Andrey Yarovoy created HDDS-17032:
-------------------------------------
Summary: Avoid building the `Preconditions` message on every write
in `ECKeyOutputStream.ECChunkBuffers.addToDataBuffer`
Key: HDDS-17032
URL: https://issues.apache.org/jira/browse/HDDS-17032
Project: Apache Ozone
Issue Type: Bug
Components: EC Client
Reporter: Andrey Yarovoy
**Problem**
`ECChunkBuffers.addToDataBuffer` runs once per `write()` call segment. It
checks the cell position with an eagerly
concatenated message:
```java
Preconditions.checkState(pos <= cellSize,
"Position(" + pos + ") is greater than the cellSize(" + cellSize + ").");
```
The message string is built (`StringConcatFactory` → `Integer.getChars`) on
every call, even though the check
virtually never fails. The number of calls scales with the caller's write size.
freon's default `--buffer` is 4096
bytes, which means about 65,000 calls per 256 MB key, and applications doing
small writes pay the same.
**Evidence** (real-cluster async-profiler wall profile, JDK 17, writer threads,
on-CPU samples)
| Writers | Share of writer CPU spent building this message |
|---|---|
| 1 rs-3-2-1024k writer | 0.79% |
| 16 rs-3-2-1024k writers | 1.81% |
**Proposal**
Use Guava's template overload with primitive arguments, so nothing is formatted
or boxed unless the check fails:
```java
Preconditions.checkState(pos <= cellSize,
"Position(%s) is greater than the cellSize(%s).", pos, cellSize);
```
The other `Preconditions` call on the per-stripe path (`generateParityCells`)
already uses a template. The
eagerly built message in `close()` (`writeOffset == offset`) runs once per key,
so it is not worth changing.
**Compatibility**
No behaviour change: the same exception type and message when the check fails.
**Testing**
Existing `TestECKeyOutputStream` / `TestOzoneECClient`. No new test is needed;
the message text is unchanged.
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