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Run Full Node to Join BNB Beacon Chain

A full node of BNB Beacon Chain is a witness, which observes the consensus messaging, downloads blocks from data seed nodes and executes business logic to achieve the consistent state as validator node (and other full node). Full nodes also help the network by accepting transactions from other nodes and then relaying them to the core BNB Chain network.

Supported Platforms​

We support running a full node on Mac OS X, Windows and Linux.

Minimum System Requirements​

The hardware must meet certain requirements to run a full node.

  • Desktop or laptop hardware running recent versions of Mac OS X, Windows, or Linux.
  • 500 GB of free disk space, accessible at a minimum read/write speed of 100 MB/s.
  • 4 cores of CPU and 8 gigabytes of memory (RAM).
  • A broadband Internet connection with upload/download speeds of at least 1 megabyte per second
  • Your full node has to run at least 4 hours per 24 hours in order to catch up with BNB Beacon Chain More hours will be better, run your node continuously for best results.

Steps to Run a Full Node​

  1. Download Binary

Open the following page and download the binaries for your platform, as well as configuration files for mainnet or testnet .

https://github.com/bnb-chain/node/releases

Please go to changelog to get the information about the latest release of full node version.

Download the configuration files according to the network you want to join in (mainnet_config.zip/testnet_config.zip).

upzip linux_binary.zip
  1. Copy the executables (i.e.bnbchaind or bnbcli) to /usr/local/bin

Initialize Home Folder​

First you need to choose a home folder $BNCHOME (i.e. ~/.bnbchaind) for BNB Beacon Chain .
You can setup this by:

mkdir ~/.bnbchaind
mkdir ~/.bnbchaind/config

Setup Configuration​

Put app.toml, config.toml and genesis.json from mainnet_config.zip/testnet_config.zip into $BNCHOME/config

Add Seed Nodes​

For a full node to function, it must connect to one or more known nodes to join BNB Beacon Chain .
There are several famous seed nodes that offer known node addresses in the network to newly joined full nodes.
They are already in config.toml file, which sits in mainnet_config.zip/testnet_config.zip.

You cat also get seeds info through a simple python script (replace domain name depending on which network you are using):

import requests, json
d = requests.get('https://dex.binance.org/api/v1/peers').text # replace dex.binance.org with testnet-dex.binance.org for testnet
l = json.loads(d)
seeds = ",".join([ (seed["id"]+"@"+seed["original_listen_addr"]) for seed in l if seed["accelerated"] == False])
print (seeds)

If you want to add seed nodes, please feel free to edit the field seeds of $BNCHOME/config/config.yaml with returned seed node info from previous request.

Config Syncing​

BNB Beacon Chain is making blocks at a very fast pace and its block height is over 60 million. As a result, it will take a long time to fast-sync (download all the blocks from genesis block). To decrease the waiting time, an innovative way of syncing a fullnode is introduced and it's called state-sync. State Sync is the default way of syncing in the published config files. If you need to switch to Fast Sync, you need to change the config.toml accordingly. You can read more in the following sections.

Additional Configuration​

  • Log: The log file is under home- the directory specified when starting bnbchaind.
    The latest log file is bnc.log. The process will create a new log file every one hour.
    To make sure you have sufficient disk space to keep the log files, we strongly recommend you to change the log location by changing logFileRoot option in $BNCHOME/config/app.toml.
  • Service Port: RPC service listens on port 27147 and P2P service listens on port 27146 by default.
    Make sure these two ports are open before starting a full node, unless the full node has to listen on other ports.
  • Store: All the state and block data will store under $BNCHOME/data, do not delete or edit any of these files.

Start your node​

Start the full node according to the place of your executables.

bnbchaind start --home $BNCHOME&

Only after catching up with BNB Beacon Chain , the fullnode can handle requests correctly.

Details on Sync Mode​

There are three ways for you to get synced with other peers in blockchain network:

  • Fast Sync
  • State Sync
  • Hot Sync

These methods can be used together.

Fast Sync​

The default way for syncing with other data seed node is fast sync.
In fast sync, you need to download all the blocks from the genesis block and execute all the transaction in every block until it is synced with its peers.
The sync speed is about 20 blocks/s, which is slower than state sync.

Configuration is located in $BNCHOME/config/config.toml:

  • fast_sync Must be set to true
  • state_sync_reactor Can be set to false or true
  • state_sync Can be set to false or true
  • state_sync_height should be less than 0, like -1
State Sync​

As explained in BEP18, State sync will get the application state of your full node to be up to date without downloading all of the blocks.The sync speed is faster than fast sync.
Now you do not need to allocate more memories to your full node for this feature to work.

Configuration is located in $BNCHOME/config/config.toml:

  • state_sync_reactor Must be set to true
  • recv_rate Must set to 102428800
  • ping_interval Recommendation is set to 10m30s
  • pong_timeout Recommendation is set to 450s
  • state_sync_height Recommendation is set to 0, so it allows to state sync from the peers's latest height. Please do not change the height to other number, unless you are doing some debug.

