prometheus
Fix resolved header in email template
Background
We use a custom email template based on alertmanager/template/email.tmpl.
Problem
The email template for resolved messages currently has a styling issue. Due to an extra </td>, the green heading is only shown in the top right corner, instead of covering the full width.
Solution
Removing the extra </td> solves the issue.
template/email.tmpl gets generated from template/email.html via the template/inline-css.js script which uses juice under the hood to inline the CSS properies into the style attributes.
IIUC juice is confused by this part and adds the extra </td>
https://github.com/prometheus/alertmanager/blob/dcc92eda2ecbb96948c1e864338bfbf32ce8885b/template/email.html#L326-L334
One way to fix it would be to duplicate the range loop like this:
{{ if gt (len .Alerts.Firing) 0 }}
<td class="alert alert-warning">
{{ .Alerts | len }} alert{{ if gt (len .Alerts) 1 }}s{{ end }} for {{ range .GroupLabels.SortedPairs }}
{{ .Name }}={{ .Value }}
{{ end }}
</td>
{{ else }}
<td class="alert alert-good">
{{ .Alerts | len }} alert{{ if gt (len .Alerts) 1 }}s{{ end }} for {{ range .GroupLabels.SortedPairs }}
{{ .Name }}={{ .Value }}
{{ end }}
</td>
{{ end }}
