1 files changed, 121 insertions, 0 deletions
diff --git a/scripts/download-downstream-artifact.rb b/scripts/download-downstream-artifact.rb
new file mode 100755
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+++ b/scripts/download-downstream-artifact.rb
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+#!/usr/bin/env ruby
+
+# frozen_string_literal: true
+
+require 'gitlab'
+
+require_relative 'api/default_options'
+
+# This class allows an upstream job to fetch an artifact from a job in a downstream pipeline.
+#
+# Until https://gitlab.com/gitlab-org/gitlab/-/issues/285100 is resolved it's not straightforward for an upstream
+# pipeline to use artifacts from a downstream pipeline. There is a workaround for parent-child pipelines (see the issue)
+# but it relies on CI_MERGE_REQUEST_REF_PATH so it doesn't work for multi-project pipelines.
+#
+# This uses the Jobs API to get pipeline bridges (trigger jobs) and the Job artifacts API to download artifacts.
+# - https://docs.gitlab.com/ee/api/jobs.html#list-pipeline-trigger-jobs
+# - https://docs.gitlab.com/ee/api/job_artifacts.html
+#
+# Note: This class also works for parent-child pipelines within the same project, it's just not necessary in that case.
+class DownloadDownstreamArtifact
+  def initialize(options)
+    @upstream_project = options.fetch(:upstream_project, API::DEFAULT_OPTIONS[:project])
+    @upstream_pipeline_id = options.fetch(:upstream_pipeline_id, API::DEFAULT_OPTIONS[:pipeline_id])
+    @downstream_project = options.fetch(:downstream_project, API::DEFAULT_OPTIONS[:project])
+    @downstream_job_name = options.fetch(:downstream_job_name)
+    @trigger_job_name = options.fetch(:trigger_job_name)
+    @downstream_artifact_path = options.fetch(:downstream_artifact_path)
+    @output_artifact_path = options.fetch(:output_artifact_path)
+
+    unless options.key?(:api_token)
+      raise ArgumentError, 'PROJECT_TOKEN_FOR_CI_SCRIPTS_API_USAGE is required to access downstream pipelines'
+    end
+
+    api_token = options.fetch(:api_token)
+
+    @client = Gitlab.client(
+      endpoint: options.fetch(:endpoint, API::DEFAULT_OPTIONS[:endpoint]),
+      private_token: api_token
+    )
+  end
+
+  def execute
+    unless downstream_pipeline
+      abort("Could not find downstream pipeline triggered via #{trigger_job_name} in project #{downstream_project}")
+    end
+
+    unless downstream_job
+      abort("Could not find job with name '#{downstream_job_name}' in #{downstream_pipeline['web_url']}")
+    end
+
+    puts "Fetching scores artifact from downstream pipeline triggered via #{trigger_job_name}..."
+    puts "Downstream pipeline is #{downstream_pipeline['web_url']}."
+    puts %(Downstream job "#{downstream_job_name}": #{downstream_job['web_url']}.)
+
+    path = downstream_artifact_path.sub('DOWNSTREAM_JOB_ID', downstream_job.id.to_s)
+    puts %(Fetching artifact "#{path}" from #{downstream_job_name}...)
+
+    download_and_save_artifact(path)
+
+    puts "Artifact saved as #{output_artifact_path} ..."
+  end
+
+  def self.options_from_env
+    API::DEFAULT_OPTIONS.merge({
+      upstream_project: API::DEFAULT_OPTIONS[:project],
+      upstream_pipeline_id: API::DEFAULT_OPTIONS[:pipeline_id],
+      downstream_project: ENV.fetch('DOWNSTREAM_PROJECT', API::DEFAULT_OPTIONS[:project]),
+      downstream_job_name: ENV['DOWNSTREAM_JOB_NAME'],
+      trigger_job_name: ENV['TRIGGER_JOB_NAME'],
+      downstream_artifact_path: ENV['DOWNSTREAM_JOB_ARTIFACT_PATH'],
+      output_artifact_path: ENV['OUTPUT_ARTIFACT_PATH']
+    }).except(:project, :pipeline_id)
+  end
+
+  private
+
+  attr_reader :downstream_artifact_path,
+    :output_artifact_path,
+    :downstream_job_name,
+    :trigger_job_name,
+    :upstream_project,
+    :downstream_project,
+    :upstream_pipeline_id,
+    :client
+
+  def bridge
+    @bridge ||= client
+      .pipeline_bridges(upstream_project, upstream_pipeline_id, per_page: 100)
+      .auto_paginate
+      .find { |job| job.name.include?(trigger_job_name) }
+  end
+
+  def downstream_pipeline
+    @downstream_pipeline ||=
+      if bridge&.downstream_pipeline.nil?
+        nil
+      else
+        client.pipeline(downstream_project, bridge.downstream_pipeline.id)
+      end
+  end
+
+  def downstream_job
+    @downstream_job ||= client
+      .pipeline_jobs(downstream_project, downstream_pipeline.id)
+      .find { |job| job.name.include?(downstream_job_name) }
+  end
+
+  def download_and_save_artifact(job_artifact_path)
+    file_response = client.download_job_artifact_file(downstream_project, downstream_job.id, job_artifact_path)
+
+    file_response.respond_to?(:read) || abort("Could not download artifact. Request returned: #{file_response}")
+
+    File.write(output_artifact_path, file_response.read)
+  end
+end
+
+if $PROGRAM_NAME == __FILE__
+  options = DownloadDownstreamArtifact.options_from_env
+
+  DownloadDownstreamArtifact.new(options).execute
+end