[GitHub] [incubator-pegasus] Smityz commented on a change in pull request #603: feat(hotkey detection): build a fundamental framework of hotkey detection

[GitBox <gi...@apache.org>]

Smityz commented on a change in pull request #603:
URL: https://github.com/apache/incubator-pegasus/pull/603#discussion_r490409485



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File path: src/server/hotkey_coarse_data_collector.h
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@@ -0,0 +1,46 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "base/pegasus_utils.h"
+
+namespace pegasus {
+namespace server {
+
+// hotkey_coarse_data_collector handles the first procedure (COARSE) of hotkey detection.
+// It captures the data without recording them, but simply divides the incoming requests
+// into a number of buckets and counts the accessed times of each bucket.
+// If the variance among the buckets exceeds the threshold, the most accessed bucket
+// is regarded to contain the hotkey.
+//
+// This technique intends to reduce the load of data recording during FINE procedure,
+// filtering what's unnecessary to catch.
+class hotkey_coarse_data_collector
+{
+public:
+    // Counts `row_cnt` for the bucket of `hash_key`.
+    void capture_data(const dsn::blob &hash_key, uint64_t size);
+
+    // returns: id of the most accessed bucket.
+    //          -1 if not hot bucket is found.
+    int analyse_data();

Review comment:
       This name is related to the overall semantics and is not recommended to be changed




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