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Node Protocol Database Release Date Release Notes GitHub Links
19.0 17 14 2019-07-11 V19.0 Release - Milestone - Changelog
Known Issue V19+: 'Too many open files'
  • Issue: The following error, or a similar one, can be seen when attempting to run a full node on some versions of macOS, Linux and possibly other operating systems. This is most common when using the built-in Qt wallet or other GUI-based wallets: "Exception while running wallet: open: Too many open files" or other errors containing "Too many open files". This is due to some systems having a very low default file descriptor limit and V19.0+ uses more of them after the move to TCP.

  • Solution: Increasing the file limits is needed to resolve this. See this known issue for more details on resolution.

Upgrade Notices

Version Limits

Upgrades from versions V17.1 and to V19 will involve a sequential database upgrade and impact participation of the node on the network. RPC calls will be unavailable for a long period of time amongst other impacts.

Upgrading from V17.1 and earlier to V19.0 not recommended

It is highly recommended that nodes are upgraded to V18.0 first or a V18.0 ledger is acquired and used when upgrading to V19.0.

Confirmation tracking considerations

The addition of confirmation height to the database requires the node to validate that blocks are confirmed before the cementing can occur. This process can take up to 24 hours or longer to complete and will cause an increase in some resource usage, particularly CPU and network bandwidth increases, but won’t impact participation on the network. For integrations watching confirmations, the existing HTTP callback, block_confirm RPC and confirmation_history RPC methods will continue to function as before.

Tracking confirmed block hashes required

It is required that tracking of confirmed block hashes outside the node is done to avoid potential duplicate notifications from causing issues. This was a requirement in previous versions and remains the same with V19.

For those looking to utilize the new WebSocket confirmation subscription or new confirmed field in block_info RPC responses, special considerations should be taken if implementing before confirmation height updates are complete:

  • If the websocket confirmation subscription is hooked up to receive all confirmations (default) then notifications for confirmations will come through during the cementing process on a new or upgrading ledger as the confirmation process will occur (it also fires for dependent confirmations)
  • Calls to block_info for blocks in the ledger before the confirmation height upgrade process began may indicate confirmed as false despite their having been confirmed on the network before. This is expected behavior.
  • To validate that confirmation height upgrade is complete, note the count value from the block_count RPC when the upgrade is started and once the cemented amount returned by this call (include the include_cemented option) is higher than that previous count, cementing is in sync.

Emitting nano_ prefixed addresses

In this and future versions, all addresses emitted from the node will use the nano_ prefix. It will continue to support input for xrb_ prefixed addresses, but all services must verify they are properly set up to handle the node outputting nano_ prefixed addresses.

Live network over TCP

Live network traffic over TCP is now available and operates on the same port (7075 for main network, 54000 for beta network) as the bootstrapping network that was already available over TCP. Because of this, existing network setups that are open inbound and outbound on port 7075 for TCP should function as expected with V19.0. For those running production services, it is still recommended to verify network ports setup and consider setting up a new node on internal networks to ensure it can connect and participate on the main network before production nodes are upgraded.

  • To check for proper connection via TCP, call the peers RPC with peer_details option and look for peers with type = tcp. This command can be used to search for these instances:
curl -sd '{"action": "peers", "peer_details":"true"}' [::1]:7076 | grep "\"type\": \"tcp\"" | wc -l

Major Updates

Confirmation Height

This provides cementing of blocks by marking on an account the highest block height that has been confirmed for the account. A more detailed look at this feature can be found in the relatd Medium article:

TCP Network

Blocks being published and voted on live are now supported via TCP, with UDP remaining as a fallback. See the TCP callouts in Upgrade Notices above for information about verifying your network setup is ready for the upgrade.

Dynamic Proof-of-Work and Prioritization

With the ability to track work difficulty seen on the network and have the node wallet produce more difficult work for local blocks, this feature allows users to get their transactions prioritized for processing. More details about this feature can be found in the Medium article:

RPC Process Options

By default the RPC server will run in the node process, but can be configured to run as a child process or completely out of process (currently limited to running on the same computer), depending on your needs. See Running Nano as a service for more details.

RPC/CLI Updates

No Breaking Changes

There were no breaking changes made in V19 for any RPC or CLI commands. It is recommended any integrations run tests against V19 before upgrading production nodes, and also explore the various changes below to improve their setups.

  • NEW unopened RPC provides the total pending balance for unopened accounts
  • NEW active_difficulty RPC allows tracking of the difficulty levels seen on the network which can be used to target higher levels of PoW to prioritize transactions
  • Using --diagnostics CLI option now validates config and generates default one if it doesn’t exist
  • wallet_create and wallet_change_seed RPCs accept seed and return restored accounts for easier seed management
  • The pending RPC can now optionally be using sorting by amount
  • Difficulty and multiplier options available in work_generate and work_validate RPCs for easier management of dynamic work levels on blocks
  • State blocks returned by block_info/blocks_info contain subtype for easier identification of block types
  • Json literals supported for block input (process, sign, and block_hash) and output (block_create, block_info, blocks_info, confirmation_info, unchecked_get and unchecked_keys) on RPC calls
  • A new optional argument include_not_found in blocks_info allows requests which contain invalid block hashes to get results that include an array of blocks_not_found instead of just an error
  • The account_history RPC now:
    • Accepts account_filter to allow filtering of results to a specific account or set of accounts
    • Allows reverse option to return details starting from the head block on the account
    • Block height on account chain now included in response
  • The accounts_pending RPC allows for sorting by amounts
  • For ledger and unopened RPCs a new optional threshold value can be used to limit results by balance
  • A new include_cemented option in block_count RPC adds return of the cemented blocks in the ledger - cemented blocks are ones that have been confirmed and are at or below the confirmation height set on the account

Node Configuration Updates


  • New active_elections_size will limit the number of active elections allowed before dropping occurs. Default is 50,000 but higher settings are recommended for nodes provisioned with 8GB RAM or more
  • New bandwidth_limit will limit the outbound voting traffic to 5MB/s by default
  • New confirmation_history_size provides an adjustable limit on the batching of confirmations return in the confirmation_history RPC. Default 2048 which will support up to ~56 confirmations/sec before confirmations may be missed. The new websocket setup with confirmation subscription is recommended over use of the confirmation_history RPC.

Advanced Configuration

New vote_generator_delay allows for tuning performance of bundling votes by hash before sending.

This new file was split out from the config.json file as the RPC server can now be run in its own process. Entries previously existing in config.json were migrated over and new values added. One setting to note: the max_request_size parameter is defaulted to 32MB - if your service is submitting data amounts larger than this you will need to adjust accordingly.

Automated config backups
Backups of config files will be made prior to upgrades. During upgrades from V18 to V19 you will see a backup created even for the new rpc_config.json - this is expected behavior given the upgrade process.

Developer/Debug Options


The following RPC calls are being deprecated and will be removed in a future release:

Other Notices

New nanorep QR code standard
A new nanorep QR code standard for easier management of representative changes was added for wallets and other services to consider supporting.

New recommended block explorer
The Nano Foundation supports a new recommended block explorer - NanoCrawler. We encourage services and exchanges linking out to block explorers to consider using NanoCrawler going forward as it provides solid design and performance for referencing blocks, accounts and more.