Teku's Syncing Process

By default, Teku uses a recently finalized checkpoint state from a community source, and only need to catch up to the current head of the blockchain. This process is relatively fast, usually taking only a few minutes to no more than an hour.

Teku's DApp and the Logs provide useful information about it's activities. To observe the syncing progress:

  1. Check the status in the Teku DApp. The status will change from syncing to in sync when it is fully synced.

  1. Inspect the Logs. Familiarizing yourself with the Logs enables you to confidently assess whether the process is running smoothly or if any issues require attention. To access the Logs, open the Teku Management Page from the My Dapps menu and scroll to the bottom.

Once Teku has started up and initialized, you should start to see the following lines in the Logs:

INFO  - Syncing     *** Target slot: 8735594, Head slot: 8735488, Remaining slots: 106, Connected peers: 5
INFO  - Syncing     *** Target slot: 8735595, Head slot: 8735491, Remaining slots: 104, Connected peers: 5
INFO  - Syncing     *** Target slot: 8735596, Head slot: 8735497, Remaining slots: 99, Connected peers: 13
INFO  - Syncing     *** Target slot: 8735597, Head slot: 8735504, Remaining slots: 93, Connected peers: 11
INFO  - Syncing     *** Target slot: 8735598, Head slot: 8735512, Remaining slots: 86, Connected peers: 11

This indicates that Teku is in "Syncing" mode. You will notice the Target slot counting up, and the Remaining slots counting down, until eventually Teku reports "Syncing completed":

INFO  - Syncing     *** Target slot: 8735604, Head slot: 8735584, Remaining slots: 20, Connected peers: 38
INFO  - Syncing     *** Target slot: 8735605, Head slot: 8735598, Remaining slots: 7, Connected peers: 36
INFO  - Syncing completed
INFO  - Slot Event  *** Slot: 8735606, Block: bff74d8385b48876def789819dce3175b4eea683d3ca185d241a7e891c6bfe16, Justified: 272986, Finalized: 272985, Peers: 43
INFO  - Slot Event  *** Slot: 8735607, Block: 3a9aa0f858e8c55ea82dc2424fb51968e6a8cf2d367efc733dc2e3a275e4e17e, Justified: 272986, Finalized: 272985, Peers: 43
INFO  - Slot Event  *** Slot: 8735608, Block: 2559cd02f5ab84a3f3c9547e0fe4683cc6eec12cf8621a0dc452adeb2dfa388c, Justified: 272986, Finalized: 272985, Peers: 47

The "Slot Event" messages indicate that Teku is fully synced and enters normal operation.


If you notice that the status in the DApp remains stuck at "Waiting for beacon chain to become ready" without any progress, or if you come across error messages in the Logs, Teku might have a problem syncing.

The most common problems are:

  • Teku fails to connect to sufficient number of peers. If you are getting a low peer count, there may be a problem with your network setting. See Opening Network Ports to learn how to resolve this by "opening port 9000" on the router (port 9006 for Gnosis Teku).

  • Teku fails to find the Execution Client. It may be the case that you have not yet installed the Execution Client, in which case once you have set up the Execution Client this error will go away.

ERROR - Execution Client request failed. Make sure the Execution Client is online and can respond to requests.

If you have already installed an Execution Client but this error persists, check that you have correctly selected the Execution Engine (Geth or Nethermind) on Teku's Settings page, to match with your installed Execution Client. Remember to click Apply changes to update the setting.

If the error persists, check the Logs of the Execution Client to see what is going on there. Sometimes a Restart of the Execution Client and the Consensus Client is all that is needed to resolve the issue. Please also feel free to reach out to our Discord channel for support.

Normal Operations

Here is an example of how the Teku Logs should look like when:

  • Teku is fully synced;

  • The Execution Client is fully synced;

  • You have loaded Validator Keys into Teku, and the Validators have become active on the Beacon Chain; and

  • You have installed and configured MEV-Boost.

Key observations:

  • White, blue, and green lines indicate positive activity.

  • Red texts require attention and may indicate issues.

  • Teku diligently tracks each slot ("Slot Event") and each epoch ("Epoch Event").

  • Blue lines represent your validator producing attestations ("Published attestation").

  • Every epoch, Teku reports the "Attestation performance" of previous epochs.

  • Empty blocks ("... empty"), "Late Block Import", or "Reorg Event" occasionally appear, which are normal and related to Ethereum network activities. However, if you see excessive empty or late blocks, it may indicate a syncing issue with your node.

  • If MEV-Boost is installed and working as expected, Teku registers your validators on the "builder network" every epoch, indicated by a line similar to: "Validator *** 6 out of 6 validator registration(s) were successfully sent to the builder network via the Beacon Node".

If you notice that your validators are missing attestations, it is often beneficial to inspect the Logs for any abnormal behavior or issues.

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