viscacha 0.2.0

Background job queue for Python. Built for AI pipelines.

Viscacha

Background jobs for Python. Built for AI pipelines — every job crash-safe, traceable, and retriable.

from viscacha import Client, Worker

client = Client()
worker = Worker(client)

@worker.job("greet")
def greet(name: str) -> dict:
    return {"message": f"Hello, {name}!"}

worker.run(blocking=False)

handle = client.enqueue("greet", name="Alice")
result = handle.wait()
print(result.result)  # {'message': 'Hello, Alice!'}

No broker. No Redis. No Docker. Just Python.

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Install

pip install uv
uv pip install -e .

Requires Python 3.10+.

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How it works

1. Submit a job
2. A worker function runs it
3. Get the result or inspect what happened

handle = client.enqueue("send_email", to="[e-mail]")

result = handle.wait(timeout=30)  # raises TimeoutError if it doesn't finish
print(result.status)   # 'done' | 'failed' | 'cancelled'
print(result.result)   # return value of the job function
print(result.error)    # set if failed, else None

handle.cancel()        # cancel a pending job

client.jobs()               # list all jobs
client.jobs(status="done")  # filter by status
client.get(handle.id)       # get one by ID

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Guarantees

• No lost jobs — a job stays in the queue until a worker completes it
• Safe retries — transient failures retry automatically
• Full traceability — every job logged with type, args, result, retries, error
• Crash-safe — if a worker dies mid-job, the lease expires and the job returns to the queue

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AI pipelines

Each Claude call is a job. Workers run in parallel. Failures retry automatically.

import anthropic
from viscacha import Client, Worker

client = Client()
worker = Worker(client)
ai = anthropic.Anthropic()

@worker.job("classify_ticket", max_retries=2)
def classify_ticket(title: str, body: str) -> dict:
    response = ai.messages.create(
        model="claude-haiku-4-5-20251001",
        max_tokens=120,
        messages=[{"role": "user", "content": f"Classify: {title}\n{body}"}],
    )
    return {"category": "bug", "priority": "high"}

worker.run(blocking=False)

handles = [client.enqueue("classify_ticket", title=t, body=b) for t, b in tickets]
results = [h.wait(timeout=30) for h in handles]

ANTHROPIC_API_KEY=sk-... python demos/demo_ai_jobs.py

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Any function works

Email, HTTP calls, reports, transforms — a worker is just a function.

@worker.job("send_email")
def send_email(to: str, subject: str, html: str) -> dict:
    return {"to": to, "sent": True}

client.enqueue("send_email", to="[e-mail]", subject="Order confirmed", html="...")

python demos/demo_email_jobs.py  # dry-run, no SMTP needed

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Retries and crash recovery

@worker.job("call_api", max_retries=5, lease_ttl=60.0)
def call_api(endpoint: str) -> dict:
    response = requests.get(endpoint, timeout=10)
    response.raise_for_status()
    return response.json()

max_retries — retries on any exception (default 3)
lease_ttl — seconds before a stalled job is reclaimed (default 30)

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Persistence

client = Client(log_path="jobs.jsonl")

Append-only log. Jobs survive restarts.

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HTTP API

Expose jobs over HTTP so workers can run anywhere:

from viscacha import Client
from viscacha.server import create_app
import uvicorn

app = create_app(Client(log_path="jobs.jsonl"))
uvicorn.run(app, host="0.0.0.0", port=8000)

curl -X POST http://localhost:8000/jobs \
  -H "Content-Type: application/json" \
  -d '{"job_type": "greet", "args": {"name": "Alice"}}'

curl http://localhost:8000/jobs?status=done

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Under the hood

Jobs are tuples in an append-only tuple space. Workers claim jobs via leases — if a worker crashes, the lease expires and the job returns to the queue automatically. The coordination layer handles ordering, crash safety, and observability. Viscacha is a thin API on top.

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Roadmap

• Priority queues
• Job chaining / workflows
• Web dashboard
• Scheduled / cron jobs
• Distributed workers (multi-process, multi-host)