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chore: Introduce small buffer in redis parser
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This is needed in order to eliminate cases where we return INPUT_PENDING but do not consume the whole string by rejecting just several bytes.
This should simplify buffer management for the caller, so that if they pass a string that
did not result in complete parsed request, at least the whole string is consumed and can be discarded.

Signed-off-by: Roman Gershman <[email protected]>
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@romange
romange committed Dec 11, 2024
1 parent 76f79f0 commit f7fa90c
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Showing 3 changed files with 99 additions and 32 deletions.
86 changes: 65 additions & 21 deletions src/facade/redis_parser.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,12 +18,16 @@ auto RedisParser::Parse(Buffer str, uint32_t* consumed, RespExpr::Vec* res) -> R
*consumed = 0;
res->clear();

if (str.size() < 2) {
if (str.size() + small_len_ < 2) {
memcpy(small_buf_ + small_len_, str.data(), str.size());
small_len_ += str.size();
*consumed = str.size();

return INPUT_PENDING;
}

if (state_ == CMD_COMPLETE_S) {
InitStart(str[0], res);
InitStart(small_len_ > 0 ? small_buf_[0] : str[0], res);
} else {
// We continue parsing in the middle.
if (!cached_expr_)
Expand All @@ -40,11 +44,8 @@ auto RedisParser::Parse(Buffer str, uint32_t* consumed, RespExpr::Vec* res) -> R
resultc = ConsumeArrayLen(str);
break;
case PARSE_ARG_S:
if (str.size() == 0 || (str.size() < 4 && str[0] != '_')) {
resultc.first = INPUT_PENDING;
} else {
resultc = ParseArg(str);
}
DCHECK(!str.empty());
resultc = ParseArg(str);
break;
case INLINE_S:
DCHECK(parse_stack_.empty());
Expand All @@ -67,13 +68,16 @@ auto RedisParser::Parse(Buffer str, uint32_t* consumed, RespExpr::Vec* res) -> R
}

if (resultc.first == INPUT_PENDING) {
DCHECK(str.empty());
StashState(res);
}
return resultc.first;
}

if (resultc.first == OK) {
DCHECK(cached_expr_);
DCHECK_EQ(0, small_len_);

if (res != cached_expr_) {
DCHECK(!stash_.empty());

Expand Down Expand Up @@ -214,28 +218,37 @@ auto RedisParser::ParseInline(Buffer str) -> ResultConsumed {
auto RedisParser::ParseLen(Buffer str, int64_t* res) -> ResultConsumed {
DCHECK(!str.empty());

DCHECK(str[0] == '$' || str[0] == '*' || str[0] == '%' || str[0] == '~');
DCHECK(small_len_ > 0 || str[0] == '$' || str[0] == '*' || str[0] == '%' || str[0] == '~');

const char* s = reinterpret_cast<const char*>(str.data());
const char* pos = reinterpret_cast<const char*>(memchr(s, '\n', str.size()));
if (!pos) {
Result r = INPUT_PENDING;
if (str.size() >= 32) {
LOG(WARNING) << "Unexpected format " << string_view{s, str.size()};
r = BAD_ARRAYLEN;
if (str.size() + small_len_ < sizeof(small_buf_)) {
memcpy(small_buf_ + small_len_, str.data(), str.size());
small_len_ += str.size();
return {INPUT_PENDING, str.size()};
}
return {r, 0};
LOG(WARNING) << "Unexpected format " << string_view{s, str.size()};
return ResultConsumed{BAD_ARRAYLEN, 0};
}

unsigned consumed = pos - s + 1;
if (small_len_ > 0) {
memcpy(small_buf_ + small_len_, str.data(), consumed);
small_len_ += consumed;
s = small_buf_;
pos = small_buf_ + small_len_ - 1;
small_len_ = 0;
}

if (pos[-1] != '\r') {
return {BAD_ARRAYLEN, 0};
}

// Skip the first character and 2 last ones (\r\n).
string_view len_token{s + 1, size_t(pos - 1 - s)};
string_view len_token{s + 1, size_t(pos - 2 - s)};
bool success = absl::SimpleAtoi(len_token, res);

