source: Alerting/Templates.md

# Templates

Templates can be assigned to a single or a group of rules and can contain any kind of text. There is also a default template which is used for any rule that isn't associated with a template. This template can be found under `Alert Templates` page and can be edited. It also has an option revert it back to its default content. 

The template-parser understands `if` and `foreach` controls and replaces certain placeholders with information gathered about the alert.

## Syntax

Controls:

- if-else (Else can be omitted):
`{if %placeholder == value}Some Text{else}Other Text{/if}`
- foreach-loop:
`{foreach %faults}Key: %key<br/>Value: %value{/foreach}`

Placeholders:

Placeholders are special variables that if used within the template will be replaced with the relevant data, I.e:

`The device %hostname has been up for %uptime seconds` would result in the following `The device localhost has been up for 30344 seconds`.

- Hostname of the Device: `%hostname`
- sysName of the Device: `%sysName`
- location of the Device: `%location`
- uptime of the Device (in seconds): `%uptime`
- short uptime of the Device (28d 22h 30m 7s): `%uptime_short`
- long uptime of the Device (28 days, 22h 30m 7s): `%uptime_long`
- description (purpose db field) of the Device: `%description`
- notes of the Device: `%notes`
- Title for the Alert: `%title`
- Time Elapsed, Only available on recovery (`%state == 0`): `%elapsed`
- Alert-ID: `%id`
- Unique-ID: `%uid`
- Faults, Only available on alert (`%state != 0`), must be iterated in a foreach (`{foreach %faults}`). Holds all available information about the Fault, accessible in the format `%value.Column`, for example: `%value.ifDescr`. Special field `%value.string` has most Identification-information (IDs, Names, Descrs) as single string, this is the equivalent of the default used.
- State: `%state`
- Severity: `%severity`
- Rule: `%rule`
- Rule-Name: `%name`
- Timestamp: `%timestamp`
- Transport name: `%transport`
- Contacts, must be iterated in a foreach, `%key` holds email and `%value` holds name: `%contacts`

Placeholders can be used within the subjects for templates as well although %faults is most likely going to be worthless.

> NOTE: Placeholder names which are contained within another need to be ordered correctly. As an example:

```text
Limit: %value.sensor_limit / %value.sensor_limit_low
```

Should be done as:

```text
Limit: %value.sensor_limit_low / %value.sensor_limit
```

The Default Template is a 'one-size-fit-all'. We highly recommend defining your own templates for your rules to include more specific information.

## Examples

Default Template:
```text
%title
Severity: %severity
{if %state == 0}Time elapsed: %elapsed{/if}
Timestamp: %timestamp
Unique-ID: %uid
Rule: {if %name}%name{else}%rule{/if}
{if %faults}Faults:
{foreach %faults}  #%key: %value.string{/foreach}{/if}
Alert sent to: {foreach %contacts}%value <%key> {/foreach}
```

Conditional formatting example, will display a link to the host in email or just the hostname in any other transport:
```text
{if %transport == mail}<a href="https://my.librenms.install/device/device=%hostname/">%hostname</a>
{else}
%hostname
{/if}
```

Note the use of double-quotes.  Single quotes (`'`) in templates will be escaped (replaced with `\'`) in the output and should therefore be avoided.

## Included

We include a few templates for you to use, these are specific to the type of alert rules you are creating. For example if you create a rule that would alert on BGP sessions then you can 
assign the BGP template to this rule to provide more information.

The included templates apart from the default template are:

  - BGP Sessions
  - Ports
  - Temperature