Skip to main content



This article requires a revision.

Log config file location

Logging in Nethermind is done via NLog library that can be configured by editing the NLog.config file.

Environment TypeNLog.config location
built from src - Debug modesrc\Nethermind\Nethermind.Runner\bin\Debug\netcoreapp3.1\NLog.config
built from src - Release modesrc\Nethermind\Nethermind.Runner\bin\Release\netcoreapp3.1\NLog.config
from downloads pagetop level directory after unzipping the package
from GitHub releases pagetop level directory after unzipping the package
dAppNode? [to be documented]

Log config file syntax

Detailed NLog configuration options can be found here:

Config or CLI log rules

Simple logging rules can be added through configuration file or command line argument.

For example this would add Trace level logs to any logger under Synchronization module and Debug level logs for BlockTree from Blockchain module:
--Init.LogRules Synchronization.*:Trace;Blockchain.BlockTree:Debug

Global logging override

Additionally there are global logging override that you can use temporarily:

Command line overrideLog level
./Nethermind.Runner --config mainnet --log TRACETRACE
./Nethermind.Runner --config mainnet --log DEBUGDEBUG
./Nethermind.Runner --config mainnet --log INFOINFO
./Nethermind.Runner --config mainnet --log WARNWARN
./Nethermind.Runner --config mainnet --log ERRORERROR

JSON RPC logging level

This can be done by including these lines in the logging configuration file:

<logger name="JsonRpc.*" minlevel="Error" writeTo="file-async"/>
<logger name="JsonRpc.*" minlevel="Error" writeTo="auto-colored-console-async" final="true"/>
<logger name="JsonRpc.*" final="true"/>

Enterprise Logging

See how to configure Seq here

Explaining Nethermind logs

You can check the supported operating systems, architectures and hardware requirements here:

After the node starts, you will see some initial info about the node and then the sync will start. Görli fast sync uses a fast blocks sync mode initially. The fast blocks sync picks some known pivot block from the past and downloads headers, bodies, and receipts downwards all the way to genesis block. All blocks from 0 to the pivot block are showed as Old Headers in the fast blocks sync logs. The console display shows the number growing from 0 to pivot, but this is just to make the display more user-friendly.

You will see some information about the sync progress, like below:

  1. Shows the number of already downloaded headers, bodies and receipts under the name Downloaded out of all to be downloaded in the fast blocks stage.
  2. Shows the current queue of already downloaded blocks, headers and receipts waiting for being saved to the database.
  3. Shows the current download speed (blocks per second - bps).
  4. Shows the average download speed (blocks per second - bps).

Fast blocks sync logs

When the fast blocks stage finishes, there will be some period of downloading blocks between the pivot and thelatest blocks which will have some additional info:

  1. Shows the last entry from the fast blocks stage.
  2. Shows the mode transition moment.
  3. Displays the speed (in blocks per second) of all headers, bodies and receipts at the same time.
  4. Additional info will appear every 30000 blocks with information about the Görli epoch being stored.

Görli fast sync logs

After the fast sync part finished, the node will transition to the state sync stage when the state trie is being downloaded. Much information is displayed about the progress, as this process may take a long time on mainnet (a few hours).

  1. Total elapsed time in state sync is displayed.
  2. The total percentage of downloaded DB size is displayed (on mainnet the sync finishes around 34GB in March 2020, on Görli around 800MB).
  3. branches stands for the percentage of downloaded branches.
  4. Download speed in kilobytes per second is displayed.
  5. accounts stands for the number of accounts data downloaded already.
  6. nodes stands for the number of Patricia trie nodes downloaded by the sync process.
  7. diagnostic shows the time spent in the DB write / read access. The higher the value, the worse. It may get much worse if you restart the node during the sync process, as we need to recreate some caches then by reading data from the DB.

Görli state sync logs

When the state sync is nearing completion, you may see a series of branch sync information reloading many times from 0% to nearly 100%. This is the node trying to retrieve the few remaining state nodes and progressing with the head block rapidly:

Görli branch sync logs

At some point, the entire state is downloaded and the node enters the full sync mode and will allow you to issue CLI / Web3 queries and send / receive transactions🥳

  1. The root is saved at the moment when the entire Patricia trie is downloaded.
  2. We also clearly state that the node transitions to the full sync.
  3. When you see the block being processed, then you are in the full sync and the newly arrived block is being calculated.
  4. Every two minutes you will see a summary of connected peers with their client version, IP address, highest synced block, and data download speeds.

Görli full sync logs

Also, every now and then, a peer report will appear like below:

  1. First bracket is for Allocated contexts. It has possible values of H for Headers, B for Bodies, R for Receipts, N for State, S for Snap, and W for Witness.
  2. Second bracket is for Sleeping contexts. It has possible values of H for Headers, B for Bodies, R for Receipts, N for State, S for Snap, and W for Witness.
  3. Third bracket contains Peer Info.
  4. Fourth bracket is for Speeds as Follows:
    • Latency
    • Headers Transfer
    • Bodies Transfer
    • Receipts Transfer
    • Node Data Transfer
    • Snap Ranges Transfer
  5. Fifth bracket is for Client Info like Client Name, Client Version, Operating System and Language Version.