Description Template

Use an alert rule Description to define the text shown on firing and recovery events. You can reference alert labels, query values, related query results, and safe Sprig functions with Go text/template, then render the result as Text or Markdown.

The template variables, Sprig function names, and behavior where label enrichment runs before Description rendering require monit-edge v0.42.0 or later. On older versions, some variables or functions may be unavailable, and enrichment results may not be available inside Description templates.

How It Works

When a rule fires or recovers, monit-edge passes the full alert event as the template root object and injects short variables for common fields. After label enrichment completes, monit-edge renders the template with the enriched event, writes the result to the event Description, and then sends the event.

For day-to-day templates, prefer $labels, $values, $value, $relates, $status, and $checkMode. Use the other short variables only for advanced templates or compatibility cases.

Sprig Function Names

monit-edge registers safe Sprig functions with their standard Sprig names. The same supported functions are also registered with a sprig_ prefix so templates can avoid naming conflicts when needed. Use:

{{ contains "Unknown column" $msg }}
{{ regexMatch "Unknown column" $msg }}
{{ regexFind "Unknown column '[^']+'" $msg }}

The prefixed form is also valid:

{{ sprig_contains "Unknown column" $msg }}
{{ sprig_regexMatch "Unknown column" $msg }}
{{ sprig_regexFind "Unknown column '[^']+'" $msg }}

If a standard Sprig name conflicts with a monit-edge custom function, the monit-edge custom function keeps the standard name and the Sprig function remains available through the sprig_ prefix.

Built-in Variables

Variable	Type	Description
`$labels`	`map[string]string`	Alert labels. Same data as `.DataLabels`.
`$values`	`map[string]float64`	Numeric values used by alert evaluation. Same data as `.Values`.
`$value`	`float64`	Main alert value. Same data as `.Value`.
`$appendLabels`	`map[string]string`	Extra labels configured on the alert rule.
`$annotations`	`map[string]string`	Rule annotations.
`$dsType`	`string`	Data source type.
`$dsName`	`string`	Data source name.
`$dsAddress`	`string`	Data source address without credentials.
`$checkMode`	`string`	Check mode.
`$relates`	`map[string][]*ResultRow`	Related query result rows.
`$status`	`string`	`firing` or `recovered`.
`$severity`	`string`	Alert severity.

Example:

{{- if eq $status "firing" }}
Alert {{ .RuleName }} fired on {{ $dsName }}. Value: {{ printf "%.2f" $value }}
{{- else }}
Alert {{ .RuleName }} recovered.
{{- end }}

Root Object Fields

Access root object fields with .FieldName.

Field	Type	Description
`.Hash`	`string`	Stable event hash. Firing and recovery events share the same hash.
`.DataSourceType`	`string`	Data source type.
`.DataSourceName`	`string`	Data source name.
`.DataSourceAddress`	`string`	Data source address without credentials.
`.RuleName`	`string`	Alert rule name.
`.RuleID`	`uint64`	Alert rule ID.
`.Queries`	`[]Query`	Rule query definitions.
`.RelateQueries`	`[]RelateQuery`	Related query definitions.
`.CheckMode`	`string`	Check mode.
`.DataLabels`	`map[string]string`	Alert labels.
`.AppendLabels`	`map[string]string`	Extra labels configured on the rule.
`.EnrichLabels`	`map[string]string`	Labels returned by the external enrichment endpoint. Enrichment runs before `Description` rendering, so templates can reference these labels.
`.Values`	`map[string]float64`	Numeric values used by alert evaluation.
`.Annotations`	`map[string]string`	Rule annotations.
`.Relates`	`map[string][]*ResultRow`	Related query result rows.
`.Status`	`string`	`firing` or `recovered`.
`.Severity`	`string`	Alert severity.
`.EvalTime`	`int64`	Evaluation timestamp in Unix seconds.
`.Description`	`string`	Rendered description. This is set after template execution.
`.DescriptionType`	`string`	Description type, for example `text` or `markdown`.
`.Value`	`float64`	Main alert value.
`.TitleRule`	`string`	Title rule configured on the edge.

Query objects in .Queries have .Name, .Expr, .LabelFields, .ValueFields, and .Args. RelateQuery objects in .RelateQueries have .Name, .Expr, and .Args. Related query results are available through $relates. The map key is the related query name, such as R1.

