Aias00 opened a new issue, #7803:
URL: https://github.com/apache/shenyu/issues/7803
### Is there an existing issue for this?
- [x] I searched existing issues. #6610 and #7463 concern queue
rejection/offer behavior, but do not cover JVM committed heap versus maximum
heap headroom.
### Current Behavior
Starting a gateway with `-Xms256m -Xmx768m` can cause its shared wheel timer
to reject scheduled tasks even when several hundred MiB remain available below
`-Xmx`.
During a local Docker deployment, the gateway HTTP health endpoint was UP,
but the timer logged task rejection and gateway heartbeat registration did not
progress normally. Increasing the initial heap to 1 GiB made the scheduled work
and heartbeat registration work.
A standalone reproduction against the same built ShenYu classes produced:
```text
# -Xms256m -Xmx768m
committedMiB=256
freeCommittedMiB=156
headroomToXmxMiB=668
accepted=false
# -Xms1g -Xmx1536m
committedMiB=1024
freeCommittedMiB=970
headroomToXmxMiB=1482
accepted=true
```
This is a custom small-heap deployment, not a claim that the stock Docker
entrypoint's 2 GiB defaults fail.
### Expected Behavior
Task admission should account for genuinely available heap, including memory
that the JVM can commit up to `-Xmx`, or clearly validate/document a minimum
initial heap. An otherwise healthy gateway should not silently lose recurring
timer/heartbeat work because its initial committed heap is below a fixed queue
threshold.
### Steps To Reproduce
1. Build the current gateway distribution.
2. Run the following with `-Xms256m -Xmx768m` and the distribution's `lib/*`
on the classpath:
```java
import org.apache.shenyu.common.concurrent.MemorySafeLinkedBlockingQueue;
public class HeapAdmissionRepro {
public static void main(String[] args) {
Runtime runtime = Runtime.getRuntime();
long used = runtime.totalMemory() - runtime.freeMemory();
MemorySafeLinkedBlockingQueue<Runnable> queue =
new MemorySafeLinkedBlockingQueue<>(256 * 1024 * 1024);
System.out.println("committedMiB=" + runtime.totalMemory() / 1024 /
1024);
System.out.println("freeCommittedMiB=" + runtime.freeMemory() / 1024
/ 1024);
System.out.println("headroomToXmxMiB=" + (runtime.maxMemory() -
used) / 1024 / 1024);
System.out.println("accepted=" + queue.offer(() -> {}));
System.exit(0);
}
}
```
3. Observe `accepted=false` despite sufficient maximum-heap headroom. A
bootstrap using `HierarchicalWheelTimer` exhibits the timer rejection below.
4. Compare with a larger initial heap.
### Environment
- ShenYu: `2.7.2-SNAPSHOT`, master `04f7c2e8b7d282f14510157a9ab0bfaab538ecac`
- Local deployment: ARM64 Linux containers, Eclipse Temurin Java 17,
macOS/OrbStack host
- Standalone admission check: Java 17
### Debug logs
```text
WARN HierarchicalWheelTimer - Dropping the expired timer task because the
timer task queue has no remaining memory
java.util.concurrent.RejectedExecutionException: Queue capacity is full.
at
org.apache.shenyu.common.concurrent.ShenyuThreadPoolExecutor.execute(...)
at
org.apache.shenyu.common.timer.HierarchicalWheelTimer.addTimerTaskEntry(...)
```
### Code evidence
- [MemoryLimitCalculator.java, lines
56–58](https://github.com/apache/shenyu/blob/04f7c2e8b7d282f14510157a9ab0bfaab538ecac/shenyu-common/src/main/java/org/apache/shenyu/common/concurrent/MemoryLimitCalculator.java#L56-L58)
sets its available-memory value to `Runtime.freeMemory()`, which describes
unused **committed** heap.
- [MemorySafeLinkedBlockingQueue.java, lines
84–95](https://github.com/apache/shenyu/blob/04f7c2e8b7d282f14510157a9ab0bfaab538ecac/shenyu-common/src/main/java/org/apache/shenyu/common/concurrent/MemorySafeLinkedBlockingQueue.java#L84-L95)
gates admission on this value.
- [HierarchicalWheelTimer.java, lines
90–95](https://github.com/apache/shenyu/blob/04f7c2e8b7d282f14510157a9ab0bfaab538ecac/shenyu-common/src/main/java/org/apache/shenyu/common/timer/HierarchicalWheelTimer.java#L90-L95)
fixes the queue threshold at `THE_256_MB`.
Please cover `Xms < Xmx` in regression tests and review the admission
calculation and the timer's fixed threshold. A possible calculation to evaluate
is `maxMemory - (totalMemory - freeMemory)`; this issue does not prescribe it
without reviewing the intended memory protection policy.
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