Update version map unsync tolerance to 200ms

Before this change version_map's reload_interval was equal to the
unsync_tolerance. This means that we would ~always miss the cache.

The check for outdated cache is as follows:
- When reading into cache set `last_reload_time = now -
  unsync_tolerance`
- When checking if cache is outdated we check whether `now -
  last_reload_time > reload_interval

This change updates the unsync tolerance to 200ms. This will mean the
cache is valid for 1.8s

Tests uncovered that we were not flushing the version_map when clearing
the storage. This change fixes this as well.

cpp/arcticdb/util/constants.hpp

@@ -19,7 +19,9 @@ constexpr auto string_nan = std::numeric_limits<position_t>::max() - 1;
 
 constexpr auto NaT = std::numeric_limits<timestamp>::min();
 
-static constexpr decltype(timestamp(0) - timestamp(0)) ONE_SECOND = 1'000'000'000;
+static constexpr decltype(timestamp(0) - timestamp(0)) ONE_MILLISECOND = 1'000'000;
+
+static constexpr decltype(timestamp(0) - timestamp(0)) ONE_SECOND = 1'000 * ONE_MILLISECOND;
 
 static constexpr decltype(timestamp(0) - timestamp(0)) ONE_MINUTE = 60 * ONE_SECOND;
 

cpp/arcticdb/version/version_map.hpp

@@ -107,7 +107,7 @@ class VersionMapImpl {
      */
     using MapType =  std::map<StreamId, std::shared_ptr<VersionMapEntry>>;
 
-    static constexpr uint64_t DEFAULT_CLOCK_UNSYNC_TOLERANCE = ONE_SECOND * 2;
+    static constexpr uint64_t DEFAULT_CLOCK_UNSYNC_TOLERANCE = ONE_MILLISECOND * 200;
     static constexpr uint64_t DEFAULT_RELOAD_INTERVAL = ONE_SECOND * 2;
     MapType map_;
     bool validate_ = false;

cpp/arcticdb/version/version_store_api.cpp

@@ -1125,6 +1125,7 @@ std::vector<SliceAndKey> PythonVersionStore::list_incompletes(const StreamId& st
 }
 
 void PythonVersionStore::clear(const bool continue_on_error) {
+    version_map()->flush();
     if (store()->fast_delete()) {
         // Most storage backends have a fast deletion method for a db/collection equivalent, eg. drop() for mongo and
         // lmdb and iterating each key is always going to be suboptimal.