detect not-found via gRPC status instead of IllegalArgumentException

Author: bachuv

exporthistory/src/main/java/com/microsoft/durabletask/exporthistory/client/DefaultExportHistoryJobClient.java

@@ -154,13 +154,35 @@ private void terminateAndPurgeOrchestration(String orchestrationInstanceId) {
             }
 
             this.durableTaskClient.purgeInstance(orchestrationInstanceId);
-        } catch (IllegalArgumentException e) {
-            // Instance not found — already deleted or never existed
-            logger.info("Orchestration instance '" + orchestrationInstanceId +
-                    "' is already purged or never existed.");
         } catch (Exception e) {
-            logger.log(Level.WARNING,
-                    "Failed to terminate/purge orchestration: " + orchestrationInstanceId, e);
+            if (isNotFound(e)) {
+                // Orchestration instance doesn't exist — already deleted or never existed.
+                logger.info("Orchestration instance '" + orchestrationInstanceId
+                        + "' is already purged or never existed.");
+            } else {
+                logger.log(Level.WARNING,
+                        "Failed to terminate/purge orchestration: " + orchestrationInstanceId, e);
+            }
+        }
+    }
+
+    /**
+     * Detects "instance not found" responses from the sidecar without taking a hard dependency on
+     * gRPC types. The Durable Task gRPC client surfaces "not found" as a {@code StatusRuntimeException}
+     * with code {@code NOT_FOUND}; we match against the exception's {@code toString()} which embeds
+     * both. This mirrors .NET's {@code catch (RpcException ex) when (ex.StatusCode == StatusCode.NotFound)}.
+     */
+    private static boolean isNotFound(Throwable t) {
+        while (t != null) {
+            String name = t.getClass().getName();
+            if ("io.grpc.StatusRuntimeException".equals(name) || "io.grpc.StatusException".equals(name)) {
+                String msg = String.valueOf(t.getMessage());
+                if (msg.contains("NOT_FOUND")) {
+                    return true;
+                }
+            }
+            t = t.getCause();
         }
+        return false;
     }
 }