Quick Reference

All sflow.yaml config fields at a glance. The Required column indicates mandatory fields.

For detailed explanations and examples, see Configuration.

Root-Level

Field	Required	Type	Default	Description
version	Yes	string	—	Schema version. Must be "0.1".
variables		dict / list	—	Global variables available to expressions and task env.
artifacts		dict / list	—	Named resources referenced by URI.
backends		dict / list	—	Compute backends (local, slurm).
operators		dict / list	—	Task execution operators (bash, srun, docker, ssh, python).
workflow	Yes	object	—	Workflow definition containing name and tasks.

Variables

YAML path: variables.<name>

Field	Required	Type	Default	Description
value	Yes	any	—	Variable value (int, float, bool, string, or list).
description		string	null	Human-readable description.
domain		list	null	Allowed values; enables replica variable sweeps. value must be in domain if set.
type		string	"string"	Type hint (string, integer, etc.).

Artifacts

YAML path: artifacts.<name>

Field	Required	Type	Default	Description
uri	Yes	string	—	Resource URI with scheme (fs://, file://, http://, s3://).
description		string	null	Human-readable description.
content		string	null	Inline file content. Only valid with file:// URI.

Backends — Common Fields

YAML path: backends.<name>

Field	Required	Type	Default	Description
type	Yes	string	—	local or slurm.
default		bool	false	Mark as the default backend (only one allowed).
gpus_per_node		int / expr	null	GPUs per node for allocation / packing.

Backends — Local

Additional fields when type: local

Field	Required	Type	Default	Description
nodes		int / expr	1	Number of synthetic local nodes.

Backends — Slurm

Additional fields when type: slurm

Field	Required	Type	Default	Description
account	Yes	string / expr	—	Slurm account.
partition	Yes	string / expr	—	Slurm partition.
time	Yes	string / expr	—	Time limit (e.g. 00:30:00).
nodes	Yes	int / expr	—	Number of nodes.
gpus_per_node	Yes	int / expr	—	GPUs per node.
extra_args		list[string]	null	Extra salloc arguments (e.g. --exclusive).
job_name		string	null	Job name; defaults to workflow name.

Operators — Common Fields

YAML path: operators.<name>

Field	Required	Type	Default	Description
type	Yes	string	—	Operator type: bash, srun, docker, ssh, or python.

Operators — srun

Additional fields when type: srun

Field	Required	Type	Default	Description
job_id		string	null	Existing Slurm job ID.
nodes		int / string	null	Node count.
nodelist		list[string]	[]	Node list.
partition		string	null	Slurm partition.
account		string	null	Slurm account.
qos		string	null	QOS.
reservation		string	null	Reservation.
time		string	null	Time limit.
constraint		string	null	Slurm constraint.
exclusive		bool	false	Exclusive node allocation.
chdir		string	null	Working directory.
cpus_per_task		int / string	null	CPUs per task.
gpus		string	null	GPU spec (e.g. all, 1, device=0).
gpus_per_task		string	null	GPUs per task.
gres		string	null	Generic resource spec.
mem		string	null	Memory.
mem_per_cpu		string	null	Memory per CPU.
ntasks		int / string	null	Number of tasks.
ntasks_per_node		int / string	null	Tasks per node.
export		string	"ALL"	Environment export setting.
label		bool	true	Prefix output with task label.
unbuffered		bool	true	Unbuffered output.
kill_on_bad_exit		bool	false	Kill job on non-zero task exit.
overlap		bool	true	Allow step overlap.
wait		int / string	null	Wait time.
container_image		string	null	Container image (Pyxis). Mutually exclusive with container_name.
container_name		string	null	Existing container name (Pyxis). Mutually exclusive with container_image.
container_mount_home		bool	false	Mount home directory in container.
container_writable		bool	true	Writable container filesystem.
container_mounts		list[string]	[]	Bind mounts (e.g. "/host:/ctr:rw").
container_workdir		string	null	Container working directory.
container_remap_root		bool	false	Remap root inside container.
mpi		string	null	MPI type (e.g. pmix, ucx).
extra_args		list[string]	[]	Extra CLI arguments.

Operators — Docker

Additional fields when type: docker

Field	Required	Type	Default	Description
image	Yes	string	—	Docker image.
workdir		string	null	Working directory inside container.
mounts		list[string]	[]	Bind mounts (e.g. "/host:/ctr:rw").
gpus		string	null	GPU spec (e.g. all, device=0).
extra_args		list[string]	[]	Extra docker run arguments.
pass_envs		bool	true	Forward host environment variables.

Operators — SSH

Additional fields when type: ssh

Field	Required	Type	Default	Description
host	Yes	string	—	SSH host.
user		string	null	SSH user.
port		int	null	SSH port.
identity_file		string	null	Path to identity file.
extra_args		list[string]	[]	Extra SSH arguments.

Operators — Python

Additional fields when type: python

Field	Required	Type	Default	Description
python_exec		string	"python"	Python executable.
extra_args		list[string]	[]	Extra Python arguments.

