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HeaderSV-core module

The HeaderSV-core module contains the business logic of HeaderSV, and its distributed as a Java Library (JAR) which can be easily added to other project, so we can get real-time information about the headers in the blockchain and use that info in our code.

The functionalities provided by this module are:

  • Connection to the blockchain and automatic synchronization of headers in the background.
  • Streaming of Events with the possibility to subscribe to them, so we can get notified when the Tips of the chain have changed or whether we are already up-to-date with the latest block.
  • It provides an API we can use to retrieve information about the Chain, common ancestors to specific Blocks, or basic information about the Peers we are connected to.

this module does NOT include a REST Api or a webserver. Its meant to be used as another Service that can be included in any application. If you also need a REST api to expose its API capabilities, check out the headerSV-rest module

How to use headerSV-core (gradle)

Declare the dependencies

headerSV-core has dependencies on both BitcoinJ-SV and the Java Component Library (JCL), so the best approach is to define the version numbers of each one in your gradle.properties file:

# BitcoinJ dependency:
bitcoinJVersion=1.0.4

# JCL dependency:
JCLVersion=2.3.2

# headerSV dependency:
headerSVVersion=2.1.0

, and then you reference them in your build.gradle file:

// bitcoinJ modules
implementation "io.bitcoinsv.bitcoinjsv:bitcoinj-base:$bitcoinJVersion"

// jcl Modules
implementation "io.bitcoinsv.jcl:jcl-net:$JCLVersion"
implementation "io.bitcoinsv.jcl:jcl-tools:$JCLVersion"
implementation "io.bitcoinsv.jcl:jcl-store:$JCLVersion"
implementation "io.bitcoinsv.jcl:jcl-store-keyValue:$JCLVersion"
implementation "io.bitcoinsv.jcl:jcl-store-levelDB:$JCLVersion"

// HeaderSV Modules
implementation "io.bitcoinsv.headerSV:headerSV-core:$headerSVVersion"

Initialize the HeaderSV Service

The headerSV-core module is composed internally of 2 different services:

  • a Network service, which connects to the network, implements the bitcoin Protocol and deals with all the logic behind messages exchange, connections and serialization
  • a Storage Service, which stores locally all the info retrieved, in this case the Block Headers and also metadata and other information about the blockchain.

Each of the Services above has a configuration class we need to configure first, afer than we can initialize the services:

// Network/blockchain we connect to:
Net net = Net.MAINNET;

// Services Configuration:
NetworkConfiguration networkConfig = NetworkConfiguration.builder()
                .net(Net.MAINNET)
                .minPeers(10)
                .maxPeers(15)
                .build();
StorageConfiguration storageConfig = StorageConfiguration.builder()
                .net(Net.MAINNET)
                .forkPrunningEnabled(true)
                .pruneAfterConfirmations(7)
                .build();
                
// General HeaderSV-core Configuration:
HeaderSvConfig headerSvConfig = HeaderSvConfig.of(net);

// We initialize and link the Services together:
NetworkService networkService = new NetworkServiceImpl(networkConfiguration);
StorageService storeService = new StorageServiceImpl(networkConfiguration, storageConfiguration);
HeaderSvService headerSVService = new HeadersSvServiceImpl(headerSvConfig, networkService, storeService);

Run the HeaderSV Service

After the HeaderSV Service is initialize, we can start and leave it running in the background, while we subscribe to some events so we can react to them:

// Before starting the Service, we subscribe to some events:

// Event triggered every time our Tips are updated buy a new Block being nnounced:
headerSVService.EVENTS().TIPS_UPDATED().forEach(e -> {
   System.out.println("TIPS_UPDATED: " + e.getUpdatedTips().size() + " tips, " + e.getNewHeaders().size() + " new headers");
});

// Event triggered when we have cought up with the tip opf the chain and are are in sync with the network
headerSVService.EVENTS().CHAIN_SYNCHRONIZED().forEach(e -> {
   System.out.println("CHAIN_SYNCHRONIZED");

});

// Now we start the Servie and keep it running for some time:
headerSVService.start();
Thread.sleep(10_000); // Events will be triggered during this time...
headerSVService.stop();

While the Service is running we can also access the API and get some information:

headerSVService.start();
headerSVService.API().getBlockHeader("000000000000000007f887a516edbe38aa0471d086eab7b916d429c9f6eac821");
headerSVService.API().getHeadersByHeight(8000, 500);
// etc...
headerSVService.stop();

Database

The default location for the networking & storage database can be located at ~/tmp/jcl.