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

Getting 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

Command Line

Using 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.

bin/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

Configuration File

fluent-bit.conf

[INPUT]
    Name mem
    Tag  mem.local

[OUTPUT]
    Name  stdout
    Match *

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard Mem.*
    Nest_under Memstats
    Remove_prefix Mem.

fluent-bit.yaml

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.

Example 2 Configuration File

fluent-bit.conf

[INPUT]
    Name mem
    Tag  mem.local

[OUTPUT]
    Name  stdout
    Match *

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard Mem.*
    Wildcard Swap.*
    Nest_under Stats
    Add_prefix NESTED

[FILTER]
    Name nest
    Match *
    Operation lift
    Nested_under Stats
    Remove_prefix NESTED

fluent-bit.yaml

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.

Example 3 Configuration File

fluent-bit.conf

[INPUT]
    Name mem
    Tag  mem.local

[OUTPUT]
    Name  stdout
    Match *

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard Mem.*
    Nest_under LAYER1

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard LAYER1*
    Nest_under LAYER2

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard LAYER2*
    Nest_under LAYER3

fluent-bit.yaml

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.

Configuration file

fluent-bit.conf

[INPUT]
    Name mem
    Tag  mem.local

[OUTPUT]
    Name  stdout
    Match *

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard Mem.*
    Nest_under LAYER1

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard LAYER1*
    Nest_under LAYER2

[FILTER]
    Name nest
    Match *
    Operation nest
    Wildcard LAYER2*
    Nest_under LAYER3

[FILTER]
    Name nest
    Match *
    Operation lift
    Nested_under LAYER3
    Add_prefix Lifted3_

[FILTER]
    Name nest
    Match *
    Operation lift
    Nested_under Lifted3_LAYER2
    Add_prefix Lifted3_Lifted2_

[FILTER]
    Name nest
    Match *
    Operation lift
    Nested_under Lifted3_Lifted2_LAYER1
    Add_prefix Lifted3_Lifted2_Lifted1_

fluent-bit.yaml

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
}