Make sure we log state machine errors

Author: slinkydeveloper

sdk-core/src/main/java23/dev/restate/sdk/core/statemachine/ffm/FfmStateMachine.java

@@ -30,6 +30,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import org.apache.logging.log4j.Logger;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -51,6 +52,11 @@
  */
 public final class FfmStateMachine implements StateMachine {
 
+  // Same logger as the native tracing bridge, so SDK- and core-emitted lines interleave.
+  private static final Logger LOG = NativeLogging.LOG;
+
+  private static final int SUSPENDED_ERROR_CODE = 599;
+
   private final MemorySegment vmHandle;
   private final String responseContentType;
   private boolean freed = false;
@@ -756,10 +762,23 @@ private void verifyNotFreed() {
   /**
    * Mark the state machine as closed and throw AbortedExecutionException.
    *
-   * <p>A subsequent notifyError will no-op.
+   * <p>A subsequent notifyError will no-op. Before aborting we surface the failure the core stashed
+   * (skipping the fetch when WARN is off, and skipping suspensions, which ride the same channel).
    */
   private void abortAfterCoreClosed() {
     cachedState = InvocationState.CLOSED;
+    if (LOG.isWarnEnabled()) {
+      try (Arena arena = Arena.ofConfined()) {
+        MemorySegment err = VmError.allocate(arena);
+        SharedCoreNative.vm_take_last_vm_error(vmHandle, err);
+        int code = VmError.code(err);
+        // takeSliceString also frees the owned message Slice, so decode it even when not logging.
+        String message = FfmEncoding.takeSliceString(VmError.message(err));
+        if (code != SUSPENDED_ERROR_CODE) {
+          LOG.warn("Invocation failed: {}", message);
+        }
+      }
+    }
     AbortedExecutionException.sneakyThrow();
   }
 

sdk-core/src/main/java23/dev/restate/sdk/core/statemachine/ffm/NativeLogging.java

@@ -52,9 +52,9 @@ final class NativeLogging {
   private NativeLogging() {}
 
   /** Dedicated logger all native (shared-core) events are routed through. */
-  static final String LOGGER_NAME = "dev.restate.sdk.core.StateMachine";
+  private static final String LOGGER_NAME = "dev.restate.sdk.core.StateMachine";
 
-  private static final Logger LOG = LogManager.getLogger(LOGGER_NAME);
+  static final Logger LOG = LogManager.getLogger(LOGGER_NAME);
 
   /**
    * Optional override for the native max level, bypassing the Log4j2-derived value. Accepts {@code