Field or Method	Type	Description
`$row.Fields`	`map[string]interface{}`	Non-numeric or display fields returned by the related query.
`$row.Values`	`map[string]float64`	Numeric fields returned by the related query.
`$row.Field "name"`	`interface{}`	Returns one field from `$row.Fields`.
`$row.Value`	`float64`	Returns the first numeric value in `$row.Values`, or `NaN` if no value exists.
`$row.Value "name"`	`float64`	Returns one numeric value from `$row.Values`, or `NaN` if the key does not exist.
`$row.String`	`string`	Returns a debug-style string representation of the row.

Example:

{{- range $row := $relates.R1 }}
- msg: {{ $row.Field "_msg" }}
- count: {{ printf "%.0f" ($row.Value "count") }}
{{- end }}

Go Template Built-in Functions

These functions are provided by Go text/template.

Function	Description	Example
`and`	Boolean AND. Evaluation stops when the result is known.	`{{ if and $a $b }}yes{{ end }}`
`or`	Boolean OR. Evaluation stops when the result is known.	`{{ if or $a $b }}yes{{ end }}`
`not`	Boolean NOT.	`{{ if not $ok }}failed{{ end }}`
`eq`	Equal.	`{{ if eq $status "firing" }}...{{ end }}`
`ne`	Not equal.	`{{ if ne $severity "Info" }}...{{ end }}`
`lt`	Less than.	`{{ if lt $value 10.0 }}...{{ end }}`
`le`	Less than or equal.	`{{ if le $value 10.0 }}...{{ end }}`
`gt`	Greater than.	`{{ if gt $value 10.0 }}...{{ end }}`
`ge`	Greater than or equal.	`{{ if ge $value 10.0 }}...{{ end }}`
`index`	Reads an item from a map, slice, or array.	`{{ index $labels "instance" }}`
`slice`	Slices a string, slice, or array.	`{{ slice "abcdef" 0 3 }}`
`len`	Returns length.	`{{ len $relates.R1 }}`
`printf`	Formats text with `fmt.Sprintf` syntax.	`{{ printf "%.2f" $value }}`
`print`	Concatenates values with default formatting.	`{{ print $dsName ":" $status }}`
`println`	Like `print`, with a trailing newline.	`{{ println $dsName }}`
`call`	Calls a function value. Rarely needed in descriptions.	`{{ call .SomeFunc }}`
`html`	Escapes text for HTML.	`{{ html $text }}`
`js`	Escapes text for JavaScript.	`{{ js $text }}`
`urlquery`	Escapes text for URL query usage.	`{{ urlquery $text }}`

monit-edge Custom Functions

These functions are registered by monit-edge without a prefix.

