Kv filter plugin v4.2.0

  • Plugin version: v4.2.0
  • Released on: 2018-07-23
  • Changelog

For other versions, see the overview list.

To learn more about Logstash, see the Logstash Reference.

Getting Help

For questions about the plugin, open a topic in the Discuss forums. For bugs or feature requests, open an issue in Github. For the list of Elastic supported plugins, please consult the Elastic Support Matrix.

Description

This filter helps automatically parse messages (or specific event fields) which are of the foo=bar variety.

For example, if you have a log message which contains ip=1.2.3.4 error=REFUSED, you can parse those automatically by configuring:

filter {
  kv { }
}

The above will result in a message of ip=1.2.3.4 error=REFUSED having the fields:

  • ip: 1.2.3.4
  • error: REFUSED

This is great for postfix, iptables, and other types of logs that tend towards key=value syntax.

You can configure any arbitrary strings to split your data on, in case your data is not structured using = signs and whitespace. For example, this filter can also be used to parse query parameters like foo=bar&baz=fizz by setting the field_split parameter to &.

Kv Filter Configuration Options

This plugin supports the following configuration options plus the Common Options described later.

Also see Common Options for a list of options supported by all filter plugins.

 

allow_duplicate_values

  • Value type is boolean
  • Default value is true

A bool option for removing duplicate key/value pairs. When set to false, only one unique key/value pair will be preserved.

For example, consider a source like from=me from=me. [from] will map to an Array with two elements: ["me", "me"]. To only keep unique key/value pairs, you could use this configuration:

filter {
  kv {
    allow_duplicate_values => false
  }
}

default_keys

  • Value type is hash
  • Default value is {}

A hash specifying the default keys and their values which should be added to the event in case these keys do not exist in the source field being parsed.

filter {
  kv {
    default_keys => [ "from", "logstash@example.com",
                     "to", "default@dev.null" ]
  }
}

exclude_keys

  • Value type is array
  • Default value is []

An array specifying the parsed keys which should not be added to the event. By default no keys will be excluded.

For example, consider a source like Hey, from=<abc>, to=def foo=bar. To exclude from and to, but retain the foo key, you could use this configuration:

filter {
  kv {
    exclude_keys => [ "from", "to" ]
  }
}

field_split

  • Value type is string
  • Default value is " "

A string of characters to use as single-character field delimiters for parsing out key-value pairs.

These characters form a regex character class and thus you must escape special regex characters like [ or ] using \.

## Example with URL Query Strings

For example, to split out the args from a url query string such as ?pin=12345~0&d=123&e=foo@bar.com&oq=bobo&ss=12345:

filter {
  kv {
    field_split => "&?"
  }
}

The above splits on both & and ? characters, giving you the following fields:

  • pin: 12345~0
  • d: 123
  • e: foo@bar.com
  • oq: bobo
  • ss: 12345

field_split_pattern

  • Value type is string
  • There is no default value for this setting.

A regex expression to use as field delimiter for parsing out key-value pairs. Useful to define multi-character field delimiters. Setting the field_split_pattern options will take precedence over the field_split option.

Note that you should avoid using captured groups in your regex and you should be cautious with lookaheads or lookbehinds and positional anchors.

For example, to split fields on a repetition of one or more colons k1=v1:k2=v2::k3=v3:::k4=v4:

filter { kv { field_split_pattern => ":+" } }

To split fields on a regex character that need escaping like the plus sign k1=v1++k2=v2++k3=v3++k4=v4:

filter { kv { field_split_pattern => "\\+\\+" } }

include_brackets

  • Value type is boolean
  • Default value is true

A boolean specifying whether to treat square brackets, angle brackets, and parentheses as value "wrappers" that should be removed from the value.

filter {
  kv {
    include_brackets => true
  }
}

For example, the result of this line: bracketsone=(hello world) bracketstwo=[hello world] bracketsthree=<hello world>

will be:

  • bracketsone: hello world
  • bracketstwo: hello world
  • bracketsthree: hello world

instead of:

  • bracketsone: (hello
  • bracketstwo: [hello
  • bracketsthree: <hello

include_keys

  • Value type is array
  • Default value is []

An array specifying the parsed keys which should be added to the event. By default all keys will be added.

