Split pregen queue metrics

- Publish in-flight pregen chunk requests as iris.pregen-queue
- Publish chunks left in the job as iris.pregen-remaining
- Mark generation timings unavailable after 10 seconds without generation

core/src/main/java/art/arcane/iris/generation/runtime/EngineTelemetrySnapshot.java

@@ -52,7 +52,12 @@ public record EngineTelemetrySnapshot(
         generationTimingsMs = sanitizeTimings(generationTimingsMs);
     }
 
-    public static EngineTelemetrySnapshot capture(Engine engine, double chunksPerSecond, long sampledAtMs) {
+    public static EngineTelemetrySnapshot capture(
+            Engine engine,
+            double chunksPerSecond,
+            boolean generationTimingsFresh,
+            long sampledAtMs
+    ) {
         if (engine == null) {
             throw new IllegalArgumentException("Engine cannot be null");
         }
@@ -85,7 +90,7 @@ public record EngineTelemetrySnapshot(
                 engine.getMantle().getLoadedRegionCount(),
                 engine.getMantle().getUnloadRegionCount(),
                 engine.getMantle().getAdjustedIdleDuration(),
-                engine.getMetrics().telemetryAverages()
+                generationTimingsFresh ? engine.getMetrics().telemetryAverages() : Map.of()
         );
     }
 

core/src/main/java/art/arcane/iris/studio/view/PregeneratorJob.java

@@ -302,7 +302,8 @@ public class PregeneratorJob implements PregenListener, PregenRenderSource {
 
     public record PregenProgress(double percent, long generated, long totalChunks, double chunksPerSecond,
                                  double overallChunksPerSecond, double thirtySecondChunksPerSecond,
-                                 double sixtySecondChunksPerSecond, long chunksRemaining, long eta, long elapsed,
+                                 double sixtySecondChunksPerSecond, long chunksRemaining, long chunksInFlight,
+                                 long eta, long elapsed,
                                  String method, boolean paused, long failed, String worldName, String worldIdentity) {
     }
 
@@ -322,6 +323,7 @@ public class PregeneratorJob implements PregenListener, PregenRenderSource {
                 Math.max(0D, lastThirtySecondChunksPerSecond),
                 Math.max(0D, lastSixtySecondChunksPerSecond),
                 Math.max(0L, lastChunksRemaining),
+                pregenerator.getInFlightChunks(),
                 lastEta,
                 lastElapsed,
                 lastMethod,

core/src/main/java/art/arcane/iris/world/pregen/AsyncOrMedievalPregenMethod.java

@@ -105,6 +105,11 @@ public class AsyncOrMedievalPregenMethod implements PregeneratorMethod {
         method.reclaimMemory();
     }
 
+    @Override
+    public int inFlightChunks() {
+        return method.inFlightChunks();
+    }
+
     @Override
     public Mantle getMantle() {
         return method.getMantle();

core/src/main/java/art/arcane/iris/world/pregen/AsyncPregenMethod.java

@@ -1127,6 +1127,11 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         return null;
     }
 
+    @Override
+    public int inFlightChunks() {
+        return Math.max(0, inFlight.get());
+    }
+
     @Override
     public Mantle getMantle() {
         if (IrisToolbelt.isIrisWorld(world)) {

core/src/main/java/art/arcane/iris/world/pregen/CachedPregenMethod.java

@@ -213,6 +213,11 @@ public class CachedPregenMethod implements PregeneratorMethod {
         method.reclaimMemory();
     }
 
+    @Override
+    public int inFlightChunks() {
+        return method.inFlightChunks();
+    }
+
     @Override
     public Mantle getMantle() {
         return method.getMantle();

core/src/main/java/art/arcane/iris/world/pregen/HybridPregenMethod.java

@@ -98,6 +98,11 @@ public class HybridPregenMethod implements PregeneratorMethod {
         inWorld.reclaimMemory();
     }
 
+    @Override
+    public int inFlightChunks() {
+        return inWorld.inFlightChunks();
+    }
+
     @Override
     public Mantle getMantle() {
         return inWorld.getMantle();

core/src/main/java/art/arcane/iris/world/pregen/IrisPregenerator.java

@@ -464,6 +464,10 @@ public class IrisPregenerator {
         return failed.get();
     }
 