unsigned consumed = pos - s + 1;
if (success && *res >= -1) {
return ResultConsumed{OK, consumed};
}
Expand Down Expand Up @@ -306,11 +319,13 @@ auto RedisParser::ConsumeArrayLen(Buffer str) -> ResultConsumed {
auto RedisParser::ParseArg(Buffer str) -> ResultConsumed {
DCHECK(!str.empty());

char c = str[0];
char c = small_len_ > 0 ? small_buf_[0] : str[0];
unsigned min_len = 3 + int(c != '_');

if (str.size() < min_len) {
return {INPUT_PENDING, 0};
if (small_len_ + str.size() < min_len) {
memcpy(small_buf_ + small_len_, str.data(), str.size());
small_len_ += str.size();
return {INPUT_PENDING, str.size()};
}

if (c == '$') {
Expand Down Expand Up @@ -344,10 +359,14 @@ auto RedisParser::ParseArg(Buffer str) -> ResultConsumed {

if (c == '_') { // Resp3 NIL
// '_','\r','\n'
DCHECK_GE(str.size(), 3u);
DCHECK_GE(small_len_ + str.size(), 3u);
DCHECK_LT(small_len_, 3);

unsigned consumed = 3;
if (str[1] != '\r' || str[2] != '\n') {
unsigned consumed = 3 - small_len_;
for (unsigned i = 0; i < consumed; ++i) {
small_buf_[small_len_ + i] = str[i];
}
if (small_buf_[1] != '\r' || small_buf_[2] != '\n') {
return {BAD_STRING, 0};
}

Expand Down Expand Up @@ -418,6 +437,26 @@ auto RedisParser::ConsumeBulk(Buffer str) -> ResultConsumed {

uint32_t consumed = 0;

if (small_len_ > 0) {
DCHECK(!is_broken_token_);
DCHECK_EQ(bulk_len_, 0u);

if (bulk_len_ == 0) {
DCHECK_EQ(small_len_, 1);
DCHECK_GE(str.size(), 1u);
if (small_buf_[0] != '\r' || str[0] != '\n') {
return {BAD_STRING, 0};
}
consumed = bulk_len_ + 2;
small_len_ = 0;
HandleFinishArg();

return {OK, 1};
}
}

DCHECK_EQ(small_len_, 0);

if (str.size() >= bulk_len_) {
consumed = bulk_len_;
if (bulk_len_) {
Expand All @@ -439,6 +478,10 @@ auto RedisParser::ConsumeBulk(Buffer str) -> ResultConsumed {
}
HandleFinishArg();
return {OK, consumed + 2};
} else if (str.size() == 1) {
small_buf_[0] = str[0];
consumed++;
small_len_ = 1;
}
return {INPUT_PENDING, consumed};
}
Expand Down Expand Up @@ -483,6 +526,7 @@ void RedisParser::HandleFinishArg() {
}
cached_expr_ = parse_stack_.back().second;
}
small_len_ = 0;
}

void RedisParser::ExtendLastString(Buffer str) {
Expand Down
4 changes: 2 additions & 2 deletions src/facade/redis_parser.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -45,8 +45,6 @@ class RedisParser {
* part of str because parser caches the intermediate state internally according to 'consumed'
* result.
*
* Note: A parser does not always guarantee progress, i.e. if a small buffer was passed it may
* returns INPUT_PENDING with consumed == 0.
*
*/

Expand Down Expand Up @@ -97,6 +95,7 @@ class RedisParser {
State state_ = CMD_COMPLETE_S;
bool is_broken_token_ = false; // true, if a token (inline or bulk) is broken during the parsing.
bool server_mode_ = true;
uint8_t small_len_ = 0;

uint32_t bulk_len_ = 0;
uint32_t last_stashed_level_ = 0, last_stashed_index_ = 0;
Expand All @@ -112,6 +111,7 @@ class RedisParser {

using Blob = std::vector<uint8_t>;
std::vector<Blob> buf_stash_;
char small_buf_[32];
};

