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/**
* Copyright (C) 2017 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/s/commands/pipeline_s.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/query/collation/collation_spec.h"
#include "mongo/db/repl/read_concern_args.h"
#include "mongo/executor/task_executor_pool.h"
#include "mongo/s/catalog_cache.h"
#include "mongo/s/commands/cluster_commands_helpers.h"
#include "mongo/s/grid.h"
#include "mongo/s/query/cluster_cursor_manager.h"
#include "mongo/s/query/establish_cursors.h"
#include "mongo/s/query/router_exec_stage.h"
namespace mongo {
using boost::intrusive_ptr;
using std::shared_ptr;
using std::string;
using std::unique_ptr;
namespace {
/**
* Determines the single shard to which the given query will be targeted, and its associated
* shardVersion. Throws if the query targets more than one shard.
*/
std::pair<ShardId, ChunkVersion> getSingleTargetedShardForQuery(
OperationContext* opCtx, const CachedCollectionRoutingInfo& routingInfo, BSONObj query) {
if (auto chunkMgr = routingInfo.cm()) {
std::set<ShardId> shardIds;
chunkMgr->getShardIdsForQuery(opCtx, query, CollationSpec::kSimpleSpec, &shardIds);
uassert(ErrorCodes::InternalError,
str::stream() << "Unable to target lookup query to a single shard: "
<< query.toString(),
shardIds.size() == 1u);
return {*shardIds.begin(), chunkMgr->getVersion(*shardIds.begin())};
}
return {routingInfo.primaryId(), ChunkVersion::UNSHARDED()};
}
/**
* Returns the routing information for the namespace set on the passed ExpressionContext. Also
* verifies that the ExpressionContext's UUID, if present, matches that of the routing table entry.
*/
StatusWith<CachedCollectionRoutingInfo> getCollectionRoutingInfo(
const intrusive_ptr<ExpressionContext>& expCtx) {
auto catalogCache = Grid::get(expCtx->opCtx)->catalogCache();
auto swRoutingInfo = catalogCache->getCollectionRoutingInfo(expCtx->opCtx, expCtx->ns);
// Additionally check that the ExpressionContext's UUID matches the collection routing info.
if (swRoutingInfo.isOK() && expCtx->uuid && swRoutingInfo.getValue().cm()) {
if (!swRoutingInfo.getValue().cm()->uuidMatches(*expCtx->uuid)) {
return {ErrorCodes::NamespaceNotFound,
str::stream() << "The UUID of collection " << expCtx->ns.ns()
<< " changed; it may have been dropped and re-created."};
}
}
return swRoutingInfo;
}
} // namespace
boost::optional<Document> PipelineS::MongoSProcessInterface::lookupSingleDocument(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const NamespaceString& nss,
UUID collectionUUID,
const Document& filter,
boost::optional<BSONObj> readConcern) {
auto foreignExpCtx = expCtx->copyWith(nss, collectionUUID);
// Create the find command to be dispatched to the shard in order to return the post-change
// document.
auto filterObj = filter.toBson();
BSONObjBuilder cmdBuilder;
bool findCmdIsByUuid(foreignExpCtx->uuid);
if (findCmdIsByUuid) {
foreignExpCtx->uuid->appendToBuilder(&cmdBuilder, "find");
} else {
cmdBuilder.append("find", nss.coll());
}
cmdBuilder.append("filter", filterObj);
cmdBuilder.append("comment", expCtx->comment);
if (readConcern) {
cmdBuilder.append(repl::ReadConcernArgs::kReadConcernFieldName, *readConcern);
}
auto swShardResult = makeStatusWith<std::vector<ClusterClientCursorParams::RemoteCursor>>();
auto findCmd = cmdBuilder.obj();
size_t numAttempts = 0;
do {
// Verify that the collection exists, with the correct UUID.
auto catalogCache = Grid::get(expCtx->opCtx)->catalogCache();
auto swRoutingInfo = getCollectionRoutingInfo(foreignExpCtx);
if (swRoutingInfo == ErrorCodes::NamespaceNotFound) {
return boost::none;
}
auto routingInfo = uassertStatusOK(std::move(swRoutingInfo));
if (findCmdIsByUuid && routingInfo.cm()) {
// Find by UUID and shard versioning do not work together (SERVER-31946). In the
// sharded case we've already checked the UUID, so find by namespace is safe. In the
// unlikely case that the collection has been deleted and a new collection with the same
// name created through a different mongos, the shard version will be detected as stale,
// as shard versions contain an 'epoch' field unique to the collection.
findCmd = findCmd.addField(BSON("find" << nss.coll()).firstElement());
findCmdIsByUuid = false;
}
// Get the ID and version of the single shard to which this query will be sent.
auto shardInfo = getSingleTargetedShardForQuery(expCtx->opCtx, routingInfo, filterObj);
// Dispatch the request. This will only be sent to a single shard and only a single result
// will be returned. The 'establishCursors' method conveniently prepares the result into a
// cursor response for us.
swShardResult =
establishCursors(expCtx->opCtx,
Grid::get(expCtx->opCtx)->getExecutorPool()->getArbitraryExecutor(),
nss,
ReadPreferenceSetting::get(expCtx->opCtx),
{{shardInfo.first, appendShardVersion(findCmd, shardInfo.second)}},
false,
nullptr);
// If it's an unsharded collection which has been deleted and re-created, we may get a
// NamespaceNotFound error when looking up by UUID.
if (swShardResult.getStatus().code() == ErrorCodes::NamespaceNotFound) {
return boost::none;
}
// If we hit a stale shardVersion exception, invalidate the routing table cache.
if (ErrorCodes::isStaleShardingError(swShardResult.getStatus().code())) {
catalogCache->onStaleConfigError(std::move(routingInfo));
}
} while (!swShardResult.isOK() && ++numAttempts < kMaxNumStaleVersionRetries);
auto shardResult = uassertStatusOK(std::move(swShardResult));
invariant(shardResult.size() == 1u);
auto& cursor = shardResult.front().cursorResponse;
auto& batch = cursor.getBatch();
// We should have at most 1 result, and the cursor should be exhausted.
uassert(ErrorCodes::InternalError,
str::stream() << "Shard cursor was unexpectedly open after lookup: "
<< shardResult.front().hostAndPort
<< ", id: "
<< cursor.getCursorId(),
cursor.getCursorId() == 0);
uassert(ErrorCodes::TooManyMatchingDocuments,
str::stream() << "found more than one document matching " << filter.toString() << " ["
<< batch.begin()->toString()
<< ", "
<< std::next(batch.begin())->toString()
<< "]",
batch.size() <= 1u);
return (!batch.empty() ? Document(batch.front()) : boost::optional<Document>{});
}
std::vector<GenericCursor> PipelineS::MongoSProcessInterface::getCursors(
const intrusive_ptr<ExpressionContext>& expCtx) const {
invariant(hasGlobalServiceContext());
auto cursorManager = Grid::get(expCtx->opCtx->getServiceContext())->getCursorManager();
invariant(cursorManager);
return cursorManager->getAllCursors();
}
} // namespace mongo
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