IFRT proxy: hacky flag for faster is_deleted().

Setting the environment variable `IFRT_PROXY_ARRAY_IS_DELETED_HACK=enabled` in the OSS-compiled version of the IFRT proxy will make all `Array::IsDeleted()` calls to immediately return false.

This is not a generally safe optimization and trades off API correctness.

This acts as an interim solution for users while proper solutions are being debated or implemented.

PiperOrigin-RevId: 697450328

xla/python/ifrt_proxy/client/BUILD

@@ -593,7 +593,11 @@ cc_library(
         "global_flags_oss.cc",
     ],
     visibility = ["//visibility:private"],
-    deps = ["@com_google_absl//absl/debugging:leak_check"],
+    deps = [
+        "@com_google_absl//absl/debugging:leak_check",
+        "@com_google_absl//absl/log:check",
+        "@com_google_absl//absl/strings",
+    ],
 )
 
 cc_library(

xla/python/ifrt_proxy/client/array.cc

@@ -240,6 +240,9 @@ Future<> Array::Delete() {
 }
 
 bool Array::IsDeleted() const {
+  if (GetGlobalClientFlags()->array_is_deleted_hack) {
+    return false;
+  }
   auto req = std::make_unique<IsArrayDeletedRequest>();
   req->set_array_handle(handle_.handle);
 

xla/python/ifrt_proxy/client/global_flags.h

@@ -33,14 +33,18 @@ struct GlobalClientFlags {
   // TODO(madthanu): Remove flag once there is confidence that the asynchronous
   // codepath works well.
   bool synchronous_host_buffer_store;
+
+  // TODO(b/375021159): Implement faster is_delete without needing a hack.
+  bool array_is_deleted_hack;
 };
 
 GlobalClientFlags* GetGlobalClientFlags();
 
 inline std::ostream& operator<<(std::ostream& os, GlobalClientFlags flags) {
   return os << "xla::ifrt::proxy::GlobalClientFlags{"
             << "synchronous_host_buffer_store="
-            << flags.synchronous_host_buffer_store << "}";
+            << flags.synchronous_host_buffer_store << ","
+            << "array_is_deleted_hack=" << flags.array_is_deleted_hack << "}";
 }
 
 }  // namespace proxy

xla/python/ifrt_proxy/client/global_flags_oss.cc

@@ -13,16 +13,37 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
+#include <cstdlib>
+#include <string>
+
 #include "absl/debugging/leak_check.h"
+#include "absl/log/check.h"
+#include "absl/strings/numbers.h"
 #include "xla/python/ifrt_proxy/client/global_flags.h"
 
 namespace xla {
 namespace ifrt {
 namespace proxy {
 
+namespace {
+
+bool GetBoolFromEnv(const char* key) {
+  if (const char* valptr = std::getenv(key)) {
+    std::string val(valptr);
+    bool result;
+    QCHECK(absl::SimpleAtob(val, &result)) << " " << key << ": '" << val << "'";
+    return result;
+  }
+  return false;
+}
+
+}  // namespace
+
 static GlobalClientFlags DefaultGlobalClientFlags() {
   GlobalClientFlags result;
   result.synchronous_host_buffer_store = false;
+  result.array_is_deleted_hack =
+      GetBoolFromEnv("IFRT_PROXY_ARRAY_IS_DELETED_HACK");
   return result;
 };