py-cluster-api 0.2.1

Generic Python library for running jobs on HPC clusters

py-cluster-api

A Python library for submitting and monitoring jobs on HPC clusters. Supports running arbitrary executables (Nextflow pipelines, Python scripts, Java tools, etc.) on LSF clusters and taking action when jobs complete via async callbacks.

Features

• Async-first — built on asyncio for non-blocking job submission and monitoring
• LSF executor — submit via bsub, monitor via bjobs -json, cancel via bkill
• Local executor — run jobs as local subprocesses for development and testing, including array jobs
• Job monitoring — polls the scheduler and fires callbacks on job completion, failure, or cancellation
• Job arrays — submit array jobs with per-element log files
• Zombie detection — jobs that disappear from the scheduler are marked as failed
• YAML config with profiles — Nextflow-style config with per-environment profiles
• Callback chaining — register on_success, on_failure, or on_exit handlers on any job

Installation

Requires Python 3.10+.

pip install py-cluster-api

Or with Pixi:

pixi add --pypi py-cluster-api

Quick Start

Single Job

import asyncio
from cluster_api import create_executor, ResourceSpec, JobMonitor

async def main():
    executor = create_executor(profile="janelia_lsf")
    monitor = JobMonitor(executor)
    await monitor.start()

    job = await executor.submit(
        command="nextflow run nf-core/rnaseq --input samples.csv",
        name="rnaseq-run",
        resources=ResourceSpec(cpus=4, memory="32 GB", walltime="24:00", queue="long"),
        env={"NXF_WORK": "/scratch/work"},
    )
    job.on_success(lambda j: print(f"Done! Job {j.job_id}, peak mem: {j.max_mem}"))
    job.on_failure(lambda j: print(f"FAILED! Job {j.job_id}, exit={j.exit_code}"))

    await monitor.wait_for(job)
    await monitor.stop()

asyncio.run(main())

Job Array

async def run_array():
    executor = create_executor(profile="janelia_lsf")
    monitor = JobMonitor(executor)
    await monitor.start()

    job = await executor.submit_array(
        command="python process.py --index $LSB_JOBINDEX",
        name="batch-process",
        array_range=(1, 50),
        resources=ResourceSpec(cpus=1, memory="4 GB", walltime="01:00"),
    )
    job.on_exit(lambda j: print(f"Array finished: {j.job_id}"))

    await monitor.wait_for(job)
    await monitor.stop()

The array index environment variable depends on the executor: LSF uses $LSB_JOBINDEX, while the local executor uses $ARRAY_INDEX.

Local Testing

async def local_test():
    executor = create_executor(executor="local")
    monitor = JobMonitor(executor, poll_interval=1.0)
    await monitor.start()

    job = await executor.submit(command="echo hello world", name="test")
    job.on_success(lambda j: print("It worked!"))

    await monitor.wait_for(job, timeout=10.0)
    await monitor.stop()

Configuration

Configuration is loaded from YAML with optional profiles. The search order is:

1. Explicit config_path argument
2. $CLUSTER_API_CONFIG environment variable
3. ./cluster_api.yaml
4. ~/.config/cluster_api/config.yaml

Example cluster_api.yaml

executor: local
poll_interval: 10
job_name_prefix: "capi"

profiles:
  janelia_lsf:
    executor: lsf
    queue: normal
    memory: "8 GB"
    walltime: "04:00"
    use_stdin: true
    script_prologue:
      - "module load java/11"

  local_dev:
    executor: local
    poll_interval: 2

Config Options

Option	Default	Description
executor	"local"	Backend: lsf or local
cpus	None	Default CPU count
memory	None	Default memory (e.g. "8 GB")
walltime	None	Default wall time (e.g. "04:00")
queue	None	Default queue/partition
poll_interval	10.0	Seconds between status polls
job_name_prefix	"capi"	Prefix for all job names
shebang	"#!/bin/bash"	Script shebang line
script_prologue	[]	Lines inserted before the command
script_epilogue	[]	Lines inserted after the command
extra_directives	[]	Additional scheduler directives
directives_skip	[]	Substrings to filter out of directives
extra_args	[]	Extra CLI args appended to the submit command (e.g. bsub)
use_stdin	false	Submit via stdin (bsub < script.sh)
lsf_units	"MB"	LSF memory units (KB, MB, GB)
suppress_job_email	true	Set LSB_JOB_REPORT_MAIL=N
command_timeout	100.0	Timeout in seconds for scheduler commands
zombie_timeout_minutes	30.0	Mark jobs as failed if unseen for this long
completed_retention_minutes	10.0	Keep finished jobs in memory for this long

API Reference

create_executor(profile=None, config_path=None, **overrides)

Factory function that loads config and returns an Executor instance.

Executor

Abstract base class. Key methods:

• submit(command, name, resources=None, prologue=None, epilogue=None, env=None, metadata=None) — submit a job, returns JobRecord
• submit_array(command, name, array_range, ...) — submit a job array
• cancel(job_id) — cancel a job by ID
• cancel_by_name(name_pattern) — cancel by name pattern (LSF only)
• cancel_all() — cancel all tracked jobs
• poll() — query scheduler and update job statuses
• jobs / active_jobs — properties returning tracked job dicts

JobRecord

Tracks a submitted job. Fields include job_id, name, status, exit_code, exec_host, max_mem, submit_time, start_time, finish_time, and metadata.

• on_success(callback) — register callback for exit code 0
• on_failure(callback) — register callback for non-zero exit
• on_exit(callback, condition=ANY) — register callback for any exit condition
• is_terminal — whether the job has finished

JobMonitor

Async polling loop that drives status updates and callback dispatch.

• start() / stop() — control the polling loop
• wait_for(*records, timeout=None) — block until jobs reach a terminal state

ResourceSpec

Resource requirements: cpus, memory, walltime, queue, work_dir, stdout_path, stderr_path, extra_directives, extra_args.

Development

See docs/Development.md for build instructions, testing, and release process.