This is a horrible way to store data on a disk, because there's almost no structure in it, just random numbers referencing even more random numbers.
The state trie in Ethereum contains hundreds of millions of nodes, most of which take the form of a single hash referencing up to 16 other hashes. Q: Why does downloading the state take so long, I have good bandwidth?Ī: State sync is mostly limited by disk IO, not bandwidth. This latter phase nowadays take a lot longer than just getting the blocks.
Ethereum wallet geth download#
Q: I'm stuck at 64 blocks behind mainnet?!Ī: As explained above, you are not stuck, just finished with the block download phase, waiting for the state download phase to complete too. It is not, rather it's discovering and downloading the trie as it goes along. This is why you might be tempted to think it's stuck on the same numbers. As we go along the download, most of the nodes will reference new ones that we didn't know about until then. That node, can refer up to 16 new nodes, so in the next step, we'll know about 16 new nodes and try to download those. When the node begins synchronizing, it knows about exactly 1 node and tries to download it. The reason is that a block in Ethereum only contains the state root, a single hash of the root node. Q: The node just hangs on importing state enties?!Ī: The node doesn't hang, it just doesn't know how large the state trie is in advance so it keeps on going and going and going until it discovers and downloads the entire thing. You'll need to wait that out too before your node comes truly online. You can see this yourself via the seemingly endless Imported state entries stream of logs. You are just done with the block download phase and still running the state downloads. If you see that you are 64 blocks behind mainnet, you aren't yet synchronized, not even close. But until you actually do gather all the data, your local node is not usable since it cannot cryptographically prove anything about any accounts. The worst part is that while you are synchronizing, the network is moving forward, and state that you begun to download might disappear while you're downloading, so your node needs to constantly follow the network while trying to gather all the recent data. This means your node needs to synchronize a dataset that is changing 200 times per second.
The part where it gets even messier is that this data is constantly morphing: at every block (15s), about 1000 nodes are deleted from this trie and about 2000 new ones are added. This itself is already a crazy number of data items. To truly have a synchronized node, you need to download all the account data, as well as all the tiny cryptographic proofs to verify that noone in the network is trying to cheat you. Ok, so why does this pose a problem? This trie data structure is an intricate interlink of hundreds of millions of tiny cryptographic proofs (trie nodes). This gigantic data structure containing all the accounts and the intermediate cryptographic proofs is called the state trie. This cryptographic linking is done by creating a tree data structure above the accounts, each level aggregating the layer below it into an ever smaller layer, until you reach the single root.
The accounts themselves are however insufficient to run a node, they need to be cryptographically linked to each block so that nodes can actually verify that the account's are not tampered with. So, what's the state trie? In the Ethereum mainnet, there are a ton of accounts already, which track the balance, nonce, etc of each user/contract.
This phase is called the state trie download and it actually runs concurrently with the block downloads alas it take a lot longer nowadays than downloading the blocks. These need to be downloaded separately and cross checked with the latest blocks.
Ethereum wallet geth code#
balances, nonces, smart contract code and data). Unfortunately this is not the case, since no transaction was executed, so we do not have any account state available (ie. Many people falsely assume that because they have the blocks, they are in sync. Downloading all the blocks is a straightforward and fast procedure and will relatively quickly reassemble the entire chain. Instead of starting from the genesis block and reprocessing all the transactions that ever occurred (which could take weeks), fast sync downloads the blocks, and only verifies the associated proof-of-works. The current default mode of sync for Geth is called fast sync. Syncing Ethereum is a pain point for many people, so I'll try to detail what's happening behind the scenes so there might be a bit less confusion.
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