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/**
* Copyright (C) 2022-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/auth/authorization_session.h"
#include "mongo/db/commands.h"
#include "mongo/logv2/log.h"
#include "mongo/platform/random.h"
#include "mongo/s/analyze_shard_key_cmd_gen.h"
#include "mongo/s/analyze_shard_key_util.h"
#include "mongo/s/cluster_commands_helpers.h"
#include "mongo/s/grid.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kCommand
namespace mongo {
namespace analyze_shard_key {
namespace {
/**
* Returns a new command object with shard version and/or database version appended to it based on
* the given routing info.
*/
BSONObj makeVersionedCmdObj(const CollectionRoutingInfo& cri,
const BSONObj& unversionedCmdObj,
ShardId shardId) {
if (cri.cm.isSharded()) {
return appendShardVersion(unversionedCmdObj, cri.getShardVersion(shardId));
}
auto versionedCmdObj = appendShardVersion(unversionedCmdObj, ShardVersion::UNSHARDED());
return appendDbVersionIfPresent(versionedCmdObj, cri.cm.dbVersion());
}
class AnalyzeShardKeyCmd : public TypedCommand<AnalyzeShardKeyCmd> {
public:
using Request = AnalyzeShardKey;
using Response = AnalyzeShardKeyResponse;
class Invocation final : public InvocationBase {
public:
using InvocationBase::InvocationBase;
Response typedRun(OperationContext* opCtx) {
const auto& nss = ns();
uassertStatusOK(validateNamespace(nss));
const auto& catalogCache = Grid::get(opCtx)->catalogCache();
const auto cri = uassertStatusOK(catalogCache->getCollectionRoutingInfo(opCtx, nss));
const auto primaryShardId = cri.cm.dbPrimary();
std::set<ShardId> candidateShardIds;
if (cri.cm.isSharded()) {
cri.cm.getAllShardIds(&candidateShardIds);
} else {
candidateShardIds.insert(primaryShardId);
}
PseudoRandom random{SecureRandom{}.nextInt64()};
// On secondaries, the database and shard version check is only performed for commands
// that specify a readConcern (that is not "available"). Therefore, to opt into the
// check, explicitly attach the readConcern.
const auto unversionedCmdObj =
CommandHelpers::filterCommandRequestForPassthrough(request().toBSON(BSON(
repl::ReadConcernArgs::kReadConcernFieldName << extractReadConcern(opCtx))));
while (true) {
// Select a random shard.
invariant(!candidateShardIds.empty());
auto shardId = [&] {
// The monotonicity check can return an incorrect result if the collection has
// gone through chunk migrations since chunk migration deletes documents from
// the donor shard and re-inserts them on the recipient shard so there is no
// guarantee that the insertion order from the client is preserved. Therefore,
// the likelihood of an incorrect result is correlated to the ratio between
// the number of documents inserted by the client and the number of documents
// inserted by chunk migrations. Prioritizing the primary shard helps lower the
// risk of incorrect results since if the collection did not start out as being
// sharded (which applies to most cases), the primary shard is likely to be the
// shard with the least number of documents inserted by chunk migrations since
// all the data starts out there.
if (candidateShardIds.find(primaryShardId) != candidateShardIds.end()) {
return primaryShardId;
}
auto it = candidateShardIds.begin();
std::advance(it, random.nextInt64(candidateShardIds.size()));
return *it;
}();
candidateShardIds.erase(shardId);
uassert(ErrorCodes::IllegalOperation,
"Cannot analyze a shard key for a collection in a fixed database",
!cri.cm.dbVersion().isFixed());
// Build a versioned command for the selected shard.
auto versionedCmdObj = makeVersionedCmdObj(cri, unversionedCmdObj, shardId);
// Execute the command against the shard.
auto shard =
uassertStatusOK(Grid::get(opCtx)->shardRegistry()->getShard(opCtx, shardId));
auto swResponse =
shard->runCommandWithFixedRetryAttempts(opCtx,
request().getReadPreference(),
DatabaseName::kAdmin.toString(),
versionedCmdObj,
Shard::RetryPolicy::kIdempotent);
auto status = Shard::CommandResponse::getEffectiveStatus(swResponse);
if (status == ErrorCodes::CollectionIsEmptyLocally) {
uassert(ErrorCodes::IllegalOperation,
str::stream() << "Cannot analyze a shard key for an empty collection: "
<< redact(status),
!candidateShardIds.empty());
LOGV2(6875300,
"Failed to analyze shard key on the selected shard since it did not "
"have any documents for the collection locally. Retrying on a different "
"shard.",
logAttrs(nss),
"shardKey"_attr = request().getKey(),
"shardId"_attr = shardId,
"error"_attr = status);
continue;
}
uassertStatusOK(status);
auto response = AnalyzeShardKeyResponse::parse(
IDLParserContext("clusterAnalyzeShardKey"), swResponse.getValue().response);
return response;
}
}
private:
NamespaceString ns() const override {
return request().getCommandParameter();
}
bool supportsWriteConcern() const override {
return false;
}
void doCheckAuthorization(OperationContext* opCtx) const override {
uassert(ErrorCodes::Unauthorized,
"Unauthorized",
AuthorizationSession::get(opCtx->getClient())
->isAuthorizedForActionsOnResource(ResourcePattern::forExactNamespace(ns()),
ActionType::analyzeShardKey));
}
};
AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
return AllowedOnSecondary::kNever;
}
bool adminOnly() const override {
return true;
}
ReadWriteType getReadWriteType() const override {
return ReadWriteType::kWrite;
}
std::string help() const override {
return "Returns metrics for evaluating a shard key for a collection.";
}
} analyzeShardKeyCmd;
} // namespace
} // namespace analyze_shard_key
} // namespace mongo
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