Workflow

YAML path: workflow

Field	Required	Type	Default	Description
name	Yes	string	—	Workflow name.
tasks	Yes	list	—	List of task definitions (must be non-empty).
timeout		string / int	null	Workflow-level timeout (e.g. 1h, 115m).
variables		dict / list	null	Workflow-scoped variables (same format as root variables).

Tasks

YAML path: workflow.tasks[]

Field	Required	Type	Default	Description
name	Yes	string	—	Task name (must be unique).
script	Yes	list[string]	—	Script lines to execute (non-empty).
operator		string / object	null	Operator name, or inline operator override object.
backend		string / dict	null	Backend name, or inline backend override.
depends_on		list[string]	null	Names of tasks this task depends on.
timeout		int / string	null	Task-level timeout.
variables		dict / list	null	Task-scoped variables.
resources		object	null	Node / GPU resource requirements.
replicas		object	null	Replication configuration.
retries		object	null	Retry configuration.
probes		object	null	Readiness and failure probes.
outputs		list	null	Output parsing configuration.

Task Resources

YAML path: workflow.tasks[].resources

Field	Required	Type	Default	Description
nodes.indices		list[int / expr]	null	Specific node indices (e.g. [0]).
nodes.count		int / expr	null	Number of nodes.
gpus.count	Yes	int / expr	—	Number of GPUs (sets CUDA_VISIBLE_DEVICES).

Task Replicas

YAML path: workflow.tasks[].replicas

Field	Required	Type	Default	Description
count		int / expr	null	Number of replicas.
policy		string / expr	"parallel"	"parallel" or "sequential".
variables		list[string]	null	Variable names for sweeps (Cartesian product of domains).

Task Retries

YAML path: workflow.tasks[].retries

Field	Required	Type	Default	Description
count	Yes	int / expr	—	Number of retries.
interval	Yes	int / expr	—	Delay between retries (seconds).
backoff		int / expr	1	Backoff multiplier.

Task Probes (Readiness / Failure)

YAML path: workflow.tasks[].probes.readiness or workflow.tasks[].probes.failure

Field	Required	Type	Default	Description
delay		int / expr	0	Initial delay before probing (seconds).
timeout		int / expr	60	Max wait time (seconds).
interval		int / expr	5	Check interval (seconds).
success_threshold		int / expr	1	Consecutive successes required.
failure_threshold		int / expr	3	Consecutive failures before failing.

Exactly one probe type must be set per probe:

Probe Type	Required Fields	Optional Fields	Description
tcp_port	port	host, on_node ("first" / "each")	TCP connection check.
http_get	url	headers	HTTP GET health check.
http_post	url	headers, body	HTTP POST health check.
log_watch	regex_pattern	logger, match_count	Match pattern in task logs.

Task Outputs

YAML path: workflow.tasks[].outputs[]

Field	Required	Type	Default	Description
pattern	Yes	string	—	Parse pattern (e.g. "TTFT: {ttft:f} ms").
source		string	"stdout"	Log source: stdout or stderr.
metrics.<key>.description		string	null	Metric description.
metrics.<key>.type		string	null	Metric type.
metrics.<key>.aggregate		string	null	Aggregation hint.

Expression Syntax

Fields marked int / expr or string / expr support ${{ ... }} expressions:

Expression	Example
Variable	${{ variables.MY_VAR }}
Backend node IP	${{ backends.slurm_cluster.nodes[0].ip_address }}
Artifact path	${{ artifacts.model_dir.path }}
Task node IP	${{ task.server.nodes[0].ip_address }}

Reserved Environment Variables

Injected by sflow into task environments

These are automatically set by sflow and available in every task script.

Variable	Description
SFLOW_WORKSPACE_DIR	Absolute path to the project workspace root.
SFLOW_OUTPUT_DIR	Global output root directory (default ./sflow_output).
SFLOW_WORKFLOW_OUTPUT_DIR	Output directory for the current workflow run (e.g. sflow_output/<run-id>).
SFLOW_TASK_OUTPUT_DIR	Output directory for the current task replica (e.g. sflow_output/<run-id>/my_task_0).
SFLOW_REPLICA_INDEX	Zero-based replica index (0, 1, 2, ...).
SFLOW_TASK_ASSIGNED_NODE_NAMES	Comma-separated hostnames of nodes assigned to this task.
SFLOW_TASK_ASSIGNED_NODE_IPS	Comma-separated IP addresses of nodes assigned to this task.
CUDA_VISIBLE_DEVICES	Comma-separated GPU indices allocated to this task (set when resources.gpus.count is used).

In addition, all resolved variables and artifacts paths are injected as environment variables accessible via ${VAR_NAME} in scripts.

Read by sflow from the host environment

sflow reads these to detect an existing Slurm allocation and skip salloc.

Variable	Description
SLURM_JOB_ID / SLURM_JOBID	Current Slurm job ID. Used to detect an existing allocation.
SLURM_JOB_NODELIST / SLURM_NODELIST	Node list for the current Slurm allocation.

Provided by Slurm at runtime

These are set by Slurm (not by sflow) and commonly used in task scripts.

Variable	Description
SLURM_NODEID	Node index within the allocation (useful for NODE_RANK).
SLURMD_NODENAME	Hostname of the node running the task.
SLURM_SUBMIT_DIR	Directory from which the job was submitted.