OpenSearch/x-pack/plugin/ml/cpp-snapshot/build.gradle

import java.net.HttpURLConnection
import org.elasticsearch.gradle.VersionProperties

apply plugin: 'distribution'

ext.version = VersionProperties.elasticsearch

// This project pulls a snapshot version of the ML cpp artifacts and sets that as the artifact
// for this project so it can be used with dependency substitution.

void getZip(File snapshotZip) {
  String zipUrl = "http://prelert-artifacts.s3.amazonaws.com/maven/org/elasticsearch/ml/ml-cpp/${version}/ml-cpp-${version}.zip"
  File snapshotMd5 = new File(snapshotZip.toString() + '.md5')
  HttpURLConnection conn = (HttpURLConnection) new URL(zipUrl).openConnection();
  
  // do a HEAD first to check the zip hash against the local file
  conn.setRequestMethod('HEAD');
  if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
    throw new GradleException('ML cpp snapshot does not exist')
  }

  String remoteMd5 = conn.getHeaderField('ETag')
  if (snapshotZip.exists()) {
    // do a HEAD first to check the zip hash against the local file
    String localMd5 = snapshotMd5.getText('UTF-8')
    if (remoteMd5.equals(localMd5)) {
      logger.info('Using cached ML snapshot')
      return
    }
  }

  snapshotZip.bytes = new URL(zipUrl).bytes
  snapshotMd5.setText(remoteMd5, 'UTF-8')
}

File snapshotZip = new File(projectDir, ".cache/ml-cpp-${version}.zip")
task downloadMachineLearningSnapshot {
  onlyIf {
    // skip if ml-cpp is being built locally
    findProject(':ml-cpp') == null &&
      // skip for offline builds - just rely on the artifact already having been downloaded before here
      project.gradle.startParameter.isOffline() == false
  }
  doFirst {
    snapshotZip.parentFile.mkdirs()
    getZip(snapshotZip)
  }
}

artifacts {
  'default' file: snapshotZip, name: 'ml-cpp', type: 'zip', builtBy: downloadMachineLearningSnapshot
}