xushiyan commented on a change in pull request #4697: URL: https://github.com/apache/hudi/pull/4697#discussion_r794632615
########## File path: rfc/rfc-46/rfc-46.md ########## @@ -0,0 +1,159 @@ +<!-- + 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. +--> +# RFC-46: Optimize Record Payload handling + +## Proposers + +- @alexeykudinkin + +## Approvers + - @vinothchandar + - @nsivabalan + - @xushiyan + +## Status + +JIRA: https://issues.apache.org/jira/browse/HUDI-3217 + +> Please keep the status updated in `rfc/README.md`. + +## Abstract + +Avro historically has been a centerpiece of the Hudi architecture: it's a default representation that many components expect +when dealing with records (during merge, column value extractions, writing into storage, etc). + +While having a single format of the record representation is certainly making implementation of some components simpler, +it bears unavoidable performance penalty of de-/serialization loop: every record handled by Hudi has to be converted +from (low-level) engine-specific representation (`Row` for Spark, `RowData` for Flink, `ArrayWritable` for Hive) into intermediate +one (Avro), with some operations (like clustering, compaction) potentially incurring this penalty multiple times (on read- +and write-paths). + +As such, goal of this effort is to remove the need of conversion from engine-specific internal representations to Avro +while handling records. + +## Background + +Historically, Avro has settled in as de-facto intermediate representation of the record's payload since the early days of Hudi. +As project matured and the scale of the installations grew, necessity to convert into an intermediate representation quickly +become a noticeable bottleneck in terms of performance of critical Hudi flows. + +At the center of it is the hierarchy of `HoodieRecordPayload`s, which is used to hold individual record's payload +providing an APIs like `preCombine`, `combineAndGetUpdateValue` to combine it with other record using some user-defined semantic. + +## Implementation + +### Revisiting Record Classes Hierarchy + +To achieve stated goals of avoiding unnecessary conversions into intermediate representation (Avro), existing Hudi workflows +operating on individual records will have to be refactored and laid out in a way that would be _unassuming about internal +representation_ of the record, ie code should be working w/ a record as an _opaque object_: exposing certain API to access +crucial data (precombine, primary, partition keys, etc), but not providing the access to the raw payload. + +Having existing workflows re-structured in such a way around a record being an opaque object, would allow us to encapsulate +internal representation of the record w/in its class hierarchy, which in turn would allow for us to hold engine-specific (Spark, Flink, etc) +representations of the records w/o exposing purely engine-agnostic components to it. + +Following (high-level) steps are proposed: + +1. Promote `HoodieRecord` to become a standardized API of interacting with a single record, that will be + 1. Replacing all accesses from `HoodieRecordPayload` + 2. Split into interface and engine-specific implementations (holding internal engine-specific representation of the payload) + 3. Implementing new standardized record-level APIs (like `getPartitionKey` , `getRecordKey`, etc) + 4. Staying **internal** component, that will **NOT** contain any user-defined semantic (like merging) +2. Extract Record Combining (Merge) API from `HoodieRecordPayload` into a standalone, stateless component (engine). Such component will be + 1. Abstracted as stateless object providing API to combine records (according to predefined semantics) for engines (Spark, Flink) of interest + 2. Plug-in point for user-defined combination semantics +3. Gradually deprecate, phase-out and eventually remove `HoodieRecordPayload` abstraction + +Phasing out usage of `HoodieRecordPayload` will also bring the benefit of avoiding to use Java reflection in the hot-path, which +is known to have poor performance (compared to non-reflection based instantiation). + +#### Combine API Engine + +Stateless component interface providing for API Combining Records will look like following: + +```java +interface HoodieRecordCombiningEngine { Review comment: Engine sounds like a class; maybe a shorter interface name `HoodieSupportsCombine` ? ########## File path: rfc/rfc-46/rfc-46.md ########## @@ -0,0 +1,159 @@ +<!