Important: This documentation is about an older version. It's relevant only to the release noted, many of the features and functions have been updated or replaced. Please view the current version.
Template functions
The text template format used in | line_format and | label_format support the usage of functions.
All labels are added as variables in the template engine. They can be referenced using they label name prefixed by a .(e.g .label_name). For example the following template will output the value of the path label:
{{ .path }}Additionally you can also access the log line using the __line__ function and the timestamp using the __timestamp__ function.
You can take advantage of pipeline to join together multiple functions. In a chained pipeline, the result of each command is passed as the last argument of the following command.
Example:
{{ .path | replace " " "_" | trunc 5 | upper }}line
This function returns the current log line.
Signature: line() string
Examples:
"{{ __line__ | lower }}"
`{{ __line__ }}`timestamp
This function returns the current log lines timestamp.
Signature: timestamp() time.Time
"{{ __timestamp__ }}"
`{{ __timestamp__ | date "2006-01-02T15:04:05.00Z-07:00" }}`
`{{ __timestamp__ | unixEpoch }}`See the blog: Parsing and formatting date/time in Go for more information.
regexReplaceAll and regexReplaceAllLiteral
regexReplaceAll returns a copy of the input string, replacing matches of the Regexp with the replacement string replacement. Inside string replacement, $ signs are interpreted as in Expand, so for instance $1 represents the text of the first sub-match. See the golang Regexp.replaceAll documentation for more examples.
Example:
`{{ regexReplaceAll "(a*)bc" .some_label "${1}a" }}`regexReplaceAllLiteral function returns a copy of the input string and replaces matches of the Regexp with the replacement string replacement. The replacement string is substituted directly, without using Expand.
Example:
`{{ regexReplaceAllLiteral "(ts=)" .timestamp "timestamp=" }}`lower
Use this function to convert to lower case.
Signature: lower(string) string
Examples:
"{{ .request_method | lower }}"
`{{ lower "HELLO"}}`The last example will return hello.
upper
Use this function to convert to upper case.
Signature: upper(string) string
Examples:
"{{ .request_method | upper }}"
`{{ upper "hello"}}`This results in HELLO.
title
Convert to title case.
Signature: title(string) string
Examples:
"{{.request_method | title}}"
`{{ title "hello world"}}`The last example will return Hello World.
trunc
Truncate a string and add no suffix.
Signature: trunc(count int,value string) string
Examples:
"{{ .path | trunc 2 }}"
`{{ trunc 5 "hello world"}}` // output: hello
`{{ trunc -5 "hello world"}}` // output: worldsubstr
Get a substring from a string.
Signature: substr(start int,end int,value string) string
If start is < 0, this calls value[:end]. If start is >= 0 and end < 0 or end bigger than s length, this calls value[start:] Otherwise, this calls value[start, end].
Examples:
"{{ .path | substr 2 5 }}"
`{{ substr 0 5 "hello world"}}` // output: hello
`{{ substr 6 11 "hello world"}}` // output: worldreplace
This function performs simple string replacement.
Signature: replace(old string, new string, src string) string
It takes three arguments:
oldstring to replacenewstring to replace withsrcsource string
Examples:
{{ .cluster | replace "-cluster" "" }}
{{ replace "hello" "world" "hello world" }}The last example will return world world.
trim
The trim function removes space from either side of a string.
Signature: trim(string) string
Examples:
{{ .ip | trim }}
{{ trim " hello " }} // output: hellotrimAll
Use this function to remove given characters from the front or back of a string.
Signature: trimAll(chars string,src string) string
Examples:
{{ .path | trimAll "/" }}
{{ trimAll "$" "$5.00" }} // output: 5.00trimSuffix
Use this function to trim just the suffix from a string.
Signature: trimSuffix(suffix string, src string) string
Examples:
{{ .path | trimSuffix "/" }}
{{ trimSuffix "-" "hello-" }} // output: hellotrimPrefix
Use this function to trim just the prefix from a string.
Signature: trimPrefix(prefix string, src string) string
Examples:
{{ .path | trimPrefix "/" }}
{{ trimPrefix "-" "-hello" }} // output: helloindent
The indent function indents every line in a given string to the specified indent width. This is useful when aligning multi-line strings.
Signature: indent(spaces int,src string) string
Example:
{{ indent 4 .query }}This indents each line contained in the .query by four (4) spaces.
nindent
The nindent function is the same as the indent function, but prepends a new line to the beginning of the string.
