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Posted to dev@pegasus.apache.org by GitBox <gi...@apache.org> on 2020/09/16 17:08:14 UTC
[GitHub] [incubator-pegasus] acelyc111 commented on a change in pull request #603: feat(hotkey detection): build a fundamental framework of hotkey detection
acelyc111 commented on a change in pull request #603:
URL: https://github.com/apache/incubator-pegasus/pull/603#discussion_r489590652
##########
File path: src/server/hotkey_collector.h
##########
@@ -0,0 +1,45 @@
+// 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.
+
+#pragma once
+
+#include <dsn/utility/string_view.h>
+
+namespace pegasus {
+namespace server {
+
+class hotkey_coarse_data_collector;
+class hotkey_fine_data_collector;
+
+// hotkey_collector is responsible to find the hot keys after the partition
+// was detected to be hot. The two types of hotkey, READ & WRITE, are detected
+// separately.
+class hotkey_collector
+{
+public:
+ // common function to find outlier in both coarse capture and fine capture
Review comment:
```suggestion
// find outlier in both coarse capture and fine capture
```
##########
File path: src/server/hotkey_collector.h
##########
@@ -0,0 +1,45 @@
+// 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.
+
+#pragma once
+
+#include <dsn/utility/string_view.h>
+
+namespace pegasus {
+namespace server {
+
+class hotkey_coarse_data_collector;
+class hotkey_fine_data_collector;
+
+// hotkey_collector is responsible to find the hot keys after the partition
+// was detected to be hot. The two types of hotkey, READ & WRITE, are detected
+// separately.
+class hotkey_collector
+{
+public:
+ // common function to find outlier in both coarse capture and fine capture
+ static int outlier_cal(const std::vector<uint64_t> &data_samples, int threshold);
+ // common function to unify the hash way in both coarse capture and fine capture
Review comment:
```suggestion
// unify the hash way in both coarse capture and fine capture
```
##########
File path: src/server/hotkey_coarse_data_collector.h
##########
@@ -0,0 +1,33 @@
+// 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.
+
+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
+{
Review comment:
Better to add interfaces of this class, even with empty implementation, then we know what you want to do by this class.
##########
File path: src/server/hotkey_fine_data_collector.h
##########
@@ -0,0 +1,32 @@
+// 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.
+
+namespace pegasus {
+namespace server {
+
+// hotkey_fine_data_collector handles the second procedure (FINE) of hotkey detection.
+// It captures only the data mapping to the "hot" bucket.
+//
+// To prevent locking on the read path, we create one queue per thread of THREAD_POOL_LOCAL_APP.
+// The read request is captured right inside its execution thread.
+//
+// For writes we do not apply this optimization.
+class hotkey_fine_data_collector
+{
Review comment:
Add interfaces
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