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The InvokeAI Download Queue#

The DownloadQueueService provides a multithreaded parallel download queue for arbitrary URLs, with queue prioritization, event handling, and restart capabilities.

Simple Example#

from import DownloadQueueService, TqdmProgress

download_queue = DownloadQueueService()
for url in ['',

    # urls start downloading as soon as download() is called,

download_queue.join()  # wait for all downloads to finish
for job in download_queue.list_jobs():
    print(job.model_dump_json(exclude_none=True, indent=4),"\n")


    "source": "",
    "dest": "/tmp/downloads",
    "id": 0,
    "priority": 10,
    "status": "completed",
    "download_path": "/tmp/downloads/a-painting-of-a-fire.png",
    "job_started": "2023-12-04T05:34:41.742174",
    "job_ended": "2023-12-04T05:34:42.592035",
    "bytes": 666734,
    "total_bytes": 666734

    "source": "",
    "dest": "/tmp/downloads",
    "id": 1,
    "priority": 10,
    "status": "completed",
    "download_path": "/tmp/downloads/birdhouse.png",
    "job_started": "2023-12-04T05:34:41.741975",
    "job_ended": "2023-12-04T05:34:42.652841",
    "bytes": 774949,
    "total_bytes": 774949

    "source": "",
    "dest": "/tmp/downloads",
    "id": 2,
    "priority": 10,
    "status": "error",
    "job_started": "2023-12-04T05:34:41.742079",
    "job_ended": "2023-12-04T05:34:42.147625",
    "bytes": 0,
    "total_bytes": 0,
    "error_type": "HTTPError(Not Found)",
    "error": "Traceback (most recent call last):\n  File \"/home/lstein/Projects/InvokeAI/invokeai/app/services/download/\", line 182, in _download_next_item\n    self._do_download(job)\n  File \"/home/lstein/Projects/InvokeAI/invokeai/app/services/download/\", line 206, in _do_download\n    raise HTTPError(resp.reason)\nrequests.exceptions.HTTPError: Not Found\n"

    "source": "",
    "dest": "/tmp/downloads",
    "id": 3,
    "priority": 10,
    "status": "completed",
    "download_path": "/tmp/downloads/xl_more_art-full_v1.safetensors",
    "job_started": "2023-12-04T05:34:42.147645",
    "job_ended": "2023-12-04T05:34:43.735990",
    "bytes": 719020768,
    "total_bytes": 719020768

The API#

The default download queue is DownloadQueueService, an implementation of ABC DownloadQueueServiceBase. It juggles multiple background download requests and provides facilities for interrogating and cancelling the requests. Access to a current or past download task is mediated via DownloadJob objects which report the current status of a job request

The Queue Object#

A default download queue is located in However, you can create additional instances if you need to isolate your queue from the main one.

queue = DownloadQueueService(event_bus=events)

DownloadQueueService() takes three optional arguments:

Argument Type Default Description
max_parallel_dl int 5 Maximum number of simultaneous downloads allowed
event_bus EventServiceBase None System-wide FastAPI event bus for reporting download events
requests_session requests.sessions.Session None An alternative requests Session object to use for the download

max_parallel_dl specifies how many download jobs are allowed to run simultaneously. Each will run in a different thread of execution.

event_bus is an EventServiceBase, typically the one created at InvokeAI startup. If present, download events are periodically emitted on this bus to allow clients to follow download progress.

requests_session is a url library requests Session object. It is used for testing.

The Job object#

The queue operates on a series of download job objects. These objects specify the source and destination of the download, and keep track of the progress of the download.