-- + 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. +--> +# RFC-46: Optimize Record Payload handling + +## Proposers + +- @alexeykudinkin + +## Approvers + - @vinothchandar + - @nsivabalan + - @xushiyan + +## Status + +JIRA: https://issues.apache.org/jira/browse/HUDI-3217 + +> Please keep the status updated in `rfc/README.md`. + +## Abstract + +Avro historically has been a centerpiece of the Hudi architecture: it's a default representation that many components expect +when dealing with records (during merge, column value extractions, writing into storage, etc). + +While having a single format of the record representation is certainly making implementation of some components simpler, +it bears unavoidable performance penalty of de-/serialization loop: every record handled by Hudi has to be converted +from (low-level) engine-specific representation (`Row` for Spark, `RowData` for Flink, `ArrayWritable` for Hive) into intermediate +one (Avro), with some operations (like clustering, compaction) potentially incurring this penalty multiple times (on read- +and write-paths). + +As such, goal of this effort is to remove the need of conversion from engine-specific internal representations to Avro +while handling records. + +## Background + +Historically, Avro has settled in as de-facto intermediate representation of the record's payload since the early days of Hudi. +As project matured and the scale of the installations grew, necessity to convert into an intermediate representation quickly +become a noticeable bottleneck in terms of performance of critical Hudi flows. + +At the center of it is the hierarchy of `HoodieRecordPayload`s, which is used to hold individual record's payload +providing an APIs like `preCombine`, `combineAndGetUpdateValue` to combine it with other record using some user-defined semantic. + +## Implementation + +### Revisiting Record Classes Hierarchy + +To achieve stated goals of avoiding unnecessary conversions into intermediate representation (Avro), existing Hudi workflows +operating on individual records will have to be refactored and laid out in a way that would be _unassuming about internal +representation_ of the record, ie code should be working w/ a record as an _opaque object_: exposing certain API to access +crucial data (precombine, primary, partition keys, etc), but not providing the access to the raw payload. + +Having existing workflows re-structured in such a way around a record being an opaque object, would allow us to encapsulate +internal representation of the record w/in its class hierarchy, which in turn would allow for us to hold engine-specific (Spark, Flink, etc) +representations of the records w/o exposing purely engine-agnostic components to it. + +Following (high-level) steps are proposed: + +1. Promote `HoodieRecord` to become a standardized API of interacting with a single record, that will be + 1. Replacing all accesses from `HoodieRecordPayload` + 2. Split into interface and engine-specific implementations (holding internal engine-specific representation of the payload) + 3. Implementing new standardized record-level APIs (like `getPartitionKey` , `getRecordKey`, etc) + 4. Staying **internal** component, that will **NOT** contain any user-defined semantic (like merging) +2. Extract Record Combining (Merge) API from `HoodieRecordPayload` into a standalone, stateless component (engine). Such component will be + 1. Abstracted as stateless object providing API to combine records (according to predefined semantics) for engines (Spark, Flink) of interest + 2. Plug-in point for user-defined combination semantics +3. Gradually deprecate, phase-out and eventually remove `HoodieRecordPayload` abstraction + +Phasing out usage of `HoodieRecordPayload` will also bring the benefit of avoiding to use Java reflection in the hot-path, which +is known to have poor performance (compared to non-reflection based instantiation). + +#### Combine API Engine + +Stateless component interface providing for API Combining Records will look like following: + +```java +interface HoodieRecordCombiningEngine { + + default HoodieRecord precombine(HoodieRecord older, HoodieRecord newer) { + if (spark) { + precombineSpark((SparkHoodieRecord) older, (SparkHoodieRecord) newer); + } else if (flink) { + // precombine for Flink + } + } + + /** + * Spark-specific implementation + */ + SparkHoodieRecord precombineSpark(SparkHoodieRecord older, SparkHoodieRecord newer); + + // ... +} +``` +Where user can provide their own subclass implementing such interface for the engines of interest. + +#### Migration from `HoodieRecordPayload` to `HoodieRecordCombiningEngine` + +To warrant backward-compatibility (BWC) on the code-level with already created subclasses of `HoodieRecordPayload` currently +already used in production by Hudi users, we will provide a BWC-bridge in the form of instance of `HoodieRecordCombiningEngine`, that will +be using user-defined subclass of `HoodieRecordPayload` to combine the records. + +Leveraging such bridge will make provide for seamless BWC migration to the 0.11 release, however will be removing the performance +benefit of this refactoring, since it would unavoidably have to