/**
 *    Copyright (C) 2019-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 "oplog_cap_maintainer_thread.h"

#include "mongo/base/error_codes.h"
#include "mongo/base/string_data.h"
#include "mongo/db/catalog_raii.h"
#include "mongo/db/client.h"
#include "mongo/db/service_context.h"
#include "mongo/logv2/log.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/exit.h"
#include "mongo/util/fail_point.h"
#include "mongo/util/time_support.h"

#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kStorage


namespace mongo {

namespace {

const auto getMaintainerThread = ServiceContext::declareDecoration<OplogCapMaintainerThread>();

MONGO_FAIL_POINT_DEFINE(hangOplogCapMaintainerThread);

}  // namespace

OplogCapMaintainerThread* OplogCapMaintainerThread::get(ServiceContext* serviceCtx) {
    return &getMaintainerThread(serviceCtx);
}

bool OplogCapMaintainerThread::_deleteExcessDocuments() {
    if (!getGlobalServiceContext()->getStorageEngine()) {
        LOGV2_DEBUG(22240, 2, "OplogCapMaintainerThread: no global storage engine yet");
        return false;
    }

    const ServiceContext::UniqueOperationContext opCtx = cc().makeOperationContext();

    // Maintaining the Oplog cap is crucial to the stability of the server so that we don't let the
    // oplog grow unbounded. We mark the operation as having immediate priority to skip ticket
    // acquisition and flow control.
    ScopedAdmissionPriorityForLock priority(opCtx->lockState(),
                                            AdmissionContext::Priority::kImmediate);

    try {
        // A Global IX lock should be good enough to protect the oplog truncation from
        // interruptions such as restartCatalog. PBWM, database lock or collection lock is not
        // needed. This improves concurrency if oplog truncation takes long time.
        AutoGetOplog oplogWrite(opCtx.get(), OplogAccessMode::kWrite);
        const auto& oplog = oplogWrite.getCollection();
        if (!oplog) {
            LOGV2_DEBUG(4562600, 2, "oplog collection does not exist");
            return false;
        }
        auto rs = oplog->getRecordStore();
        if (!rs->yieldAndAwaitOplogDeletionRequest(opCtx.get())) {
            return false;  // Oplog went away.
        }
        rs->reclaimOplog(opCtx.get());
    } catch (const ExceptionFor<ErrorCodes::InterruptedDueToStorageChange>& e) {
        LOGV2_DEBUG(5929700,
                    1,
                    "Caught an InterruptedDueToStorageChange exception, "
                    "but this thread can safely continue",
                    "error"_attr = e.toStatus());
    } catch (const DBException& ex) {
        if (!opCtx->checkForInterruptNoAssert().isOK()) {
            return false;
        }

        LOGV2_FATAL_NOTRACE(6761100, "Error in OplogCapMaintainerThread", "error"_attr = ex);
    } catch (const std::exception& e) {
        LOGV2_FATAL_NOTRACE(22243, "Error in OplogCapMaintainerThread", "error"_attr = e.what());
    } catch (...) {
        LOGV2_FATAL_NOTRACE(5184100, "Unknown error in OplogCapMaintainerThread");
    }
    return true;
}

void OplogCapMaintainerThread::run() {
    LOGV2_DEBUG(5295000, 1, "Oplog cap maintainer thread started", "threadName"_attr = _name);
    ThreadClient tc(_name, getGlobalServiceContext());

    {
        stdx::lock_guard<Client> lk(*tc.get());
        tc.get()->setSystemOperationUnkillableByStepdown(lk);
    }

    while (!globalInShutdownDeprecated()) {
        if (MONGO_unlikely(hangOplogCapMaintainerThread.shouldFail())) {
            LOGV2(5095500, "Hanging the oplog cap maintainer thread due to fail point");
            hangOplogCapMaintainerThread.pauseWhileSet();
        }

        if (!_deleteExcessDocuments() && !globalInShutdownDeprecated()) {
            sleepmillis(1000);  // Back off in case there were problems deleting.
        }
    }
}

void OplogCapMaintainerThread::waitForFinish() {
    if (running()) {
        LOGV2_INFO(7474902, "Shutting down oplog cap maintainer thread");
        wait();
        LOGV2(7474901, "Finished shutting down oplog cap maintainer thread");
    }
}

}  // namespace mongo