard<stdx::mutex> lk(m);
    std::shared_ptr<BgInfo> bgInfo = mapFindWithDefault(dbsInProg, db, std::shared_ptr<BgInfo>());
    if (!bgInfo)
        return 0;
    return bgInfo->getOpsInProgCount();
}

bool BackgroundOperation::inProgForNs(StringData ns) {
    stdx::lock_guard<stdx::mutex> lk(m);
    return nsInProg.find(ns) != nsInProg.end();
}

void BackgroundOperation::assertNoBgOpInProgForDb(StringData db) {
    uassert(ErrorCodes::BackgroundOperationInProgressForDatabase,
            mongoutils::str::stream()
                << "cannot perform operation: a background operation is currently running for "
                   "database "
                << db,
            !inProgForDb(db));
}

void BackgroundOperation::assertNoBgOpInProgForNs(StringData ns) {
    uassert(ErrorCodes::BackgroundOperationInProgressForNamespace,
            mongoutils::str::stream()
                << "cannot perform operation: a background operation is currently running for "
                   "collection "
                << ns,
            !inProgForNs(ns));
}

void BackgroundOperation::awaitNoBgOpInProgForDb(StringData db) {
    stdx::unique_lock<stdx::mutex> lk(m);
    awaitNoBgOps(lk, &dbsInProg, db);
}

void BackgroundOperation::awaitNoBgOpInProgForNs(StringData ns) {
    stdx::unique_lock<stdx::mutex> lk(m);
    awaitNoBgOps(lk, &nsInProg, ns);
}

BackgroundOperation::BackgroundOperation(StringData ns) : _ns(ns) {
    stdx::lock_guard<stdx::mutex> lk(m);
    recordBeginAndInsert(dbsInProg, _ns.db());
    recordBeginAndInsert(nsInProg, _ns.ns());
}

BackgroundOperation::~BackgroundOperation() {
    stdx::lock_guard<stdx::mutex> lk(m);
    recordEndAndRemove(dbsInProg, _ns.db());
    recordEndAndRemove(nsInProg, _ns.ns());
}

void BackgroundOperation::dump(std::ostream& ss) {
    stdx::lock_guard<stdx::mutex> lk(m);
    if (nsInProg.size()) {
        ss << "\n<b>Background Jobs in Progress</b>\n";
        for (BgInfoMapIterator i = nsInProg.begin(); i != nsInProg.end(); ++i)
            ss << "  " << i->first << '\n';
    }
    for (BgInfoMapIterator i = dbsInProg.begin(); i != dbsInProg.end(); ++i) {
        if (i->second->getOpsInProgCount())
            ss << "database " << i->first << ": " << i->second->getOpsInProgCount() << '\n';
    }
}

}  // namespace mongo