gt highNoFork error reported when synchronizing blocks

[jakamobiii]

Software Versions

OS : Linux
JVM : Oracle Corporation 1.8.0_161 amd64
Version : 4.7.7

Expected behavior

The node is running normally and no exception should be thrown.

Actual behavior

I deployed a private chain locally. When I checked one of the fullnode logs, I found an exception. I want to know what this exception is, whether it has any impact on the system, and whether it will affect block synchronization?

Frequency

Only appeared once.

[zeusoo001]

@jakamobiii Can you send the last interaction information with peer 185.126.81.120?

[Sunny6889]

@jakamobiii Although this scenario is extremely rare, it can occur when the peer's highest block number is close with the node and the network experiences jitter. However, this condition does not impact the subsequent synchronization functionality.

[jakamobiii]

The following is the final interactive information：

04:50:24.600 INFO  [peerWorker-6] [net](PeerConnection.java:175) Send peer /185.126.81.120:60846 message type: SYNC_BLOCK_CHAIN
size: 5, start block: Num:10950289,ID:0000000000a71691b951f017ed1bfd30b1c62289fd7b6edc81327d41a69f3c66, end block Num:10950309,ID:0000000000a716a5de7007d3abd0abe22bc9070bfef093581e82d144e578457b
04:50:54.624 INFO  [peerWorker-6] [net](P2pEventHandlerImpl.java:168) Receive message from  peer: /185.126.81.120:60846, type: BLOCK_CHAIN_INVENTORY
size: 2001, first blockId: Num:10950309,ID:0000000000a716a5de7007d3abd0abe22bc9070bfef093581e82d144e578457b, end blockId: Num:10952309,ID:0000000000a71e752d4f1b874294c8c8773678bcafd29e1fc5f2340a5e0f2905, remain_num: 37463370
04:50:54.652 INFO  [peerWorker-6] [net](ChainInventoryMsgHandler.java:80) Block Num:10952309,ID:0000000000a71e752d4f1b874294c8c8773678bcafd29e1fc5f2340a5e0f2905 from /185.126.81.120 is processed
04:50:54.662 INFO  [sync-handle-block] [DB](DynamicPropertiesStore.java:2184) Update latest block header number = 10953379.
04:50:54.662 INFO  [sync-handle-block] [DB](DynamicPropertiesStore.java:2176) Update latest block header timestamp = 1605761031000.
04:50:54.663 ERROR [peerWorker-6] [net](SyncService.java:127) Peer /185.126.81.120 sync failed, reason: {}
org.tron.core.exception.P2pException: low: 10953358 gt highNoFork: 10952309

[zeusoo001]

@jakamobiii Thank you for providing the log. From the log, we can see that there was a 30s delay when receiving the BLOCK_CHAIN_INVENTORY message during block synchronization. During this period, many blocks have been synchronized from other nodes, and the blockchain solidified block number has exceeded the maximum block number carried by BLOCK_CHAIN_INVENTORY message. This is the reason for the error.

The probability of this scenario occurring is extremely low, which will cause the connection to be disconnected. It currently has little impact on the system and will not affect block synchronization and broadcasting.

[xxo1shine]

@zeusoo001 Do you have any good solution to fix the problem?

[abn2357]

@zeusoo001 Do you have any good solution to fix the problem?

After reviewing the relevant code, the log level here shouldn't be an error. It's a normal scenario for the current node to outpace its peer in blockchain height. Before calling syncNext or at the very beginning of the syncNext function, we can add a check: if blockBothHave.height <= latestSolidifiedBlockNum.height, then stop syncing from the peer.

[Jake151987]

@zeusoo001 Do you have any good solution to fix the problem?

After reviewing the relevant code, the log level here shouldn't be an error. It's a normal scenario for the current node to outpace its peer in blockchain height. Before calling syncNext or at the very beginning of the syncNext function, we can add a check: if blockBothHave.height <= latestSolidifiedBlockNum.height, then stop syncing from the peer.

Will the check be added in the next version or maybe later?

[xxo1shine]

@Jake151987 It will be fixed in the next version.