Add README to metric router

internal/metricRouter/README.md

@@ -0,0 +1,50 @@
+# CC Metric Router
+
+The CCMetric router sits in between the collectors and the sinks and can be used to add and remove tags to/from traversing [CCMetrics](../ccMetric/README.md).
+
+# Configuration
+
+```json
+{
+    "add_tags" : [
+        {
+            "key" : "cluster",
+            "value" : "testcluster",
+            "if" : "*"
+        },
+        {
+            "key" : "test",
+            "value" : "testing",
+            "if" : "name == 'temp_package_id_0'"
+        }
+    ],
+    "delete_tags" : [
+        {
+            "key" : "unit",
+            "value" : "*",
+            "if" : "*"
+        }
+    ],
+    "interval_timestamp" : true
+}
+```
+
+There are three main options `add_tags`, `delete_tags` and `interval_timestamp`. `add_tags` and `delete_tags` are lists consisting of dicts with `key`, `value` and `if`. The `value` can be omitted in the `delete_tags` part as it only uses the `key` for removal. The `interval_timestamp` setting means that a unique timestamp is applied to all metrics traversing the router during an interval.
+
+# Conditional manipulation of tags
+
+The `if` setting allows conditional testing of a single metric like in the example:
+
+```json
+{
+    "key" : "test",
+    "value" : "testing",
+    "if" : "name == 'temp_package_id_0'"
+}
+```
+
+If the CCMetric name is equal to 'temp_package_id_0', it adds an additional tag `test=testing` to the metric.
+
+In order to match all metrics, you can use `*`, so in order to add a flag per default, like the `cluster=testcluster` tag in the example.
+
+