The only job type currently implemented is DownloadJob, a pydantic object with the following fields:

Field Type Default Description
Fields passed in at job creation time
source AnyHttpUrl Where to download from
dest Path Where to download to
access_token str [optional] string containing authentication token for access
on_start Callable [optional] callback when the download starts
on_progress Callable [optional] callback called at intervals during download progress
on_complete Callable [optional] callback called after successful download completion
on_error Callable [optional] callback called after an error occurs
id int auto assigned Job ID, an integer >= 0
priority int 10 Job priority. Lower priorities run before higher priorities
Fields updated over the course of the download task
status DownloadJobStatus Status code
download_path Path Path to the location of the downloaded file
job_started float Timestamp for when the job started running
job_ended float Timestamp for when the job completed or errored out
job_sequence int A counter that is incremented each time a model is dequeued
bytes int 0 Bytes downloaded so far
total_bytes int 0 Total size of the file at the remote site
error_type str String version of the exception that caused an error during download
error str String version of the traceback associated with an error
cancelled bool False Set to true if the job was cancelled by the caller

When you create a job, you can assign it a priority. If multiple jobs are queued, the job with the lowest priority runs first.

Every job has a source and a dest. source is a pydantic.networks AnyHttpUrl object. The dest is a path on the local filesystem that specifies the destination for the downloaded object. Its semantics are described below.

When the job is submitted, it is assigned a numeric id. The id can then be used to fetch the job object from the queue.

The status field is updated by the queue to indicate where the job is in its lifecycle. Values are defined in the string enum DownloadJobStatus, a symbol available from Possible values are:

Value String Value ** Description **
WAITING waiting Job is on the queue but not yet running
RUNNING running The download is started
COMPLETED completed Job has finished its work without an error
ERROR error Job encountered an error and will not run again

job_started and job_ended indicate when the job was started (using a python timestamp) and when it completed.

In case of an error, the job's status will be set to DownloadJobStatus.ERROR, the text of the Exception that caused the error will be placed in the error_type field and the traceback that led to the error will be in error.

A cancelled job will have status DownloadJobStatus.ERROR and an error_type field of "DownloadJobCancelledException". In addition, the job's cancelled property will be set to True.


Download jobs can be associated with a series of callbacks, each with the signature Callable[["DownloadJob"], None]. The callbacks are assigned using optional arguments on_start, on_progress, on_complete and on_error. When the corresponding event occurs, the callback wil be invoked and passed the job. The callback will be run in a try: context in the same thread as the download job. Any exceptions that occur during execution of the callback will be caught and converted into a log error message, thereby allowing the download to continue.


The module defines a class named TqdmProgress which can be used as an on_progress handler to display a completion bar in the console. Use as follows:

from import TqdmProgress'http://some.server.somewhere/some_file',


If the queue was initialized with the InvokeAI event bus (the case when using, then download events will also be issued on the bus. The events are:

  • download_started -- This is issued when a job is taken off the queue and a request is made to the remote server for the URL headers, but before any data has been downloaded. The event payload will contain the keys source and download_path. The latter contains the path that the URL will be downloaded to.

  • download_progress -- This is issued periodically as the download runs. The payload contains the keyssource,download_path,current_bytesandtotal_bytes`. The latter two fields can be used to display the percent complete.

  • download_complete -- This is issued when the download completes successfully. The payload contains the keys source, download_path and total_bytes.

  • download_error -- This is issued when the download stops because of an error condition. The payload contains the fields error_type and error. The former is the text representation of the exception, and the latter is a traceback showing where the error occurred.

Job control#

To create a job call the queue's download() method. You can list all jobs using list_jobs(), fetch a single job by its with id_to_job(), cancel a running job with cancel_job(), cancel all running jobs with cancel_all_jobs(), and wait for all jobs to finish with join().

job =, dest, priority, access_token)#

Create a new download job and put it on the queue, returning the DownloadJob object.

jobs = queue.list_jobs()#

Return a list of all active and inactive DownloadJobs.

job = queue.id_to_job(id)#

Return the job corresponding to given ID.

Return a list of all active and inactive DownloadJobs.


Remove inactive (complete or errored) jobs from the listing returned by list_jobs().


Block until all pending jobs have run to completion or errored out.