perform conversion to intermediate representation (Avro). To realize +full-suite of benefits of this refactoring, users will have to migrate their merging logic out of `HoodieRecordPayload` subclass and into +new `HoodieRecordCombiningEngine` implementation. + +### Refactoring Flows Directly Interacting w/ Records: + +As was called out prior to achieve the goal of being able to sustain engine-internal representations being held by `HoodieRecord` +class w/o compromising major components' neutrality (ie being engine-agnostic), such components directly interacting w/ +records' payloads today will have to be refactored to instead interact w/ standardized `HoodieRecord`s API. + +Following major components will be refactored: + +1. `WriteHandle`s will be + 1. Accepting `HoodieRecord` instead of raw Avro payload (avoiding Avro conversion) + 2. Using Combining API engine to merge records (when necessary) + 3. Passes `HoodieRecord` as is to `FileWriter` +2. `FileWriter`s will be + 1. Accepting `HoodieRecord` + 2. Will be engine-specific (so that they're able to handle internal record representation) +3. `RecordReader`s + 1. API will be returning opaque `HoodieRecord` instead of raw Avro payload Review comment: was trying to look for the exact classes: are they `HoodieWriteHandle`, `HoodieFileWriter` and `HoodieFileReader` ? ########## File path: rfc/rfc-46/rfc-46.md ########## @@ -0,0 +1,159 @@ +<!-- + 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. +--> +# RFC-46: Optimize Record Payload handling + +## Proposers + +- @alexeykudinkin + +## Approvers + - @vinothchandar + - @nsivabalan + - @xushiyan + +## Status + +JIRA: https://issues.apache.org/jira/browse/HUDI-3217 + +> Please keep the status updated in `rfc/README.md`. + +## Abstract + +Avro historically has been a centerpiece of the Hudi architecture: it's a default representation that many components expect +when dealing with records (during merge, column value extractions, writing into storage, etc). + +While having a single format of the record representation is certainly making implementation of some components simpler, +it bears unavoidable performance penalty of de-/serialization loop: every record handled by Hudi has to be converted +from (low-level) engine-specific representation (`Row` for Spark, `RowData` for Flink, `ArrayWritable` for Hive) into intermediate +one (Avro), with some operations (like clustering, compaction) potentially incurring this penalty multiple times (on read- +and write-paths). + +As such, goal of this effort is to remove the need of conversion from engine-specific internal representations to Avro +while handling records. + +## Background + +Historically, Avro has settled in as de-facto intermediate representation of the record's payload since the early days of Hudi. +As project matured and the scale of the installations grew, necessity to convert into an intermediate representation quickly +become a noticeable bottleneck in terms of performance of critical Hudi flows. + +At the center of it is the hierarchy of `HoodieRecordPayload`s, which is used to hold individual record's payload +providing an APIs like `preCombine`, `combineAndGetUpdateValue` to combine it with other record using some user-defined semantic. + +## Implementation + +### Revisiting Record Classes Hierarchy + +To achieve stated goals of avoiding unnecessary conversions into intermediate representation (Avro), existing Hudi workflows +operating on individual records will have to be refactored and laid out in a way that would be _unassuming about internal +representation_ of the record, ie code should be working w/ a record as an _opaque object_: exposing certain API to access +crucial data (precombine, primary, partition keys, etc), but not providing the access to the raw payload. + +Having existing workflows re-structured in such a way around a record being an opaque object, would allow us to encapsulate +internal representation of the record w/in its class hierarchy, which in turn would allow for us to hold engine-specific (Spark, Flink, etc) +representations of the records w/o exposing purely engine-agnostic components to it. + +Following (high-level) steps are proposed: + +1. Promote `HoodieRecord` to become a standardized API of interacting with a single record, that will be + 1. Replacing all accesses from `HoodieRecordPayload` + 2. Split into interface and engine-specific implementations (holding internal engine-specific representation of the payload) + 3. Implementing new standardized record-level APIs (like `getPartitionKey` , `getRecordKey`, etc) + 4. Staying **internal** component, that will **NOT** contain any user-defined semantic (like merging) +2. Extract Record Combining (Merge) API from `HoodieRecordPayload` into a standalone, stateless component (engine). Such component will be + 