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I have an alternative approach to pose based on learnings from this patch - 
using a DBMS as a key-value document store.  This could be ~2 levels of 
abstraction higher and involve implementing `Storage` rather than 
`StreamManager`.  Similar to `LogStorage`, we would persist mutations as they 
happen, and only read to sync a replica.  Warm standby could be implemented by 
incrementally fetching based on modification timestamps.

- Bill Farner


On Nov. 28, 2017, 5:40 p.m., Bill Farner wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/64126/
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> 
> (Updated Nov. 28, 2017, 5:40 p.m.)
> 
> 
> Review request for Aurora, David McLaughlin, Jordan Ly, and Stephan Erb.
> 
> 
> Repository: aurora
> 
> 
> Description
> -------
> 
> This introduces an alternative implementation of `StreamManager`, which is the
> primary persistence mechanism used in `LogStorage`.  There are two distinct 
> parts
> of this patch:
> 
>   - a storage 'business logic' layer that exposes a stream-oriented 
> append-only
>     storage interface.  This contains components to:
>     - extract keys for any log `Op`
>     - hash keys to constrain the keyspace
>     - [de]serialize `LogEntries` and limit record sizes (using existing 
> Framing)
>     - provide simple transactional behavior
>   - a key-value store interface, with an implementation based on ZooKeeper
> 
> This achieves the following results:
> 
>   - no inherent need for periodic Snapshot or failover to cull storage
>   - atomic multi-operation transactions even for a key-value store that does 
> not
>     support multi-key transactions
>   - storage operations that amortize to a single storage round-trip
>     (in the case of ZooKeeper, using ZK `multi()`)
>   - straightforward path to warm standby for failover
> 
> 
> **Note**: there are still a few rough edges that must be rounded out before 
> this can be used even in integration tests, but the storage 'business logic' 
> layers are reasonably polished and well-tested.  I opted to use this as a 
> moment to pause and gather feedback.
> 
> **Reviewers**: I suggest starting with `AbstractStreamManagerTest.java` as it 
> most succinctly captures the features sought in the new layers.  A first pass 
> review on the general approach would be most useful, after which we can move 
> on to specifics.
> 
> 
> Diffs
> -----
> 
>   build.gradle af119910e84c48f75f2573ababcfa287c3b986fc 
>   
> commons/src/main/java/org/apache/aurora/common/zookeeper/testing/ZooKeeperTestServer.java
>  a4504b8d1307ca15de3bb92674b8d77c6aea8467 
>   src/main/java/org/apache/aurora/codec/ThriftBinaryCodec.java 
> 3c12532acca9107f5a54df48fc59348d70af29c6 
>   src/main/java/org/apache/aurora/scheduler/app/SchedulerMain.java 
> 7ffcf4f471b97e32426c82972472115c5c5c4d02 
>   src/main/java/org/apache/aurora/scheduler/config/CliOptions.java 
> b7f43e0d6efbddcac640c3d39c7bc56400e68e68 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/AbstractStreamTransaction.java
>  PRE-CREATION 
>   src/main/java/org/apache/aurora/scheduler/storage/log/Entries.java 
> ab7cd2d40013827122e27275f557e9c8fff9dbb7 
>   src/main/java/org/apache/aurora/scheduler/storage/log/EntrySerializer.java 
> 90c5383febc0ac49b0bf8b369fe0107f1fa8a6b3 
>   src/main/java/org/apache/aurora/scheduler/storage/log/Framing.java 
> PRE-CREATION 
>   src/main/java/org/apache/aurora/scheduler/storage/log/LogStorageModule.java 
> c8dc7ad141f27318f18afdc440250afc42f0bc6d 
>   src/main/java/org/apache/aurora/scheduler/storage/log/StreamManager.java 
> ea147c0ba6aaa6d113144be0a8330bd2f73d2453 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/StreamManagerFactory.java
>  52b2e83efc0c289366b5246aff32553a546b1a70 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/StreamManagerImpl.java 
> baf2647c54f1f9918139584e5151873a3853e83c 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/StreamManagerModule.java
>  PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/StreamTransaction.java 
> a51fd18ad00537bf244419442078548d8545a841 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/AppendOnlyStore.java 
> PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/HashedKeyValueStore.java
>  PRE-CREATION 
>   src/main/java/org/apache/aurora/scheduler/storage/log/kv/KeyValueStore.java 
> PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/KeyValueStreamModule.java
>  PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/KeyedStreamManager.java
>  PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/LogEntrySerializingStore.java
>  PRE-CREATION 
>   src/main/java/org/apache/aurora/scheduler/storage/log/kv/LogOpStore.java 
> PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/TransactionalKeyValueStore.java
>  PRE-CREATION 
>   
> src/main/java/org/apache/aurora/scheduler/storage/log/kv/zookeeper/ZooKeeperKeyValueStore.java
>  PRE-CREATION 
>   src/test/java/org/apache/aurora/scheduler/app/SchedulerIT.java 
> 4929ecdec90a1ccbcafa4857dea83cec1e2d7fd4 
>   src/test/java/org/apache/aurora/scheduler/config/CommandLineTest.java 
> 5cb5310ed096ca1fb47b980401e3712948271ac4 
>   src/test/java/org/apache/aurora/scheduler/storage/log/LogManagerTest.java 
> 3f445595a81a5655c6c486791a9b55d8dc7f2f76 
>   
> src/test/java/org/apache/aurora/scheduler/storage/log/NonVolatileStorageTest.java
>  f43a836a4176c465fa3f496c77ef6dc1cbc1691a 
>   
> src/test/java/org/apache/aurora/scheduler/storage/log/kv/AbstractStreamManagerTest.java
>  PRE-CREATION 
>   
> src/test/java/org/apache/aurora/scheduler/storage/log/kv/InMemoryStreamManagerTest.java
>  PRE-CREATION 
>   
> src/test/java/org/apache/aurora/scheduler/storage/log/kv/KeyValueNonVolatileStorageTest.java
>  PRE-CREATION 
>   
> src/test/java/org/apache/aurora/scheduler/storage/log/kv/MapKeyValueStore.java
>  PRE-CREATION 
>   
> src/test/java/org/apache/aurora/scheduler/storage/log/kv/zookeeper/ZooKeeperKeyedStreamManagerTest.java
>  PRE-CREATION 
> 
> 
> Diff: https://reviews.apache.org/r/64126/diff/1/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> Bill Farner
> 
>

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