Signature: nindent(spaces int,src string) string
Example:
{{ nindent 4 .query }}This will indent every line of text by 4 space characters and add a new line to the beginning.
repeat
Use this function to repeat a string multiple times.
Signature: repeat(c int,value string) string
Example:
{{ repeat 3 "hello" }} // output: hellohellohellocontains
Use this function to test to see if one string is contained inside of another.
Signature: contains(s string, src string) bool
Examples:
{{ if .err contains "ErrTimeout" }} timeout {{end}}
{{ if contains "he" "hello" }} yes {{end}}hasPrefix and hasSuffix
The hasPrefix and hasSuffix functions test whether a string has a given prefix or suffix.
Signatures:
hasPrefix(prefix string, src string) boolhasSuffix(suffix string, src string) bool
Examples:
{{ if .err hasSuffix "Timeout" }} timeout {{end}}
{{ if hasPrefix "he" "hello" }} yes {{end}}add
Sum numbers. Supports multiple numbers
Signature: func(i ...interface{}) int64
Example:
{{ add 3 2 5 }} // output: 10sub
Subtract numbers.
Signature: func(a, b interface{}) int64
Example:
{{ sub 5 2 }} // output: 3mul
Mulitply numbers. Supports multiple numbers.
Signature: func(a interface{}, v ...interface{}) int64
Example:
{{ mul 5 2 3}} // output: 30div
Integer divide numbers.
Signature: func(a, b interface{}) int64
Example:
{{ div 10 2}} // output: 5addf
Sum numbers. Supports multiple numbers.
Signature: func(i ...interface{}) float64
Example:
{{ addf 3.5 2 5 }} // output: 10.5subf
Subtract numbers. Supports multiple numbers.
Signature: func(a interface{}, v ...interface{}) float64
Example:
{{ subf 5.5 2 1.5 }} // output: 2mulf
Mulitply numbers. Supports multiple numbers
Signature: func(a interface{}, v ...interface{}) float64
Example:
{{ mulf 5.5 2 2.5 }} // output: 27.5divf
Divide numbers. Supports multiple numbers.
Signature: func(a interface{}, v ...interface{}) float64
Example:
{{ divf 10 2 4}} // output: 1.25mod
Modulo wit mod.
Signature: func(a, b interface{}) int64
Example:
{{ mod 10 3}} // output: 1max
Return the largest of a series of integers:
Signature: max(a interface{}, i ...interface{}) int64
Example:
{{ max 1 2 3 }} //output 3min
Return the smallest of a series of integers.
Signature: min(a interface{}, i ...interface{}) int64
Example:
{{ max 1 2 3 }} //output 1maxf
Return the largest of a series of floats:
Signature: maxf(a interface{}, i ...interface{}) float64
Example:
{{ maxf 1 2.5 3 }} //output 3minf
Return the smallest of a series of floats.
Signature: minf(a interface{}, i ...interface{}) float64
Example:
{{ minf 1 2.5 3 }} //output 1.5ceil
Returns the greatest float value greater than or equal to input value
Signature: ceil(a interface{}) float64
Example:
{{ ceil 123.001 }} //output 124.0floor
Returns the greatest float value less than or equal to input value
Signature: floor(a interface{}) float64
Example:
{{ floor 123.9999 }} //output 123.0round
Returns a float value with the remainder rounded to the given number of digits after the decimal point.
Signature: round(a interface{}, p int, rOpt ...float64) float64
Example:
{{ round 123.555555 3 }} //output 123.556We can also provide a roundOn number as third parameter
Example:
{{ round 123.88571428571 5 .2 }} //output 123.88572With default roundOn of .5 the above value would be 123.88571
int
Convert value to an int.
Signature: toInt(v interface{}) int
Example:
{{ "3" | int }} //output 3float64
Convert to a float64.
Signature: toFloat64(v interface{}) float64
Example:
{{ "3.5" | float64 }} //output 3.5fromJson
Decodes a JSON document into a structure. If the input cannot be decoded as JSON the function will return an empty string.
Signature: fromJson(v string) interface{}
Example:
fromJson "{\"foo\": 55}"Example of a query to print a newline per queries stored as a json array in the log line:
{job="loki/querier"} |= "finish in prometheus" | logfmt | line_format "{{ range $q := fromJson .queries }} {{ $q.query }} {{ end }}"now
Returns the current time in the local timezone of the Loki server.
