Use git submodules to load metrics.yaml files

Author: tylerbenson

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "dd-java-agent/agent-jmxfetch/integrations-core"]
+	path = dd-java-agent/agent-jmxfetch/integrations-core
+	url = https://github.com/DataDog/integrations-core.git

dd-java-agent/agent-jmxfetch/agent-jmxfetch.gradle

@@ -27,3 +27,19 @@ shadowJar {
 jar {
   classifier = 'unbundled'
 }
+
+task submodulesUpdate(type:Exec) {
+  group 'Build Setup'
+  description 'Initializes and updates integrations-core git submodule'
+  commandLine 'git', 'submodule', 'update', '--init', 'integrations-core'
+}
+
+task copyMetricConfigs(type:Exec) {
+  group 'Build Setup'
+  description 'Copy metrics.yaml files from integrations-core into resources'
+  commandLine './copy-metric-configs.sh', 'integrations-core', sourceSets.main.output.resourcesDir
+}
+
+processResources.dependsOn copyMetricConfigs
+copyMetricConfigs.dependsOn submodulesUpdate
+// Runs the copy task before processResources, so duplicate files in the local repo would overwrite imported ones.

dd-java-agent/agent-jmxfetch/copy-metric-configs.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+
+# Debug mode:
+# set -x
+
+function print_usage() {
+  echo "Usage: $0 search_directory build_resources_output_directory"
+}
+
+search_directory=$1
+if [ ! -d "$search_directory" ]; then
+  echo "Must specify a valid search_directory"
+  print_usage
+  exit 1
+fi
+
+build_resources_output_directory=$2
+if [ ! -d "$build_resources_output_directory" ]; then
+  echo "Must specify a valid build_resources_output_directory"
+  print_usage
+  exit 1
+fi
+# Add the full package path.
+build_resources_output_directory="$build_resources_output_directory/datadog/trace/agent/jmxfetch"
+
+# Find all the metrics.yaml files containing "jmx_metrics:"
+metrics_files=$(grep --include=metrics.yaml -rwl $search_directory -e 'jmx_metrics:')
+
+if [ -z "$metrics_files" ]; then
+  echo "No metrics.yaml files with jmx_metrics blocks found."
+  print_usage
+  exit 1
+fi
+
+# reset file and ensure directories exists
+> $build_resources_output_directory/metricconfigs.txt
+mkdir -p $build_resources_output_directory/metricconfigs
+
+for input_file in $metrics_files ; do
+  # generate new name based on integration folder name which should look like this:
+  # integrations-core/<integration_name>/datadog_checks/<integration_name>/data/metrics.yaml
+  output_file=$(echo "$input_file" | awk -F/ '{print $2}')
+
+  # save file name in metricconfigs.txt
+  echo "$output_file.yaml" >> $build_resources_output_directory/metricconfigs.txt
+
+  # copy to output location
+  output_file="$build_resources_output_directory/metricconfigs/$output_file.yaml"
+  cp $input_file $output_file
+done
+

dd-java-agent/agent-jmxfetch/integrations-core

@@ -1,8 +1,8 @@
 # Metric Configs
 
-These files are copied directly from [integrations-core](https://github.com/DataDog/integrations-core/search?q=jmx_metrics&unscoped_q=jmx_metrics)
-where the only modification is updating the file name.
+Files from [integrations-core](https://github.com/DataDog/integrations-core/search?q=jmx_metrics&unscoped_q=jmx_metrics)
+are copied here at build time by the `copy-metric-configs.sh` script which is called by gradle after initializing the submodule.
 
-These will be bundled in `dd-java-agent.jar`. Due to limitations in Java, it is non-trivial
+These are then bundled in `dd-java-agent.jar`. Due to limitations in Java, it is non-trivial
 to get all these files from within the jar without knowing their names.
 Consequently, we list out each integration in `metricconfigs.txt` so the agent can reference them.