For example, consider a source like Hey, from=<abc>, to=def foo=bar. To include from and to, but exclude the foo key, you could use this configuration:

filter {
  kv {
    include_keys => [ "from", "to" ]
  }
}

prefix

  • Value type is string
  • Default value is ""

A string to prepend to all of the extracted keys.

For example, to prepend arg_ to all keys:

filter { kv { prefix => "arg_" } }

recursive

  • Value type is boolean
  • Default value is false

A boolean specifying whether to drill down into values and recursively get more key-value pairs from it. The extra key-value pairs will be stored as subkeys of the root key.

Default is not to recursive values.

filter {
  kv {
    recursive => "true"
  }
}

remove_char_key

  • Value type is string
  • There is no default value for this setting.

A string of characters to remove from the key.

These characters form a regex character class and thus you must escape special regex characters like [ or ] using \.

Contrary to trim option, all characters are removed from the key, whatever their position.

For example, to remove < > [ ] and , characters from keys:

filter {
  kv {
    remove_char_key => "<>\[\],"
  }
}

remove_char_value

  • Value type is string
  • There is no default value for this setting.

A string of characters to remove from the value.

These characters form a regex character class and thus you must escape special regex characters like [ or ] using \.

Contrary to trim option, all characters are removed from the value, whatever their position.

For example, to remove <, >, [, ] and , characters from values:

filter {
  kv {
    remove_char_value => "<>\[\],"
  }
}

source

  • Value type is string
  • Default value is "message"

The field to perform key=value searching on

For example, to process the not_the_message field:

filter { kv { source => "not_the_message" } }

target

  • Value type is string
  • There is no default value for this setting.

The name of the container to put all of the key-value pairs into.

If this setting is omitted, fields will be written to the root of the event, as individual fields.

For example, to place all keys into the event field kv:

filter { kv { target => "kv" } }

transform_key

  • Value can be any of: lowercase, uppercase, capitalize
  • There is no default value for this setting.

Transform keys to lower case, upper case or capitals.

For example, to lowercase all keys:

filter {
  kv {
    transform_key => "lowercase"
  }
}

transform_value

  • Value can be any of: lowercase, uppercase, capitalize
  • There is no default value for this setting.

Transform values to lower case, upper case or capitals.

For example, to capitalize all values:

filter {
  kv {
    transform_value => "capitalize"
  }
}

trim_key

  • Value type is string
  • There is no default value for this setting.

A string of characters to trim from the key. This is useful if your keys are wrapped in brackets or start with space.

These characters form a regex character class and thus you must escape special regex characters like [ or ] using \.

Only leading and trailing characters are trimed from the key.

For example, to trim < > [ ] and , characters from keys:

filter {
  kv {
    trim_key => "<>\[\],"
  }
}

trim_value

  • Value type is string
  • There is no default value for this setting.

Constants used for transform check A string of characters to trim from the value. This is useful if your values are wrapped in brackets or are terminated with commas (like postfix logs).

These characters form a regex character class and thus you must escape special regex characters like [ or ] using \.

Only leading and trailing characters are trimed from the value.

For example, to trim <, >, [, ] and , characters from values:

filter {
  kv {
    trim_value => "<>\[\],"
  }
}

value_split

  • Value type is string
  • Default value is "="

A non-empty string of characters to use as single-character value delimiters for parsing out key-value pairs.

These characters form a regex character class and thus you must escape special regex characters like [ or ] using \.

For example, to identify key-values such as key1:value1 key2:value2:

filter { kv { value_split => ":" } }

value_split_pattern

  • Value type is string
  • There is no default value for this setting.

A regex expression to use as value delimiter for parsing out key-value pairs. Useful to define multi-character value delimiters. Setting the value_split_pattern options will take precedence over the value_split option.

