Add the --exclude CLI option for filtering out unwanted consumer groups

Fixes #34

src/main/groovy/com/github/lookout/verspaetung/Main.groovy

@@ -38,6 +38,7 @@ class Main {
         String statsdHost = 'localhost'
         Integer statsdPort = 8125
         Integer delayInSeconds = 5
+        String[] excludeGroups = []
 
         CommandLine cli = parseCommandLine(args)
 
@@ -57,6 +58,10 @@ class Main {
             delayInSeconds = cli.getOptionValue('d').toInteger()
         }
 
+        if (cli.hasOption('x')) {
+            excludeGroups = cli.getOptionValues('x')
+        }
+
         logger.info("Running with: ${args}")
         logger.warn('Using: zookeepers={} statsd={}:{}', zookeeperHosts, statsdHost, statsdPort)
         logger.info('Reporting every {} seconds', delayInSeconds)
@@ -106,7 +111,9 @@ class Main {
          * one
          */
         Closure gaugeRegistrar = { KafkaConsumer consumer ->
-            registerMetricFor(consumer, consumerGauges, consumerOffsets, topicOffsets)
+            if (!shouldExcludeConsumer(excludeGroups, consumer)) {
+                registerMetricFor(consumer, consumerGauges, consumerOffsets, topicOffsets)
+            }
         }
 
         StandardTreeWatcher consumerWatcher = new StandardTreeWatcher(client,
@@ -158,6 +165,9 @@ class Main {
                                   ConcurrentHashMap<KafkaConsumer, ConsumerGauge> consumerGauges,
                                   ConcurrentHashMap<KafkaConsumer, Integer> consumerOffsets,
                                   ConcurrentHashMap<TopicPartition, Long> topicOffsets) {
+        /*
+         * Bail early if we already ahve our Consumer registered
+         */
         if (consumerGauges.containsKey(consumer)) {
             return
         }
@@ -183,6 +193,12 @@ class Main {
                                         .withValueSeparator(',' as char)
                                         .create('z')
 
+        Option excludeGroups = OptionBuilder.withArgName('EXCLUDES')
+                                            .hasArgs()
+                                            .withDescription('Regular expression for consumer groups to exclude from reporting (can be declared multiple times)')
+                                            .withLongOpt('exclude')
+                                            .create('x')
+
         Option statsdHost = OptionBuilder.withArgName('STATSD')
                                          .hasArg()
                                          .withType(String)
@@ -226,6 +242,7 @@ class Main {
         options.addOption(dryRun)
         options.addOption(stormSpouts)
         options.addOption(delaySeconds)
+        options.addOption(excludeGroups)
 
         return options
     }
@@ -249,4 +266,12 @@ class Main {
             System.exit(1)
         }
     }
+
+    /**
+     * Return true if we should exclude the given KafkaConsumer from reporting
+     */
+
+    static boolean shouldExcludeConsumer(String[] excludeGroups, KafkaConsumer consumer) {
+        return null != excludeGroups?.find { String excludeRule -> consumer?.name.matches(excludeRule) }
+    }
 }

src/test/groovy/com/github/lookout/verspaetung/MainSpec.groovy

@@ -0,0 +1,49 @@
+package com.github.lookout.verspaetung
+
+
+import spock.lang.*
+
+/**
+ */
+class MainSpec extends Specification {
+    def "shouldExcludeGroups() shuold return false by default"() {
+        expect:
+        Main.shouldExcludeConsumer(new String[0], null) == false
+    }
+
+    def "shouldExcludeGroups() with a matching exclude should return true"() {
+        given:
+        final String[] groups = ['foo'] as String[]
+        final KafkaConsumer consumer = new KafkaConsumer('spock-topic', 0, 'foo')
+
+        expect:
+        Main.shouldExcludeConsumer(groups, consumer)
+    }
+
+    def "shouldExcludeGroups() with a matching regex should return true"() {
+        given:
+        final String[] groups = ['.*foo'] as String[]
+        final KafkaConsumer consumer = new KafkaConsumer('spock-topic', 0, 'spockfoo')
+
+        expect:
+        Main.shouldExcludeConsumer(groups, consumer)
+    }
+
+    def "shouldExcludeGroups() with multiple regexes that don't match should return false"() {
+        given:
+        final String[] groups = ['.*foo', 'bar(.*)'] as String[]
+        final KafkaConsumer consumer = new KafkaConsumer('spock-topic', 0, 'spock')
+
+        expect:
+        Main.shouldExcludeConsumer(groups, consumer) == false
+    }
+
+    def "shouldExcludeGroups() with multiple regexes which match should return true"() {
+        given:
+        final String[] groups = ['.*foo', 'bar(.*)'] as String[]
+        final KafkaConsumer consumer = new KafkaConsumer('spock-topic', 0, 'barstool')
+
+        expect:
+        Main.shouldExcludeConsumer(groups, consumer)
+    }
+}