Module smoldot::sync

Syncing, short for synchronizing, consists in synchronizing the state of a local chain with the state of the chain contained in other machines, called remotes or sources.

Note: While the above summary is a bit abstract, in practice it is almost always done by exchanging messages through a peer-to-peer network.

Multiple strategies exist for syncing, one for each sub-module, and which one to employ depends on the amount of information that is desired (e.g. is it required to know the header and/or body of every single block, or can some blocks be skipped?) and the distance between the highest block of the local chain and the highest block available on the remotes.

The all module represents a good combination of all syncing strategies and should be the default choice for most clients.

About safety

While there exists various trade-offs between syncing strategies, safety is never part of these trade-offs. All syncing strategies are safe, in the sense that malicious remotes cannot corrupt the state of the local chain.

It is possible, however, for a malicious remote to omit some information, such as the existence of a specific block. If all the remotes that are being synchronized from are malicious and collude to omit the same information, there is no way for the local node to learn this information or even to be aware that it is missing an information. This is called an eclipse attack.

For this reason, it is important to ensure a large number and a good distribution of the sources. In the context of a peer-to-peer network where machines are picked randomly, a minimum threshold of around 7 peers is generally considered acceptable. Similarly, in the context of a peer-to-peer network, it is important to establish outgoing connections to other nodes and not only rely on incoming connections, as there is otherwise the possibility of a single actor controlling all said incoming connections.

Modules

all

All syncing strategies (optimistic, warp sync, all forks) grouped together.

all_forks

All-forks header and body syncing.

grandpa_warp_sync

Grandpa warp syncing.

optimistic

Optimistic header and body syncing.

para

Parachains and parathreads syncing.