Note that you should avoid using captured groups in your regex and you should be cautious with lookaheads or lookbehinds and positional anchors.

See field_split_pattern for examples.

whitespace

  • Value can be any of: lenient, strict
  • Default value is lenient

An option specifying whether to be lenient or strict with the acceptance of unnecessary whitespace surrounding the configured value-split sequence.

By default the plugin is run in lenient mode, which ignores spaces that occur before or after the value-splitter. While this allows the plugin to make reasonable guesses with most input, in some situations it may be too lenient.

You may want to enable whitespace => strict mode if you have control of the input data and can guarantee that no extra spaces are added surrounding the pattern you have defined for splitting values. Doing so will ensure that a field-splitter sequence immediately following a value-splitter will be interpreted as an empty field.

Common Options

The following configuration options are supported by all filter plugins:

add_field

  • Value type is hash
  • Default value is {}

If this filter is successful, add any arbitrary fields to this event. Field names can be dynamic and include parts of the event using the %{field}.

Example:

filter {
  kv {
    add_field => { "foo_%{somefield}" => "Hello world, from %{host}" }
  }
}
# You can also add multiple fields at once:
filter {
  kv {
    add_field => {
      "foo_%{somefield}" => "Hello world, from %{host}"
      "new_field" => "new_static_value"
    }
  }
}

If the event has field "somefield" == "hello" this filter, on success, would add field foo_hello if it is present, with the value above and the %{host} piece replaced with that value from the event. The second example would also add a hardcoded field.

add_tag

  • Value type is array
  • Default value is []

If this filter is successful, add arbitrary tags to the event. Tags can be dynamic and include parts of the event using the %{field} syntax.

Example:

filter {
  kv {
    add_tag => [ "foo_%{somefield}" ]
  }
}
# You can also add multiple tags at once:
filter {
  kv {
    add_tag => [ "foo_%{somefield}", "taggedy_tag"]
  }
}

If the event has field "somefield" == "hello" this filter, on success, would add a tag foo_hello (and the second example would of course add a taggedy_tag tag).

enable_metric

  • Value type is boolean
  • Default value is true

Disable or enable metric logging for this specific plugin instance by default we record all the metrics we can, but you can disable metrics collection for a specific plugin.

id

  • Value type is string
  • There is no default value for this setting.

Add a unique ID to the plugin configuration. If no ID is specified, Logstash will generate one. It is strongly recommended to set this ID in your configuration. This is particularly useful when you have two or more plugins of the same type, for example, if you have 2 kv filters. Adding a named ID in this case will help in monitoring Logstash when using the monitoring APIs.

filter {
  kv {
    id => "ABC"
  }
}

periodic_flush

  • Value type is boolean
  • Default value is false

Call the filter flush method at regular interval. Optional.

remove_field

  • Value type is array
  • Default value is []

If this filter is successful, remove arbitrary fields from this event. Example:

filter {
  kv {
    remove_field => [ "foo_%{somefield}" ]
  }
}
# You can also remove multiple fields at once:
filter {
  kv {
    remove_field => [ "foo_%{somefield}", "my_extraneous_field" ]
  }
}

If the event has field "somefield" == "hello" this filter, on success, would remove the field with name foo_hello if it is present. The second example would remove an additional, non-dynamic field.

remove_tag

  • Value type is array
  • Default value is []

If this filter is successful, remove arbitrary tags from the event. Tags can be dynamic and include parts of the event using the %{field} syntax.

Example:

filter {
  kv {
    remove_tag => [ "foo_%{somefield}" ]
  }
}
# You can also remove multiple tags at once:
filter {
  kv {
    remove_tag => [ "foo_%{somefield}", "sad_unwanted_tag"]
  }
}

If the event has field "somefield" == "hello" this filter, on success, would remove the tag foo_hello if it is present. The second example would remove a sad, unwanted tag as well. :plugin: kv :type: filter