1. Abstracted as stateless object providing API to combine records (according to predefined semantics) for engines (Spark, Flink) of interest + 2. Plug-in point for user-defined combination semantics +3. Gradually deprecate, phase-out and eventually remove `HoodieRecordPayload` abstraction + +Phasing out usage of `HoodieRecordPayload` will also bring the benefit of avoiding to use Java reflection in the hot-path, which +is known to have poor performance (compared to non-reflection based instantiation). + +#### Combine API Engine + +Stateless component interface providing for API Combining Records will look like following: + +```java +interface HoodieRecordCombiningEngine { + + default HoodieRecord precombine(HoodieRecord older, HoodieRecord newer) { + if (spark) { + precombineSpark((SparkHoodieRecord) older, (SparkHoodieRecord) newer); + } else if (flink) { + // precombine for Flink + } + } + + /** + * Spark-specific implementation + */ + SparkHoodieRecord precombineSpark(SparkHoodieRecord older, SparkHoodieRecord newer); + + // ... +} +``` +Where user can provide their own subclass implementing such interface for the engines of interest. + +#### Migration from `HoodieRecordPayload` to `HoodieRecordCombiningEngine` + +To warrant backward-compatibility (BWC) on the code-level with already created subclasses of `HoodieRecordPayload` currently +already used in production by Hudi users, we will provide a BWC-bridge in the form of instance of `HoodieRecordCombiningEngine`, that will +be using user-defined subclass of `HoodieRecordPayload` to combine the records. Review comment: So in https://github.com/apache/hudi/pull/3893 we have `HoodieAvroRecord` mostly for compatible migration purpose. Maybe we name it `HoodieLegacyAvroRecord` so code change can be manageable. A second migration would be needed for `HoodieLegacyAvroRecord` -> `SparkHoodieRecord` / `FlinkHoodieRecord` ########## File path: rfc/rfc-46/rfc-46.md ########## @@ -0,0 +1,159 @@ +<!-- + 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. +--> +# RFC-46: Optimize Record Payload handling + +## Proposers + +- @alexeykudinkin + +## Approvers + - @vinothchandar + - @nsivabalan + - @xushiyan + +## Status + +JIRA: https://issues.apache.org/jira/browse/HUDI-3217 + +> Please keep the status updated in `rfc/README.md`. + +## Abstract + +Avro historically has been a centerpiece of the Hudi architecture: it's a default representation that many components expect +when dealing with records (during merge, column value extractions, writing into storage, etc). + +While having a single format of the record representation is certainly making implementation of some components simpler, +it bears unavoidable performance penalty of de-/serialization loop: every record handled by Hudi has to be converted +from (low-level) engine-specific representation (`Row` for Spark, `RowData` for Flink, `ArrayWritable` for Hive) into intermediate +one (Avro), with some operations (like clustering, compaction) potentially incurring this penalty multiple times (on read- +and write-paths). + +As such, goal of this effort is to remove the need of conversion from engine-specific internal representations to Avro +while handling records. + +## Background + +Historically, Avro has settled in as de-facto intermediate representation of the record's payload since the early days of Hudi. +As project matured and the scale of the installations grew, necessity to convert into an intermediate representation quickly +become a noticeable bottleneck in terms of performance of critical Hudi flows. + +At the center of it is the hierarchy of `HoodieRecordPayload`s, which is used to hold individual record's payload +providing an APIs like `preCombine`, `combineAndGetUpdateValue` to combine it with other record using some user-defined semantic. + +## Implementation + +### Revisiting Record Classes Hierarchy + +To achieve stated goals of avoiding unnecessary conversions into intermediate representation (Avro), existing Hudi workflows +operating on individual records will have to be refactored and laid out in a way that would be _unassuming about internal +representation_ of the record, ie code should be working w/ a record as an _opaque object_: exposing certain API to access +crucial data (precombine, primary, partition keys, etc), but not providing the access to the raw payload. + +Having existing workflows re-structured in such a way around a record being an opaque object, would allow us to encapsulate +internal representation of the record w/in its class hierarchy, which in turn would allow for us to hold engine-specific (Spark, Flink, etc) +representations of the records w/o exposing purely engine-agnostic components to it. + +Following (high-level) steps are proposed: + +1. Promote `HoodieRecord` to become a standardized API of interacting with a single