Structured Data File (SDF) generation can last anywhere from a few seconds to
hours. The task is done when the done
field in the Operation
is True
.
An Operation
is identified by a name of the format /sdfdownloadtasks/operations/{id}
. Regularly retrieve the Operation
with
this name using sdfdownloadtasks.operations.get
to see if
the task is finished. This process is known as "polling."
If done
is True
, either the response
or error
field will be set. A failed task sets the error
field. The assigned Status
object provides details about the
failure. A successful task sets the response
field. Download the
resulting SDFs from response.resourceName
.
Inefficient polling can consume a lot of API request quota . Limit retries and conserve quota using exponential backoff .
Here's how to poll a SDF download task using exponential backoff:
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);
