cfce89ffab
This modifies the block index hash -> node mapping to use shortened keys
with fallback to the full 32-byte key in the event of a collision in the
shortened key. This saves a significant amount of memory because there
are hundreds of thousands of nodes in the index and Go maps duplicate
keys. As an added bonus, due to the implementation choices, it also
results in slightly faster overall lookups on average. This is because
even though lookups of colliding keys are slightly slower, lookups of
non-colliding keys are slightly faster and non-colliding keys are by far
the most common case (typically > 99.5%).
It accomplishes this by taking advantage of the fact the full hash is
part of the node itself and therefore can be used to disambiguate any
collisions in the shortened key and splitting the non-colliding entries
from the colliding entries across two maps where one is keyed by the
shorter key and the other by the full key.
The shortened key is chosen to be the big-endian uint32 formed by the
first 4 bytes of the full hash. The primary reasons for this choice
are:
- The hash function used to produce the block hashes is a
uniformly-random distribution, so the number of collisions will
coincide with the expected value of a uniform distribution
- The bits zeroed by the mining process start at the end of the array,
so there would need to be effectively impossible to achieve hash rates
exceeding ~2^215.77 hashes/sec (aka ~89.8 peta yotta yotta hashes/sec)
in order to start zeroing out the chosen bits
- Using 4 bytes per node results in a savings of 28 bytes per node minus
a small amount of amortized overhead for the collision handling
- 4-byte keys produce a relatively small expected number of collisions
- The cutoff point where the overhead of the collisions is expected to
reach just 10% of the savings gained is around 5800 years given the
average mainnet block production rate
- Conversion of the bytes to a uint32 is basically free in terms of
processing overhead
Profiling of the implemented code as well as simulations show that both
the actual number of observed collisions and observed memory savings
match the expected theoretical values. Specifically, as of block height
575166 on mainnet, there are 35 collisions in the shortened keys and the
memory savings is around 30 MiB.
|
||
|---|---|---|
| .github | ||
| addrmgr | ||
| bech32 | ||
| blockchain | ||
| certgen | ||
| chaincfg | ||
| cmd | ||
| connmgr | ||
| container/apbf | ||
| contrib | ||
| crypto | ||
| database | ||
| dcrec | ||
| dcrjson | ||
| dcrutil | ||
| docs | ||
| gcs | ||
| hdkeychain | ||
| internal | ||
| lru | ||
| peer | ||
| rpc/jsonrpc/types | ||
| rpcclient | ||
| rpctest | ||
| sampleconfig | ||
| txscript | ||
| wire | ||
| .dockerignore | ||
| .gitignore | ||
| blockdb.go | ||
| cert_test.go | ||
| CHANGES | ||
| config_test.go | ||
| config.go | ||
| dcrd.go | ||
| doc.go | ||
| Dockerfile | ||
| Dockerfile.alpine | ||
| go.mod | ||
| go.sum | ||
| ipc.go | ||
| LICENSE | ||
| log.go | ||
| networkparams_test.go | ||
| params.go | ||
| README.md | ||
| require.go | ||
| rpcadaptors.go | ||
| run_tests.sh | ||
| server.go | ||
| service_windows.go | ||
| signal_unix.go | ||
| signal.go | ||
| upnp.go | ||
dcrd
Decred Overview
Decred is a blockchain-based cryptocurrency with a strong focus on community
input, open governance, and sustainable funding for development. It utilizes a
hybrid proof-of-work and proof-of-stake mining system to ensure that a small
group cannot dominate the flow of transactions or make changes to Decred without
the input of the community. A unit of the currency is called a decred (DCR).
Latest Downloads
Core software:
- dcrd: a Decred full node daemon (this)
- dcrwallet: a CLI Decred wallet daemon
- dcrctl: a CLI client for dcrd and dcrwallet
Bundles:
- Decrediton: a GUI bundle for
dcrdanddcrwallet - CLI app suite:
a CLI bundle for
dcrdanddcrwallet
What is dcrd?
dcrd is a full node implementation of Decred written in Go (golang).
It acts as a fully-validating chain daemon for the Decred cryptocurrency. dcrd maintains the entire past transactional ledger of Decred and allows relaying of transactions to other Decred nodes around the world.
This software is currently under active development. It is extremely stable and has been in production use since February 2016.
It important to note that dcrd does NOT include wallet functionality. Users who desire a wallet will need to use dcrwallet(CLI) or Decrediton(GUI).
What is a full node?
The term 'full node' is short for 'fully-validating node' and refers to software that fully validates all transactions and blocks, as opposed to trusting a 3rd party. In addition to validating transactions and blocks, nearly all full nodes also participate in relaying transactions and blocks to other full nodes around the world, thus forming the peer-to-peer network that is the backbone of the Decred cryptocurrency.
The full node distinction is important, since full nodes are not the only type of software participating in the Decred peer network. For instance, there are 'lightweight nodes' which rely on full nodes to serve the transactions, blocks, and cryptographic proofs they require to function, as well as relay their transactions to the rest of the global network.
