How to Use the Atlas Network

This section teaches you how to use the Atlas network, it contains the following sections:


While the Blockstack software stack expects that Atlas-hosted data is made up of DNS zone files, Atlas itself does not enforce this (nor does it care about the format of its chunks). It is designed as a general-purpose chunk store. Nevertheless, the ubiquitous use of Atlas to store data as DNS zone files has had an influence on its API design—fields and method names frequently allude to zone files and zone file hashes. This is intentional.

The public BNS API endpoint does not support resolving Atlas chunks that do not encode Gaia routing information or subdomain information. To directly interact with Atlas, developers will need to install Blockstack Core and use its Python client libraries for these examples.

Looking up Chunks

All Atlas chunks are addressed by the RIPEMD160 hash of the SHA256 hash of the chunk data. A client can query up to 100 chunks in one RPC call.

A client can look up a chunk with the get_zonefiles() method. If successful, the returned payload will be a dict with a zonefiles key that maps the chunk hashes to their respective data.

>>> import blockstack
>>> data = blockstack.lib.client.get_zonefiles('', ['1b89a685f4c4ea245ce9433d0b29166c22175ab4'])
>>> print data['zonefiles']['1b89a685f4c4ea245ce9433d0b29166c22175ab4']
$TTL 3600
tor TXT "3g2upl4pq6kufc4m.onion"


(This particular chunk happens to be associated with the BNS name

Adding a New Chunk

The only way to add a chunk to Atlas is to do so through an on-chain name in BNS. Adding a new chunk is a two-step process:

  • The name owner announces the chunk hash as a name’s state via a NAME_REGISTRATION, NAME_UPDATE, NAME_RENEWAL, or NAME_IMPORT transaction.
  • Once the transaction is confirmed and processed by BNS, the name owner broadcasts the matching zone file.

Setting a name’s state to be the hash of a chunk is beyond the scope of this document, since it needs to be done through a BNS client. See the relevant documentation for blockstack.js and the Blockstack Browser for doing this.

Once the name operation is confirmed, you can announce the data to the Atlas network. You can do so with the Python client as follows:

>>> import blockstack
>>> import base64
>>> data = "..."   # this is the chunk data you will announce
>>> data_b64 = base64.b64encode(data)
>>> result = blockstack.lib.client.put_zonefiles('', [data_b64])
>>> assert result['saved'][0] == 1

At most five chunks can be announced in one RPC call. Note that the data must be base64-encoded before it can be announced.

When the put_zonefiles() method succeeds, it returns a dict with a list under the saved key. Here, result['saved'][i] will be 1 if the ith chunk given to put_zonefiles() was saved by the node, and 0 if not. The node will not save a chunk if it is too big, or if it has not yet processed the name operation that contained the chunk’s hash.

The put_zonefiles() method is idempotent.

Propagating Chunks

Atlas peers will each store a copy of the chunks you announce. In the background, they will asynchronously announce to one another which chunks they have available, and replicate them to one another in a rarest-first order (much like how BitTorrent works). Eventually, every Atlas peer will receive the chunk.

However, developers can accelerate this process by eagerly propagating chunks. To do so, they can ask an Atlas peer for its immediate neighbors in the Atlas peer graph, and replicate the chunk to each of them as well.

For example, this code will replicate the chunk to not only, but also to its immediate neighbors.

>>> import blockstack
>>> import base64
>>> data = "..."   # this is the chunk you will replicate widely
>>> data_b64 = base64.b64encode(data)
>>> result = blockstack.lib.client.get_atlas_peers('')
>>> neighbors = result['peers']
>>> print ", ".join(neighbors),,,,,,,
>>> for neighbor in neighbors:
...    result = blockstack.lib.client.put_zonefiles(neighbor, [data_b64])
...    assert result['saved'][0] == 1

This is not strictly necessary, but it does help accelerate chunk replication and makes it less likely that a chunk will get lost due to individual node failures.