+    public int getInFlightChunks() {
+        return generator.inFlightChunks();
+    }
+
     public PregenRates getRates() {
         return rates;
     }

core/src/main/java/art/arcane/iris/world/pregen/MedievalPregenMethod.java

@@ -52,6 +52,7 @@ public class MedievalPregenMethod implements PregeneratorMethod {
     private static final long UNLOAD_TIMEOUT_SECONDS = 120L;
     private final World world;
     private final KList<CompletableFuture<?>> futures;
+    private final AtomicInteger inFlight;
     private final Map<Chunk, Long> lastUse;
     private final int maxFutures;
     private final AtomicBoolean directAsyncDisabled;
@@ -67,6 +68,7 @@ public class MedievalPregenMethod implements PregeneratorMethod {
         this.chunkFlush = new PregenSerialWorker("Iris Pregen Chunk Flush", world == null ? "unknown" : world.getName());
         this.chunkIoExecutor = chunkFlush.executor();
         futures = new KList<>();
+        this.inFlight = new AtomicInteger();
         this.lastUse = new ConcurrentHashMap<>();
         int configuredThreads = IrisSettings.getThreadCount(IrisSettings.get().getConcurrency().getParallelism());
         this.maxFutures = J.isFolia() ? Math.max(2, Math.min(64, configuredThreads)) : Math.max(16, Math.min(128, configuredThreads * 4));
@@ -229,6 +231,7 @@ public class MedievalPregenMethod implements PregeneratorMethod {
         }
 
         listener.onChunkGenerating(x, z);
+        inFlight.incrementAndGet();
         // Single choke point for failure accounting: without onChunkFailed a lossy run can
         // never satisfy allVisitsComplete, so a finished pregen reports as aborted forever.
         CompletableFuture<?> chunkFuture = J.isFolia()
@@ -247,6 +250,7 @@ public class MedievalPregenMethod implements PregeneratorMethod {
                 })
                 : scheduleChunkLoad(x, z, listener);
         futures.add(chunkFuture.whenComplete((r, err) -> {
+            inFlight.decrementAndGet();
             if (err != null) {
                 listener.onChunkFailed(x, z);
             }
@@ -358,6 +362,11 @@ public class MedievalPregenMethod implements PregeneratorMethod {
         }
     }
 
+    @Override
+    public int inFlightChunks() {
+        return Math.max(0, inFlight.get());
+    }
+
     @Override
     public Mantle getMantle() {
         if (IrisToolbelt.isIrisWorld(world)) {

core/src/main/java/art/arcane/iris/world/pregen/PregeneratorMethod.java

@@ -95,5 +95,9 @@ public interface PregeneratorMethod {
     default void reclaimMemory() {
     }
 
+    default int inFlightChunks() {
+        return 0;
+    }
+
     Mantle getMantle();
 }

core/src/test/java/art/arcane/iris/world/pregen/CachedPregenMethodCompletionTest.java

@@ -62,6 +62,13 @@ public class CachedPregenMethodCompletionTest {
         assertEquals(1, listener.generated.get());
     }
 
+    @Test
+    public void inFlightChunksReportTheWrappedMethodsOutstandingRequests() {
+        underlying.inFlight.set(37);
+
+        assertEquals(37, method.inFlightChunks());
+    }
+
     @Test
     public void generateChunkFailureIsNotCached() {
         method.generateChunk(6, 9, listener);
@@ -186,11 +193,17 @@ public class CachedPregenMethodCompletionTest {
         private final AtomicInteger centerBlockX = new AtomicInteger();
         private final AtomicInteger centerBlockZ = new AtomicInteger();
         private final AtomicReference<PregenListener> capturedListener = new AtomicReference<>();
+        private final AtomicInteger inFlight = new AtomicInteger();
 
         @Override
         public void init() {
         }
 
+        @Override
+        public int inFlightChunks() {
+            return inFlight.get();
+        }
+
         @Override
         public void close() {
         }