Too many MOVED error in # Errorstats section of INFO ALL

[chakaz]

Dragonfly saves count per error here:

dragonfly/src/facade/reply_builder.cc

Lines 321 to 336 in 7815c8d

	void RedisReplyBuilderBase::SendError(std::string_view str, std::string_view type) {
	ReplyScope scope(this);
	if (type.empty()) {
	type = str;
	if (type == kSyntaxErr)
	type = kSyntaxErrType;
	}
	tl_facade_stats->reply_stats.err_count[type]++;
	last_error_ = str;
	if (str[0] != '-')
	WritePieces("-ERR ", str, kCRLF);
	else
	WritePieces(str, kCRLF);
	}

The issue is that, we type is empty (which it is for MOVED replies), then we save an entry per str, which could be 16k in a regular situation, or more if we do slot migrations.

Then, all INFO replies fetch this information (from all threads), even if the ERRORSTATS section is not requested.

This is a general problem in the way we do error handling, but hopefully most errors contain constant strings instead of slot id + host.

To fix this only for MOVED (like I propose) we could simply add some special handling in the above code (if starts with MOVED then...)

[romange]

@chakaz type was designed exactly for this.