Description Template

Configure Go Template variables, related query results, and Sprig functions for Monitors alert rule descriptions.

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 Rows

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.