Add an 'exclude_tags' list to the configuration: fix #103

This is usefull to filter out unique tags like host/client id, ...
This may/should be use in combination with the 'histogram' metric_type to avoid loosing metric points.

src/main/java/org/datadog/jmxfetch/Filter.java

@@ -10,6 +10,7 @@ class Filter {
     HashMap<String, Object> filter;
     Pattern domainRegex;
     ArrayList<Pattern> beanRegexes = null;
+    ArrayList<String> excludeTags = null;
 
     /**
      * A simple class to manipulate include/exclude filter elements more easily
@@ -105,6 +106,21 @@ public ArrayList<Pattern> getBeanRegexes() {
         return this.beanRegexes;
     }
 
+    public ArrayList<String> getExcludeTags() {
+        // Return excluded tags  as an ArrayList whether it's defined as a list or not
+
+        if (this.excludeTags == null) {
+            if (filter.get("exclude_tags") == null){
+                this.excludeTags = new ArrayList<String>();
+            } else {
+                final Object exclude_tags = filter.get("exclude_tags");
+                this.excludeTags = toStringArrayList(exclude_tags);
+            }
+        }
+
+        return this.excludeTags;
+    }
+
     public String getDomain() {
         return (String) filter.get("domain");
     }

src/main/java/org/datadog/jmxfetch/JMXAttribute.java

@@ -28,7 +28,7 @@ public abstract class JMXAttribute {
     protected static final String ALIAS = "alias";
     protected static final String METRIC_TYPE = "metric_type";
     private final static Logger LOGGER = Logger.getLogger(JMXAttribute.class.getName());
-    private static final List<String> EXCLUDED_BEAN_PARAMS = Arrays.asList("domain", "domain_regex", "bean_name", "bean", "bean_regex", "attribute");
+    private static final List<String> EXCLUDED_BEAN_PARAMS = Arrays.asList("domain", "domain_regex", "bean_name", "bean", "bean_regex", "attribute", "exclude_tags");
     private static final String FIRST_CAP_PATTERN = "(.)([A-Z][a-z]+)";
     private static final String ALL_CAP_PATTERN = "([a-z0-9])([A-Z])";
     private static final String METRIC_REPLACEMENT = "([^a-zA-Z0-9_.]+)|(^[^a-zA-Z]+)";
@@ -73,6 +73,23 @@ public abstract class JMXAttribute {
         this.defaultTagsList = sanitizeParameters(beanParametersList);
     }
 
+    /**
+     * Remove tags listed in the 'exclude_tags' list from configuration.
+     */
+    private void applyTagsBlackList() {
+        Filter include = this.matchingConf.getInclude();
+        if (include != null) {
+
+            for (String excludedTagName : include.getExcludeTags()) {
+                for (String tag: this.defaultTagsList) {
+                    if (tag.startsWith(excludedTagName + ":")) {
+                        this.defaultTagsList.remove(tag);
+                    }
+                }
+            }
+        }
+    }
+
     public static HashMap<String, String> getBeanParametersHash(String beanParametersString) {
         String[] beanParameters = beanParametersString.split(",");
         HashMap<String, String> beanParamsMap = new HashMap<String, String>(beanParameters.length);
@@ -349,6 +366,9 @@ public Configuration getMatchingConf() {
 
     public void setMatchingConf(Configuration matchingConf) {
         this.matchingConf = matchingConf;
+
+        // Now that we have the matchingConf, we can filter out excluded tags
+        applyTagsBlackList();
     }
 
     MBeanAttributeInfo getAttribute() {

src/test/java/org/datadog/jmxfetch/TestApp.java

@@ -366,6 +366,31 @@ public void testMetricTypes() throws Exception {
         assertMetric("test.counter", 0.0, commonTags, 5, "counter");
     }
 
+    @Test
+    public void testExcludeTags() throws Exception {
+        // We expose a few metrics through JMX
+        SimpleTestJavaApp testApp = new SimpleTestJavaApp();
+        registerMBean(testApp, "org.datadog.jmxfetch.test:type=SimpleTestJavaApp");
+
+        // We do a first collection
+        initApplication("jmx_exclude_tags.yml");
+        run();
+        LinkedList<HashMap<String, Object>> metrics = getMetrics();
+
+        // We test for the presence and the value of the metrics we want to collect.
+        // Tags "type", "newTag" and "env" should be excluded
+        List<String> commonTags = Arrays.asList(
+            "instance:jmx_test_instance",
+            "jmx_domain:org.datadog.jmxfetch.test");
+
+        // 15 = 13 metrics from java.lang + the 2 collected (gauge and histogram)
+        assertEquals(15, metrics.size());
+
+        // There should only left 2 tags per metric
+        assertMetric("test1.gauge", 1000.0, commonTags, 2, "gauge");
+        assertMetric("test1.histogram", 424242, commonTags, 2, "histogram");
+    }
+
     /**
      * FIXME: Split this test in multiple sub-tests.
      */

src/test/resources/jmx_exclude_tags.yml

@@ -0,0 +1,22 @@
+init_config:
+
+instances:
+    -   process_name_regex: .*surefire.*
+        name: jmx_test_instance
+        tags:
+            env: stage
+            newTag: test
+        conf:
+            - include:
+               domain: org.datadog.jmxfetch.test
+               exclude_tags:
+                    - env
+                    - type
+                    - newTag
+               attribute:
+                    ShouldBe1000:
+                        metric_type: gauge
+                        alias: test1.gauge
+                    Int424242:
+                        metric_type: histogram
+                        alias: test1.histogram