Create documentation about metric creation.

docs/metrics/create-metric.md

@@ -0,0 +1,54 @@
+# Create a metric
+
+This documentation will guide you through the metric creation.  
+You need to know [what is a metric][1].
+
+## Filling the form
+
+Creating a metric is as simple as filling a form. You just need to know what do
+the fields mean.
+
+To access to the metrics creation, follow these steps:
+
+- Log into your Cachet instance.
+- Once on the Dashboard click `Metrics` in the sidebar.
+- Click the `Create a metric` button.
+
+And you are there! You should be able to see the metric form.  
+Let's explain the fields:
+
+- `Name`: The name of the metric as it will be shown on the status page.
+  Example: "API response time".
+- `Suffix`: The suffix that will be added in the tooltip when you put your mouse
+  over the point on the metric. Usually it's the unit of the raw data. Example:
+  "ms". If you send "42" to the metric, then "42ms" would be show in the
+  tooltip.
+- `Description`: A description of the metric. What is the usage of the metric?
+  What does it measure? Example: "The average response time of our API".
+- `Calculation of metrics`: What computation should be done on your data before
+  displaying them in the metric? It may be either _Sum_ or _Average_. Example:
+  _Average_ to compute the average reponse time for a given time.
+- `Default view`: The default view of the metric. Viewing the datas of 1 year
+  ago is not useful, but it's about your preference to see datas of the last
+  hour, 12 hours, week or month. Example: _Last 12 hours_ because you want to
+  see the last 12 hours of data by default. It's only the default view, this can
+  be changed in a select box.
+- `Decimal places` The number of decimal of the point that is displayed. If you
+  are computing the average of something it's almost sure that you'll get an
+  average with a coma, line 42,424242. Example: 2 to get 42,42 instead of a long
+  number.
+- `How many minutes of threshold between metric points?`: The number of minutes
+  between the points in the metric. According to your needs it may be 1, 5 or
+  even 30. It's really up to you. Example: 60 to get one point every hour.
+- `Display chart on the status page?`: If checked, this chart will be displayed
+  on the status page. But it's possible to create the metric and not showing it.
+- `Visibility`: Who should be able to see the chart? You have three choices:
+    - `Visible to authenticated users`: It means that people won't be able to
+      see it except if they are authenticated. Useful if it's an internal metric.
+    - `Visible to everybody`: It means that every user, even not authenticated,
+      will be able to see the chart.
+    - `Always hidden`: It means that nobody will be able to see the chart.
+
+
+
+[1]: index.md