caption-flow 0.2.3

Self-contained distributed community captioning system

CaptionFlow

scalable, fault-tolerant vLLM-powered image captioning. this "first round" focuses on a fast websocket orchestrator plus lightweight gpu workers that batch requests through vLLM.

• orchestrator: hands out work in chunked shards, collects captions, checkpoints progress, and keeps simple stats.
• workers (vLLM): connect to the orchestrator, stream in image samples, batch them, and generate 1..N captions per image using prompts supplied by the orchestrator.
• config-driven: all components read YAML config; flags can override.
• tui monitor (optional): a monitor client is wired into the CLI; ship a monitor module to enable it.

no conda. just venv + pip.

---

install

python -m venv .venv
source .venv/bin/activate  # windows: .venv\Scripts\activate
pip install --upgrade pip
pip install -e .  # installs the `caption-flow` command

quickstart (single box)

1. copy + edit the sample configs

cp examples/orchestrator/local_image_files.yaml my-orchestrator.yaml
cp examples/worker.yaml my-worker.yaml
cp examples/monitor.yaml my-monitor.yaml   # optional terminal interface

set a unique shared token in both my-orchestrator.yaml and my-worker.yaml (see auth.worker_tokens in the orchestrator config and worker.token in the worker config).

if you use private hugging face datasets/models, export HUGGINGFACE_HUB_TOKEN before starting anything.

2. start the orchestrator

caption-flow orchestrator --config my-orchestrator.yaml

3. start one or more vLLM workers

# gpu 0 on the same host
caption-flow worker --config my-worker.yaml --gpu-id 0

# your second GPU
caption-flow worker --config my-worker.yaml --gpu-id 1

# on a remote host
caption-flow worker --config my-worker.yaml --server ws://your.hostname.address:8765

4. (optional) start the monitor

caption-flow monitor --config my-monitor.yaml

---

how it’s wired

orchestrator

• websocket server (default 0.0.0.0:8765) with three client roles: workers, data-feeders, and admin.
• dataset control: the orchestrator centrally defines the dataset (huggingface or local) and version/name. it chunk-slices shards and assigns work.
• vLLM config broadcast: model, tp size, dtype, max seq len, memory targets, batching, sampling params, and inference prompts are all pushed to workers; workers can apply many changes without a model reload.
• storage + checkpoints: captions buffer to disk with periodic checkpoints. chunk state is tracked so restarts don’t double-work.
• auth: token lists for worker, monitor, and admin roles.

start flags you’ll likely use:

--config PATH                # yaml config for the orchestrator
--port INT, --host STR       # bind controls
--data-dir PATH              # overrides storage.data_dir
--cert PATH, --key PATH      # enable TLS (or use --no-ssl for ws:// in dev)
--vllm                       # use the vLLM-style orchestrator (webdataset/hf)

vLLM worker

• one process per gpu. select the device with --gpu-id (or worker.gpu_id in YAML).
• gets its marching orders from the orchestrator: dataset info, model, prompts, batch size, and sampling.
• resilient: detects disconnects, abandons the current chunk cleanly, clears queues, reconnects, and resumes.
• batched generate(): images are resized down for consistent batching; each image can get multiple captions (one per prompt).

start flags you’ll likely use:

--config PATH                 # yaml for the worker
--server URL                  # ws(s)://host:port
--token STR                   # must match an allowed worker token on the orchestrator
--name STR                    # display name
--batch-size INT              # override vLLM batch size
--vllm                        # use the vLLM worker implementation
--gpu-id INT                  # which gpu to use
--precision STR, --model STR  # optional overrides for dtype/model
--no-verify-ssl               # accept self-signed certs in dev

(optional) monitor

• a CLI entry exists for a TUI monitor; wire in a monitor module to enable it. config lives in monitor.yaml or inside orchestrator.yaml under monitor:.

---

configuration

config discovery order

for any component, the CLI looks for config in this order (first match wins):

1. --config /path/to/file.yaml
2. ./<component>.yaml (current directory)
3. ~/.caption-flow/<component>.yaml
4. $XDG_CONFIG_HOME/caption-flow/<component>.yaml
5. /etc/caption-flow/<component>.yaml
6. any $XDG_CONFIG_DIRS entries under caption-flow/
7. ./examples/<component>.yaml (fallback)

orchestrator.yaml (highlights)

orchestrator:
  host: 0.0.0.0
  port: 8765
  # ssl:
  #   cert: /path/fullchain.pem
  #   key:  /path/privkey.pem

  dataset:
    type: huggingface
    path: <hf-dataset-or-local-path>
    name: <logical-name>
    version: "1.0"

  vllm:
    model: Qwen/Qwen2.5-VL-3B-Instruct
    tensor_parallel_size: 1
    max_model_len: 16384
    dtype: float16
    gpu_memory_utilization: 0.92
    enforce_eager: true
    disable_mm_preprocessor_cache: true
    limit_mm_per_prompt: { image: 1 }

    batch_size: 8

    sampling:
      temperature: 0.7
      top_p: 0.95
      max_tokens: 256
      repetition_penalty: 1.05
      skip_special_tokens: true
      stop: ["<|end|>", "<|endoftext|>", "<|im_end|>"]

    inference_prompts:
      - "describe this image in detail"
      - "provide a comprehensive description of the visual content"
      - "what are the key elements in this image?"

