Add support for gauge deltas.

* Add tests for gauges and new gauge deltas.
* Add support for +/- prefix for gauge values to support modifying
  gauge values in-place.

Author: James Socol

stats.js

@@ -191,7 +191,11 @@ config.configFile(process.argv[2], function (config, oldConfig) {
             timers[key].push(Number(fields[0] || 0));
             timer_counters[key] += (1 / sampleRate);
           } else if (fields[1].trim() == "g") {
-            gauges[key] = Number(fields[0] || 0);
+            if (gauges[key] && fields[0].match(/^[-+]/)) {
+              gauges[key] += Number(fields[0] || 0);
+            } else {
+              gauges[key] = Number(fields[0] || 0);
+            }
           } else if (fields[1].trim() == "s") {
             if (! sets[key]) {
               sets[key] = new set.Set();

test/graphite_tests.js

@@ -298,5 +298,75 @@ module.exports = {
           });
       });
     });
+  },
+
+  gauges_are_valid: function(test) {
+    test.expect(3);
+
+    var testvalue = 70;
+    var me = this;
+    this.acceptor.once('connection', function(c) {
+      statsd_send('a_test_value:' + testvalue + '|g', me.sock, '127.0.0.1', 8125, function() {
+        collect_for(me.acceptor, me.myflush*2, function(strings) {
+          test.ok(strings.length > 0, 'should receive some data');
+          var hashes = _.map(strings, function(x) {
+            var chunks = x.split(' ');
+            var data = {};
+            data[chunks[0]] = chunks[1];
+            return data;
+          });
+          var numstat_test = function(post) {
+            var mykey = 'statsd.numStats';
+            return _.include(_.keys(post), mykey) && (post[mykey] == 1);
+          };
+          test.ok(_.any(hashes, numstat_test), 'statsd.numStats should be 1');
+
+          var gaugevalue_test = function(post) {
+            var mykey = 'stats.gauges.a_test_value';
+            return _.include(_.keys(post), mykey) && (post[mykey] == testvalue);
+          };
+          test.ok(_.any(hashes, gaugevalue_test), 'stats.gauges.a_test_value should be ' + testvalue);
+
+          test.done();
+        });
+      });
+    });
+  },
+
+  gauge_modifications_are_valid: function(test) {
+    test.expect(3);
+
+    var teststartvalue = 50;
+    var testdeltavalue = '-3';
+    var testresult = teststartvalue + Number(testdeltavalue);
+    var me = this;
+    this.acceptor.once('connection', function(c) {
+      statsd_send('test_value:' + teststartvalue + '|g', me.sock, '127.0.0.1', 8125, function() {
+        statsd_send('test_value:' + testdeltavalue + '|g', me.sock, '127.0.0.1', 8125, function() {
+          collect_for(me.acceptor, me.myflush * 2, function(strings) {
+            test.ok(strings.length > 0, 'should receive some data');
+            var hashes = _.map(strings, function(x) {
+              var chunks = x.split(' ');
+              var data = {};
+              data[chunks[0]] = chunks[1];
+              return data;
+            });
+            var numstat_test = function(post) {
+              var mykey = 'statsd.numStats';
+              return _.include(_.keys(post), mykey) && (post[mykey] == 1);
+            };
+            test.ok(_.any(hashes, numstat_test), 'statsd.numStats should be 1');
+
+            var gaugevalue_test = function(post) {
+              var mykey = 'stats.gauges.test_value';
+              return _.include(_.keys(post), mykey) && (post[mykey] == testresult);
+            };
+            test.ok(_.any(hashes, gaugevalue_test), 'stats.gauges.test_value should be ' + testresult);
+
+            test.done();
+          });
+        });
+      });
+    });
   }
 }