State sync can help fullnode in same status with other peers within short time (according to our test, a one month ~800M DB snapshot in BNB Beacon Chain testnet can be synced in around 45 minutes) so that you can receive latest blocks/transactions and query latest status of orderbook, account balances etc.. But state sync DOES NOT download historical blocks before state sync height, if you start your node with state sync and it synced at height 10000, then your local database would only have blocks after height 10000.

If full node has already started, suggested way is to delete the (after backup) $BNCHOME/data directory and $BNCHOME/config/priv_validator_key.json before enabling state sync.

State sync will run only once after you start your full node. Once state sync succeeds, later fullnode restart would not state sync anymore. But if you do want state sync again, you need to delete $BNCHOME/data/STATESYNC.LOCK.

If you turn on the state_sync_reactor, the snapshots of heights will be saved at $HOME/data/snapshot/<height> automatically. To save disk space, you can delete the directory or turn off the state_sync_reactor.

Hot Sync​

Please note that this feature is still expreimental and is not recommended.

In BNB Beacon Chain network, almost every fullnode operator will first enable state-sync to get synced with peers. After downloading all the state machine changes, the fullnode will go back to fast-sync mode and eventually in consensus mode. In fast-sync mode, the fullnode will have high delay because it needs to be aware of peers’ heights. It downloads all the blocks in parallel and verifying their commits. On the other hand, when a fullnode is under consensus state, it will consume a lot of bandwidth and CPU resources because it receives a lot of redundant messages for consensus engine and writes more WAL. To increase the efficiency for fullnodes, the hot-sync protocol is introduced. A fullnode under hot-sync protocol will pull the blocks from its peers and it will subscribe these blocks in advance. It will skip the message for prevotes and only subscribe to maj23 precommit and block proposal messages. At the same time, it will put its peers in different buckets and subscribe to peers in active buckets. Hot-Sync can help fullnodes gossip blocks in low latency, while cost less network, memory, cpu and disk resources than Tendermint consensus protocol. Even cheap hardware can easily run a fullnode, and a fullnode can connect with more peers than before by saving network and CPU resources.

The state transition of a hot sync reactor can be of three part:

                              Hot --> Consensus
                                 ^    ^
                                 |   /
                                 |  /
                                Mute
  1. Mute: will only answer subscribe requests from others, will not sync from others or from consensus reactor. The Hot Sync reactor stays in Mute when it is fast syncing.
  2. Hot: handle subscribe requests from other peers as a publisher, also subscribe block messages from other peers as a subscriber. A non-validators will stay in Hot when the peer have catch up after fast syncing.
  3. Consensus: handle subscribes requests from other peers as a publisher, but get block/commit message from consensus reactor. A sentry node should stay in Consensus. Or a non-validator should switch from Hot to Consensus when it become a validator.

Configuration is located in $BNCHOME/config/config.toml:

  • hot_sync_reactor Must be set to true
  • hot_sync Can be set to false or true
  • hot_sync_timeout is the max wait time for subscribe a block. It only takes effect when hot_sync is true
Monitor Syncing Process​

You can verify if state sync is done by curl localhost:27147/status several times and see whether latest_block_height is increasing in response.

"sync_info": {
  ...
  "latest_block_height": "878092",
  "latest_block_time": "2019-04-15T00:01:22.610803768Z",
  ...
}

If state sync did not succeed, please repeat deletion of $BNCHOME/data directory and $BNCHOME/config/priv_validator_key.json before starting full node next time in case of data inconsistency.

Once state sync succeeded, later full node restart would not state sync anymore (in case the local blocks are not continuous).
But if you do want state sync again (don't care that there are missing blocks between last stop and latest state sync snapshot) and you want to keep already synced blocks, you can just delete $BNCHOME/data/STATESYNC.LOCK.

For example, you start your full node at Jan 1st with state sync at height 10000 and after a while you shut it down at height 22000 on Feb 10th.
Now its Mar 1st, latest sync-able block height is 50000, you don't care blocks between 22000 and 50000, you can delete $BNCHOME/data/STATESYNC.LOCK before start your node.
Then the full node would continue state sync from height 50000.

Turning off state_sync_reactor and state_sync can save your memory after you successfully state synced.

Upgrading Full Node​

In most cases, download the new binary and replace it, then restart the full node.
In special cases, you may have to do extra steps for an incompatible version (hard fork).

Monitoring​

Prometheus is enabled on port 28660 by default, and the endpoint is /metrics.

Get Extra Data From Your Full Node​

Full node has the same RPC interface as the one listed here rpc-api

If you want to get extra information about order book, balance changes or block fee changes from blocks, please refer to getting extra data from fullnode.

Common Issues and Solutions​

Please refer to this doc to find answers to common issues.