From a7d021ee57ffc19a11dd17b0630e45750719ca90 Mon Sep 17 00:00:00 2001
From: Calle Wilund <calle@scylladb.com>
Date: Wed, 2 Sep 2020 15:37:44 +0000
Subject: [PATCH] alternator: Fix sequence number range using wrong format

Fixes #7158

A streams shard  descriptions has a sequence range describing start/end
(if available) of the shard. This is specified as being "numeric only".

Alternator incorrectly used UUID here, which breaks kinesis.

v2:
* Fix uint128_t parsing from string. bmp::number constructor accepted
  sstring, but did not interpret it as std::string/chars. Weird results.
---
 alternator/streams.cc | 50 +++++++++++++++++++++++++++++++++++++++----
 1 file changed, 46 insertions(+), 4 deletions(-)

diff --git a/alternator/streams.cc b/alternator/streams.cc
index 14fb1f2619..dc9be5f2b7 100644
--- a/alternator/streams.cc
+++ b/alternator/streams.cc
@@ -22,6 +22,7 @@
 #include <type_traits>
 #include <boost/lexical_cast.hpp>
 #include <boost/io/ios_state.hpp>
+#include <boost/multiprecision/cpp_int.hpp>
 
 #include "base64.hh"
 #include "log.hh"
@@ -240,6 +241,38 @@ shard_id::shard_id(const sstring& s) {
     id = cdc::stream_id(from_hex(s.substr(j + 1)));
 }
 
+struct sequence_number {
+    utils::UUID uuid;
+
+    sequence_number(utils::UUID uuid)
+        : uuid(uuid)
+    {}
+    sequence_number(std::string_view);
+
+    operator const utils::UUID&() const {
+        return uuid;
+    }
+
+    friend std::ostream& operator<<(std::ostream& os, const sequence_number& num) {
+        boost::io::ios_flags_saver fs(os);
+
+        using namespace boost::multiprecision;
+
+        uint128_t hi = uint64_t(num.uuid.get_most_significant_bits());
+        uint128_t lo = uint64_t(num.uuid.get_least_significant_bits());
+
+        return os << std::dec << ((hi << 64) | lo);
+    }
+};
+
+sequence_number::sequence_number(std::string_view v) 
+    : uuid([&] {
+        using namespace boost::multiprecision;
+        uint128_t tmp{v};
+        return utils::UUID(uint64_t(tmp >> 64), uint64_t(tmp & std::numeric_limits<uint64_t>::max()));
+    }())
+{}
+
 }
 
 template<typename ValueType>
@@ -247,6 +280,11 @@ struct rapidjson::internal::TypeHelper<ValueType, alternator::shard_id>
     : public from_string_helper<ValueType, alternator::shard_id>
 {};
 
+template<typename ValueType>
+struct rapidjson::internal::TypeHelper<ValueType, alternator::sequence_number>
+    : public from_string_helper<ValueType, alternator::sequence_number>
+{};
+
 namespace alternator {
 
 enum class stream_view_type {
@@ -438,6 +476,9 @@ future<executor::request_return_type> executor::describe_stream(client_state& cl
 
         for (; limit > 0 && i != e; prev = i, ++i) {
             auto& [ts, sv] = *i;
+
+            last = std::nullopt;
+
             for (auto& id : sv.streams()) {
                 if (shard_start && shard_start->id != id) {
                     continue;
@@ -464,9 +505,9 @@ future<executor::request_return_type> executor::describe_stream(client_state& cl
                 rjson::set(shard, "ShardId", *last);
 
                 auto range = rjson::empty_object();
-                rjson::set(range, "StartingSequenceNumber", utils::UUID_gen::min_time_UUID(ts.time_since_epoch().count()));
+                rjson::set(range, "StartingSequenceNumber", sequence_number(utils::UUID_gen::min_time_UUID(ts.time_since_epoch().count())));
                 if (sv.expired() && *sv.expired() < threshold) {
-                    rjson::set(range, "EndingSequenceNumber", utils::UUID_gen::max_time_UUID((*sv.expired() + confidence_interval(db)).time_since_epoch().count()));
+                    rjson::set(range, "EndingSequenceNumber", sequence_number(utils::UUID_gen::max_time_UUID((*sv.expired() + confidence_interval(db)).time_since_epoch().count())));
                 }
 
                 rjson::set(shard, "SequenceNumberRange", std::move(range));
@@ -476,6 +517,7 @@ future<executor::request_return_type> executor::describe_stream(client_state& cl
                     break;
                 }
 
+                last = std::nullopt;
             }
         }
 
@@ -587,7 +629,7 @@ future<executor::request_return_type> executor::get_shard_iterator(client_state&
     _stats.api_operations.get_shard_iterator++;
 
     auto type = rjson::get<shard_iterator_type>(request, "ShardIteratorType");
-    auto seq_num = rjson::get_opt<utils::UUID>(request, "SequenceNumber");
+    auto seq_num = rjson::get_opt<sequence_number>(request, "SequenceNumber");
     
     if (type < shard_iterator_type::TRIM_HORIZON && !seq_num) {
         throw api_error::validation("Missing required parameter \"SequenceNumber\"");
@@ -807,7 +849,7 @@ future<executor::request_return_type> executor::get_records(client_state& client
                 describe_single_item(*selection, row, key_names, keys);
                 rjson::set(dynamodb, "Keys", std::move(keys));
                 rjson::set(dynamodb, "ApproximateCreationDateTime", utils::UUID_gen::unix_timestamp_in_sec(ts).count());
-                rjson::set(dynamodb, "SequenceNumber", ts);
+                rjson::set(dynamodb, "SequenceNumber", sequence_number(ts));
                 rjson::set(dynamodb, "StreamViewType", type);
                 //TODO: SizeInBytes
             }