minetestmapper/db-redis.cpp

#include <stdexcept>
#include <sstream>
#include <fstream>
#include "db-redis.h"
#include "types.h"
#include "util.h"

#define DB_REDIS_HMGET_NUMFIELDS 30

#define REPLY_TYPE_ERR(reply, desc) do { \
	throw std::runtime_error(std::string("Unexpected type for " desc ": ") \
			+ replyTypeStr((reply)->type)); \
	} while(0)

static inline int64_t stoi64(const std::string &s)
{
	std::stringstream tmp(s);
	int64_t t;
	tmp >> t;
	return t;
}


static inline std::string i64tos(int64_t i)
{
	std::ostringstream os;
	os << i;
	return os.str();
}

std::string get_setting_default(std::string name, std::istream &is, const std::string def)
{
	try {
		return get_setting(name, is);
	} catch(std::runtime_error e) {
		return def;
	}
}

DBRedis::DBRedis(const std::string &mapdir)
{
	std::ifstream ifs((mapdir + "/world.mt").c_str());
	if(!ifs.good())
		throw std::runtime_error("Failed to read world.mt");
	std::string tmp;
	try {
		tmp = get_setting("redis_address", ifs);
		ifs.seekg(0);
		hash = get_setting("redis_hash", ifs);
		ifs.seekg(0);
	} catch(std::runtime_error e) {
		throw std::runtime_error("Set redis_address and redis_hash in world.mt to use the redis backend");
	}
	const char *addr = tmp.c_str();
	int port = stoi64(get_setting_default("redis_port", ifs, "6379"));
	ctx = redisConnect(addr, port);
	if(!ctx)
		throw std::runtime_error("Cannot allocate redis context");
	else if(ctx->err) {
		std::string err = std::string("Connection error: ") + ctx->errstr;
		redisFree(ctx);
		throw std::runtime_error(err);
	}

	loadPosCache();
}


DBRedis::~DBRedis()
{
	redisFree(ctx);
}


std::vector<BlockPos> DBRedis::getBlockPos()
{
	return posCache;
}


std::string DBRedis::replyTypeStr(int type) {
	switch(type) {
		case REDIS_REPLY_STATUS:
			return "REDIS_REPLY_STATUS";
		case REDIS_REPLY_ERROR:
			return "REDIS_REPLY_ERROR";
		case REDIS_REPLY_INTEGER:
			return "REDIS_REPLY_INTEGER";
		case REDIS_REPLY_NIL:
			return "REDIS_REPLY_NIL";
		case REDIS_REPLY_STRING:
			return "REDIS_REPLY_STRING";
		case REDIS_REPLY_ARRAY:
			return "REDIS_REPLY_ARRAY";
		default:
			return "unknown";
	}
}


void DBRedis::loadPosCache()
{
	redisReply *reply;
	reply = (redisReply*) redisCommand(ctx, "HKEYS %s", hash.c_str());
	if(!reply)
		throw std::runtime_error("Redis command HKEYS failed");
	if(reply->type != REDIS_REPLY_ARRAY)
		REPLY_TYPE_ERR(reply, "HKEYS reply");
	for(size_t i = 0; i < reply->elements; i++) {
		if(reply->element[i]->type != REDIS_REPLY_STRING)
			REPLY_TYPE_ERR(reply->element[i], "HKEYS subreply");
		posCache.push_back(decodeBlockPos(stoi64(reply->element[i]->str)));
	}

	freeReplyObject(reply);
}


void DBRedis::HMGET(const std::vector<BlockPos> &positions, std::vector<ustring> *result)
{
	const char *argv[DB_REDIS_HMGET_NUMFIELDS + 2];
	argv[0] = "HMGET";
	argv[1] = hash.c_str();

	std::vector<BlockPos>::const_iterator position = positions.begin();
	std::size_t remaining = positions.size();
	while (remaining > 0) {
		const std::size_t batch_size =
			(remaining > DB_REDIS_HMGET_NUMFIELDS) ? DB_REDIS_HMGET_NUMFIELDS : remaining;

		redisReply *reply;
		{
			// storage to preserve validity of .c_str()
			std::string keys[batch_size];
			for (std::size_t i = 0; i < batch_size; ++i) {
				keys[i] = i64tos(encodeBlockPos(*position++));
				argv[i+2] = keys[i].c_str();
			}
			reply = (redisReply*) redisCommandArgv(ctx, batch_size + 2, argv, NULL);
		}

		if(!reply)
			throw std::runtime_error("Redis command HMGET failed");
		if (reply->type != REDIS_REPLY_ARRAY) {
			freeReplyObject(reply);
			REPLY_TYPE_ERR(reply, "HKEYS subreply");
		}
		if (reply->elements != batch_size) {
			freeReplyObject(reply);
			throw std::runtime_error("HMGET wrong number of elements");
		}
		for (std::size_t i = 0; i < batch_size; ++i) {
			redisReply *subreply = reply->element[i];
			if(!subreply)
				throw std::runtime_error("Redis command HMGET failed");
			if (subreply->type != REDIS_REPLY_STRING) {
				freeReplyObject(reply);
				REPLY_TYPE_ERR(reply, "HKEYS subreply");
			}
			if (subreply->len == 0) {
				freeReplyObject(reply);
				throw std::runtime_error("HMGET empty string");
			}
			result->push_back(ustring((const unsigned char *) subreply->str, subreply->len));
		}
		freeReplyObject(reply);
		remaining -= batch_size;
	}
}


void DBRedis::getBlocksOnZ(std::map<int16_t, BlockList> &blocks, int16_t zPos)
{
	std::vector<BlockPos> z_positions;
	for (std::vector<BlockPos>::const_iterator it = posCache.begin(); it != posCache.end(); ++it) {
		if (it->z != zPos) {
			continue;
		}
		z_positions.push_back(*it);
	}
	std::vector<ustring> z_blocks;
	HMGET(z_positions, &z_blocks);

	std::vector<ustring>::const_iterator z_block = z_blocks.begin();
	for (std::vector<BlockPos>::const_iterator pos = z_positions.begin();
			pos != z_positions.end();
			++pos, ++z_block) {
		blocks[pos->x].push_back(Block(*pos, *z_block));
	}
}