Description

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The Parser Function can be used to extract fields out of events, or to reserialize (rewrite) events with a subset of fields. Reserialization will maintain the format of the events.

For example: If an event contains comma-delimited fields, and fieldA and fieldB are filtered out, those fields' positions will be set to null, but not deleted completely.

Parser will not remove fields that it did not create. The Eval Function can do so.

Usage

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Filter: Filter expression (JS) that selects data to be fed through the Function. Defaults to true, meaning that all events will be evaluated.

Description: Simple description about this Function. Defaults to empty.

Final: If true, stops data from being fed to the downstream Functions. Defaults to No.

Operation mode: Extract will create new fields. Reserialize will extract, filter fields, and then reserialize. Serialize will put fields in a certain format. Defaults to Extract.

Source field: Field that contains text to be parsed. Not usually needed in Serialize mode.

Destination field: Field in which to add extracted fields (Extract mode only).

Destination field: Name of field in which to add extracted and serialized fields. (Extract and Serialize modes only.)

Type: Parser/Formatter type to use. Options:

• CSV
• JSON
• K=V Pairs
• Extended Log File Format (ELFF)
• Common Log Format (CLF)

Library: Select an option from the Parsers Library.

List of fields: Fields expected to be extracted, in order. If not specified, Parser will auto-generate fields.

Fields to keep: List of fields to keep. Supports wildcards (*). Takes precedence over Fields to remove. Nested addressing supported.

Fields to remove: List of fields to remove. Supports wildcards (*). Cannot remove fields matching Fields to keep. Nested addressing supported.

📘

Negated terms are supported in both Fields to remove and Fields to keep. When you use negated terms, the list is order-sensitive. E.g., !foobar, foo* means "All fields that start with foo, except foobar." However, !foo*, * means "All fields, except for those that start with foo."

Fields filter expression: Expression to evaluate against {index, name, value} context of each field. Return truthy to keep, falsy to remove field. Index is zero-based.

How Fields Settings Interact

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The Fields to keep, Fields to remove, and Fields filter expression settings interact as follows:

• Order of evaluation: Fields to keep > Fields to remove > Fields filter expression.

• If a field is in both Fields to keep and Fields to remove, Fields to keep takes precedence.

• If a field is in both Fields to remove and Fields filter expression, Fields to remove takes precedence.

Example 1

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Insert the following sample, using Preview > Add a Sample > Paste a Sample:
2019/06/24 05:10:55 PM Z a=000,b=001,c=002,d=003,e=004,f=005,g1=006,g2=007,g3=008

Create the following test Parser Function (or import this Pipeline: https://github.com/weeb-cribl/cribl-samples/blob/master/parser/functions/parser/parser_1.json).

First, set the Parser type to Key=Value Pairs.

Scenario A:

Keep fields a, b, c. Drop the rest.

Expected result: a, b, c

• Fields to Keep: a, b, c
• Fields to Remove: *
• Fields Filter Expression:

Result: The event will gain four new fields and values, as follows.

• a: 000
• b: 001
• c: 002
• cribl_pipe: parser2

You can check your stats by clicking the Preview pane’s Basic Statistics (chart) button. In the resulting pop-up, the Number of Fields should have incremented ty four.

Now that you have the hang of it, try out the other simple scenarios below.

Scenario B:

Keep fields a, b, those that start with g. Drop the rest.

Expected result: a, b, g1, g2, g3

• Fields to keep: a, b
• Fields to remove: [empty]
• Fields filter expression: name.startsWith('g')

Scenario C:

Keep fields a, b, those that start with g but only if value is 007. Drop the rest.

Expected result: a, b, g2

• Fields to keep: a, b
• Fields to remove: [empty]
• Fields filter expression: name.startsWith('g') && value=='007'

Scenario D:

Keep fields a, b, c, those that start with g, unless it's g1. Drop the rest.

Expected result: a, b, c, g2, g3

• Fields to keep: a, b, c
• Fields to remove: g1
• Fields filter expression: name.startsWith('g')

Scenario E:

Keep fields a, b, c, those that start with g but only if index is greater than 6. Drop the rest.

Expected result: a, b, c, g2, g3

• Fields to keep: a, b, c
• Fields to remove: [empty]
• Fields filter expression: name.startsWith('g') && index>6

📘

The index refers to the location of a field in the array of all fields extracted by this Parser. It is zero-based. In the case above, g2 and g3 have index values of 7 and 8, respectively.

Example 2

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Assume we have a JSON event that needs to be reserialized, given these requirements:

1. Remove the level field only if it's set to info.
2. Remove the startTime field, and all fields in the values.total. path that end in Cxn.

Parser Function configuration:

JSON event after being processed by the Function:

Example 3

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Insert the following sample, using Preview > Add a Sample > Paste a Sample:

2019/06/24 15:25:36 PM Z a=000,b=001,c=002,d=003,e=004,f=005,g1=006,g2=007,g3=008,

For all scenarios below, first create a Parser Function to extract all fields, by setting the Parser type to Key=Value Pairs. Then add a second Parser Function with the configuration shown under Parser 2.

Scenario A:

Serialize fields a, b, c, d in CSV format.

Expected result: _raw field will have this value 000,001,002,003

Parser 2:

• Operation mode: Serialize
• Source field: [empty]
• Destination field: [empty]
• Type: CSV
• List of fields: a, b, c, d (needed for positional formats)

Scenario B:

Serialize fields a, b, c in JSON format, under a field called bar.

Expected result: bar field will be set to: {"a":"000","b":"001","c":"002","d":"003"}

Parser 2:

• Operation mode: Serialize
• Source field: [empty]
• Destination field: bar
• Type: JSON
• List of fields: [empty]
• Fields to keep: a, b, c, d