Ritesh Shukla created HDDS-11897:
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Summary: This tracks the work needed to change request processing
execution order for performance improvements and fixing certain edge cases for
correctness.
Key: HDDS-11897
URL: https://issues.apache.org/jira/browse/HDDS-11897
Project: Apache Ozone
Issue Type: Epic
Components: Ozone Manager
Reporter: Ritesh Shukla
The following challenges and solutions are proposed as part of this epic.
# The current implementation depends on consensus on the order of requests
received rather than on consensus on the processing of the requests.
## This can lead to subtle bugs due to discrepancies in the actual execution
of requests on the leader vs the followers.
# The double buffer implementation is currently meant to optimize the rate at
which writes get flushed to RocksDB, but the effective batching achieved is 1.2
at best. It is also a source of continuous bugs and added complexity for new
features.
## The new implementation will not depend on the double buffer behavior.
# The number of transactions that can be pushed through Ratis currently
averages around 25k.
## Requests will be batched before sending them to Ratis for consensus.
# Readers and writers are not separated, and there is potential contention
between readers and writers.
# Although FSO and OBS bucket types can have finer-grained locking,
coarse-grained locks are held at the Bucket level.
## The new implementation will introduce locking at the start of the request
processing to serialize requests that must be linearized against each other.
These changes and related changes together should result
# Significant performance improvement in the rate of request processing (3x)
# Better code quality and test coverage
# Elimination of subtle bugs arising from the write-back cache design of
double buffer writes post Ratis
# Fine grained locking such that requests that can be processed in parallel
are run without locking.
# Separation of resources for readers and writers. This will also help process
reads from followers using Ratis' capabilities for linearized reads from
followers.
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