UFO 0.14 Released
April 13, 2018
Uniform Fiscal Object
Validation speed and network propagation performance have been greatly improved, leading to much shorter sync and initial block download times.
- The script signature cache has been reimplemented as a “cuckoo cache”, allowing for more signatures to be cached and faster lookups.
- Assumed-valid blocks have been introduced which allows script validation to be skipped for ancestors of known-good blocks, without changing the security model. See below for more details.
- In some cases, compact blocks are now relayed before being fully validated as per BIP152.
- P2P networking has been refactored with a focus on concurrency and throughput. Network operations are no longer bottlenecked by validation. As a result, block fetching is several times faster than previous releases in many cases.
- The UTXO cache now claims unused mempool memory. This speeds up initial block download as UTXO lookups are a major bottleneck there, and there is no use for the mempool at that stage.
Bitcoin Core has supported automatically pruning the blockchain since 0.11. Pruning the blockchain allows for significant storage space savings as the vast majority of the downloaded data can be discarded after processing so very little of it remains on the disk.
Manual block pruning can now be enabled by setting
-prune=1. Once that is set, the RPC command
pruneblockchain can be used to prune the blockchain up to the specified height or timestamp.
getinfo RPC command has been deprecated. Each field in the RPC call has been moved to another command’s output with that command also giving additional information that
getinfo did not provide. The following table shows where each field has been moved to:
ZMQ On Windows
Previously the ZeroMQ notification system was unavailable on Windows due to various issues with ZMQ. These have been fixed upstream and now ZMQ can be used on Windows. Please see this document for help with using ZMQ in general.
Nested RPC Commands in Debug Console
The ability to nest RPC commands has been added to the debug console. This allows users to have the output of a command become the input to another command without running the commands separately.
The nested RPC commands use bracket syntax (i.e.
getwalletinfo()) and can be nested (i.e.
getblock(getblockhash(1))). Simple queries can be done with square brackets where object values are accessed with either an array index or a non-quoted string (i.e.
listunspent()&<a href="https://github.com/bitcoin/bitcoin/pull/91">#91</a>;0&<a href="https://github.com/bitcoin/bitcoin/pull/93">#93</a>;[txid]). Both commas and spaces can be used to separate parameters in both the bracket syntax and normal RPC command syntax.
Network Activity Toggle
A RPC command and GUI toggle have been added to enable or disable all p2p network activity. The network status icon in the bottom right hand corner is now the GUI toggle. Clicking the icon will either enable or disable all p2p network activity. If network activity is disabled, the icon will be grayed out with an X on top of it.
setnetworkactive RPC command has been added which does the same thing as the GUI icon. The command takes one boolean parameter,
trueenables networking and
false disables it.
Out-of-sync Modal Info Layer
When Bitcoin Core is out-of-sync on startup, a semi-transparent information layer will be shown over top of the normal display. This layer contains details about the current sync progress and estimates the amount of time remaining to finish syncing. This layer can also be hidden and subsequently unhidden by clicking on the progress bar at the bottom of the window.
Support for JSON-RPC Named Arguments
Commands sent over the JSON-RPC interface and through the
bitcoin-cli binary can now use named arguments. This follows the JSON-RPC specification for passing parameters by-name with an object.
bitcoin-cli has been updated to support this by parsing
name=value arguments when the
-named option is given.
src/bitcoin-cli -named help command="help" src/bitcoin-cli -named getblockhash height=0 src/bitcoin-cli -named getblock blockhash=000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f src/bitcoin-cli -named sendtoaddress address="(snip)" amount="1.0" subtractfeefromamount=true
The order of arguments doesn’t matter in this case. Named arguments are also useful to leave out arguments that should stay at their default value. The rarely-used arguments
sendtoaddress, for example, can be left out. However, this is not yet implemented for many RPC calls, this is expected to land in a later release.
The RPC server remains fully backwards compatible with positional arguments.
Opt into RBF When Sending
A new startup option,
-walletrbf, has been added to allow users to have all transactions sent opt into RBF support. The default value for this option is currently
false, so transactions will not opt into RBF by default. The new
bumpfee RPC can be used to replace transactions that opt into RBF.
Sensitive Data Is No Longer Stored In Debug Console History
The debug console maintains a history of previously entered commands that can be accessed by pressing the Up-arrow key so that users can easily reuse previously entered commands. Commands which have sensitive information such as passphrases and private keys will now have a
(...) in place of the parameters when accessed through the history.
