Method writeTransactionInfo

fdbserver/LogSystem.cpp:349–389

}

bool LogPushData::writeTransactionInfo(int location, uint32_t subseq) {
	if (!FLOW_KNOBS->WRITE_TRACING_ENABLED || logSystem->getTLogVersion() < TLogVersion::V6 ||
	    writtenLocations.count(location) != 0) {
		return false;
	}

	CODE_PROBE(true, "Wrote SpanContextMessage to a transaction log");
	writtenLocations.insert(location);

	BinaryWriter& wr = messagesWriter[location];
	int offset = wr.getLength();
	wr << uint32_t(0) << subseq << uint16_t(prev_tags.size());
	for (auto& tag : prev_tags)
		wr << tag;
	if (logSystem->getTLogVersion() >= TLogVersion::V7) {
		OTELSpanContextMessage contextMessage(spanContext);
		wr << contextMessage;
	} else {
		// When we're on a TLog version below 7, but the front end of the system (i.e. proxy, sequencer, resolver)
		// is using OpenTelemetry tracing (i.e on or above 7.2), we need to convert the OpenTelemetry Span data model
		// i.e. 16 bytes for traceId, 8 bytes for spanId, to the OpenTracing spec, which is 8 bytes for traceId
		// and 8 bytes for spanId. That means we need to drop some data.
		//
		// As a workaround for this special case we've decided to drop is the 8 bytes
		// for spanId. Therefore we're passing along the full 16 byte traceId to the storage server with 0 for spanID.
		// This will result in a follows from relationship for the storage span within the trace rather than a
		// parent->child.
		SpanContextMessage contextMessage;
		if (spanContext.isSampled()) {
			CODE_PROBE(true, "Converting OTELSpanContextMessage to traced SpanContextMessage");
			contextMessage = SpanContextMessage(UID(spanContext.traceID.first(), spanContext.traceID.second()));
		} else {
			CODE_PROBE(true, "Converting OTELSpanContextMessage to untraced SpanContextMessage");
			contextMessage = SpanContextMessage(UID(0, 0));
		}
		wr << contextMessage;
	}
	int length = wr.getLength() - offset;
	*(uint32_t*)((uint8_t*)wr.getData() + offset) = length - sizeof(uint32_t);
	return true;
}

void LogPushData::setMutations(uint32_t totalMutations, VectorRef<StringRef> mutations) {
	ASSERT_EQ(subsequence, 1);