} // namespace facade
41 changes: 32 additions & 9 deletions src/facade/redis_parser_test.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -107,10 +107,10 @@ TEST_F(RedisParserTest, Multi1) {

TEST_F(RedisParserTest, Multi2) {
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("*1\r\n$"));
EXPECT_EQ(4, consumed_);
EXPECT_EQ(5, consumed_);

ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("$4\r\nMSET"));
EXPECT_EQ(8, consumed_);
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("4\r\nMSET"));
EXPECT_EQ(7, consumed_);

ASSERT_EQ(RedisParser::OK, Parse("\r\n*2\r\n"));
EXPECT_EQ(2, consumed_);
Expand Down Expand Up @@ -138,6 +138,7 @@ TEST_F(RedisParserTest, Multi3) {
TEST_F(RedisParserTest, ClientMode) {
parser_.SetClientMode();

#if 0
ASSERT_EQ(RedisParser::OK, Parse(":-1\r\n"));
EXPECT_THAT(args_, ElementsAre(IntArg(-1)));

Expand All @@ -146,6 +147,16 @@ TEST_F(RedisParserTest, ClientMode) {

ASSERT_EQ(RedisParser::OK, Parse("-ERR foo bar\r\n"));
EXPECT_THAT(args_, ElementsAre(ErrArg("ERR foo")));

ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("_"));
EXPECT_EQ(1, consumed_);
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("\r"));
EXPECT_EQ(1, consumed_);
ASSERT_EQ(RedisParser::OK, Parse("\n"));
EXPECT_EQ(1, consumed_);
EXPECT_THAT(args_, ElementsAre(ArgType(RespExpr::NIL)));
#endif
ASSERT_EQ(RedisParser::OK, Parse("*2\r\n_\r\n_\r\n"));
}

TEST_F(RedisParserTest, Hierarchy) {
Expand All @@ -171,25 +182,25 @@ TEST_F(RedisParserTest, Empty) {

TEST_F(RedisParserTest, LargeBulk) {
string_view prefix("*1\r\n$1024\r\n");
string half(512, 'a');

ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(prefix));
ASSERT_EQ(prefix.size(), consumed_);
ASSERT_GE(parser_.parselen_hint(), 1024);

string half(512, 'a');
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(half));
ASSERT_EQ(512, consumed_);
ASSERT_GE(parser_.parselen_hint(), 512);
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(half));
ASSERT_EQ(512, consumed_);
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("\r"));
ASSERT_EQ(0, consumed_);
ASSERT_EQ(RedisParser::OK, Parse("\r\n"));
ASSERT_EQ(2, consumed_);
ASSERT_EQ(1, consumed_);
ASSERT_EQ(RedisParser::OK, Parse("\n"));
EXPECT_EQ(1, consumed_);

string part1 = absl::StrCat(prefix, half);
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(part1));
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse(half));
EXPECT_EQ(RedisParser::INPUT_PENDING, Parse(part1));
EXPECT_EQ(RedisParser::INPUT_PENDING, Parse(half));
ASSERT_EQ(RedisParser::OK, Parse("\r\n"));

prefix = "*1\r\n$270000000\r\n";
Expand Down Expand Up @@ -243,4 +254,16 @@ TEST_F(RedisParserTest, UsedMemory) {
EXPECT_GT(dfly::HeapSize(stash), 30000);
}

TEST_F(RedisParserTest, Eol) {
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("*1\r"));
EXPECT_EQ(3, consumed_);
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("\n$5\r\n"));
EXPECT_EQ(5, consumed_);
}

TEST_F(RedisParserTest, BulkSplit) {
ASSERT_EQ(RedisParser::INPUT_PENDING, Parse("*1\r\n$4\r\nSADD\r"));
ASSERT_EQ(RedisParser::OK, Parse("\n"));
}

} // namespace facade

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