I have a test environment of Parity POA of with 5 nodes. 3 nodes are synchronizing with each other but 2 are not able to synchronize. I am getting following error in the logs of nodes not synchronizing;
2018-03-13 17:19:13 Stage 3 block verification failed for #427607 (62e9…9621)
Error: Block(TooManyUncles(OutOfBounds { min: None, max: Some(0), found: 1 }))
Anyone experiencing same problem?
In my case 2 nodes are using parity client version 1.8.10, and other 3 nodes are using parity client version 1.8.3. Nodes with parity 1.8.10 are throwing the above error.
After looking for this issue, I found out that parity clients with version 1.8.4 and above has default value 0 for a parameter "maximumUncleCount". Few blocks in my blockchain has uncle blocks (don't know the reason, why) which cannot be imported by nodes using parity 1.8.10 and they give the error. For now I set the "maximumUncleCount" value to 2 in the nodes with parity 1.8.10 (in blockchain-spec.json file) and now they are synchronizing with no problem. A maximumUncleCount = 0 is recommended in POA environments by parity. I am going to hard fork to use maximumUncleCount = 0 soon.