record, that will be + 1. Replacing all accesses from `HoodieRecordPayload` + 2. Split into interface and engine-specific implementations (holding internal engine-specific representation of the payload) + 3. Implementing new standardized record-level APIs (like `getPartitionKey` , `getRecordKey`, etc) + 4. Staying **internal** component, that will **NOT** contain any user-defined semantic (like merging) +2. Extract Record Combining (Merge) API from `HoodieRecordPayload` into a standalone, stateless component (engine). Such component will be + 1. Abstracted as stateless object providing API to combine records (according to predefined semantics) for engines (Spark, Flink) of interest + 2. Plug-in point for user-defined combination semantics +3. Gradually deprecate, phase-out and eventually remove `HoodieRecordPayload` abstraction + +Phasing out usage of `HoodieRecordPayload` will also bring the benefit of avoiding to use Java reflection in the hot-path, which +is known to have poor performance (compared to non-reflection based instantiation). + +#### Combine API Engine + +Stateless component interface providing for API Combining Records will look like following: + +```java +interface HoodieRecordCombiningEngine { + + default HoodieRecord precombine(HoodieRecord older, HoodieRecord newer) { + if (spark) { + precombineSpark((SparkHoodieRecord) older, (SparkHoodieRecord) newer); + } else if (flink) { + // precombine for Flink + } + } + + /** + * Spark-specific implementation + */ + SparkHoodieRecord precombineSpark(SparkHoodieRecord older, SparkHoodieRecord newer); + + // ... +} +``` +Where user can provide their own subclass implementing such interface for the engines of interest. + +#### Migration from `HoodieRecordPayload` to `HoodieRecordCombiningEngine` + +To warrant backward-compatibility (BWC) on the code-level with already created subclasses of `HoodieRecordPayload` currently +already used in production by Hudi users, we will provide a BWC-bridge in the form of instance of `HoodieRecordCombiningEngine`, that will +be using user-defined subclass of `HoodieRecordPayload` to combine the records. + +Leveraging such bridge will make provide for seamless BWC migration to the 0.11 release, however will be removing the performance +benefit of this refactoring, since it would unavoidably have to perform conversion to intermediate representation (Avro). To realize +full-suite of benefits of this refactoring, users will have to migrate their merging logic out of `HoodieRecordPayload` subclass and into +new `HoodieRecordCombiningEngine` implementation. + +### Refactoring Flows Directly Interacting w/ Records: + +As was called out prior to achieve the goal of being able to sustain engine-internal representations being held by `HoodieRecord` +class w/o compromising major components' neutrality (ie being engine-agnostic), such components directly interacting w/ +records' payloads today will have to be refactored to instead interact w/ standardized `HoodieRecord`s API. + +Following major components will be refactored: + +1. `WriteHandle`s will be + 1. Accepting `HoodieRecord` instead of raw Avro payload (avoiding Avro conversion) + 2. Using Combining API engine to merge records (when necessary) + 3. Passes `HoodieRecord` as is to `FileWriter` +2. `FileWriter`s will be + 1. Accepting `HoodieRecord` + 2. Will be engine-specific (so that they're able to handle internal record representation) +3. `RecordReader`s + 1. API will be returning opaque `HoodieRecord` instead of raw Avro payload + + +## Rollout/Adoption Plan + + - What impact (if any) will there be on existing users? + - Users of the Hudi will observe considerably better performance for most of the routine operations: writing, reading, compaction, clustering, etc due to avoiding the superfluous intermediate de-/serialization penalty + - By default, modified hierarchy would still leverage + - Users will need to rebase their logic of combining records by creating a subclass of `HoodieRecordPayload`, and instead subclass newly created interface `HoodieRecordCombiningEngine` to get full-suite of performance benefits + - If we are changing behavior how will we phase out the older behavior? + - Older behavior leveraging `HoodieRecordPayload` for merging will be marked as deprecated in 0.11, and subsequently removed in 0.1x + - If we need special migration tools, describe them here. + - No special migration tools will be necessary (other than BWC-bridge to make sure users can use 0.11 out of the box, and there are no breaking changes to the public API) + - When will we remove the existing behavior + - In subsequent releases (either 0.12 or 0.13) Review comment: the roadmap is like after 0.12 it'll be 1.0 -- This is an automated message from the Apache Git Service. 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