apurtell opened a new pull request, #8077:
URL: https://github.com/apache/hbase/pull/8077

   On EBS-backed deployments in AWS, or equivalents in other cloud 
infrastructure providers, HBase compaction and replication throughput can be 
constrained by per-volume IOPS limits rather than bandwidth. A faithful 
device-level simulator within the test harness allows developers to reproduce, 
analyze, and validate fixes for such performance issues without requiring 
actual cloud infrastructure.
   
   This proposed change adds a test-only EBS device layer that operates at the 
DataNode storage level within `MiniDFSCluster` by replacing the `FsDatasetSpi` 
implementation via Hadoop's pluggable factory mechanism. This allows HBase 
integration tests to simulate realistic cloud block storage characteristics, 
such as per-volume bandwidth budgets, IOPS limits, sequential IO coalescing, 
and per-IO device latency, enabling identification and reproduction of IO 
bottlenecks.
   
   The simulator wraps the real `FsDatasetImpl` with a 
`java.lang.reflect.Proxy` that intercepts the three `FsDatasetSpi` methods 
where DataNode local IO actually engages the underlying block device, without 
compile-time coupling to internal Hadoop classes.
   
   Each proxy gets its own set of `EBSVolumeDevice` instances with independent 
budgets. Block-to-volume resolution uses `delegate.getVolume(block)`, providing 
real HDFS placement decisions. A single configuration applies to all volumes, 
but each volume maintains its own token buckets, matching production where all 
attached block devices to a host share the same SKU but have independent 
throughput budgets, and where the host itself has a cap on maximum aggregate 
throughput.
   
   EBS merges sequential IOs up to 1 MiB before counting them as a single IOPS 
token. The simulator tracks read streams and write streams independently.
   
   After each IOPS token consumption, the simulator sleeps for a configurable 
duration (default 1 ms), modeling physical device service time.
   
   `IntegrationTestCompactionWithDeviceSimulator` provides an end-to-end 
example of using the simulator


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