Function	Description	Example
`pathEscape text`	URL path escaping.	`{{ pathEscape "a/b c" }}`
`queryEscape text`	URL query escaping.	`{{ queryEscape "level=error msg" }}`
`getvalue values key [format]`	Reads a numeric value from a `map[string]float64` and formats it. Default format is `%.4f`. Returns `template_function_error: ...` text if the key is invalid or missing.	`{{ getvalue $values "$A" "%.2f" }}`
`getfvalue values key`	Reads a numeric value from a `map[string]float64`. Returns `NaN` if the key is invalid or missing.	`{{ if gt (getfvalue $values "$A") 10.0 }}high{{ end }}`
`trunc count text`	Alias of `truncRune`. Truncates by Unicode characters, not bytes. Negative count keeps characters from the end.	`{{ trunc 10 $msg }}`
`truncRune count text`	Truncates by Unicode characters.	`{{ truncRune -8 "abcdef hello" }}`
`runeCount text`	Counts Unicode characters.	`{{ runeCount "hello" }}`
`args ...`	Builds a map with keys `arg0`, `arg1`, and so on.	`{{ args "a" 1 }}`
`reReplaceAll pattern repl text`	Regex replacement. Argument order is `pattern`, `replacement`, `text`. Invalid regex fails rendering.	`{{ reReplaceAll ".id=([0-9]+)." "$1" $msg }}`
`safeHtml text`	Converts text to `html/template.HTML`. Description templates are rendered with `text/template`, so this does not sanitize HTML or change escaping behavior. Avoid it for normal text or Markdown.	`{{ safeHtml "<b>OK</b>" }}`
`match pattern text`	Regex match. Equivalent to Go `regexp.MatchString`. Invalid regex fails rendering.	`{{ if match "Unknown column" $msg }}...{{ end }}`
`toUpper text`	Converts text to uppercase.	`{{ toUpper $severity }}`
`toLower text`	Converts text to lowercase.	`{{ toLower $status }}`
`stripPort hostPort`	Removes port from `host:port`. If parsing fails, returns the original value.	`{{ stripPort "example.com:9100" }}`
`stripDomain hostPort`	Removes domain suffix from hostname while preserving port. IP addresses are returned unchanged.	`{{ stripDomain "node01.prod.local:9100" }}`
`humanize value`	Formats a number using SI units.	`{{ humanize 12345 }}`
`humanize1024 value`	Formats a number using base-1024 units.	`{{ humanize1024 1048576 }}`
`humanizeDuration seconds`	Formats seconds as a readable duration.	`{{ humanizeDuration 3661 }}`
`humanizePercentage value`	Formats a ratio as a percentage.	`{{ humanizePercentage 0.1234 }}`
`humanizeTimestamp seconds`	Converts a Unix timestamp in seconds to UTC time text.	`{{ humanizeTimestamp .EvalTime }}`
`toTime seconds`	Converts a Unix timestamp in seconds to a `time.Time`.	`{{ (toTime .EvalTime).Format "2006-01-02 15:04:05" }}`
`nanoTime value [tzOffset]`	Converts a Unix nanosecond timestamp to `time.Time`. Optional timezone offset is in hours.	`{{ (nanoTime $row.Fields.__time__ 8).Format "2006-01-02 15:04:05" }}`
`timeFormat value format [tzOffset]`	Formats a `time.Time`, `*time.Time`, RFC3339 string, or RFC3339Nano string. Optional timezone offset is in hours.	`{{ timeFormat "2026-01-06T11:48:12Z" "2006-01-02 15:04:05" 8 }}`
`parseDuration duration`	Parses a duration string and returns seconds.	`{{ parseDuration "5m" }}`
`add a b`	Numeric addition.	`{{ add 1 2 }}`
`sub a b`	Numeric subtraction.	`{{ sub 10 3 }}`
`mul a b`	Numeric multiplication.	`{{ mul $value 100 }}`
`div a b`	Numeric division. Division by zero fails rendering.	`{{ div $value 1024 }}`
`now`	Current time as `time.Time`.	`{{ now.Format "2006-01-02 15:04:05" }}`
`toString value`	Converts a value to string using `fmt.Sprint`.	`{{ toString $row.Fields._msg }}`

Sprig Functions

monit-edge registers safe Sprig functions with standard Sprig names and also with a sprig_ prefix. Sprig functions come from Masterminds/sprig. Check that repository for upstream function behavior. Common examples:

{{ contains "error" $msg }}
{{ regexMatch "Unknown column" $msg }}
{{ regexFind "Unknown column '[^']+'" $msg }}

Important regex note: regexFind and sprig_regexFind return the full matched substring. They do not return a capture group. To extract a capture group, use regexReplaceAll or sprig_regexReplaceAll:

{{- $msg := "Unknown column 'community_posts.comment_count' in 'field list'" }}
{{- regexReplaceAll ".*Unknown column '([^']+)'.*" $msg "$1" }}

The result is:

community_posts.comment_count

Common Sprig Functions

Function	Description	Example
`contains substr text`	Checks whether `text` contains `substr`.	`{{ if contains "Unknown column" $msg }}...{{ end }}`
`hasPrefix prefix text`	Checks prefix.	`{{ hasPrefix "prod-" $name }}`
`hasSuffix suffix text`	Checks suffix.	`{{ hasSuffix ".log" $file }}`
`regexMatch pattern text`	Regex match.	`{{ regexMatch "error\|failed" $msg }}`
`regexFind pattern text`	Returns the first full regex match.	`{{ regexFind "trace_id=[a-z0-9]+" $msg }}`
`regexFindAll pattern text n`	Returns up to `n` full regex matches. Use `-1` for all.	`{{ regexFindAll "id=[0-9]+" $msg -1 }}`
`regexReplaceAll pattern text repl`	Regex replacement. Argument order is `pattern`, `text`, `replacement`.	`{{ regexReplaceAll ".id=([0-9]+)." $msg "$1" }}`
`trim text`	Trims leading and trailing whitespace.	`{{ trim $msg }}`
`lower text`	Lowercase.	`{{ lower $severity }}`
`upper text`	Uppercase.	`{{ upper $severity }}`
`default default value`	Uses a default value when `value` is empty.	`{{ default "unknown" (index $labels "instance") }}`
`toJson value`	Converts a value to JSON.	`{{ toJson $labels }}`
`dict ...`	Creates a dictionary.	`{{ dict "name" $dsName "status" $status }}`
`list ...`	Creates a list.	`{{ list "a" "b" "c" }}`

The same functions can also be called with sprig_ prefixes, such as sprig_contains and sprig_regexReplaceAll.