Retaining the Mempool Across Restarts
The mempool will be saved to the data directory prior to shutdown to a
mempool.datfile. This file preserves the mempool so that when the node restarts the mempool can be filled with transactions without waiting for new transactions to be created. This will also preserve any changes made to a transaction through commands such as
prioritisetransaction so that those changes will not be lost.
The Alert System was disabled and deprecated in Bitcoin Core 0.12.1 and removed in 0.13.0. The Alert System was retired with a maximum sequence final alert which causes any nodes supporting the Alert System to display a static hard-coded “Alert Key Compromised” message which also prevents any other alerts from overriding it. This final alert is hard-coded into this release so that all old nodes receive the final alert.
- After resetting the options by clicking the
Reset Optionsbutton in the options dialog or with the
-resetguioptionsstartup option, the user will be prompted to choose the data directory again. This is to ensure that custom data directories will be kept after the option reset which clears the custom data directory set via the choose datadir dialog.
- Multiple peers can now be selected in the list of peers in the debug window. This allows for users to ban or disconnect multiple peers simultaneously instead of banning them one at a time.
- An indicator has been added to the bottom right hand corner of the main window to indicate whether the wallet being used is a HD wallet. This icon will be grayed out with an X on top of it if the wallet is not a HD wallet.
Low-level RPC changes
importprunedfundsonly accepts two required arguments. Some versions accept an optional third arg, which was always ignored. Make sure to never pass more than two arguments.
- The first boolean argument to
getaddednodeinfohas been removed. This is an incompatible change.
- RPC command
getmininginfoloses the “testnet” field in favor of the more generic “chain” (which has been present for years).
- A new RPC command
preciousblockhas been added which marks a block as precious. A precious block will be treated as if it were received earlier than a competing block.
- A new RPC command
importmultihas been added which receives an array of JSON objects representing the intention of importing a public key, a private key, an address and script/p2sh
- Use of
getrawtransactionfor retrieving confirmed transactions with unspent outputs has been deprecated. For now this will still work, but in the future it may change to only be able to retrieve information about transactions in the mempool or if
- A new RPC command
getmemoryinfohas been added which will return information about the memory usage of Bitcoin Core. This was added in conjunction with optimizations to memory management. See #8753. for more information.
- A new RPC command
bumpfeehas been added which allows replacing an unconfirmed wallet transaction that signaled RBF (see the
-walletrbfstartup option above) with a new transaction that pays a higher fee, and should be more likely to get confirmed quickly.
HTTP REST Changes
- UTXO set query (
GET /rest/getutxos/<checkmempool>/<txid>-<n>/<txid>-<n> /.../<txid>-<n>.<bin|hex|json>) responses were changed to return status code
HTTP_BAD_REQUEST(400) instead of
HTTP_INTERNAL_SERVER_ERROR(500) when requests contain invalid parameters.
Minimum Fee Rate Policies
Since the changes in 0.12 to automatically limit the size of the mempool and improve the performance of block creation in mining code it has not been important for relay nodes or miners to set
-minrelaytxfee. With this release the following concepts that were tied to this option have been separated out: – incremental relay fee used for calculating BIP 125 replacement and mempool limiting. (1000 satoshis/kB) – calculation of threshold for a dust output. (effectively 3 * 1000 satoshis/kB) – minimum fee rate of a package of transactions to be included in a block created by the mining code. If miners wish to set this minimum they can use the new
-blockmintxfee option. (defaults to 1000 satoshis/kB)
-minrelaytxfee option continues to exist but is recommended to be left unset.
Fee Estimation Changes
- Since 0.13.2 fee estimation for a confirmation target of 1 block has been disabled. The fee slider will no longer be able to choose a target of 1 block. This is only a minor behavior change as there was often insufficient data for this target anyway.
estimatefee 1will now always return -1 and
estimatesmartfee 1will start searching at a target of 2.
- The default target for fee estimation is changed to 6 blocks in both the GUI (previously 25) and for RPC calls (previously 2).
Removal of Priority Estimation
- Estimation of “priority” needed for a transaction to be included within a target number of blocks has been removed. The RPC calls are deprecated and will either return -1 or 1e24 appropriately. The format for
fee_estimates.dathas also changed to no longer save these priority estimates. It will automatically be converted to the new format which is not readable by prior versions of the software.
