jmx-scraper add missing custom yaml support

jmx-scraper/src/integrationTest/java/io/opentelemetry/contrib/jmxscraper/JmxScraperContainer.java

@@ -100,6 +100,12 @@ public JmxScraperContainer withExtraJar(String jarPath) {
     return this;
   }
 
+  /**
+   * Adds custom metrics yaml from classpath resource
+   *
+   * @param yamlPath path to resource in classpath
+   * @return this
+   */
   @CanIgnoreReturnValue
   public JmxScraperContainer withCustomYaml(String yamlPath) {
     this.customYamlFiles.add(yamlPath);

jmx-scraper/src/integrationTest/java/io/opentelemetry/contrib/jmxscraper/target_systems/JvmIntegrationTest.java

@@ -30,7 +30,10 @@ protected GenericContainer<?> createTargetContainer(int jmxPort) {
   @Override
   protected JmxScraperContainer customizeScraperContainer(
       JmxScraperContainer scraper, GenericContainer<?> target, Path tempDir) {
-    return scraper.withTargetSystem("jvm");
+    return scraper
+        .withTargetSystem("jvm")
+        // also testing custom yaml
+        .withCustomYaml("custom-metrics.yaml");
   }
 
   @Override
@@ -48,6 +51,16 @@ protected MetricsVerifier createMetricsVerifier() {
         nameAttributeMatchers("PS MarkSweep", "PS Scavenge");
 
     return MetricsVerifier.create()
+        // custom metric in custom-metrics.yaml
+        .add(
+            "custom.jvm.uptime",
+            metric ->
+                metric
+                    .hasDescription("JVM uptime in milliseconds")
+                    .hasUnit("ms")
+                    .isCounter()
+                    .hasDataPointsWithoutAttributes())
+        // metrics for 'jvm' target system
         .add(
             "jvm.classes.loaded",
             metric ->

jmx-scraper/src/integrationTest/resources/custom-metrics.yaml

@@ -0,0 +1,11 @@
+---
+
+rules:
+
+  - bean: java.lang:type=Runtime
+    mapping:
+      Uptime:
+        metric: custom.jvm.uptime
+        type: counter
+        unit: ms
+        desc: JVM uptime in milliseconds

jmx-scraper/src/main/java/io/opentelemetry/contrib/jmxscraper/JmxScraper.java

@@ -18,6 +18,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -225,7 +226,9 @@ private static MetricConfiguration getMetricConfig(JmxScraperConfig scraperConfi
     for (String system : scraperConfig.getTargetSystems()) {
       addRulesForSystem(system, config);
     }
-    // TODO : add ability for user to provide custom yaml configurations
+    for (String file : scraperConfig.getJmxConfig()) {
+      addRulesFromFile(file, config);
+    }
     return config;
   }
 
@@ -234,13 +237,25 @@ private static void addRulesForSystem(String system, MetricConfiguration conf) {
     try (InputStream inputStream =
         JmxScraper.class.getClassLoader().getResourceAsStream(yamlResource)) {
       if (inputStream != null) {
-        RuleParser parserInstance = RuleParser.get();
-        parserInstance.addMetricDefsTo(conf, inputStream, system);
+        RuleParser.get().addMetricDefsTo(conf, inputStream, system);
       } else {
         throw new IllegalArgumentException("No support for system " + system);
       }
     } catch (Exception e) {
       throw new IllegalStateException("Error while loading rules for system " + system, e);
     }
   }
+
+  private static void addRulesFromFile(String file, MetricConfiguration conf) {
+    Path path = Paths.get(file);
+    if (!Files.isReadable(path)) {
+      throw new IllegalArgumentException("Unable to read file: " + path);
+    }
+
+    try (InputStream inputStream = Files.newInputStream(path)) {
+      RuleParser.get().addMetricDefsTo(conf, inputStream, file);
+    } catch (IOException e) {
+      throw new IllegalArgumentException("Error while loading rules from file: " + file, e);
+    }
+  }
 }