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Nest

The Nest filter plugin lets you operate on or with nested data. Its modes of operation are:

  • nest: Take a set of records and place them in a map.

  • lift Take a map by key and lift its records up.

Example usage for nest

As an example using JSON notation, to nest keys matching the Wildcard value Key* under a new key NestKey the transformation becomes:

Input:

{
  "Key1"     : "Value1",
  "Key2"     : "Value2",
  "OtherKey" : "Value3"
}

Output:

{
  "OtherKey" : "Value3"
  "NestKey"  : {
    "Key1"     : "Value1",
    "Key2"     : "Value2",
  }
}

Example usage for lift

As an example using JSON notation, to lift keys nested under the Nested_under value NestKey* the transformation becomes:

Input:

{
  "OtherKey" : "Value3"
  "NestKey"  : {
    "Key1"     : "Value1",
    "Key2"     : "Value2",
  }
}

Output:

{
  "Key1"     : "Value1",
  "Key2"     : "Value2",
  "OtherKey" : "Value3"
}

Configuration parameters

The plugin supports the following configuration parameters:

Key
Value format
Operation
Description

Operation

ENUM [nest or lift]

Select the operation nest or lift

Wildcard

FIELD WILDCARD

nest

Nest records which field matches the wildcard

Nest_under

FIELD STRING

nest

Nest records matching the Wildcard under this key

Nested_under

FIELD STRING

lift

Lift records nested under the Nested_under key

Add_prefix

FIELD STRING

Any

Prefix affected keys with this string

Remove_prefix

FIELD STRING

Any

Remove prefix from affected keys if it matches this string

Get started

To start filtering records, run the filter from the command line or through the configuration file. The following example invokes the Memory Usage input plugin, which outputs the following:

[0] memory: [1488543156, {"Mem.total"=>1016044, "Mem.used"=>841388, "Mem.free"=>174656, "Swap.total"=>2064380, "Swap.used"=>139888, "Swap.free"=>1924492}]

Example 1 - nest

Use nest from the command line

Using the command line mode requires quotes to parse the wildcard properly. The use of a configuration file is recommended.

The following command loads the mem plugin. Then the nest filter matches the wildcard rule to the keys and nests the keys matching Mem.* under the new key NEST.

$ ./fluent-bit -i mem -p 'tag=mem.local' -F nest -p 'Operation=nest' -p 'Wildcard=Mem.*' -p 'Nest_under=Memstats' -p 'Remove_prefix=Mem.' -m '*' -o stdout

Nest configuration file

pipeline:
    inputs:
        - name: mem
          tag: mem.local

    filters:
        - name: nest
          match: '*'
          operation: nest
          wildcard: Mem.*
          nest_under: Memstats
          remove_prefix: Mem.

    outputs:
        - name: stdout
          match: '*'

Nest result

The output of both the command line and configuration invocations should be identical and result in the following output.

[2018/04/06 01:35:13] [ info] [engine] started
[0] mem.local: [1522978514.007359767, {"Swap.total"=>1046524, "Swap.used"=>0, "Swap.free"=>1046524, "Memstats"=>{"total"=>4050908, "used"=>714984, "free"=>3335924}}]

Example 2 - nest and lift undo

This example nests all Mem.* and Swap.* items under the Stats key and then reverses these actions with a lift operation. The output appears unchanged.

nest and lift undo configuration file

pipeline:
    inputs:
        - name: mem
          tag: mem.local

    filters:
        - name: nest
          match: '*'
          Operation: nest
          Wildcard:
            - Mem.*
            - Swap.*
          Nest_under: Stats
          Add_prefix: NESTED

        - name: nest
          match: '*'
          Operation: lift
          Nested_under: Stats
          Remove_prefix: NESTED

    outputs:
        - name: stdout
          match: '*'

nest and lift undo result

[2018/06/21 17:42:37] [ info] [engine] started (pid=17285)
[0] mem.local: [1529566958.000940636, {"Mem.total"=>8053656, "Mem.used"=>6940380, "Mem.free"=>1113276, "Swap.total"=>16532988, "Swap.used"=>1286772, "Swap.free"=>15246216}]

Example 3 - nest 3 levels deep

This example takes the keys starting with Mem.* and nests them under LAYER1, which is then nested under LAYER2, which is nested under LAYER3.

Deep nest configuration file

pipeline:
    inputs:
        - name: mem
          tag: mem.local

    filters:
        - name: nest
          match: '*'
          Operation: nest
          Wildcard: Mem.*
          Nest_under: LAYER1

        - name: nest
          match: '*'
          Operation: nest
          Wildcard: LAYER1*
          Nest_under: LAYER2

        - name: nest
          match: '*'
          Operation: nest
          Wildcard: LAYER2*
          Nest_under: LAYER3

    outputs:
        - name: stdout
          match: '*'

Deep nest Result

[0] mem.local: [1524795923.009867831, {"Swap.total"=>1046524, "Swap.used"=>0, "Swap.free"=>1046524, "LAYER3"=>{"LAYER2"=>{"LAYER1"=>{"Mem.total"=>4050908, "Mem.used"=>1112036, "Mem.free"=>2938872}}}}]


{
  "Swap.total"=>1046524,
  "Swap.used"=>0,
  "Swap.free"=>1046524,
  "LAYER3"=>{
    "LAYER2"=>{
      "LAYER1"=>{
        "Mem.total"=>4050908,
        "Mem.used"=>1112036,
        "Mem.free"=>2938872
      }
    }
  }
}

Example 4 - multiple nest and lift filters with prefix

This example uses the 3-level deep nesting of Example 2 and applies the lift filter three times to reverse the operations. The end result is that all records are at the top level, without nesting, again. One prefix is added for each level that's lifted.

nest and lift prefix configuration file

pipeline:
    inputs:
        - name: mem
          tag: mem.local

    filters:
        - name: nest
          match: '*'
          Operation: nest
          Wildcard: Mem.*
          Nest_under: LAYER1

        - name: nest
          match: '*'
          Operation: nest
          Wildcard: LAYER1*
          Nest_under: LAYER2

        - name: nest
          match: '*'
          Operation: nest
          Wildcard: LAYER2*
          Nest_under: LAYER3

        - name: nest
          match: '*'
          Operation: lift
          Nested_under: LAYER3
          Add_prefix: Lifted3_

        - name: nest
          match: '*'
          Operation: lift
          Nested_under: Lifted3_LAYER2
          Add_prefix: Lifted3_Lifted2_

        - name: nest
          match: '*'
          Operation: lift
          Nested_under: Lifted3_Lifted2_LAYER1
          Add_prefix: Lifted3_Lifted2_Lifted1_

    outputs:
        - name: stdout
          match: '*'

nest and lift prefix result

[0] mem.local: [1524862951.013414798, {"Swap.total"=>1046524, "Swap.used"=>0, "Swap.free"=>1046524, "Lifted3_Lifted2_Lifted1_Mem.total"=>4050908, "Lifted3_Lifted2_Lifted1_Mem.used"=>1253912, "Lifted3_Lifted2_Lifted1_Mem.free"=>2796996}]

{
  "Swap.total"=>1046524,
  "Swap.used"=>0,
  "Swap.free"=>1046524,
  "Lifted3_Lifted2_Lifted1_Mem.total"=>4050908,
  "Lifted3_Lifted2_Lifted1_Mem.used"=>1253912,
  "Lifted3_Lifted2_Lifted1_Mem.free"=>2796996
}

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