  storage:
    data_dir: ./caption_data
    checkpoint_dir: ./checkpoints
    caption_buffer_size: 100
    checkpoint_interval: 1000

  # chunking/queueing
  chunk_size: 1000
  chunks_per_request: 2
  chunk_buffer_multiplier: 3
  min_chunk_buffer: 10

  auth:
    worker_tokens:
      - { token: "example-worker-token", name: "Example Worker" }
    monitor_tokens:
      - { token: "letmein", name: "Default monitor" }
    admin_tokens:
      - { token: "admin-secret-2024", name: "Admin" }

worker.yaml (highlights)

worker:
  server: ws://localhost:8765   # use wss:// in prod
  token: example-worker-token
  name: local-gpu
  gpu_id: 0
  vllm: true

  # local queues
  readahead_size: 256
  inference_queue_size: 128

monitor.yaml (optional)

monitor:
  server: ws://localhost:8765
  token: letmein
  refresh_rate: 1.0
  show_contributors: true
  show_quality_metrics: true
  max_activity_items: 20
  show_chunk_progress: true
  show_worker_queues: true
  show_throughput_graph: true

---

tls / certificates

use the built-in helpers during development:

# self-signed certs for quick local testing
caption-flow generate_cert --self-signed --domain localhost --output-dir ./certs

# inspect any certificate file
caption-flow inspect_cert ./certs/fullchain.pem

then point the orchestrator at the resulting cert/key (or run --no-ssl for dev-only ws://).

---

tips & notes

• multi-gpu: start one worker process per gpu (set --gpu-id or worker.gpu_id).
• throughput: tune vllm.batch_size in the orchestrator config (or override with --batch-size at worker start). higher isn’t always better; watch VRAM.
• prompts: add more strings under vllm.inference_prompts to get multiple captions per image; the worker returns only non-empty generations.
• private HF: if your dataset/model needs auth, export HUGGINGFACE_HUB_TOKEN before caption-flow worker ....
• self-signed ssl: pass --no-verify-ssl to workers/monitors in dev.
• recovery: if you hard-crash mid-run, caption-flow scan_chunks --fix can reset abandoned chunks so the orchestrator can reissue them cleanly.

---

roadmap

• hot config reload via the admin websocket path.
• dedicated data-feeder clients (separate from gpu workers) that push samples into the orchestrator.
• richer monitor TUI.

PRs welcome. keep it simple and fast.

architecture

┌─────────────┐     WebSocket      ┌─────────────┐
│   Worker    │◄──────────────────►│             │
└─────────────┘                    │             │     ┌──────────────┐
                                   │ Orchestrator│────►│Arrow/Parquet │
┌─────────────┐                    │             │     │   Storage    │
│   Worker    │◄──────────────────►│             │     └──────────────┘
└─────────────┘                    └─────────────┘
                                           ▲
┌─────────────┐                           │
│   Monitor   │◄──────────────────────────┘
└─────────────┘

Storage Schema

captions.parquet

• job_id: Unique job identifier

• dataset: Dataset name
• shard: Shard identifier
• item_key: Item within shard
• caption: Generated caption text
• contributor_id: Worker who generated it
• timestamp: Generation time
• quality_score: Optional quality metric

jobs.parquet

• job_id: Unique identifier

• dataset: Dataset name
• shard: Shard identifier
• status: pending/processing/completed/failed
• assigned_to: Worker ID
• timestamp: Status change time

contributors.parquet

• contributor_id: Unique identifier

• name: Display name
• total_captions: Lifetime count
• trust_level: Quality tier (0-5)

Development

# Install with dev dependencies
pip install -e ".[dev]"

# Run tests
pytest

# Format code
black src/
ruff --fix src/

# Type checking
mypy src/

Community Contribution

To contribute compute:

1. Install caption-flow: pip install caption-flow
2. Get a worker token from the project maintainer
3. Run: caption-flow worker --server wss://project.domain.com:8765 --token YOUR_TOKEN

Your contributions will be tracked and attributed in the final dataset!

License

MIT