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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.
*/
#pragma once
#include "mongo/platform/basic.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/shard_filterer.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/s/scoped_collection_metadata.h"
namespace mongo {
class CanonicalQuery;
class Collection;
class CollectionPtr;
class OperationContext;
class BSONObj;
class Document;
namespace write_stage_common {
class PreWriteFilter {
public:
/**
* This class represents the different kind of actions we can take when handling a write
* operation:
* - kWrite: perform the current write operation.
* - kWriteAsFromMigrate: perform the current write operation but marking it with the
* fromMigrate flag.
* - kSkip: skip the current write operation.
*/
enum class Action { kWrite, kWriteAsFromMigrate, kSkip };
PreWriteFilter(OperationContext* opCtx, NamespaceString nss);
void saveState() {}
void restoreState();
/**
* Returns which PreWriteFilterAction we should take for the current write operation over doc.
*/
Action computeAction(const Document& doc);
/**
* Computes the required action for the current write operation over the 'doc' and logs cases
* of 'kSkip' or 'kWriteAsFromMigrate'.
*
* - Returns 'kWRite' if the 'doc' is writeable
* - Returns 'kSkip' if the 'doc' is not writeable and should be skipped.
* - Returns 'kWriteAsFromMigrate' meaning that the 'doc' should be written to orphan chunk.
*/
Action computeActionAndLogSpecialCases(const Document& doc,
StringData opKind,
const NamespaceString& collNs) {
const auto action = computeAction(doc);
if (action == Action::kSkip) {
logSkippingDocument(doc, opKind, collNs);
} else if (action == Action::kWriteAsFromMigrate) {
logFromMigrate(doc, opKind, collNs);
}
return action;
}
/**
* Checks if the 'doc' is NOT writable and additionally handles the StaleConfig error. This
* method should be called in a context of single update / delete.
*
* Returns a pair of [optional immediate StageState return code, bool fromMigrate].
* - Returns {{}, false} if the 'doc' is simply writable.
* - Returns PlanStage::StageState if the 'doc' is not writable and the caller should return
* immediately with the state.
* - Returns bool for 'fromMigrate' flag meaning that the 'doc' should be written to orphan
* chunk.
*/
template <typename F>
std::pair<boost::optional<PlanStage::StageState>, bool> checkIfNotWritable(
const Document& doc, StringData opKind, const NamespaceString& collNs, F&& yieldHandler) {
try {
auto action = computeActionAndLogSpecialCases(doc, opKind, collNs);
// If the 'doc' should be skipped in a context of single update / delete, the caller
// should return immediately with NEED_TIME state. When action is 'kSkip', 'fromMigrate'
// is a 'don't care' condition but we just fill it with false.
if (action == Action::kSkip) {
return {PlanStage::NEED_TIME, false};
}
return {{}, action == Action::kWriteAsFromMigrate};
} catch (const ExceptionFor<ErrorCodes::StaleConfig>& ex) {
// If the placement version is IGNORED and we encountered a critical section, then
// yield, wait for the critical section to finish and then we'll resume the write from
// the point we had left. We do this to prevent large multi-writes from repeatedly
// failing due to StaleConfig and exhausting the mongos retry attempts.
if (ShardVersion::isPlacementVersionIgnored(ex->getVersionReceived()) &&
ex->getCriticalSectionSignal()) {
yieldHandler(ex);
return {PlanStage::NEED_YIELD, false};
}
throw;
}
}
private:
/**
* Returns true if the operation is not versioned or if the doc is owned by the shard.
*
* May throw a ShardKeyNotFound if the document has an invalid shard key.
*/
bool _documentBelongsToMe(const BSONObj& doc);
static void logSkippingDocument(const Document& doc,
StringData opKind,
const NamespaceString& collNs);
static void logFromMigrate(const Document& doc,
StringData opKind,
const NamespaceString& collNs);
OperationContext* _opCtx;
NamespaceString _nss;
const bool _skipFiltering;
std::unique_ptr<ShardFilterer> _shardFilterer;
};
/**
* This class represents a cached sharding collection description. When resuming from a yield, the
* cache needs to be invalidated.
*/
class CachedShardingDescription {
public:
CachedShardingDescription(const NamespaceString& nss) : _nss(nss) {}
void restoreState();
const ScopedCollectionDescription& getCollectionDescription(OperationContext* opCtx);
private:
const NamespaceString _nss;
boost::optional<ScopedCollectionDescription> _collectionDescription;
};
/**
* Returns true if the document referred to by 'id' still exists and matches the query predicate
* given by 'cq'. Returns true if the document still exists and 'cq' is null. Returns false
* otherwise.
*
* May throw a WriteConflictException if there was a conflict while searching to see if the document
* still exists.
*/
bool ensureStillMatches(const CollectionPtr& collection,
OperationContext* opCtx,
WorkingSet* ws,
WorkingSetID id,
const CanonicalQuery* cq);
/**
* Returns true if we are running retryable write or retryable internal multi-document transaction.
*/
bool isRetryableWrite(OperationContext* opCtx);
} // namespace write_stage_common
} // namespace mongo
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