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Arkadiy Paronyan
52b0a4845f
* Transaction storage guide and fixes * Apply suggestions from code review Co-authored-by: Bruno Škvorc <bruno@skvorc.me> * Update frame/transaction-storage/README.md Co-authored-by: Bruno Škvorc <bruno@skvorc.me> * Extended example Co-authored-by: Bruno Škvorc <bruno@skvorc.me>
83 lines
3.1 KiB
Markdown
83 lines
3.1 KiB
Markdown
# Transaction Storage Pallet
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Indexes transactions and manages storage proofs.
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Allows storing arbitrary data on the chain. Data is automatically removed after `StoragePeriod` blocks, unless the storage is renewed.
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Validators must submit proof of storing a random chunk of data for block `N - StoragePeriod` when producing block `N`.
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# Running a chain
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The following describes how to set up a new storage chain.
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Start with generating a chain spec.
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```bash
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cargo run --release -- build-spec --chain=local > sc_init.json
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```
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Edit the json chain spec file to customise the chain. The storage chain genesis params are configured in the `transactionStorage` section.
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Note that `storagePeriod` is specified in blocks and changing it also requires code changes at the moment.
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Build a raw spec from the init spec.
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```bash
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cargo run --release build-spec --chain=sc_init.json --raw > sc.json
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```
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Run a few validator nodes.
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```bash
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cargo run --release -- --chain=sc.json -d /tmp/alice --storage-chain --keep-blocks=100800 --ipfs-server --validator --alice
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cargo run --release -- --chain=sc.json -d /tmp/bob --storage-chain --keep-blocks=100800 --ipfs-server --validator --bob
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```
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`--storage-chain` enables transaction indexing.
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`--keep-blocks=100800` enables block pruning. The value here should be greater or equal than the storage period.
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`--ipfs-server` enables serving stored content over IPFS.
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Once the network is started, any other joining nodes need to sync with `--sync=fast`. Regular sync will fail because block pruning removes old blocks. The chain does not keep full block history.
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```bash
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cargo run --release -- --chain=sc.json -d /tmp/charlie --storage-chain --keep-blocks=100800 --ipfs-server --validator --charlie --sync=fast
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```
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# Making transactions
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To store data use the `transactionStorage.store` extrinsic. And IPFS CID can be generated from the Blake2-256 hash of the data.
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```js
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const util_crypto = require('@polkadot/util-crypto');
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const keyring_api = require('@polkadot/keyring');
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const polkadot_api = require('@polkadot/api');
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const fs = require('fs');
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const multihash = require('multihashes');
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const CID = require('cids')
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const wsProvider = new polkadot_api.WsProvider();
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const api = await polkadot_api.ApiPromise.create({ provider: wsProvider });
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const keyring = new keyring_api.Keyring({ type: "sr25519" });
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const alice = keyring.addFromUri("//Alice");
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const file = fs.readFileSync('cute_kitten.jpeg');
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const hash = util_crypto.blake2AsU8a(file)
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const encoded_hash = multihash.encode(hash, 'blake2b-256');
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const cid = new CID(1, 'blake2b-256', encoded_hash)
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console.log(cid.toString());
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const txHash = await api.tx.transactionStorage.store('0x' + file.toString('hex')).signAndSend(alice);
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```
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Data can be queried over IPFS
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```bash
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ipfs swarm connect <substrate peer address>
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ipfs block get /ipfs/<CID> > kitten.jpeg
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```
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To renew data and prevent it from being disposed after the storage period, use `transactionStorage.renew(block, index)`
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where `block` is the block number of the previous store or renew transction, and index is the index of that transaction in the block.
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License: Apache-2.0
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