- Support for “priority” (coin age) transaction sorting for mining is considered deprecated in Core and will be removed in the next major version. This is not to be confused with the
prioritisetransactionRPC which will remain supported by Core for adding fee deltas to transactions.
P2P connection management
- Peers manually added through the
addnodeRPC now have their own limit of eight connections which does not compete with other inbound or outbound connection usage and is not subject to the limitation imposed by the
- New connections to manually added peers are performed more quickly.
Introduction of assumed-valid blocks
- A significant portion of the initial block download time is spent verifying scripts/signatures. Although the verification must pass to ensure the security of the system, no other result from this verification is needed: If the node knew the history of a given block were valid it could skip checking scripts for its ancestors.
- A new configuration option ‘assumevalid’ is provided to express this knowledge to the software. Unlike the ‘checkpoints’ in the past this setting does not force the use of a particular chain: chains that are consistent with it are processed quicker, but other chains are still accepted if they’d otherwise be chosen as best. Also unlike ‘checkpoints’ the user can configure which block history is assumed true, this means that even outdated software can sync more quickly if the setting is updated by the user.
- Because the validity of a chain history is a simple objective fact it is much easier to review this setting. As a result the software ships with a default value adjusted to match the current chain shortly before release. The use of this default value can be disabled by setting -assumevalid=0
Fundrawtransaction change address reuse
- Before 0.14,
fundrawtransactionwas by default wallet stateless. In almost all cases
fundrawtransactiondoes add a change-output to the outputs of the funded transaction. Before 0.14, the used keypool key was never marked as change-address key and directly returned to the keypool (leading to address reuse). Before 0.14, calling
fundrawtransactiondid generate the same address as the change-output address.
- Since 0.14, fundrawtransaction does reserve the change-output-key from the keypool by default (optional by setting
reserveChangeKey, default =
- Users should also consider using
getrawchangeaddress()in conjunction with
Unused mempool memory used by coincache
- Before 0.14, memory reserved for mempool (using the
-maxmempooloption) went unused during initial block download, or IBD. In 0.14, the UTXO DB cache (controlled with the
-dbcacheoption) borrows memory from the mempool when there is extra memory available. This may result in an increase in memory usage during IBD for those previously relying on only the
-dbcacheoption to limit memory during that time.
- The first positional argument of
createrawtransactionwas renamed from
- The argument of
disconnectnodewas renamed from
These interface changes break compatibility with 0.14.0, when the named arguments functionality, introduced in 0.14.0, is used. Client software using these calls with named arguments needs to be updated.
In previous versions, getblocktemplate required segwit support from downstream clients/miners once the feature activated on the network. In this version, it now supports non-segwit clients even after activation, by removing all segwit transactions from the returned block template. This allows non-segwit miners to continue functioning correctly even after segwit has activated.
Due to the limitations in previous versions, getblocktemplate also recommended non-segwit clients to not signal for the segwit version-bit. Since this is no longer an issue, getblocktemplate now always recommends signalling segwit for all miners. This is safe because ability to enforce the rule is the only required criteria for safe activation, not actually producing segwit-enabled blocks.
UTXO memory accounting
Memory usage for the UTXO cache is being calculated more accurately, so that the configured limit (
-dbcache) will be respected when memory usage peaks during cache flushes. The memory accounting in prior releases is estimated to only account for half the actual peak utilization.
-dbcache has also been changed in this release to 450MiB. Users who currently set
-dbcache to a high value (e.g. to keep the UTXO more fully cached in memory) should consider increasing this setting in order to achieve the same cache performance as prior releases. Users on low-memory systems (such as systems with 1GB or less) should consider specifying a lower value for this parameter.
Additional information relating to running on low-memory systems can be found here: reducing-bitcoind-memory-usage.md.
Bundled miniupnpc was updated to 2.0.20170509. This fixes an integer signedness error (present in MiniUPnPc v1.4.20101221 through v2.0) that allows remote attackers (within the LAN) to cause a denial of service or possibly have unspecified other impact.
This only affects users that have explicitly enabled UPnP through the GUI setting or through the
-upnp option, as since the last UPnP vulnerability (in Bitcoin Core 0.10.3) it has been disabled by default.
If you use this option, it is recommended to upgrade to this version as soon as possible.
Uniform Fiscal Object 0.14 has been released and can be obtained from: