support mapNameToDimensionsFn map

README.md

@@ -155,6 +155,71 @@ you can use the `instances` key under `cloudwatch` to configure a list of config
         }
     }
 
+## Mapping a Graphite key to a metric name + dimension
+
+You can map a metric key name to a new metricName and to a set of
+dimensions to pass to CloudWatch. For example if you have a
+graphite-like keys in the form:
+
+SERVICE_TYPE.INSTANCE_ID.connections.CONNECTION_ID.METRIC_NAME
+
+you might want to map this name to a corresponding CloudWatch metric
+with METRIC with dimensions serviceType, instanceId, connectionId
+and the metric value.
+
+For example if you have:
+
+prod.i-deadbeef42.connections.123.errors
+
+You may want to generate a metric with name "errors" and the following
+dimensions:
+
+     [
+        { Name: "serviceType", Value: "prod" },
+        { Name: "instanceId",  Value: "i-deadbeef42" },
+        { Name: "serviceType",  Value: "123" },
+     ]
+
+This can be done by defining a mapping function in the configuration
+mapNameToDimensionsFn field.
+
+The mapNameToDimensionsFn function must accept a function taking a
+metricName and a metricType (either "count" or "gauge" or "timer" or
+"set"), and returning an object in the form { metricName,
+metricDimensions } or null in case you want to skip to send the metric
+altogether.
+metricDimensions must be an array in the form [ { "Name": ...,
+"Value": ...}, ...,  { "Name:" ..., "Value: ... } ].
+
+Continuing with the former example, a valid implementation would be:
+
+        mapNameToDimensionsFn: function (metricName, metricType) {
+            // ignore the metricType
+
+            var dimensions = [];
+            var origMetricName = metricName;
+
+            console.log("matching: " + metricName);
+
+            if ((res = /([^.]+)\.([^.]+)\.connections\.([^.]+)\.(.*)/g.exec(metricName)) != null) {
+                // match rule: SERVICE_TYPE.INSTANCE_ID.connections.CONNECTION_ID.METRIC_NAME
+                dimensions = [
+                    { Name: "serviceType", Value: res[1] },
+                    { Name: "instanceId", Value: res[2] },
+                    { Name: "connectionId", Value: res[3] },
+                ];
+                metricName = res[4];
+            }
+            else {
+		console.log("discarding metric " + metricName);
+		return null;
+	    }
+
+            var res = { metricName: metricName, metricDimensions: dimensions };
+            console.log(origMetricName + " => " + JSON.stringify(res));
+            return res;
+        }
+
 
 ## Tutorial
 

lib/aws-cloudwatch-statsd-backend.js

@@ -55,6 +55,7 @@ CloudwatchBackend.prototype.flush = function(timestamp, metrics) {
   var gauges = metrics.gauges;
   var timers = metrics.timers;
   var sets = metrics.sets;
+  var mapFn = this.config.mapNameToDimensionsFn;
 
   for (key in counters) {
 	  if (key.indexOf('statsd.') == 0)
@@ -68,10 +69,22 @@ CloudwatchBackend.prototype.flush = function(timestamp, metrics) {
     var names = this.config.processKeyForNamespace ? this.processKey(key) : {};
     var namespace = this.config.namespace || names.namespace || "AwsCloudWatchStatsdBackend";
     var metricName = this.config.metricName || names.metricName || key;
+    var metricDimensions = [];
+    var mapRes;
+
+    if (mapFn) {
+        mapRes = mapFn(metricName, "count");
+        if (!mapRes) // skip this
+            continue;
+
+        metricName = mapRes.metricName;
+        metricDimensions = mapRes.metricDimensions;
+    }
 
     this.cloudwatch.putMetricData({
       MetricData : [{
-                     MetricName : metricName,
+      MetricName : metricName,
+      Dimensions: metricDimensions,
       Unit : 'Count',
       Timestamp: new Date(timestamp*1000).toISOString(),
       Value : counters[key]
@@ -105,7 +118,7 @@ CloudwatchBackend.prototype.flush = function(timestamp, metrics) {
       var sum = min;
       var mean = min;
       var maxAtThreshold = max;
-
+      var metricDimensions = [];
       var message = "";
 
       var key2;
@@ -117,9 +130,20 @@ CloudwatchBackend.prototype.flush = function(timestamp, metrics) {
       var namespace = this.config.namespace || names.namespace || "AwsCloudWatchStatsdBackend";
       var metricName = this.config.metricName || names.metricName || key;
 
+      if (mapFn) {
+        mapRes = mapFn(metricName, "timer");
+
+        if (!mapRes) // skip this
+          continue;
+
+        metricName = mapRes.metricName;
+        metricDimensions = mapRes.metricDimensions;
+      }
+
       this.cloudwatch.putMetricData({
         MetricData : [{
           MetricName : metricName,
+          Dimensions: metricDimensions,
           Unit : 'Milliseconds',
           Timestamp: new Date(timestamp*1000).toISOString(),
           StatisticValues: {
@@ -148,10 +172,21 @@ CloudwatchBackend.prototype.flush = function(timestamp, metrics) {
     var names = this.config.processKeyForNamespace ? this.processKey(key) : {};
     var namespace = this.config.namespace || names.namespace || "AwsCloudWatchStatsdBackend";
     var metricName = this.config.metricName || names.metricName || key;
+    var metricDimensions = [];
+
+    if (mapFn) {
+        mapRes = mapFn(metricName, "gauge");
+        if (!mapRes) // skip this
+          continue;
+
+      metricName = mapRes.metricName;
+      metricDimensions = mapRes.metricDimensions;
+    }
 
     this.cloudwatch.putMetricData({
       MetricData : [{
-                     MetricName : metricName,
+      MetricName : metricName,
+      Dimensions: metricDimensions,
       Unit : 'None',
       Timestamp: new Date(timestamp*1000).toISOString(),
       Value : gauges[key]
@@ -175,10 +210,21 @@ CloudwatchBackend.prototype.flush = function(timestamp, metrics) {
     var names = this.config.processKeyForNamespace ? this.processKey(key) : {};
     var namespace = this.config.namespace || names.namespace || "AwsCloudWatchStatsdBackend";
     var metricName = this.config.metricName || names.metricName || key;
+    var metricDimensions = [];
+
+    if (mapFn) {
+      mapRes = mapFn(metricName, "set");
+      if (!mapRes) // skip this
+        continue;
+
+      metricName = mapRes.metricName;
+      metricDimensions = mapRes.metricDimensions;
+    }
 
     this.cloudwatch.putMetricData({
       MetricData : [{
-                     MetricName : metricName,
+      MetricName : metricName,
+      Dimensions: metricDimensions,
       Unit : 'None',
       Timestamp: new Date(timestamp*1000).toISOString(),
       Value : sets[key].values().length