[GitHub] [hadoop-ozone] elek commented on pull request #1208: HDDS-3755. Storage-class support for Ozone

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

elek commented on pull request #1208:
URL: https://github.com/apache/hadoop-ozone/pull/1208#issuecomment-680882568


   Thanks for the help from @maobaolong , it's ready to review.
   
   The key points of the patch:
   
   1. o3fs/ofs are not changed just ozone sh.
   
   Instead of:
   
   ```
   ozone sh key put -r THREE -t RATIS ....
   ```
   
   you can use:
   
   ```
   ozone sh key put --storage-class STANDARD ...
   ```
   
   2. Storage classes are hard coded in this version (see `StaticStorageClassRegistry.java`). There is no way to configure or introduce new one.
   
   3. Should be backward compatible. If storage class is not used but the old factory/type is sent from the client, it's converted to storage class:
   
   ```
   +    String storageClass = null;
   +    if (info.hasStorageClass()) {
   +      storageClass = info.getStorageClass();
   +    }
   +    if (StringUtils.isBlank(storageClass)) {
   +      storageClass = StorageClassConverter.convert(
   +          null, info.getReplicationFactor(),
   +          info.getReplicationType()).getName();
   +    }
   ```
   
   4. But under the hood, the storage class abstraction is used.
   
   5. SCM allocates block as before (`BlockManagerImpl.java`)
   
   ```
   +    final ReplicationFactor factor =
   +        storageClass.getOpenStateConfiguration().getReplicationFactor();
   +
   +    final ReplicationType type =
   +        storageClass.getOpenStateConfiguration().getReplicationType();
   ```
   Remaining logic is the same.
   
   6. `ReplicationManager` works as before, but the expected number of the replicas are got from the storage class:
   
   ```
   +      StorageClass storageClass =
   +          storageClassRegistry.getStorageClass(container.getStorageClass());
   ```
   
   7. `ContainerStateManager` is slightly modified. Until containers are sorted by "owner" now they are sorted by "owner" and "storageClass". Logic is the same. If there is a container with the same owner and storageClass it can be returned.
   
   8. `storageClasss` is stored and send as string (make it possible to use ANY storage class in the future), but inside the services type-safe objects are used. 
   


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