Implementation:Ollama Ollama Imagegen Transfer Download

Knowledge Sources	Ollama
Domains	Image Generation, Transfer
Last Updated	2025-02-15 00:00 GMT

Overview

Implements parallel blob downloading with streaming SHA256 verification, stall detection, and adaptive retry logic for tensor model transfer.

Description

The download.go file provides the downloader struct and download logic for fetching model blobs from an OCI registry. Downloads are whole-blob (no chunking) with inline SHA256 hash verification during streaming. The system detects download stalls (no data for stallTimeout) and slow transfers (below 10% of median speed), with separate retry logic for each: stall retries do not count against the limit, slow retries require 3 occurrences before counting. Already-downloaded blobs are detected by matching file size and skipped. The progress tracker reports completed bytes including pre-existing blobs for accurate resume display. Concurrency is controlled via semaphore (default 64 parallel downloads).

Usage

Used when pulling tensor-based image generation models that consist of many small blobs rather than few large ones.

Code Reference

Source Location

• Repository: Ollama
• File: x/imagegen/transfer/download.go
• Lines: 1-329

Signature

type downloader struct {
	client       *http.Client
	baseURL      string
	destDir      string
	repository   string
	token        *string
	getToken     func(context.Context, AuthChallenge) (string, error)
	userAgent    string
	stallTimeout time.Duration
	progress     *progressTracker
	speeds       *speedTracker
}

func download(ctx context.Context, opts DownloadOptions) error
func (d *downloader) download(ctx context.Context, blob Blob) error
func (d *downloader) downloadOnce(ctx context.Context, blob Blob) (int64, error)

Import

import "github.com/ollama/ollama/x/imagegen/transfer"

I/O Contract

Inputs

Name	Type	Required	Description
ctx	context.Context	Yes	Context for cancellation
opts	DownloadOptions	Yes	Download configuration with blobs, URLs, auth

Outputs

Name	Type	Description
error	error	Error if any blob fails after max retries

Usage Examples

err := transfer.Download(ctx, transfer.DownloadOptions{
    Blobs:       blobs,
    BaseURL:     "https://registry.ollama.ai",
    DestDir:     "/home/user/.ollama/blobs",
    Repository:  "library/flux2-klein",
    Concurrency: 64,
    Progress: func(completed, total int64) {
        fmt.Printf("%.1f%%\n", float64(completed)/float64(total)*100)
    },
})

Related Pages

• Principle:Ollama_Ollama_ImageGeneration