Disabled Sprig Functions

For predictable and safe alert rendering, monit-edge does not register Sprig functions that can read process environment variables, perform DNS lookup, generate random output, create credentials or certificates, encrypt or decrypt data, or intentionally fail rendering. The following Sprig functions are unavailable in both standard and sprig_ forms:

env / sprig_env
expandenv / sprig_expandenv
getHostByName / sprig_getHostByName
bcrypt / sprig_bcrypt
htpasswd / sprig_htpasswd
derivePassword / sprig_derivePassword
genPrivateKey / sprig_genPrivateKey
buildCustomCert / sprig_buildCustomCert
genCA / sprig_genCA
genCAWithKey / sprig_genCAWithKey
genSelfSignedCert / sprig_genSelfSignedCert
genSelfSignedCertWithKey / sprig_genSelfSignedCertWithKey
genSignedCert / sprig_genSignedCert
genSignedCertWithKey / sprig_genSignedCertWithKey
encryptAES / sprig_encryptAES
decryptAES / sprig_decryptAES
randBytes / sprig_randBytes
uuidv4 / sprig_uuidv4
randAlphaNum / sprig_randAlphaNum
randAlpha / sprig_randAlpha
randAscii / sprig_randAscii
randNumeric / sprig_randNumeric
randInt / sprig_randInt
shuffle / sprig_shuffle
fail / sprig_fail

If a template uses one of these functions, parsing fails with an error like function "env" not defined or function "sprig_env" not defined.

Complete Example: Extract MySQL Unknown Column

{{- if eq $status "firing" }}
In the last 5 minutes, database operations produced missing-field errors {{ $value | printf "%.0f" }} times.
{{- range $x := $relates.R1 }}
  {{- $msg := printf "%v" ($x.Field "_msg") }}
  {{- if contains "Unknown column" $msg }}
    {{- $field := regexReplaceAll ".*Unknown column '([^']+)'.*" $msg "$1" }}

- Missing field: {{ $field }}
- View logs: https://example.com/logs?query={{ queryEscape "Unknown column" }}
  {{- end }}
{{- end }}
{{- else }}
The database missing-field error has recovered.
{{- end }}

Troubleshooting

function "contains" not defined means the rule is running on an older monit-edge build that has not enabled standard Sprig names. Upgrade monit-edge, or use sprig_contains as a compatibility workaround if that build supports the prefixed form. function "env" not defined or function "sprig_env" not defined means the template used a disabled Sprig function. Remove it or replace it with deterministic template logic. regexFind or sprig_regexFind returning Unknown column 'x' instead of x is expected. Use regexReplaceAll or sprig_regexReplaceAll to extract capture groups.

Quick Start

Data Sources

Alert Engine

Alert Rules

Active Alerts

Rule Repository

Folder Management

FAQ

How It Works

Sprig Function Names

Built-in Variables

Root Object Fields

Go Template Built-in Functions

monit-edge Custom Functions

Sprig Functions

Common Sprig Functions

Disabled Sprig Functions

Complete Example: Extract MySQL Unknown Column

Troubleshooting

Quick Start

Data Sources

Alert Engine

Alert Rules

Active Alerts

Rule Repository

Folder Management

FAQ

Documentation Index

​How It Works

​Sprig Function Names

​Built-in Variables

​Root Object Fields

​Related Query Rows

​Go Template Built-in Functions

​monit-edge Custom Functions

​Sprig Functions

​Common Sprig Functions

​Disabled Sprig Functions

​Complete Example: Extract MySQL Unknown Column

​Troubleshooting

How It Works

Sprig Function Names

Built-in Variables

Root Object Fields

Related Query Rows

Go Template Built-in Functions

monit-edge Custom Functions

Sprig Functions

Common Sprig Functions

Disabled Sprig Functions

Complete Example: Extract MySQL Unknown Column

Troubleshooting