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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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/platform/basic.h"
#include "mongo/s/query/establish_cursors.h"
#include "mongo/client/remote_command_retry_scheduler.h"
#include "mongo/client/remote_command_targeter.h"
#include "mongo/db/cursor_id.h"
#include "mongo/db/query/cursor_response.h"
#include "mongo/db/query/getmore_request.h"
#include "mongo/db/query/killcursors_request.h"
#include "mongo/executor/remote_command_request.h"
#include "mongo/executor/remote_command_response.h"
#include "mongo/s/grid.h"
#include "mongo/s/multi_statement_transaction_requests_sender.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/log.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
std::vector<RemoteCursor> establishCursors(OperationContext* opCtx,
std::shared_ptr<executor::TaskExecutor> executor,
const NamespaceString& nss,
const ReadPreferenceSetting readPref,
const std::vector<std::pair<ShardId, BSONObj>>& remotes,
bool allowPartialResults,
Shard::RetryPolicy retryPolicy) {
// Construct the requests
std::vector<AsyncRequestsSender::Request> requests;
for (const auto& remote : remotes) {
requests.emplace_back(remote.first, remote.second);
}
// Send the requests
MultiStatementTransactionRequestsSender ars(
opCtx, executor, nss.db().toString(), std::move(requests), readPref, retryPolicy);
std::vector<RemoteCursor> remoteCursors;
try {
// Get the responses
while (!ars.done()) {
try {
auto response = ars.next();
// Note the shardHostAndPort may not be populated if there was an error, so be sure
// to do this after parsing the cursor response to ensure the response was ok.
// Additionally, be careful not to push into 'remoteCursors' until we are sure we
// have a valid cursor, since the error handling path will attempt to clean up
// anything in 'remoteCursors'
auto cursors = CursorResponse::parseFromBSONMany(
uassertStatusOK(std::move(response.swResponse)).data);
for (auto& cursor : cursors) {
if (cursor.isOK()) {
RemoteCursor remoteCursor;
remoteCursor.setCursorResponse(std::move(cursor.getValue()));
remoteCursor.setShardId(std::move(response.shardId));
remoteCursor.setHostAndPort(*response.shardHostAndPort);
remoteCursors.push_back(std::move(remoteCursor));
}
}
// Throw if there is any error and then the catch block below will do the cleanup.
for (auto& cursor : cursors) {
uassertStatusOK(cursor.getStatus());
}
} catch (const ExceptionForCat<ErrorCategory::RetriableError>&) {
// Retriable errors are swallowed if 'allowPartialResults' is true.
if (allowPartialResults) {
continue;
}
throw; // Fail this loop.
}
}
return remoteCursors;
} catch (const DBException&) {
// If one of the remotes had an error, we make a best effort to finish retrieving responses
// for other requests that were already sent, so that we can send killCursors to any cursors
// that we know were established.
try {
// Do not schedule any new requests.
ars.stopRetrying();
// Collect responses from all requests that were already sent.
while (!ars.done()) {
auto response = ars.next();
// Check if the response contains an established cursor, and if so, store it.
StatusWith<CursorResponse> swCursorResponse(
response.swResponse.isOK()
? CursorResponse::parseFromBSON(response.swResponse.getValue().data)
: response.swResponse.getStatus());
if (swCursorResponse.isOK()) {
RemoteCursor cursor;
cursor.setShardId(std::move(response.shardId));
cursor.setHostAndPort(*response.shardHostAndPort);
cursor.setCursorResponse(std::move(swCursorResponse.getValue()));
remoteCursors.push_back(std::move(cursor));
}
}
// Schedule killCursors against all cursors that were established.
killRemoteCursors(opCtx, executor.get(), std::move(remoteCursors), nss);
} catch (const DBException&) {
// Ignore the new error and rethrow the original one.
}
throw;
}
}
void killRemoteCursors(OperationContext* opCtx,
executor::TaskExecutor* executor,
std::vector<RemoteCursor>&& remoteCursors,
const NamespaceString& nss) {
for (auto&& remoteCursor : remoteCursors) {
killRemoteCursor(opCtx, executor, std::move(remoteCursor), nss);
}
}
void killRemoteCursor(OperationContext* opCtx,
executor::TaskExecutor* executor,
RemoteCursor&& cursor,
const NamespaceString& nss) {
BSONObj cmdObj = KillCursorsRequest(nss, {cursor.getCursorResponse().getCursorId()}).toBSON();
executor::RemoteCommandRequest request(
cursor.getHostAndPort(), nss.db().toString(), cmdObj, opCtx);
// We do not process the response to the killCursors request (we make a good-faith
// attempt at cleaning up the cursors, but ignore any returned errors).
executor->scheduleRemoteCommand(request, [](auto const&) {}).getStatus().ignore();
}
} // namespace mongo
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