lighthouse/book/src/faq.md

Frequently Asked Questions

Why does it take so long for a validator to be activated?

After validators create their Eth1 deposit transaction there are two waiting periods before they can start producing blocks and attestations:

1. Waiting for the beacon chain to recognise the Eth1 block containing the deposit (generally 4 to 7.4 hours).
2. Waiting in the queue for validator activation (generally 6.4 minutes for every 4 validators in the queue).

Detailed answers below:

1. Waiting for the beacon chain to detect the Eth1 deposit

Since the beacon chain uses Eth1 for validator on-boarding, beacon chain validators must listen to event logs from the deposit contract. Since the latest blocks of the Eth1 chain are vulnerable to re-orgs due to minor network partitions, beacon nodes follow the Eth1 chain at a distance of 1,024 blocks (~4 hours) (see ETH1_FOLLOW_DISTANCE). This follow distance protects the beacon chain from on-boarding validators that are likely to be removed due to an Eth1 re-org.

Now we know there's a 4 hours delay before the beacon nodes even consider an Eth1 block. Once they are considering these blocks, there's a voting period where beacon validators vote on which Eth1 to include in the beacon chain. This period is defined as 32 epochs (~3.4 hours, see ETH1_VOTING_PERIOD). During this voting period, each beacon block producer includes an Eth1Data in their block which counts as a vote towards what that validator considers to be the head of the Eth1 chain at the start of the voting period (with respect to ETH1_FOLLOW_DISTANCE, of course). You can see the exact voting logic here.

These two delays combined represent the time between an Eth1 deposit being included in an Eth1 data vote and that validator appearing in the beacon chain. The ETH1_FOLLOW_DISTANCE delay causes a minimum delay of ~4 hours and ETH1_VOTING_PERIOD means that if a validator deposit happens just before the start of a new voting period then they might not notice this delay at all. However, if the validator deposit happens just after the start of the new voting period the validator might have to wait ~3.4 hours for next voting period. In times of very, very severe network issues, the network may even fail to vote in new Eth1 blocks, stopping all new validator deposits!

Note: you can see the list of validators included in the beacon chain using our REST API: /beacon/validators/all

2. Waiting for a validator to be activated

If a validator has provided an invalid public key or signature, they will never be activated or even show up in /beacon/validators/all. They will simply be forgotten by the beacon chain! But, if those parameters were correct, once the Eth1 delays have elapsed and the validator appears in the beacon chain, there's another delay before the validator becomes "active" (canonical definition here) and can start producing blocks and attestations.

Firstly, the validator won't become active until their beacon chain balance is equal to or greater than MAX_EFFECTIVE_BALANCE (32 ETH on mainnet, usually 3.2 ETH on testnets). Once this balance is reached, the validator must wait until the start of the next epoch (up to 6.4 minutes) for the process_registry_updates routine to run. This routine activates validators with respect to a churn limit; it will only allow the number of validators to increase (churn) by a certain amount. Up until there are about 330,000 validators this churn limit is set to 4 and it starts to very slowly increase as the number of validators increases from there.

If a new validator isn't within the churn limit from the front of the queue, they will need to wait another epoch (6.4 minutes) for their next chance. This repeats until the queue is cleared.

Once a validator has been activated, there's no more waiting! It's time to produce blocks and attestations!

3. Do I need to set up any port mappings

It is not strictly required to open any ports for Lighthouse to connect and participate in the network. Lighthouse should work out-of-the-box. However, if your node is not publicly accessible (you are behind a NAT or router that has not been configured to allow access to Lighthouse ports) you will only be able to reach peers who have a set up that is publicly accessible.

There are a number of undesired consequences of not making your Lighthouse node publicly accessible.

Firstly, it will make it more difficult for your node to find peers, as your node will not be added to the global DHT and other peers will not be able to initiate connections with you. Secondly, the peers in your peer store are more likely to end connections with you and be less performant as these peers will likely be overloaded with subscribing peers. The reason being, that peers that have correct port forwarding (publicly accessible) are in higher demand than regular peers as other nodes behind NAT's will also be looking for these peers. Finally, not making your node publicly accessible degrades the overall network, making it more difficult for other peers to join and degrades the overall connectivity of the global network.

For these reasons, we recommend that you make your node publicly accessible.

Lighthouse supports UPnP. If you are behind a NAT with a router that supports UPnP you can simply ensure UPnP is enabled (Lighthouse will inform you in its initial logs if a route has been established). You can also manually set up port mappings in your router to your local Lighthouse instance. By default, Lighthouse uses port 9000 for both TCP and UDP. Opening both these ports will make your Lighthouse node maximally contactable.

4. I have a low peer count and it is not increasing

If you cannot find ANY peers at all. It is likely that you have incorrect testnet configuration settings. Ensure that the network you wish to connect to is correct (the beacon node outputs the network it is connecting to in the initial boot-up log lines). On top of this, ensure that you are not using the same datadir as a previous network. I.e if you have been running the pyrmont testnet and are now trying to join a new testnet but using the same datadir (the datadir is also printed out in the beacon node's logs on boot-up).

If you find yourself with a low peer count and is not reaching the target you expect. Try setting up the correct port forwards as described in 3. above.