sebastianhillig-db opened a new pull request, #59593:
URL: https://github.com/apache/spark/pull/59593
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### What changes were proposed in this pull request?
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This PR makes `JavaUtils.isTesting()` look up the `SPARK_TESTING`
environment variable once, caching it in a `private static final boolean`,
instead of calling `System.getenv("SPARK_TESTING")` on every invocation. The
`spark.testing` system property is still read on every call, and the evaluation
order (env first, then property) is unchanged.
`Utils.isTesting` and `SparkEnvUtils.isTesting` delegate to this method, so
they benefit too.
### Why are the changes needed?
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On Linux, `System.getenv(String)` goes through
`java.lang.ProcessEnvironment`, which wraps the name in a new byte[]-backed
`Variable` on every lookup, so each `isTesting()` call allocates (56 bytes per
call in the measurement below). `isTesting` is on hot paths. For example,
`AnalysisHelper.assertNotAnalysisRule` calls it from the `LogicalPlan`
overrides of `transformDownWithPruning` / `transformUpWithPruning` /
`transformAllExpressionsWithPruning`, which run once per plan node visited by
every transform. In a JFR allocation profile of driver-side query planning,
these call sites accounted for roughly 1.8% of driver allocation and about 1-2%
of CPU.
A JVM's environment cannot change after startup, so caching the env lookup
is safe. The system property cannot be cached: tests set and clear it at
runtime (`SparkTestSuite.beforeAll`, `BenchmarkBase`,
`KryoSerializerBenchmark`). The only code that mutates the process environment
reflectively (`SparkConnectClientSuite.withEnvs`, `JavaXmlSuite.setEnv`)
touches `SPARK_REMOTE` / `SPARK_LOCAL_IP`, not `SPARK_TESTING`. Code that sets
`SPARK_TESTING` for a child process via `ProcessBuilder.environment()` is
unaffected, because the child is a new JVM.
### Does this PR introduce _any_ user-facing change?
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No.
### How was this patch tested?
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Existing tests:
```
build/sbt common-utils-java/test common-utils/test 'network-common/testOnly
*JavaUtilsSuite' catalyst/compile
```
All passed (common-utils-java: 25, common-utils: 121, JavaUtilsSuite: 2),
and catalyst compiled.
I also ran a manual allocation check (not committed): 1M calls on one
thread, measured with `ThreadMXBean.getThreadAllocatedBytes`, `SPARK_TESTING`
unset, JDK 17, after warm-up:
| | bytes / 1M calls | time / 1M calls |
|---|---|---|
| before (`System.getenv` + `System.getProperty`) | 56,000,000 (56 B/call) |
~25-43 ms |
| after | 0 | ~2-2.5 ms |
The same check confirmed that setting and clearing `spark.testing` at
runtime still flips the result (`false` / `true` / `false`), and that with
`SPARK_TESTING=1` the result is `true` as before.
### Was this patch authored or co-authored using generative AI tooling?
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Generated-by: Isaac (Claude Opus 5.5)
This pull request and its description were written by Isaac.
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