Signature: Now() time.Time
Example:
{{ now }}toDate
Parses a formatted string and returns the time value it represents using the local timezone of the server running Loki.
For more consistency between Loki installations, it’s recommended to use toDateInZone
The format string must use the exact date as defined in the golang datetime layout
Signature: toDate(fmt, str string) time.Time
Examples:
{{ toDate "2006-01-02" "2021-11-02" }}
{{ .foo | toDate "2006-01-02T15:04:05.999999999Z" }}toDateInZone
Parses a formatted string and returns the time value it represents in the provided timezone.
The format string must use the exact date as defined in the golang datetime layout
The timezone value can be Local, UTC, or any of the IANA Time Zone database values
Signature: toDateInZone(fmt, zone, str string) time.Time
Examples:
{{ toDateInZone "2006-01-02" "UTC" "2021-11-02" }}
{{ .foo | toDateInZone "2006-01-02T15:04:05.999999999Z" "UTC" }}date
Returns a textual representation of the time value formatted according to the provided golang datetime layout.
Signature: date(fmt string, date interface{}) string
Example:
{{ date "2006-01-02" now }}unixEpoch
Returns the number of seconds elapsed since January 1, 1970 UTC.
Signature: unixEpoch(date time.Time) string
Examples:
{{ unixEpoch now }}
{{ .foo | toDateInZone "2006-01-02T15:04:05.999999999Z" "UTC" | unixEpoch }}Example of a query to filter Loki querier jobs which create time is 1 day before:
{job="loki/querier"} | label_format nowEpoch=`{{(unixEpoch now)}}`,createDateEpoch=`{{unixEpoch (toDate "2006-01-02" .createDate)}}` | label_format dateTimeDiff="{{sub .nowEpoch .createDateEpoch}}" | dateTimeDiff > 86400unixEpochMillis
Returns the number of milliseconds elapsed since January 1, 1970 UTC.
Signature: unixEpochMillis(date time.Time) string
Examples:
{{ unixEpochMillis now }}
{{ .foo | toDateInZone "2006-01-02T15:04:05.999999999Z" "UTC" | unixEpochMillis }}unixEpochNanos
Returns the number of nanoseconds elapsed since January 1, 1970 UTC.
Signature: unixEpochNanos(date time.Time) string
Examples:
{{ unixEpochNanos now }}
{{ .foo | toDateInZone "2006-01-02T15:04:05.999999999Z" "UTC" | unixEpochNanos }}default
Checks whether the string(src) is set, and returns default(d) if not set.
Signature: default(d string, src string) string
Examples:
{{ default "-" "" }} // output: -
{{ default "-" "foo" }} // output: fooExample of a query to print a - if the http_request_headers_x_forwarded_for label is empty:
{job="access_log"} | json | line_format `{{.http_request_headers_x_forwarded_for | default "-"}}`count
Counts occurrences of the regex (regex) in (src).
Signature: count(regex string, src string) int
Examples:
{{ count "a|b" "abab" }} // output: 4
{{ count "o" "foo" }} // output: 2Example of a query to print how many times XYZ occurs in a line:
{job="xyzlog"} | line_format `{{ __line__ | count "XYZ"}}`urlencode
Use this function to urlencode a string.
Signature: urlencode(string) string
Examples:
"{{ .request_url | urlencode }}"
`{{ urlencode .request_url}}`urldecode
Use this function to urldecode a string.
Signature: urldecode(string) string
Examples:
"{{ .request_url | urldecode }}"
`{{ urldecode .request_url}}`b64enc
Base64 encode a string.
Signature: b64enc(string) string
Examples:
"{{ .foo | b64enc }}"
`{{ b64enc .foo }}`b64dec
Base64 decode a string.
Signature: b64dec(string) string
Examples:
"{{ .foo | b64dec }}"
`{{ b64dec .foo }}`bytes
Convert a humanized byte string to bytes using go-humanize
Signature: bytes(string) string
Examples:
"{{ .foo | bytes }}"
`{{ bytes .foo }}`duration
An alias for duration_seconds
Examples:
"{{ .foo | duration }}"
`{{ duration .foo }}`duration_seconds
Convert a humanized time duration to seconds using time.ParseDuration
Signature: duration_seconds(string) float64
Examples:
"{{ .foo | duration_seconds }}"
`{{ duration_seconds .foo }}`Was this page helpful?
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