Peers not syncing on PoA private network

Question

I've got a private network with two PoA geth nodes, with each node running on a separate machine. One node has been running for some time (in instamine mode) and has mined 6909 blocks. I've just setup the other node and was able to connect both nodes using admin.addPeer.

Output of admin.peers confirms that the peers are connected, and both nodes are using the same genesis block.

Output of eth.syncing shows that my second node knows about the blocks on my first node :

{ currentBlock: 4859, highestBlock: 6909, knownStates: 45954, pulledStates: 45954, startingBlock: 6844 }

The syncing process however does not actually start. Verbose output of my second node shows some warnings :

Node data write error err="state node c84891...25d151 failed with all peers (1 tries, 1 peers)

...

Synchronisation failed, retrying err="state node c84891...25d151 failed with all peers (1 tries, 1 peers)

Both machines are using fixed IP's and TCP traffic is allowed on port 30303.

I have read all similar questions/answers and open issues but cannot figure out what the problem is. What am I missing?

Geth version: 1.8.23-stable & OS version: Ubuntu 18.04.2 LTS

Answer 1

Probably some issue regarding the instamine mode ("period": 0 in genesis config).

I just created a new chain on machine 1 with a fixed 3 second blocktime, leaving all other config options intact. When starting my node on machine 2 and adding machine 1 as a peer the syncing process starts immediately.

Opened github issue: https://github.com/ethereum/go-ethereum/issues/19178