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Posted to dev@pegasus.apache.org by GitBox <gi...@apache.org> on 2020/09/18 09:03:51 UTC
[GitHub] [incubator-pegasus] hycdong commented on a change in pull request #603: feat(hotkey detection): build a fundamental framework of hotkey detection
hycdong commented on a change in pull request #603:
URL: https://github.com/apache/incubator-pegasus/pull/603#discussion_r490799358
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File path: src/server/hotkey_coarse_data_collector.h
##########
@@ -0,0 +1,49 @@
+// 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 frequently 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:
+ // capture `hash_key` into the internal bucket
+ void capture_data(const dsn::blob &hash_key, uint64_t size);
Review comment:
What the `size` used for?
##########
File path: src/server/hotkey_coarse_data_collector.cpp
##########
@@ -0,0 +1,18 @@
+// 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 "hotkey_coarse_data_collector.h"
Review comment:
I suggest adding consturctor function, the same as other classes
##########
File path: src/server/hotkey_collector.h
##########
@@ -0,0 +1,53 @@
+// 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>
+#include <rrdb/rrdb_types.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
Review comment:
I suggest adding the process graph in this class to show the process of finding the hotkey.
##########
File path: src/server/hotkey_collector.h
##########
@@ -0,0 +1,53 @@
+// 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>
+#include <rrdb/rrdb_types.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:
+ // size: the cu size of raw_key/hash_key calculated by `capacity_unit_calculator`
Review comment:
I think size is not suitable enough to show cu.
##########
File path: src/server/hotkey_coarse_data_collector.h
##########
@@ -0,0 +1,49 @@
+// 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 frequently 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:
+ // capture `hash_key` into the internal bucket
+ void capture_data(const dsn::blob &hash_key, uint64_t size);
+
+ // Timely to analyze the data of the internal storage structure
+ // returns: id of the most accessed bucket.
+ // -1 if not hot bucket is found.
+ int get_hotest_bucket();
+
+private:
+ // internal storage structure of hotkey_coarse_data_collector
+ // store the captured key into a hash table
+ // key:hash(hash_key)->value:count of this hash bucket
+ std::vector<std::atomic<uint64_t>> _hash_buckets;
Review comment:
It seems `_hash_buckets` should be a map, not a vector.
##########
File path: src/server/hotkey_coarse_data_collector.h
##########
@@ -0,0 +1,49 @@
+// 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 frequently 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:
+ // capture `hash_key` into the internal bucket
+ void capture_data(const dsn::blob &hash_key, uint64_t size);
+
+ // Timely to analyze the data of the internal storage structure
+ // returns: id of the most accessed bucket.
Review comment:
What is the `the most accessed bucket`? Is it the hotest bucket?
##########
File path: src/server/hotkey_collector.h
##########
@@ -0,0 +1,53 @@
+// 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>
+#include <rrdb/rrdb_types.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:
+ // size: the cu size of raw_key/hash_key calculated by `capacity_unit_calculator`
+ void capture_raw_key(const dsn::blob &raw_key, uint64_t size);
+ void capture_hash_key(const dsn::blob &hash_key, uint64_t size);
+ // analyse_data is a periodic task, only valid when _state == collector_state::COARSE
+ // || collector_state::FINE
+ void analyse_data();
+ bool handle_operation(dsn::apps::hotkey_detect_action::type action, std::string &err_hint);
+ // find outlier in both coarse capture and fine capture
+ static int cal_outlier(const std::vector<uint64_t> &data_samples, int threshold);
+ // unify the hash way in both coarse capture and fine capture
+ static int get_bucket_id(dsn::string_view data);
+
Review comment:
I could not figure out what the functions uage by function definitions and comments. I suggest you remove some function in this pull request, otherwise, you should explain what those functions used for clearly.
##########
File path: src/server/hotkey_fine_data_collector.h
##########
@@ -0,0 +1,52 @@
+// 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"
+#include <readerwriterqueue/readerwriterqueue.h>
+
+namespace pegasus {
+namespace server {
+
+typedef std::vector<moodycamel::ReaderWriterQueue<std::pair<dsn::blob, uint64_t>>>
+ lockfree_capture_queues;
+
+// 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
+{
+public:
+ // capture `hash_key` into internal storage structure
+ void capture_data(const dsn::blob &hash_key, uint64_t size);
Review comment:
The three classes have function `capture_data` or `capture_hash_key`, what is the difference between them?
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