parse_kv

Parses a string as Key-Value pairs.

parse_kv(input:string, [field_split:string, value_split: string, quotes=string,
         schema=string, selector=string, schema_only=bool,
         raw=bool, unflatten=string]) -> record

Description

The parse_kv function parses a string as Key-Value pairs.

The string is first split into fields according to field_split. This can be a regular expression. For example, the input foo: bar, baz: 42 can be split into foo: bar and baz: 42 with the regular expression r",\s*" (a comma, followed by any amount of whitespace) as the field splitter. Note that the matched separators are removed when splitting a string.

Afterwards, the extracted fields are split into their key and value by value_split, which can again be a regular expression. In our example, r":\s*" could be used to split foo: bar into the key foo and its value bar, and similarly baz: 42 into baz and 42. The result would thus be {"foo": "bar", "baz": 42}. If the regex matches multiple substrings, only the first match is used.

The supported regular expression syntax is RE2. In particular, this means that lookahead (?=...) and lookbehind (?<=...) are not supported by parse_kv at the moment. However, if the regular expression has a capture group, it is assumed that only the content of the capture group shall be used as the separator. This means that unsupported regular expressions such as (?=foo)bar(?<=baz) can be effectively expressed as foo(bar)baz instead.

Quoted Values

The parser is aware of double-quotes ("). If the field_split or value_split are found within enclosing quotes, they are not considered matches. This means that both the key and the value may be enclosed in double-quotes.

For example, given field_split \s*,\s* and value_split =, the input

"key"="nested = value",key2="value, and more"

will parse as

{
  key: "nested = value",
  key2: "value, and more",
}

input: string

The string to parse.

field_split: string (optional)

The regular expression used to separate individual fields.

Defaults to r"\s".

value_split: string (optional)

The regular expression used to separate a key from its value.

Defaults to "=".

quotes = string (optional)

A string of not escaped characters that are supposed to be considered as quotes.

Defaults to the characters "'.

raw = bool (optional)

Use only the raw types that are native to the parsed format. Fields that have a type specified in the chosen schema will still be parsed according to the schema.

schema = string (optional)

Provide the name of a schema to be used by the parser.

If a schema with a matching name is installed, the result will always have all fields from that schema.

• Fields that are specified in the schema, but did not appear in the input will be null.
• Fields that appear in the input, but not in the schema will also be kept. schema_only=true can be used to reject fields that are not in the schema.

If the given schema does not exist, this option instead assigns the output schema name only.

The schema option is incompatible with the selector option.

selector = string (optional)

Designates a field value as schema name with an optional dot-separated prefix.

The string is parsed as <fieldname>[:<prefix>]. The prefix is optional and will be prepended to the field value to generate the schema name.

For example, the Suricata EVE JSON format includes a field event_type that contains the event type. Setting the selector to event_type:suricata causes an event with the value flow for the field event_type to map onto the schema suricata.flow.

The selector option is incompatible with the schema option.

schema_only = bool (optional)

When working with an existing schema, this option will ensure that the output schema has only the fields from that schema.

If the schema name is obtained via a selector and it does not exist, this has no effect.

This option requires either schema or selector to be set.

unflatten = string (optional)

A delimiter that, if present in keys, causes values to be treated as values of nested records.

A popular example of this is the Zeek JSON format. It includes the fields id.orig_h, id.orig_p, id.resp_h, and id.resp_p at the top-level. The data is best modeled as an id record with four nested fields orig_h, orig_p, resp_h, and resp_p.

Without an unflatten separator, the data looks like this:

Without unflattening

{
  "id.orig_h": "1.1.1.1",
  "id.orig_p": 10,
  "id.resp_h": "1.1.1.2",
  "id.resp_p": 5
}

With the unflatten separator set to ., Tenzir reads the events like this:

With 'unflatten'

{
  "id": {
    "orig_h": "1.1.1.1",
    "orig_p": 10,
    "resp_h": "1.1.1.2",
    "resp_p": 5
  }
}

Examples

parse comma-separated key-value pairs

from { input: "surname: John, family_name: Smith, date_of_birth: 1995-05-26"}
output = input.parse_kv(r"\s*,\s*", r"\s*:\s*")

{
  input: "surname: John, family_name: Smith, date_of_birth: 1995-05-26",
  output: {
    surname: "John",
    family_name: "Smith",
    date_of_birth: 1995-05-26,
  },
}

See Also

read_kv