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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 <string>
#include <vector>
#include "mongo/base/status_with.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/bson/oid.h"
#include "mongo/s/chunk_version.h"
namespace mongo {
class ChunkType;
class NamespaceString;
class OperationContext;
class ShardCollectionType;
class ShardDatabaseType;
namespace shardmetadatautil {
/**
* Structure representing the generated query and sort order for a chunk diffing operation.
*/
struct QueryAndSort {
const BSONObj query;
const BSONObj sort;
};
/**
* Returns the query needed to find incremental changes to the chunks collection on a shard server.
*
* The query has to find all the chunks $gte the current max version. Currently, any splits, merges
* and moves will increment the current max version. Querying by lastmod is essential because we
* want to use the {lastmod} index on the chunks collection. This makes potential cursor yields to
* apply split/merge/move updates safe: updates always move or insert documents at the end of the
* index (because the document updates always have higher lastmod), so changed always come *after*
* our current cursor position and are seen when the cursor recommences.
*
* The sort must be by ascending version so that the updates can be applied in-memory in order. This
* is important because it is possible for a cursor to read updates to the same _id document twice,
* due to the yield described above. If updates are applied in ascending version order, the newer
* update is applied last.
*/
QueryAndSort createShardChunkDiffQuery(const ChunkVersion& collectionPlacementVersion);
/**
* Writes a persisted signal to indicate that it is once again safe to read from the chunks
* collection for 'nss' and updates the collection's collection placement version to
* 'refreshedVersion'. It is essential to call this after updating the chunks collection so that
* secondaries know they can safely use the chunk metadata again.
*
* It is safe to call this multiple times: it's an idempotent action.
*
* refreshedVersion - the new collection placement version for the completed refresh.
*
* Note: if there is no document present in the collections collection for 'nss', nothing is
* updated.
*/
Status unsetPersistedRefreshFlags(OperationContext* opCtx,
const NamespaceString& nss,
const ChunkVersion& refreshedVersion);
/**
* Represents a subset of a collection's config.cache.collections entry that relates to refresh
* state.
*/
struct RefreshState {
bool operator==(const RefreshState& other) const;
std::string toString() const;
// The current generation of the collection.
CollectionGeneration generation;
// Whether a refresh is currently in progress.
bool refreshing;
// The collection placement version after the last complete refresh. Indicates change if
// refreshing has started and finished since last loaded.
ChunkVersion lastRefreshedCollectionPlacementVersion;
};
/**
* Reads the persisted refresh signal for 'nss' and returns those settings.
*/
StatusWith<RefreshState> getPersistedRefreshFlags(OperationContext* opCtx,
const NamespaceString& nss);
/**
* Reads the shard server's collections collection entry identified by 'nss'.
*/
StatusWith<ShardCollectionType> readShardCollectionsEntry(OperationContext* opCtx,
const NamespaceString& nss);
/**
* Reads the shard server's databases collection entry identified by 'dbName'.
*/
StatusWith<ShardDatabaseType> readShardDatabasesEntry(OperationContext* opCtx, StringData dbName);
/**
* Updates the collections collection entry matching 'query' with 'update' using local write
* concern.
*
* If 'upsert' is true, expects 'lastRefreshedCollectionPlacementVersion' to be absent in the
* update: these refreshing fields should only be added to an existing document.
*/
Status updateShardCollectionsEntry(OperationContext* opCtx,
const BSONObj& query,
const BSONObj& update,
bool upsert);
/**
* Updates the databases collection entry matching 'query' with 'update' using local write
* concern.
*
* Uses the $set operator on the update so that updates can be applied without resetting everything.
* 'inc' can be used to specify fields and their increments: it will be assigned to the $inc
* operator.
*
* 'inc' should not specify 'upsert' true.
*/
Status updateShardDatabasesEntry(OperationContext* opCtx,
const BSONObj& query,
const BSONObj& update,
const BSONObj& inc,
bool upsert);
/**
* Reads the shard server's chunks collection corresponding to 'nss' for chunks matching 'query',
* returning at most 'limit' chunks in 'sort' order. 'epoch' populates the returned chunks' version
* fields, because we do not yet have UUIDs to replace epochs nor UUIDs associated with namespaces.
*/
StatusWith<std::vector<ChunkType>> readShardChunks(OperationContext* opCtx,
const NamespaceString& nss,
const BSONObj& query,
const BSONObj& sort,
boost::optional<long long> limit,
const OID& epoch,
const Timestamp& timestamp);
/**
* Takes a vector of 'chunks' and updates the shard's chunks collection for 'nss'. Any chunk
* documents in config.cache.chunks.<ns> that overlap with a chunk in 'chunks' is removed as the
* updated chunk document is inserted. If the epoch of a chunk in 'chunks' does not match
* 'currEpoch', a ConflictingOperationInProgress error is returned and no more updates are applied.
*
* Note: two threads running this function in parallel for the same collection can corrupt the
* collection data!
*
* nss - the collection namespace for which chunk metadata is being updated.
* chunks - chunks retrieved from the config server, sorted in ascending chunk version order.
* currEpoch - what this shard server expects the collection epoch to be.
*
* Returns:
* - ConflictingOperationInProgress if the chunk version epoch of any chunk in 'chunks' is different
* than 'currEpoch'.
* - Other errors if unable to do local writes/reads to the config.chunks.ns collection.
*/
Status updateShardChunks(OperationContext* opCtx,
const NamespaceString& nss,
const std::vector<ChunkType>& chunks,
const OID& currEpoch);
/**
* Deletes locally persisted chunk metadata associated with 'nss': drops the chunks collection
* and removes the collections collection entry.
*
* The order is important because the secondary observes changes to the config.collections entries.
* If the chunks were dropped first, the secondary would keep refreshing until it exceeded its
* retries, rather than returning with a useful error message.
*/
Status dropChunksAndDeleteCollectionsEntry(OperationContext* opCtx, const NamespaceString& nss);
/**
* Drops locally persisted chunk metadata associated with 'nss': only drops the chunks collection.
*/
void dropChunks(OperationContext* opCtx, const NamespaceString& nss);
/**
* Deletes locally persisted database metadata associated with 'dbName': removes the databases
* collection entry.
*/
Status deleteDatabasesEntry(OperationContext* opCtx, StringData dbName);
} // namespace shardmetadatautil
} // namespace mongo
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