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/**
* 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/session_killer.h"
#include "mongo/db/client.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/service_context.h"
#include "mongo/util/destructor_guard.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
namespace {
const auto getSessionKiller = ServiceContext::declareDecoration<std::shared_ptr<SessionKiller>>();
} // namespace
SessionKiller::SessionKiller(ServiceContext* sc, KillFunc killer)
: _killFunc(std::move(killer)), _urbg(std::random_device{}()), _reapResults() {
_thread = stdx::thread([this, sc] {
// This is the background killing thread
Client::setCurrent(sc->makeClient("SessionKiller"));
stdx::unique_lock<Latch> lk(_mutex);
// While we're not in shutdown
while (!_inShutdown) {
// Wait until we're woken up, and should either shutdown, or have something new to reap.
_killerCV.wait(lk, [&] { return _inShutdown || _nextToReap.size(); });
// If we're in shutdown we're done
if (_inShutdown) {
return;
}
// Otherwise make an opctx and head into kill
auto opCtx = cc().makeOperationContext();
_periodicKill(opCtx.get(), lk);
}
});
}
SessionKiller::~SessionKiller() {
DESTRUCTOR_GUARD([&] {
{
stdx::lock_guard<Latch> lk(_mutex);
_inShutdown = true;
}
_killerCV.notify_one();
_callerCV.notify_all();
_thread.join();
}());
}
SessionKiller::ReapResult::ReapResult() : result(std::make_shared<boost::optional<Result>>()) {}
SessionKiller::Matcher::Matcher(KillAllSessionsByPatternSet&& patterns)
: _patterns(std::move(patterns)) {
for (const auto& pattern : _patterns) {
if (pattern.getUid()) {
_uids.emplace(pattern.getUid().get(), &pattern);
} else if (pattern.getLsid()) {
_lsids.emplace(pattern.getLsid().get(), &pattern);
} else {
// If we're killing everything, it's the only pattern we care about.
decltype(_patterns) onlyKillAll{{pattern}};
using std::swap;
swap(_patterns, onlyKillAll);
_killAll = &(*_patterns.begin());
break;
}
}
}
const KillAllSessionsByPatternSet& SessionKiller::Matcher::getPatterns() const {
return _patterns;
}
const KillAllSessionsByPattern* SessionKiller::Matcher::match(const LogicalSessionId& lsid) const {
if (_killAll) {
return _killAll;
}
{
auto iter = _lsids.find(lsid);
if (iter != _lsids.end()) {
return iter->second;
}
}
{
auto iter = _uids.find(lsid.getUid());
if (iter != _uids.end()) {
return iter->second;
}
}
return nullptr;
}
SessionKiller* SessionKiller::get(ServiceContext* service) {
return getSessionKiller(service).get();
}
SessionKiller* SessionKiller::get(OperationContext* ctx) {
return get(ctx->getServiceContext());
}
std::shared_ptr<SessionKiller::Result> SessionKiller::kill(
OperationContext* opCtx, const KillAllSessionsByPatternSet& toKill) {
stdx::unique_lock<Latch> lk(_mutex);
// Save a shared_ptr to the current reapResults (I.e. the next thing to get killed).
auto reapResults = _reapResults;
// Dump all your lsids in.
for (const auto& item : toKill) {
_nextToReap.emplace(item);
}
// Wake up the killer.
_killerCV.notify_one();
// Wait until our results are there, or the killer is shutting down.
opCtx->waitForConditionOrInterrupt(
_callerCV, lk, [&] { return reapResults.result->is_initialized() || _inShutdown; });
// If the killer is shutting down, throw.
uassert(ErrorCodes::ShutdownInProgress, "SessionKiller shutting down", !_inShutdown);
// Otherwise, alias (via the aliasing ctor of shared_ptr) a shared_ptr to the actual results
// (inside the optional) to keep our contract. That ctor form returns a shared_ptr which
// returns one type, while keeping a refcount on a control block from a different type.
return {reapResults.result, reapResults.result->get_ptr()};
}
void SessionKiller::_periodicKill(OperationContext* opCtx, stdx::unique_lock<Latch>& lk) {
// Pull our current workload onto the stack. Swap it for empties.
decltype(_nextToReap) nextToReap;
decltype(_reapResults) reapResults;
{
using std::swap;
swap(nextToReap, _nextToReap);
swap(reapResults, _reapResults);
}
// Drop the lock and run the killer.
lk.unlock();
Matcher matcher(std::move(nextToReap));
boost::optional<Result> results;
try {
results.emplace(_killFunc(opCtx, matcher, &_urbg));
} catch (...) {
results.emplace(exceptionToStatus());
}
lk.lock();
invariant(results);
// Expose the results and notify callers
*(reapResults.result) = std::move(results);
_callerCV.notify_all();
};
void SessionKiller::set(ServiceContext* sc, std::shared_ptr<SessionKiller> sk) {
getSessionKiller(sc) = sk;
}
} // namespace mongo
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