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/**
* Copyright (C) 2020-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/s/resharding/resharding_donor_oplog_iterator.h"
#include <tuple>
#include <utility>
#include "mongo/bson/bsonmisc.h"
#include "mongo/bson/json.h"
#include "mongo/db/client.h"
#include "mongo/db/pipeline/document_source_lookup.h"
#include "mongo/db/pipeline/document_source_match.h"
#include "mongo/db/pipeline/document_source_replace_root.h"
#include "mongo/db/pipeline/document_source_sort.h"
#include "mongo/db/pipeline/document_source_unwind.h"
#include "mongo/db/pipeline/process_interface/mongo_process_interface.h"
#include "mongo/db/s/resharding/resharding_server_parameters_gen.h"
#include "mongo/db/s/resharding/resharding_util.h"
#include "mongo/logv2/log.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/future_util.h"
#include "mongo/util/scopeguard.h"
#include "mongo/util/str.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kResharding
namespace mongo {
using namespace fmt::literals;
namespace {
/**
* Extracts the oplog id from the oplog.
*/
ReshardingDonorOplogId getId(const repl::OplogEntry& oplog) {
return ReshardingDonorOplogId::parse(
IDLParserErrorContext("ReshardingDonorOplogIterator::getOplogId"),
oplog.get_id()->getDocument().toBson());
}
} // anonymous namespace
ReshardingDonorOplogIterator::ReshardingDonorOplogIterator(
NamespaceString oplogBufferNss,
ReshardingDonorOplogId resumeToken,
resharding::OnInsertAwaitable* insertNotifier)
: _oplogBufferNss(std::move(oplogBufferNss)),
_resumeToken(std::move(resumeToken)),
_insertNotifier(insertNotifier) {}
std::unique_ptr<Pipeline, PipelineDeleter> ReshardingDonorOplogIterator::makePipeline(
OperationContext* opCtx, std::shared_ptr<MongoProcessInterface> mongoProcessInterface) {
using Doc = Document;
using Arr = std::vector<Value>;
using V = Value;
StringMap<ExpressionContext::ResolvedNamespace> resolvedNamespaces;
resolvedNamespaces[_oplogBufferNss.coll()] = {_oplogBufferNss, std::vector<BSONObj>{}};
auto expCtx = make_intrusive<ExpressionContext>(opCtx,
boost::none, /* explain */
false, /* fromMongos */
false, /* needsMerge */
false, /* allowDiskUse */
false, /* bypassDocumentValidation */
false, /* isMapReduceCommand */
_oplogBufferNss,
boost::none, /* runtimeConstants */
nullptr, /* collator */
std::move(mongoProcessInterface),
std::move(resolvedNamespaces),
boost::none /* collUUID */);
Pipeline::SourceContainer stages;
stages.emplace_back(
DocumentSourceMatch::create(BSON("_id" << BSON("$gt" << _resumeToken.toBSON())), expCtx));
stages.emplace_back(DocumentSourceSort::create(expCtx, BSON("_id" << 1)));
return Pipeline::create(std::move(stages), std::move(expCtx));
}
std::vector<repl::OplogEntry> ReshardingDonorOplogIterator::_fillBatch(Pipeline& pipeline) {
std::vector<repl::OplogEntry> batch;
int numBytes = 0;
do {
auto doc = pipeline.getNext();
if (!doc) {
break;
}
auto obj = doc->toBson();
auto& entry = batch.emplace_back(obj.getOwned());
numBytes += obj.objsize();
if (resharding::isFinalOplog(entry)) {
// The ReshardingOplogFetcher should never insert documents after the reshardFinalOp
// entry. We defensively check each oplog entry for being the reshardFinalOp and confirm
// the pipeline has been exhausted.
if (auto nextDoc = pipeline.getNext()) {
tasserted(6077499,
fmt::format("Unexpectedly found entry after reshardFinalOp: {}",
redact(nextDoc->toString())));
}
}
} while (numBytes < resharding::gReshardingOplogBatchLimitBytes.load() &&
batch.size() < std::size_t(resharding::gReshardingOplogBatchLimitOperations.load()));
return batch;
}
ExecutorFuture<std::vector<repl::OplogEntry>> ReshardingDonorOplogIterator::getNextBatch(
std::shared_ptr<executor::TaskExecutor> executor,
CancellationToken cancelToken,
CancelableOperationContextFactory factory) {
if (_hasSeenFinalOplogEntry) {
invariant(!_pipeline);
return ExecutorFuture(std::move(executor), std::vector<repl::OplogEntry>{});
}
auto batch = [&] {
auto opCtx = factory.makeOperationContext(&cc());
ScopeGuard guard([&] { dispose(opCtx.get()); });
// A primary which steps down may briefly continue running the ReshardingDonorOplogIterator
// as a secondary. AutoGetCollectionForReadBase forbids reads on a secondary from using the
// default RecoveryUnit::ReadSource of kNoTimestamp when the operation expects to conflict
// with secondary oplog application. We opt out of acquiring the PBWM lock to avoid
// triggering an fassert() when briefly running as a secondary. This is acceptable because
// the PBWM lock isn't needed as a primary and any inconsistent reads as a secondary won't
// have a real effect because the node won't be able to perform more writes.
ShouldNotConflictWithSecondaryBatchApplicationBlock shouldNotConflictBlock(
opCtx->lockState());
Timer fetchTimer;
if (_pipeline) {
_pipeline->reattachToOperationContext(opCtx.get());
} else {
auto pipeline = makePipeline(opCtx.get(), MongoProcessInterface::create(opCtx.get()));
_pipeline = pipeline->getContext()
->mongoProcessInterface->attachCursorSourceToPipelineForLocalRead(
pipeline.release());
_pipeline.get_deleter().dismissDisposal();
}
auto batch = _fillBatch(*_pipeline);
if (!batch.empty()) {
const auto& lastEntryInBatch = batch.back();
_resumeToken = getId(lastEntryInBatch);
if (resharding::isFinalOplog(lastEntryInBatch)) {
_hasSeenFinalOplogEntry = true;
// Skip returning the final oplog entry because it is known to be a no-op.
batch.pop_back();
} else {
_pipeline->detachFromOperationContext();
guard.dismiss();
}
}
return batch;
}();
if (batch.empty() && !_hasSeenFinalOplogEntry) {
return ExecutorFuture(executor)
.then([this, cancelToken] {
return future_util::withCancellation(_insertNotifier->awaitInsert(_resumeToken),
cancelToken);
})
.then([this, cancelToken, executor, factory] {
return getNextBatch(std::move(executor), cancelToken, factory);
});
}
return ExecutorFuture(std::move(executor), std::move(batch));
}
void ReshardingDonorOplogIterator::dispose(OperationContext* opCtx) {
if (_pipeline) {
_pipeline->dispose(opCtx);
_pipeline.reset();
}
}
} // namespace mongo
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