Task Execution Service (TES) Backend
The Task Execution Service (TES) backend submits tasks to a remote server using the TES API.
Implementations of the TES API include:
Authentication
The TES backend supports two authentication schemes to communicate with the TES API server:
- Basic HTTP authentication (i.e. username and password)
- Bearer token
The TES backend does not currently support authentication schemes such as OAuth; if the TES API server requires a bearer token, the token itself must be derived through external means and specified verbatim in Sprocket's configuration.
Task inputs
As task execution is remote when using the TES backend, local inputs are transferred to the remote server by uploading them to cloud storage and providing the TES API server with the upload locations.
To prevent duplicate uploads of the same data, the TES backend will calculate a Blake3 digest of the input to be transferred and uses an upload path of file/<hex-digest> (for File inputs) or directory/<hex-digest> (for Directory inputs). If an object exists at that path in cloud storage, it is assumed to match and the upload of the input is skipped; Sprocket will not download the object from cloud storage to verify that it matches the local input.
Sprocket also supports specifying paths to files and directories by remote URL (either http://, https://, or using a cloud storage URL). If an input is already a remote URL, it is passed to the TES API server without transferring any data to cloud storage.
Task outputs
The TES backend requests that the TES API server uploads task outputs to a cloud storage location using a unique prefix for the task's execution.
Sprocket will not attempt to download an executed task's outputs until an output is needed by workflow evaluation. For example, if a task outputs a File, the File remains a remote URL to the cloud storage location of the output. If that value is used in a read_* call from the WDL standard library, Sprocket will download the file unless already cached locally.
If the task's output is used as an input to another task, the existing remote cloud storage location is passed to the TES API server and no data is transferred to cloud storage for the input.
Configuration
The TES backend supports the following configuration:
[run.backends.default]
type = "tes"
# The URL of the TES API server
url = "<tes-server-url>"
# The cloud storage URL where Sprocket will upload inputs
inputs = "<cloud-storage-url>"
# The cloud storage URL where the TES API server will upload outputs
outputs = "<cloud-storage-url>"
# The polling interval for task status updates (defaults to 60 seconds)
interval = 60
# If basic authentication is required:
[run.backends.default.auth]
type = "basic"
username = "<username>"
password = "<password>"
# If bearer token authentication is required:
[run.backends.default.auth]
type = "bearer"
token = "<token>"WARNING
On Unix operating systems, it is recommended that your sprocket.toml has an access permission of 0600 if it contains secrets like TES API server passwords or tokens.