Quá trình tạo tệp dữ liệu có cấu trúc (SDF) có thể kéo dài từ vài giây đến vài giờ. Việc cần làm sẽ hoàn tất khi trường done trong Operation là True.
Một Operation được xác định bằng tên có định dạng /sdfdownloadtasks/operations/{id}. Thường xuyên truy xuất Operation có tên này bằng cách sử dụng sdfdownloadtasks.operations.get để xem liệu tác vụ đã hoàn tất hay chưa. Quá trình này được gọi là "bỏ phiếu".
Nếu done là True, thì trường response hoặc error sẽ được đặt. Một tác vụ không thành công sẽ đặt trường error. Đối tượng Status được chỉ định cung cấp thông tin chi tiết về lỗi. Một tác vụ thành công sẽ đặt trường response. Tải các SDF thu được xuống từ response.resourceName.
Việc thăm dò ý kiến không hiệu quả có thể tiêu tốn nhiều hạn mức yêu cầu API. Giới hạn số lần thử lại và tiết kiệm hạn mức bằng cách sử dụng thuật toán thời gian đợi luỹ thừa.
Sau đây là cách thăm dò một tác vụ tải SDF xuống bằng cách sử dụng thời gian đợi luỹ thừa:
Java
// Provide the name of the sdfdownloadtask operation. String operationName = operation-name; // Configure the Operations.get request. Sdfdownloadtasks.Operations.Get operationRequest = service.sdfdownloadtasks().operations().get(operationName); // Configure exponential backoff for checking the status of our operation. ExponentialBackOff backOff = new ExponentialBackOff.Builder() .setInitialIntervalMillis(5000) // setting initial interval to five seconds .setMaxIntervalMillis(5000 * 60) // setting max interval to five minutes .setMaxElapsedTimeMillis(5000 * 60 * 60) // setting max elapsed time to five hours .build(); long backoffMillis = 0; // Create default operation variable. Operation operation = new Operation(); do { // Sleep before retrieving operation again. Thread.sleep(backoffMillis); // Retrieve operation. operation = operationRequest.execute(); // If operation is not done, calculate next sleep period. if (operation.getDone() == null) { backoffMillis = backOff.nextBackOffMillis(); if (backoffMillis == ExponentialBackOff.STOP) { System.out.printf("The operation has taken more than five hours to complete.%n"); break; } System.out.printf( "Operation %s is still running, sleeping for %s milliseconds.%n", operationName, backoffMillis); } } while (operation.getDone() == null); // Check whether operation finished with an error, or is completed and ready to download. if (operation.getDone() != null) { if (operation.getError() != null) { System.out.printf( "The operation finished in error with code %s: %s%n", operation.getError().getCode(), operation.getError().getMessage()); } else { System.out.printf( "The operation completed successfully. Resource %s was created.%n", operation.getResponse().get("resourceName").toString()); } }
Python
# Provide the name of the sdfdownloadtask operation. operation_name = operation-name # Set the following values that control retry behavior while the operation # is running. # Minimum amount of time between polling requests. Defaults to 5 seconds. min_retry_interval = 5 # Maximum amount of time between polling requests. Defaults to 5 minutes. max_retry_interval = 5 * 60 # Maximum amount of time to spend polling. Defaults to 5 hours. max_retry_elapsed_time = 5 * 60 * 60 def next_sleep_interval(previous_sleep_interval): """Calculates the next sleep interval based on the previous.""" min_interval = previous_sleep_interval or min_retry_interval max_interval = previous_sleep_interval * 3 or min_retry_interval return min(max_retry_interval, random.randint(min_interval, max_interval)) # Configure the sdfdownloadtasks.operations.get request. get_request = service.sdfdownloadtasks().operations().get(name=operation_name) sleep = 0 start_time = time.time() while True: # Retrieve the operation. operation = get_request.execute() if "done" in operation: if "error" in operation: print( f"The operation finished in error with code " f'{operation["error"]["code"]}: {operation["error"]["message"]}' ) else: print( f"The operation completed successfully. The resulting files can be " f'downloaded at {operation["response"]["resourceName"]}.' ) break elif time.time() - start_time > max_retry_elapsed_time: print("SDF generation deadline exceeded.") break sleep = next_sleep_interval(sleep) print( f"Operation {operation_name} is still running, sleeping for " f"{sleep} seconds." ) time.sleep(sleep)
PHP
// The following values control retry behavior while the task is processing. // Minimum amount of time between polling requests. Defaults to 5 seconds. $minRetryInterval = 5; // Maximum amount of time between polling requests. Defaults to 5 minutes. $maxRetryInterval = 300; // Maximum amount of time to spend polling. Defaults to 5 hours. $maxRetryElapsedTime = 18000; // Provide the name of the sdfdownloadtask operation. $operationName = operation-name; // Poll operation. $sleep = 0; $startTime = time(); do { try { // Call the API, retrieving the SDF Download Task. $operation = $this->service->sdfdownloadtasks_operations->get( $operationName ); } catch (\Exception $e) { $this->renderError($e); return; } // Check if retrieved operation is finished. if ($operation->getDone() === true) { if($operation->getError() !== null) { $error = $operation->getError(); printf( 'The operation finished in error with code %s: %s<br>', $error->setCode(), $error->setMessage() ); break; } else { $response = $operation->getResponse(); printf( 'The operation completed successfully. Resource %s ' . 'was created.<br>', $response['resourceName'] ); break; } } elseif (time() - $startTime > self::MAX_RETRY_ELAPSED_TIME) { print '<p>SDF download task processing deadline exceeded</p>'; break; } // Generate next sleep interval. $minInterval = max($minRetryInterval, $sleep); $maxInterval = max( $minRetryInterval, $sleep * 3 ); $sleep = min($maxRetryInterval, rand($minInterval, $maxInterval)); // Sleep a determined amount of time before retrieving the operation // again. printf( 'Operation %s is still running, sleeping for %d seconds<br>', $operationName, $sleep ); sleep($sleep); } while (true);