decdn-client

Part of deCDN — a decentralized CDN where nodes cache and serve BLAKE3-addressed blobs over iroh QUIC, and clients pay per megabyte in USDC with off-chain vouchers backed by a shared on-chain payment pool.

Status: early implementation. deCDN runs a public testnet on Arbitrum Sepolia and is pre-mainnet. Wire formats, APIs and on-chain interfaces change without compatibility shims until mainnet.

The deCDN client SDK: fetch BLAKE3-addressed blobs from deCDN nodes, pay for them per megabyte from a USDC payment pool, and verify every byte as it arrives. Two entry points cover most uses:

• Downloader saves a blob, or a set of blobs, to files at full throughput across every holder, and resumes a partial download.
• Streamer reads one blob in order, and pays only for what the reader reaches plus one read-ahead window.

The crate documentation has the setup sequence, the guarantees, and the mistakes to avoid. The download and stream examples run the whole sequence end to end against a live deployment. They read the deployment and the buyer from environment variables: DECDN_RPC_URL, DECDN_CHAIN_ID, DECDN_PAYMENT_POOL, DECDN_SLASH_JUDGE, DECDN_CAPACITY_BOND, DECDN_KEYSTORE, DECDN_KEYSTORE_PASSWORD, DECDN_DATA_DIR, and DECDN_DEPOSIT (the pool deposit in USDC base units, used only when the buyer has no pool yet). The hash argument is the blob's BLAKE3 hash as 64 hex characters:

cargo run -p decdn-client --example download -- <blake3-hash-hex> <output-path>

The decdn CLI's fetch and bundle pull are built on this crate, and so is a node's own cache-miss pull: a node that misses in its cache is a paying client of the node upstream of it. The crate links no blob store and no AWS SDK, and CI checks that its dependencies stay that way. Its public API is snapshot-tested in CI.

License

Licensed under either of Apache-2.0 or MIT at your option.