Smityz commented on a change in pull request #631:
URL: https://github.com/apache/incubator-pegasus/pull/631#discussion_r513904935
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File path: src/server/hotkey_collector.cpp
##########
@@ -251,5 +261,107 @@ void
hotkey_coarse_data_collector::analyse_data(detect_hotkey_result &result)
}
}
+hotkey_fine_data_collector::hotkey_fine_data_collector(
+ replica_base *base,
+ dsn::replication::hotkey_type::type hotkey_type,
+ int target_bucket_index,
+ int max_queue_size)
+ : internal_collector_base(base),
+ _hotkey_type(hotkey_type),
+ _max_queue_size(max_queue_size),
+ _target_bucket_index(target_bucket_index)
+{
+ // Distinguish between single-threaded and multi-threaded environments
+ if (_hotkey_type == dsn::replication::hotkey_type::READ) {
+
+ auto threads = dsn::get_threadpool_threads_info(THREAD_POOL_LOCAL_APP);
+ int queue_num = threads.size();
+
+ _string_capture_queue_vec.reserve(queue_num);
+ for (int i = 0; i < queue_num; i++) {
+ _thread_queue_map.insert(std::make_pair(threads[i]->native_tid(),
i));
+
+ // Create a vector of the ReaderWriterQueue whose size =
_max_queue_size
+ _string_capture_queue_vec.emplace_back(_max_queue_size);
+ }
+
+ } else { // WRITE
+ _string_capture_queue_vec.emplace_back(_max_queue_size);
+ }
+}
+
+void hotkey_fine_data_collector::capture_data(const dsn::blob &hash_key,
uint64_t weight)
+{
+ if (get_bucket_id(hash_key) != _target_bucket_index) {
+ return;
+ }
+
_string_capture_queue_vec[get_queue_index()].try_emplace(std::make_pair(hash_key,
weight));
+}
+
+struct blob_hash
+{
+ std::size_t operator()(const dsn::blob &str) const
+ {
+ dsn::string_view cp(str);
+ return boost::hash_range(cp.begin(), cp.end());
+ }
+};
+struct blob_equal
+{
+ std::size_t operator()(const dsn::blob &lhs, const dsn::blob &rhs) const
+ {
+ return dsn::string_view(lhs) == dsn::string_view(rhs);
+ }
+};
+
+int hotkey_fine_data_collector::get_queue_index()
+{
+ if (_hotkey_type == dsn::replication::hotkey_type::WRITE) {
+ return 0;
+ }
+
+ int thread_native_tid = dsn::utils::get_current_tid();
+ auto result = _thread_queue_map.find(thread_native_tid);
+ dassert(result != _thread_queue_map.end(), "Can't find the queue
corresponding to the thread");
+ return result->second;
+}
+
+void hotkey_fine_data_collector::analyse_data(detect_hotkey_result &result)
+{
+ std::unordered_map<dsn::blob, uint64_t, blob_hash, blob_equal>
hash_key_accessed_cnt;
+ for (auto &rw_queue : _string_capture_queue_vec) {
+ std::pair<dsn::blob, int> hash_key_pair;
+ // prevent endless loop
+ int collect_sum = 0;
+ while (rw_queue.try_dequeue(hash_key_pair) && ++collect_sum <=
_max_queue_size) {
+ hash_key_accessed_cnt[hash_key_pair.first] += hash_key_pair.second;
+ }
+ }
+
+ if (hash_key_accessed_cnt.empty()) {
+ return;
+ }
+
+ std::vector<uint64_t> counts;
+ counts.reserve(FLAGS_data_capture_hash_bucket_num);
+ dsn::string_view count_max_key;
+ uint64_t count_max = 0;
+ for (const auto &iter : hash_key_accessed_cnt) {
+ counts.push_back(iter.second);
+ if (iter.second > count_max) {
+ count_max = iter.second;
+ count_max_key = iter.first; // the key with the max accessed count.
+ }
+ }
+
+ // if the accessed counts differ hugely (depends on the variance
threshold),
+ // the max key is the hotkey.
+ int hot_index;
+ if (counts.size() < 3 ||
+ find_outlier_index(counts, FLAGS_fine_data_variance_threshold,
hot_index)) {
+ result.hot_hash_key = std::string(count_max_key);
+ }
Review comment:
Only depends on the hottest data is not accurate, we must ensure that
it's an outlier in its hash bucket
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