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/**
* Copyright (C) 2021-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/pipeline/document_source_change_stream_ensure_resume_token_present.h"
#include "mongo/db/pipeline/change_stream_start_after_invalidate_info.h"
#include "mongo/db/query/query_feature_flags_gen.h"
namespace mongo {
DocumentSourceChangeStreamEnsureResumeTokenPresent::
DocumentSourceChangeStreamEnsureResumeTokenPresent(
const boost::intrusive_ptr<ExpressionContext>& expCtx, ResumeTokenData token)
: DocumentSourceChangeStreamCheckResumability(expCtx, std::move(token)) {}
boost::intrusive_ptr<DocumentSourceChangeStreamEnsureResumeTokenPresent>
DocumentSourceChangeStreamEnsureResumeTokenPresent::create(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const DocumentSourceChangeStreamSpec& spec) {
auto resumeToken = DocumentSourceChangeStream::resolveResumeTokenFromSpec(spec);
tassert(5666902,
"Expected non-high-water-mark resume token",
!ResumeToken::isHighWaterMarkToken(resumeToken));
return new DocumentSourceChangeStreamEnsureResumeTokenPresent(expCtx, std::move(resumeToken));
}
const char* DocumentSourceChangeStreamEnsureResumeTokenPresent::getSourceName() const {
return kStageName.rawData();
}
StageConstraints DocumentSourceChangeStreamEnsureResumeTokenPresent::constraints(
Pipeline::SplitState) const {
StageConstraints constraints{StreamType::kStreaming,
PositionRequirement::kNone,
// If this is parsed on mongos it should stay on mongos. If we're
// not in a sharded cluster then it's okay to run on mongod.
HostTypeRequirement::kLocalOnly,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kNotAllowed,
TransactionRequirement::kNotAllowed,
LookupRequirement::kNotAllowed,
UnionRequirement::kNotAllowed,
ChangeStreamRequirement::kChangeStreamStage};
// The '$match' and 'DocumentSourceSingleDocumentTransformation' stages can swap with this
// stage, allowing filtering and reshaping to occur earlier in the pipeline. For sharded cluster
// pipelines, swaps can allow $match and 'DocumentSourceSingleDocumentTransformation' stages to
// execute on the shards, providing inter-node parallelism and potentially reducing the amount
// of data sent form each shard to the mongoS.
constraints.canSwapWithMatch = true;
constraints.canSwapWithSingleDocTransform = true;
return constraints;
}
DocumentSource::GetNextResult DocumentSourceChangeStreamEnsureResumeTokenPresent::doGetNext() {
// If we have already verified the resume token is present, return the next doc immediately.
if (_resumeStatus == ResumeStatus::kSurpassedToken) {
return pSource->getNext();
}
auto nextInput = GetNextResult::makeEOF();
// If we are starting after an 'invalidate' and the invalidating command (e.g. collection drop)
// occurred at the same clusterTime on more than one shard, then we may see multiple identical
// resume tokens here. We swallow all of them until the resume status becomes kSurpassedToken.
while (_resumeStatus != ResumeStatus::kSurpassedToken) {
// Delegate to DocumentSourceChangeStreamCheckResumability to consume all events up to the
// token. This will also set '_resumeStatus' to indicate whether we have seen or surpassed
// the token.
nextInput = _tryGetNext();
// If there are no more results, return EOF. We will continue checking for the resume token
// the next time the getNext method is called. If we hit EOF, then we cannot have surpassed
// the resume token on this iteration.
if (!nextInput.isAdvanced()) {
invariant(_resumeStatus != ResumeStatus::kSurpassedToken);
return nextInput;
}
// When we reach here, we have either found the resume token or surpassed it.
invariant(_resumeStatus != ResumeStatus::kCheckNextDoc);
// If the resume status is kFoundToken, record the fact that we have seen the token. When we
// have surpassed the resume token, we will assert that we saw the token before doing so. We
// cannot simply assert once and then assume we have surpassed the token, because in certain
// cases we may see 1..N identical tokens and must swallow them all before proceeding.
_hasSeenResumeToken = (_hasSeenResumeToken || _resumeStatus == ResumeStatus::kFoundToken);
}
// Assert that before surpassing the resume token, we observed the token itself in the stream.
uassert(ErrorCodes::ChangeStreamFatalError,
str::stream() << "cannot resume stream; the resume token was not found. "
<< nextInput.getDocument()["_id"].getDocument().toString(),
_hasSeenResumeToken);
// At this point, we have seen the token and swallowed it. Return the next event to the client.
invariant(_hasSeenResumeToken && _resumeStatus == ResumeStatus::kSurpassedToken);
return nextInput;
}
DocumentSource::GetNextResult DocumentSourceChangeStreamEnsureResumeTokenPresent::_tryGetNext() {
try {
return DocumentSourceChangeStreamCheckResumability::doGetNext();
} catch (const ExceptionFor<ErrorCodes::ChangeStreamStartAfterInvalidate>& ex) {
const auto extraInfo = ex.extraInfo<ChangeStreamStartAfterInvalidateInfo>();
tassert(5779200, "Missing ChangeStreamStartAfterInvalidationInfo on exception", extraInfo);
const DocumentSource::GetNextResult nextInput =
Document::fromBsonWithMetaData(extraInfo->getStartAfterInvalidateEvent());
_resumeStatus =
DocumentSourceChangeStreamCheckResumability::compareAgainstClientResumeToken(
pExpCtx, nextInput.getDocument(), _tokenFromClient);
// This exception should always contain the client-provided resume token.
tassert(5779201,
"Client resume token did not match with the resume token on the invalidate event",
_resumeStatus == ResumeStatus::kFoundToken);
return nextInput;
}
}
Value DocumentSourceChangeStreamEnsureResumeTokenPresent::serialize(
boost::optional<ExplainOptions::Verbosity> explain) const {
// We only serialize this stage in the context of explain.
if (explain) {
return Value(DOC(DocumentSourceChangeStream::kStageName
<< DOC("stage"
<< "internalEnsureResumeTokenPresent"_sd
<< "resumeToken" << ResumeToken(_tokenFromClient).toDocument())));
}
MONGO_UNREACHABLE_TASSERT(5467611);
}
} // namespace mongo
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