Why run dcrd?
As described in the previous section, the Decred cryptocurrency relies on having a peer-to-peer network of nodes that fully validate all transactions and blocks and then relay them to other full nodes.
Running a full node with dcrd contributes to the overall security of the network, increases the available paths for transactions and blocks to relay, and helps ensure there are an adequate number of nodes available to serve lightweight clients, such as Simplified Payment Verification (SPV) wallets.
Without enough full nodes, the network could be unable to expediently serve users of lightweight clients which could force them to have to rely on centralized services that significantly reduce privacy and are vulnerable to censorship.
In terms of individual benefits, since dcrd fully validates every block and transaction, it provides the highest security and privacy possible when used in conjunction with a wallet that also supports directly connecting to it in full validation mode, such as dcrwallet (CLI) and Decrediton (GUI).
Minimum Recommended Specifications (dcrd only)
- 12 GB disk space (as of April 2020, increases over time)
- 2GB memory (RAM)
- ~150MB/day download, ~1.5GB/day upload
- Plus one-time initial download of the entire block chain
- Windows 10 (server preferred), macOS, Linux
- High uptime
Getting Started
So, you've decided to help the network by running a full node. Great! Running dcrd is simple. All you need to do is install dcrd on a machine that is connected to the internet and meets the minimum recommended specifications, and launch it.
Also, make sure your firewall is configured to allow inbound connections to port 9108.
Installing and updating
Binaries (Windows/Linux/macOS)
Binary releases are provided for common operating systems and architectures. The easiest method is to download Decrediton from the link below, which will include dcrd. Advanced users may prefer the Command-line app suite, which includes dcrd and dcrwallet.
https://decred.org/downloads/
- How to verify binaries before installing: https://docs.decred.org/advanced/verifying-binaries/
- How to install the CLI Suite: https://docs.decred.org/wallets/cli/cli-installation/
- How to install Decrediton: https://docs.decred.org/wallets/decrediton/decrediton-setup/
Build from source (all platforms)
Install Dependencies
-
Go 1.14 or 1.15
Installation instructions can be found here: https://golang.org/doc/install. Ensure Go was installed properly and is a supported version:
$ go version $ go env GOROOT GOPATHNOTE:
GOROOTandGOPATHmust not be on the same path. Since Go 1.8 (2016),GOROOTandGOPATHare set automatically, and you do not need to change them. However, you still need to add$GOPATH/binto yourPATHin order to run binaries installed bygo getandgo install(On Windows, this happens automatically).Unix example -- add these lines to .profile:
PATH="$PATH:/usr/local/go/bin" # main Go binaries ($GOROOT/bin) PATH="$PATH:$HOME/go/bin" # installed Go projects ($GOPATH/bin) -
Git
Installation instructions can be found at https://git-scm.com or https://gitforwindows.org.
$ git version
Windows Example
PS> git clone https://github.com/decred/dcrd $env:USERPROFILE\src\dcrd
PS> cd $env:USERPROFILE\src\dcrd
PS> go install . .\cmd\...
PS> dcrd -V
Run the dcrd executable now installed in "$(go env GOPATH)\bin".
Unix Example
This assumes you have already added $GOPATH/bin to your $PATH as described
in dependencies.
$ git clone https://github.com/decred/dcrd $HOME/src/dcrd
$ git clone https://github.com/decred/dcrctl $HOME/src/dcrctl
$ (cd $HOME/src/dcrd && go install . ./...)
$ (cd $HOME/src/dcrctl && go install)
$ dcrd -V
Run the dcrd executable now installed in $GOPATH/bin.
Docker
Running dcrd
You can run a decred node from inside a docker container. To build the image yourself, use the following command:
docker build -t decred/dcrd .
Or you can create an alpine based image (requires Docker 17.05 or higher):
docker build -t decred/dcrd:alpine -f Dockerfile.alpine .
You can then run the image using:
docker run decred/dcrd
You may wish to use an external volume to customize your config and persist the data in an external volume:
docker run --rm -v /home/user/dcrdata:/root/.dcrd/data decred/dcrd
For a minimal image, you can use the decred/dcrd:alpine tag. This is typically a more secure option while also being a much smaller image.
You can run dcrctl from inside the image. For example, run an image (mounting
your data from externally) with:
docker run --rm -ti --name=dcrd-1 -v /home/user/.dcrd:/root/.dcrd \
decred/dcrd:alpine
And then run dcrctl commands against it. For example:
docker exec -ti dcrd-1 dcrctl getbestblock
Running Tests
All tests and linters may be run using the script run_tests.sh. Generally,
Decred only supports the current and previous major versions of Go.
./run_tests.sh
Contact
If you have any further questions you can find us at:
https://decred.org/community/
Issue Tracker
The integrated github issue tracker is used for this project.
Documentation
The documentation for dcrd is a work-in-progress. It is located in the docs folder.
License
dcrd is licensed under the copyfree ISC License.