Advanced Transfer Client Usage

This is a collection of examples of advanced usage patterns leveraging the TransferClient.

Relative Task Deadlines

One of the lesser-known features of the Globus Transfer service is the ability for users to set a deadline by which a Transfer or Delete task must complete. If the task is still in progress when the deadline is reached, it is aborted.

You can use this, for example, to enforce that a Transfer Task which takes too long results in errors (even if it is making slow progress).

Because the deadline is accepted as an ISO 8601 date, you can use python’s built-in datetime library to compute a timestamp to pass to the service.

Start out by computing the current time as a datetime:

import datetime

now = datetime.datetime.utcnow()

Then, compute a relative timestamp using timedelta:

future_1minute = now + datetime.timedelta(minutes=1)

This value can be passed to a TransferData, as in

import globus_sdk

# get various components needed for a Transfer Task
# beyond the scope of this example
transfer_client = globus_sdk.TransferClient(...)
source_endpoint_uuid = ...
dest_endpoint_uuid = ...

# note how `future_1minute` is used here
submission_data = globus_sdk.TransferData(

Retrying Task Submission

Globus Transfer and Delete Tasks are often scheduled and submitted by automated systems and scripts. In these scenarios, it’s often desirable to retry submission in the event of network or service errors to ensure that the job is really submitted.

There are two key pieces to doing this correctly: Once and Only Once Submission, and logging captured errors.

For once-and-only-once task submission, you can explicitly invoke TransferClient.get_submission_id(), which is a unique ID used to ensure exactly this. However, TransferData and DeleteData both implicitly invoke this method if they are initialized without an explicit submission_id.

For proper logging, we’ll rely on the standard library logging package.

In this example, we’ll retry task submission 5 times, and we’ll want to separate retry logic from the core task submission logic.

import logging
from globus_sdk import GlobusAPIError, NetworkError

# putting logger objects named by the module name into the module-level
# scope is a common best practice -- for more details, you should look
# into the python logging documentation
logger = logging.getLogger(__name__)

def retry_globus_function(func, retries=5, func_name="<func>"):
    Define what it means to retry a "Globus Function", some function or
    method which produces Globus SDK errors on failure.

    def actually_retry():
        Helper: run the next retry
        return retry_globus_function(func, retries=(retries - 1), func_name=func_name)

    def check_for_reraise():
        Helper: check if we should reraise an error
                logs an error message on reraise
                must be run inside an exception handler
        if retries < 1:
            logger.error("Retried {} too many times.".format(func_name))

        return func()
    except NetworkError:
        # log with exc_info=True to capture a full stacktrace as a
        # debug-level log
            ("Globus func {} experienced a network error".format(func_name)),
    except GlobusAPIError:
        # again, log with exc_info=True to capture a full stacktrace
            ("Globus func {} experienced a network error".format(func_name)),

    # if we reach this point without returning or erroring, retry
    return actually_retry()

The above is a fairly generic tool for retrying any function which throws globus_sdk.NetworkError and globus_sdk.GlobusAPIError errors. It is not even specific to task resubmission, so you could use it against other retry-safe Globus APIs.

Now, moving on to creating a retry-safe function to put into it, things get a little bit tricky. The retry handler above requires a function which takes no arguments, so we’ll have to define a function dynamically which fits that constraint:

def submit_transfer_with_retries(transfer_client, transfer_data):
    # create a function with no arguments, for our retry handler
    def locally_bound_func():
        return transfer_client.submit_transfer(transfer_data)

    return retry_globus_function(locally_bound_func, func_name="submit_transfer")

Now we’re finally all-set to create a TransferData and submit it:

from globus_sdk import TransferClient, TransferData

# get various components needed for a Transfer Task
# beyond the scope of this example
transfer_client = TransferClient(...)
source_endpoint_uuid = ...
dest_endpoint_uuid = ...

submission_data = TransferData(
    transfer_client, source_endpoint_uuid, dest_endpoint_uuid

# add any number of items to the submission data
submission_data.add_item("/source/path", "dest/path")

# do it!
submit_transfer_with_retries(transfer_client, submission_data)

The same exact approach can be applied to TransferClient.submit_delete, and a wide variety of other SDK methods.