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new 07dde50e40 [CELEBORN-2395] Reduce allocations in Utils.split* methods
07dde50e40 is described below
commit 07dde50e4043e096e385197c53208e21e8d316ce
Author: yew1eb <[email protected]>
AuthorDate: Mon Aug 3 10:34:01 2026 +0800
[CELEBORN-2395] Reduce allocations in Utils.split* methods
## What changes were proposed in this pull request?
Rewrite the three `String.split("-")`-based key splitters in `Utils` to
locate the `-` separator once and slice with `substring`, instead of
regex-splitting and rejoining:
- `splitShuffleKey` → `lastIndexOf('-')` + two `substring` calls
- `splitPartitionLocationUniqueId` → `lastIndexOf('-')` + two `substring`
calls
- `splitAttemptKey` → `indexOf('-')` + two `substring` calls
This removes the regex compilation, the intermediate `String[]`, the
`dropRight(1)` array copy, and the `StringBuilder` + new `String` from
`mkString`.
## Why are the changes needed?
`splitShuffleKey` is on the per-push-message hot path, called from both
`recordAppActiveConnection` (default-on per-app metrics) and `checkAuth`. A
production async-profiler CPU flame graph on `celeborn-worker` (80,611 samples;
true stack-reconstruction, self sum = 100%) shows the frame's self cost is near
zero, but its inclusive cost is ~4.23%, of which ~2.95% comes through the
default-on `recordAppActiveConnection` path and ~1.27% through the always-on
`checkAuth` path.
<img width="1619" height="260" alt="image"
src="https://github.com/user-attachments/assets/6a807653-fcdd-4037-8d16-117ebe70046e";
/>
<img width="1686" height="244" alt="image"
src="https://github.com/user-attachments/assets/240be695-4985-4f8a-abc1-e32c21c6d0ee";
/>
The allocation reduction also lowers young-GC pressure under high push QPS.
## Does this PR resolve a correctness bug?
No
## Does this PR introduce any user-facing change?
No
## How was this patch tested?
- Added unit tests in `UtilsSuite` covering `splitShuffleKey` (including
`applicationId` containing `-`, plus a `makeShuffleKey` round-trip),
`splitPartitionLocationUniqueId`, and `splitAttemptKey`.
- `./build/mvn -pl common -Dtest=UtilsSuite test` — all `split*` tests
pass. (Two unrelated `CelebornConfSuite` failures — `Fallback to parent
module's config...` and `rpc_service and rpc_client...` — are pre-existing on a
clean `upstream/main`; verified by stashing this change and re-running.)
- `./build/mvn -pl common spotless:check` — clean.
Closes #3771 from yew1eb/CELEBORN-2395.
Authored-by: yew1eb <[email protected]>
Signed-off-by: Nicholas Jiang <[email protected]>
---
.../org/apache/celeborn/common/util/Utils.scala | 23 +++++++++++-----------
.../apache/celeborn/common/util/UtilsSuite.scala | 21 ++++++++++++++++++++
2 files changed, 32 insertions(+), 12 deletions(-)
diff --git a/common/src/main/scala/org/apache/celeborn/common/util/Utils.scala
b/common/src/main/scala/org/apache/celeborn/common/util/Utils.scala
index 9a634c77d0..da7d69244a 100644
--- a/common/src/main/scala/org/apache/celeborn/common/util/Utils.scala
+++ b/common/src/main/scala/org/apache/celeborn/common/util/Utils.scala
@@ -698,17 +698,17 @@ object Utils extends Logging {
}
def splitShuffleKey(shuffleKey: String): (String, Int) = {
- val splits = shuffleKey.split("-")
- val appId = splits.dropRight(1).mkString("-")
- val shuffleId = splits.last.toInt
- (appId, shuffleId)
+ // shuffleId is always the last '-'-delimited segment (see makeShuffleKey),
+ // and applicationId may itself contain '-' (e.g. Spark's
application_<ts>_<id>),
+ // so locate the last '-' once instead of regex-splitting and rejoining.
+ val idx = shuffleKey.lastIndexOf('-')
+ (shuffleKey.substring(0, idx), shuffleKey.substring(idx + 1).toInt)
}
def splitPartitionLocationUniqueId(uniqueId: String): (Int, Int) = {
- val splits = uniqueId.split("-")
- val partitionId = splits.dropRight(1).mkString("-").toInt
- val epoch = splits.last.toInt
- (partitionId, epoch)
+ // epoch is the last segment; partitionId (Int) never contains '-'.
+ val idx = uniqueId.lastIndexOf('-')
+ (uniqueId.substring(0, idx).toInt, uniqueId.substring(idx + 1).toInt)
}
def makeReducerKey(shuffleId: Int, partitionId: Int): String = {
@@ -728,10 +728,9 @@ object Utils extends Logging {
}
def splitAttemptKey(attemptKey: String): (Int, Int) = {
- val splits = attemptKey.split("-")
- val mapId = splits(0).toInt
- val attemptId = splits(1).toInt
- (mapId, attemptId)
+ // Fixed two-segment layout: "<mapId>-<attemptId>", both Int.
+ val idx = attemptKey.indexOf('-')
+ (attemptKey.substring(0, idx).toInt, attemptKey.substring(idx + 1).toInt)
}
def shuffleKeyPrefix(shuffleKey: String): String = {
diff --git
a/common/src/test/scala/org/apache/celeborn/common/util/UtilsSuite.scala
b/common/src/test/scala/org/apache/celeborn/common/util/UtilsSuite.scala
index c83a83b95a..ac4842bf56 100644
--- a/common/src/test/scala/org/apache/celeborn/common/util/UtilsSuite.scala
+++ b/common/src/test/scala/org/apache/celeborn/common/util/UtilsSuite.scala
@@ -138,6 +138,27 @@ class UtilsSuite extends CelebornFunSuite {
assert((1, 1).equals(Utils.splitPartitionLocationUniqueId("1-1")))
}
+ test("splitShuffleKey") {
+ // plain appId without '-'
+ assert(("app0", 1).equals(Utils.splitShuffleKey("app0-1")))
+ // applicationId containing '-' (e.g. Spark application_<timestamp>_<id>)
+ assert(("application_1690000000000_0001", 7)
+ .equals(Utils.splitShuffleKey("application_1690000000000_0001-7")))
+ // round-trip with makeShuffleKey
+ val key = Utils.makeShuffleKey("application_1690000000000_0001", 42)
+ assert(("application_1690000000000_0001",
42).equals(Utils.splitShuffleKey(key)))
+ }
+
+ test("splitPartitionLocationUniqueId multiple segments") {
+ // partitionId is an Int and never contains '-'; only the trailing epoch
is sliced off.
+ assert((123, 5).equals(Utils.splitPartitionLocationUniqueId("123-5")))
+ }
+
+ test("splitAttemptKey") {
+ assert((0, 0).equals(Utils.splitAttemptKey("0-0")))
+ assert((12, 34).equals(Utils.splitAttemptKey("12-34")))
+ }
+
test("bytesToInt") {
assert(1229202015 == Utils.bytesToInt(Array(73.toByte, 68.toByte,
34.toByte, 95.toByte)))
